Frost in the Attic

[Reis Pearson]

Forgive me, but we here in Seattle don't see many freezing temperatures (until this week) and I haven't seen frost buildup in the attic space. How concerned should I be about this?? The situation is a 2000 build, the North side of the sheathing (from the attic) had a layer of frost. I had adequate ventilation and adequate insulation (aside from a few areas where there were footprints). Is this "normal" for freezing temps or should I never, under any circumstances have frost buildup on the sheathing?? Thanks in advance!

[Bruce Breedlove]

Looks to me that you have a moisture problem in the attic. Do bathroom or kitchen exhaust fans discharge into the attic?

[John Kogel]

Any ice is too much. There should never be that much moisture in the attic.

Most likely, warm air is leaking up from the living space somehow. I would call for a repair, further investigation, etc.

[Ken Rowe]

Pretty common to see in older houses here in MN. Additional insulation and possibly ventilation is needed in the attic.

[Jim Luttrall]

I have to agree that any ice is too much, BUT, you are in a very wet area, no?
Think about your weather before the temperature dropped and how rapidly it dropped.
If you had a 80+% humidity at say 50 degrees and the temperature drops quickly to below freezing, then the moisture is already in the attic and will plate out on the cold surfaces.
It bears looking into, but if you did not see any evidence of moisture damage on a 9 year old house, combined with funky weather, maybe it is just an anomaly.

[Roy Cooke sr]

Frost in attic is caused from warm Moist air getting into attic .It is caused by stack effect.
Look for Exhaust from bath or Kitchen vents into attic,
they must go to the outside ( not to Roof vents or to soffit.
You can also look to Attic door not gasketed and insulated it might need more weight to help seal the gasketed door..
pot lights not sealed they should have a dry wall box enclosing them .
All electric boxes in ceiling can be leaking into attic .
There could considerable heat being lost via these vent holes .
Insulation added still will not stop this warm moist air getting in to attic .
Another cause could be over venting the attic with electric or air operated roof vents puling more aid from the home.
You could have negative pressure in attic with no soffit vents .
Roy Cooke

[Phillip Norman]

I do not work as a Home Inspector, but have been reading this Forum for several weeks, and think I "belong." I think I have methods to share, in ability to produce informative reports.

Please consult the attached pdf document, to understand a report of mold in roof sheathing of a home in Portland Oregon. At issue is whether mold would be controlled by vacuuming cellulose from accessible reaches into sloped ceilings below the upper attic.

I seek a consensus test of my assertion that mold in a roof is always due to a roof problem. Further, I assert such problems are subtle, with periodic wetting and not with flow that would produce complaint and repair. An example, and a common issue, is improper placement of felt paper under asphalt shingles. Felt paper error might run the full length of a roof.

Portland is really cold right now, and I imagine photos in this attic would be interesting. I imagine I will be up there again, soon.


At March, 2010, I redirect the reader to consensus advice in this thread. Get rid of the moisture source! My customer fixed his problem, with major re-roof over a troublesome bathroom. The re-roof allowed installation of a proper through-roof bath fan. My insulation of the attic did not need any correction. A lot of insulation did aggravate the mold problem, with roof sheathing running colder. The attached file has been replaced, where viewed through the link in my second post to this thread, at an editable collection of documents on my Google Sites web page. I assert that a Google Sites web page, accepting pdf attachment, is a way for home inspectors to set up a personal report vault for each customer, viewable without download, and amenable to corrections. I face storage limit problems with my posts. I think the limit is 200 MB. I will look to free up space by not directly uploading pictures, rather referencing them at Picasa Web Albums.

[Roy Cooke sr]

Research Report Download

Unvented Roof Summary Article

by Kohta Ueno — last modified 2009/07/10


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[Ken Rowe]

I do not work as a Home Inspector, but have been reading this Forum for several weeks, and think I "belong." I think I have methods to share, in ability to produce informative reports.

Please consult the attached pdf document, to understand a report of mold in roof sheathing of a home in Portland Oregon. At issue is whether mold would be controlled by vacuuming cellulose from accessible reaches into sloped ceilings below the upper attic.

I seek a consensus test of my assertion that mold in a roof is always due to a roof problem. Further, I assert such problems are subtle, with periodic wetting and not with flow that would produce complaint and repair. An example, and a common issue, is improper placement of felt paper under asphalt shingles. Felt paper error might run the full length of a roof.

Portland is really cold right now, and I imagine photos in this attic would be interesting. I imagine I will be up there again, soon.


I don't believe your mold in the attic was caused by frost. Generally mold in the attic is caused by high humidity levels in the home. A furnace humidifier set too high for long periods of time, moisture intrusion in the basement or even excessive amounts of plants in the home. As someone stated earlier, stack effect. Humidity in the home rises to the attic and gets trapped. Another contributing factor would be the lack of proper ventilation of the attic space. Generally you'd like low and high ventilation, roof or ridge and soffit vents.

[Roger Hankey]

In my 34 years as an inspector in a cold climate, Twin Cities, Minnesota, I believe that nearly all frosted attics have their source of moisture from inside the house:

1. Air leaks from the house to the attic at various penetrations: aka attic bypasses. The amount of frost depends on the indoor relative humidity, the total cross sectional area of the bypasses, and on the pressure differential between the house and the attic (stack effect). These are most common here in homes built before 1985. Since then most penetrations get sealed with sheet metal or foam caulk. Homes with damp basements often have frosted - moldy attics if bypasses are present.

2. Unvented or poorly vented range hoods and bathroom fans. (Recently shown as a concern on an episode of "Ask this Old House".)

3. Loose or deteriorated vents from combustion appliances. (This is the worst and will ruin the roof sheathing in one season if not corrected.) This condition will produce so much moisture that ceiling leaks will develop during periods of extreme cold when the heating plant is frequently operating and while attic temps are very cold.

Attic ventilation RARELY solves these problems. The solution is to control indoor humidity AND eliminate the pathways for moisture to reach the attic. (seal bypasses, fix vents, etc.) Increasing attic ventilation alone simply increases the flow of moisture INTO the attic and further lowers attic temps, which actually worsens the problem.

[mathew stouffer]

Somethings wrong. Any frost is too much. It has been 5 to 10 below here for the last week and I don't see frost in the attic. Plus it can cause mold over time. During the nigh frost forms, then when the sun hits the roof it melts and absorbs into the OSB. This cylce continues for a while, then in the spring when it warm up and the OSB is saturated. Poof, mold and mildew.

[Bill Barnes]

Not sure of the construction style (slab, basement or crawlspace) but it is not uncommon to see frost, sometimes much more severe than your example, caused from a wet crawlspace. Physics. Water vapor rising from a damp/wet crawlspace will plate out on the cold underside of the roof deck and freeze. We have the related issue with mold growth in the attic then with the repeated wetting and drying of the roof deck.

Bill

[Brian Hoagland]

That much water on roof sheathing is a problem, even though it is frozen water. I would report it and recommend further evaluation. What we don't know is why it is there. What we do know is that it should not be. There is a possibility that it is an anomally which may not reoccurr but as it was observed so should it be reported. There are times when we may be unable to ascertain the cause of a defect due to the time restrictions of the inspection period. Further evaluation is waranted here as this condition may have both structural and health related consequences.

[Rick Bunzel]

Reis,

I am an inspector who operates north of Seattle. The moisture has always been present you just didn't see it. I noticed in the first picture that the a vent fan hose is disconnected and probably laying in the insulation. As other have said you need to look for the source of moisture that is coming from the living space. The mold/mildew will always show up on the north side of the roof and in advanced cases migrate to other exposures.

Pictured is a home I inspected yesterday. Picture on left is next to gable end. I thought the roof had fire damage at first glance but mold/mildew hadn't turned into rot/fungus yet. Source of moisture was attic hatch that only partially cover hatch opening.

Your attic looks pretty well ventilated but you may want to consider a fan hooked to a humidstat.

//Rick

[Jerry Peck]

I had adequate ventilation and adequate insulation ...

Reis,

Whenever you see things like in your photo, I would hesitate before stating there was "adequate" ventilation as better ventilation may well hep prevent that, which would mean that what is there is no "adequate".

Now, if by "adequate" you mean 'the code required' amount of ventilation, then I would stay away from the term "adequate" anyway.

Like others (or so it seems as I read the above), I suspect two things:
- too much air exfiltration from the living space into the attic
- the humidity may have already been in the attic and a sudden and dramatic temperature drop simply freezes the moisture in place
- which gets back to 'too much air exfiltration from the living space into the attic'

Which indicate inadequate ventilation (allowing air exfiltration from the living space into the attic means that more ventilation is needed to off set it. Which is not so much of a ventilation problem as much as an air exfiltration problem.

[Roy Cooke sr]

("Your attic looks pretty well ventilated but you may want to consider a fan hooked to a humidstat. //Rick ")

I think I would be carefull in adding a fan exhaust as this could lower the pressure in the attic and cause more of a problem by drawing More warm moist air from the home .

I expect not to far in the future we could stop venting attics ,it is done with some homes now and they did not vent homes many years ago.

Roy Cooke

[Phillip Norman]

I have moved in on this thread, with alternative discussion of a home with attic mold. I hope this is beneficial, that frost/ humidity/ mold are all the same for cause and action.

My first, and only previous post, offered a pdf report that includes report-making methods that I am proud of. I hope the report-making will warrant a separate, new thread. I offer not only good pdf reports, but a better way to display and discuss them. Here is a link to an update of my report, and the action I recommend based on the good judgements I have observed in this thread. All inspectors might choose Google Sites web sites where their customers could view personalized reports via confidential links.

Post to Inspection News, 12-11-2009 (Services by Phil Norman) (http://sites.google.com/site/phillipnormanatticaccess/post-to-inspection-news-12-11-2009?pageReverted=3)

I consciously do not post my conclusions here, wanting readers to follow my link. Please know, you will be able to view my new pdf without download. I hope with direct view, as with pictures in this forum, more people will bother to look.

Phillip Norman
Attic Access
Portland, OR
Home (Services by Phil Norman) (http://sites.google.com/site/phillipnormanatticaccess/)

[Jon Errickson]

Roger – as a newer inspector in Minnesota your insights are greatly appreciated. I have seen a lot of signs of moisture in attics especially in homes built in the ‘50s and ‘60s. One thing I’ve noticed in those homes is, if they have their original windows (double-hung, single pane with storms), the windows show signs of having moisture on them (or right now with how cold it is out you can see the moisture on the inside of them). Are these two issues usually related, or is it just that the windows are older and probably leaking like a sieve? Do you generally recommend that people monitor the humidity levels (turning down the humidifiers, etc.) in their homes when these issues are present? Does weather-stripping help those windows at all, or is replacement really the only way to stop the moisture build-up in the winter?

Sorry for all the questions, but it's something i see a lot around here. Thanks.

[Roy Cooke sr]

I would say that many homes are getting more air tight, this, with out removing the cause of humidity in the home can cause grief.
I seldom see homes that now require a humidifier.
I recommend get a recording device the shows what the humidity is in the home .
I have a tight home and exhaust all Baths and kitchen fans to the outside on Timers .
CMHC has Measuring Humidity in Your Home | CMHC (http://www.cmhc-schl.gc.ca/en/co/maho/yohoyohe/momo/momo_002.cfm) some ideas to follow .
My outside temp is 16° F inside 73°F and inside humidity is 40% no moisture on any windows .
Long( to the floor ) curtains and drapes tend to have cold windows and moisture on them.
I have a dehumidifier set at 50% setting drain hose to Laundry tub to help the high humidity if necessary.

Roy

[Cobra Cook]

You know that an attic is supposed to be a lot colder than the conditioned space?, and the house has to breathe without pulling too much of the air from the conditioned space into the attic and the vapor barrier is supposed to help prevent interior moisture, if any, from entering the attic. The outside of the walls from the foundition up are supposed to go up through the attic and out, this removes any moisture trapped in the walls. If you install too much insullation and cover the ends of the rafters and soffits then the attic will have a hard time venting what needs to be vented. I can not right now put a number of inches that start to no better but i am sure some one will post it, i hope. In the attic all ofthe white insulation it actually looks like too much, was there any vapor barrier at all installed in the attic? Maybe the frost is occuring fo a short time due to the roof not having the proper roofing material under the shingles and that is causing the roof to keep moisture to stay. Lots to look into.:)

[Jerry Peck]

The outside of the walls from the foundition up are supposed to go up through the attic and out, this removes any moisture trapped in the walls.

Not following what you are saying, but ... as I am understanding what you are saying (while acknowledging that I do not fully understand what you are saying) ... the exterior walls are required to be fireblocked and sealed at the floor and ceiling levels, which means there is no venting of the wall cavities.

Please explain what you are saying better.

[Roger Hankey]

Roger – as a newer inspector in Minnesota your insights are greatly appreciated. I have seen a lot of signs of moisture in attics especially in homes built in the ‘50s and ‘60s. One thing I’ve noticed in those homes is, if they have their original windows (double-hung, single pane with storms), the windows show signs of having moisture on them (or right now with how cold it is out you can see the moisture on the inside of them). Are these two issues usually related, or is it just that the windows are older and probably leaking like a sieve?
1.


Do you generally recommend that people monitor the humidity levels (turning down the humidifiers, etc.) in their homes when these issues are present?
2.

Does weather-stripping help those windows at all, or is replacement really the only way to stop the moisture build-up in the winter?

3. & 4.



Sorry for all the questions, but it's something i see a lot around here.



Thanks.


1. Related? Yes. Indoor humidity is high and will condense on any surface colder than the dew point of the indoor air. Both the glass and the roof sheathing are below the dewpoint, or they would not be wet from the condensation.

2. YES


3. Weatherstripping is a good idea, but will rarely stop the condensation.

4. Window replacement might be useful, but not necessarily cost effective.

A low cost tool is a digital relative humidity gauge. This instrument reads the temperature of the air, its relative humidity and dewpoint. I find it useful to be able to show clients and homeowners the dewpoint of the air to help them understand why I recommend lowering the humidity in the house.

[Joe Klampfer]

Reis, Someone mentioned it earlier but I didn't see a response, can you tell us if the home is on a crawlspace or not? and if it is, is there a well sealed vapour barrier or is the dirt exposed ? I have often seen that to be the problem. Your attic may appear to be adequatly sealed and ventilated but it can simply be a matter of the ventilation being overwhelmed and not being able to "catch-up" due to the amount of humidity coming up from your crawlspace.

[David Bell]

Seattle huh? Geez you guys never have moister problems. But really, the frost you are seeing is most likely from a bathroom vent fan thats not exhausted correctly.

[David Bell]

moisture

[Cobra Cook]

Jerry of course wall cavities are fire blocked at the top and bottom but i was referring to the outer wall between the siding or brick which have weep holes to provide an airflow to help reduce the humidity in the dead air space. this space is ususlly not air tight at the top or bottom and is vented through the soffits to the attic also

[Andrew Christel]

What was the condition of the HVAC duct system.?

[Jerry Peck]

Jerry of course wall cavities are fire blocked at the top and bottom but i was referring to the outer wall between the siding or brick which have weep holes to provide an airflow to help reduce the humidity in the dead air space. this space is ususlly not air tight at the top or bottom and is vented through the soffits to the attic also


That air space is also supposed to be fireblocked at the top so it does not go up into the attic.

Weep holes at the bottom - good, supposed to be there.

Vent holes at the top - good, that helps create air flow for ventilation and drying out the air space ... good as long as the holes do not go up into the attic of soffit, that the holes vent to the exterior of the wall.

[Ernie Tate]

The frost in the attic is a pre-curser to the developement of attic mold if left unchecked. This frost is indeed caused by moisture from within the home or building. It is however allowed to freeze on the attic sheathing due to a lack of ventilation in the attic space. Warm moisture laden air if not allowed to vent out of the attic will naturally cool within the attic. As the air cools condensation is the natural by product of the air cooling. I inspect homes in south eastern Idaho and see this condition all the time. I would suggest that in order to cure this condition that you advise additional ventilation be installed, and that indoor relative humidity be controlled by using exhuast fans when showering/ bathing, cooking, possibly installing a vapor barrier if needed in the crawl space. I have seen this condition develop when home owners used vaporizers extensively, or exhaust a clothe dryer into the home also. In my opinion the lack of ventilation is the biggest cuprit here, and ventilation definetly will not add to this problem. That opinion is definetly off base, not trying to be rude, but facts are facts.

Ernie Tate
TCS Home Inspections
Idaho Falls, Idaho
Builder for 35 years
Full time home inspector for over 10 years

[Roy Cooke sr]

And some Facts are not facts .
Adding more ventilation could take more air out of the attic now with negative pressure in the attic we will get more air into the attic and much could come from the home .
Stack effect is our problem
This could only make the problem worse .
Experience is a good teacher and reading will also help .
I have both a good start is read this . Roy
the house needs to be sealed better and close all holes to the attic.



Measuring Humidity in Your Home | CMHC (http://www.cmhc-schl.gc.ca/en/co/maho/yohoyohe/momo/momo_002.cfm)

[chris mcintyre]

Adding more ventilation could take more air out of the attic now with negative pressure in the attic we will get more air into the attic and much could come from the home .

I agree with this 100% (assuming we are talking about mechanical ventilation.)

I have now read several post that mentioned the VB in the crawl space. Is it really possible for enough moister from the crawl space to cause condensation problems in the attic?

[Roy Cooke sr]

I just helped a person who had a simular concern . He also had snow melt on the roof Finnaly he went to the spot under the snow melt pulled back insulation found a 3inch hole in the attic some one had left all the way to basement in centre of wall . Roy

[Ernie Tate]

In reply to Chis's question about moisture in a crawl space, and in conjucntion to Roy's reply concerning the stack effect, which is indeed a real phenomena in a home. It is my opinion that properly installed vapor barrier in a crawl space is one of the most important items in home construction. Even if for no other reason than to keep soil odors from drifting up into the home in well drained gravel area's. Not only that it keeps the home inspector cleaner after checking out the crawl space.

As far as the ventilation goes I should have made one issue very clear, under no circumstance for moisture elimination do I suggest mechanical ventilation, as far as that goes I never suggest mechanical ventilation in an attic area, a crawl space is a totally different matter. It has been my experience that the largest percentage of power ventilation in attics never get serviced and are not operational at the time of inspection. Secondly mechanical ventilation is designed to work in the summer with their thermostatic controls and will not turn on in the winter months due to lower attic temperatures. Passive ventilation in the correct amounts is vitally important in an attic to allow moisture laden warm air which has already passed through the thermal insulation layer in conventional attics. At that point this additional heat and moisture in an attic becomes your home's worst enemy. Adequate ventilation in an attic is also the biggest factor in eliminating ice damming and related problems. This again is a proven Fact. To not install ventilation into an attic in a colder heating climate such as Minnesota, Idaho and Washington is a serious mistake. Roofing material life has proven to be extended with proper ventilation. One item not accounted for in modern building codes in the installation of black roofing shingles. It is not uncommon for me to encounter truss chord temperatures in the summer of as high as 165 degrees F. A lack of ventilation only makes this worse and a roof will constantly expand and contract which also breaks the sealing of shingle tab's and allows for higher rates of shingle blow off primarily with three tab shingles.

It's a free world advise your clients as you wish, I so choose to advise mine in a manner which will help them maintain a home in good condition. :)

TCS HOME NSPECTIONS
Knowledgeable and Thorough

PS: If properly installed combustion air,and or ventilation makeup air is installed in a home, and air leakage is controlled from within the conditioned area of a home this stack effect, if present should be minimal.

[David Bell]

With the increased amount of "tight" homes being built,,combustion air is the single most cause of air infiltration. Without proper introduction of combustion air to any fuel burning equipment ,the risk is there for infiltration from unwanted areas.

[Roy Cooke sr]

Great group good discusion . Big help to many and many thoughts traded . Thanks to all... Roy

[Bert de Haan]

("Your attic looks pretty well ventilated but you may want to consider a fan hooked to a humidstat. //Rick ")

I think I would be carefull in adding a fan exhaust as this could lower the pressure in the attic and cause more of a problem by drawing More warm moist air from the home .

I expect not to far in the future we could stop venting attics ,it is done with some homes now and they did not vent homes many years ago.

Roy Cooke
Is there a way to mechanically vent attic space by adding air instead of exhausting air? A fan in the soffit maybe? Maybe this has not been done for good reason; I just can't think of that reason now. If the attic is sealed from the living space this won't be necessary of course but older houses that were insulated without being able install a vapour barrier might benefit.
Any thoughts on that?
Thanks.

[David Bell]

Pressurizing your attic will only make things worse,,to exhaust attic air will supply new air thru soffits or ridge vent or gable vents, Air changes in attic space are critical to moisture removal

[Bert de Haan]

Pressurizing your attic will only make things worse,,to exhaust attic air will supply new air thru soffits or ridge vent or gable vents, Air changes in attic space are critical to moisture removalEither way will exhaust attic air. The one way by creating a negative pressure which will "suck" air through places like the soffit and exhaust them through the fan. The other way by creating a positive pressure by pushing air in through the soffit and exhausting it through the roof, gable, or the other soffit vents. The advantage I can see with the positive pressure is that the moist house air will not get forced into the attic.

[Michael Carson]

Either way will exhaust attic air. The one way by creating a negative pressure which will "suck" air through places like the soffit and exhaust them through the fan. The other way by creating a positive pressure by pushing air in through the soffit and exhausting it through the roof, gable, or the other soffit vents. The advantage I can see with the positive pressure is that the moist house air will not get forced into the attic.

Be careful with fans in the attic area especially the size of fan. If the living spaces are not air sealed properly, can lights, cantilevers, penetrations, etc you can very well depressurize the attic and living area cause backdrafting, decrease energy efficiency. Just my thought/theory.

What about the idea of consulting an energy rater to test the home?

[Jerry Peck]

The advantage I can see with the positive pressure is that the moist house air will not get forced into the attic.


Correct, but the outdoor air will now be forced down into the living space, taking all of its moisture, cold, etc., with it.

The LAST THING you want to do is to pressurize the attic, right next to that is to de-pressurize the attic with an exhaust fan (that will have other unintended consequences, such as sucking the conditioned air out of the house) ... you want the attic to be relatively neutral and as close to outdoor pressure as can be, and for the house to be slightly (but not even that noticeably so) ... ;) ... pressurized in relation to the outdoors (and thus the attic).

[Bert de Haan]

Be careful with fans in the attic area especially the size of fan. If the living spaces are not air sealed properly, can lights, cantilevers, penetrations, etc you can very well depressurize the attic and living area cause backdrafting, decrease energy efficiency.
I understand but I am asking about fans blowing air INTO the attic. This would pressurize rather than depressurize the attic. It could force some cold (and dry) air into the living area but that is not as big a deal as sucking warm (and moist) air into the attic. Both ways is a decrease in energy efficiency though.


Correct, but the outdoor air will now be forced down into the living space, taking all of its moisture, cold, etc., with it. Up here in the great white North there is very little moisture in the air during the winter so theoretically having a positive pressure in the attic would be less harmful than having a negative pressure. Air from the house interior leaking into the attic will add moisture to the attic.
I'm not trying to be argumentative but I am just trying to learn.
Thanks

[David Bell]

A correctly vented attic is almost always in a negative pressure due to winds and the natural draft effect,,to pressurize it is to keep it from doing what it is meant to do.

[Ernie Tate]

Hello Bert

Great question, but I believe David was right on the money with the air exchanges being the key idea in attic ventilation. To fully understand attic ventilation is to understand the reason's for venting an attic. Seasonal needs will basically change the reason for venting an attic. Eliminating unwanted heat in an attic in the summer to supplement a cooling system is as important as venting super heated air prior to producing condensation in the attic in the winter months.

To more fully answer your question about mechanically venting an attic by inducing air into the soffit. This method of ventilation would not accomplish any more than having a mechanical roof top ventilator with no soffit ventilation. This is the reason that the building codes are specific as to where and how much ventilation needs to be installed in soffits, and upper elevations of the roof decks.

I had the opportunity this past year to inspect a LEED certified home in Sun Valley which had an air to air ventilation system installed, with the heat exchanger unit installed in the attic. The builder had used a full closed cell foam insulation system blown onto the roof deck and upper truss chords (7 inches thick). The upper floor system was a singular truss system which included the floor deck, upper floor exterior and interior wall, and roof frame. The entire outer shell of the structure was sealed and insulated with this closed cell foam. The air exhchanger unit circulated the air for the entire attic space, upper floor, and main floor living area. In this manner the air exchanges for the entire home, and the indoor air pressures were strictly regulated. This is fairly easy to do in new construction, and with the correct understanding of indoor air pressures, and needed air exchanges in a home, with enough work and ingenuity you can somewhat accomplish the same idea with nearly any home. The first step in my opinion would be have a duct blaster test of your forced air system (assuming that is the case), and secondly have a quality blower door test of the home. You can't fix what you do not understand. If a crawl space is involved I would also suggest having the foundation perimeter walls and rim joist area sealed with a closed cell foam, a quality vapor barrier installed, and topped off with a proper conditioned crawl space ventilation system. These are in my opinion the foundation steps to controlling/ understanding indoor air pressures in home/ structure.

I am sure I have not answered a single question but possibly I have allowed you to expand the horizon of what a simple attic ventilation question can possibly lead to. My favorite expression is that "it is easy to criticize that which you do not fully understand". Really of no relevance in this discussion, but some times it can be bent to enter any conversation.

Air movement in a home is indeed a science, one that admittedly I have not mastered but I enjoy trying. The photos above are taken in the attic area of the home in Sun Valley I referenced.

[Jerry Peck]

A correctly vented attic is almost always in a negative pressure due to winds and the natural draft effect, ...

Due to the natural draft effect and the winds, an attic is ... basically neutral as one area has a higher pressure (the windward side) and another has a lower pressure (the leeward side), making the interior of the attic have varying degrees of pressure, but overall on, on balance, it should be (if one could average the pressures out) at the same pressure as the outdoors (where the pressures are changing anyway).


... to pressurize it is to keep it from doing what it is meant to do.

Agree with that 100%.

To depressurize the attic does the same thing.

Yes, one can pressurize, or depressurize, the attic and *MAKE* it vent, but there are consequences to those actions which one probably would not like in a modern, insulated, and somewhat sealed house.

[Nick Ostrowski]

I just saw this in a house about a week ago. The soffit vents in the attic were blocked with insulation. The roof had soffit vents and gables. I told the buyer he needed to pull the insulation about a foot away from the the soffit and should upgrade to a ridge vent.

[Bert de Haan]

Thanks a lot guys! Very helpful.

[GerryM]

Hi Everyone,

I need your help! I have just discovered massive frost in my attic. RH in the home is around 28-40% depending on the day (with occasional spikes to 50) at a temperature of approx. 70 to 77 degrees C. This is a townhome/condo end unit. Insulation is fiberglass pink and there appears to be a vapour barrier beneath.

You can see from the photos the frost is thick throughout the roof area.

My questions are as follows - what should I do about the frost there now? It's going to melt and then what?

What is causing it? Looking around the attic I can see the bathroom vent goes out through the roof. The furnace (natural gas) and hot water tank share the another vent out the roof. I can see a rectangular hole in the roof that may lead to a vent but an unable to see light there. There is soffitt around the outside of the roof (I will check to see if it's blocked). There is a reverse flow furnace in the house(hot air leaves via the bottom) with the cold air runs above it and a vent that seems to pull air from the attic into the run (is this normal?).

What should be my first step in this?

Thanks,

Gerry

[Roy Cooke sr]

I do not think you have enough frost to be concirned about the water from it.
Yes it is not a good thing .
I do think it is very cold in your area at this time .
I expect you have warm home air getting into the attic .
Is the access door Properly insulated & gasketed and is and is the door heavy enough to stop air from the house getting up there .
A simple quick fix this time of the year is to get some stripable caulking and caulk the door if this is where air is getting to the attic.
Next warm season strip the gasket and fix the attic entrance properly .

Roy Cooke Royshomeinspection.com

Attic Venting, Attic Moisture and Ice Dams | CMHC (http://www.cmhc-schl.gc.ca/en/co/maho/gemare/gemare_001.cfm)

[Ernie Tate]

Hello Jerry

There is enough moisture/ frost in that attic to cause a black mold problem. Ventilation in a adequate amount is needed to allow the warm moist air to escap from the attic. As mentioned earlier a couple of times in this discussion on attic frost "any warm air when cooled in an attic will condense". As the warm air cools it will condense and deposit the condensation onto the attic sheathing as it is the coldest portion of the attic. Note in your photos that this frost extends fully to the peak of the attic. Normally this condition will begin at the lower portions of a roof slope and work its way up. The installed insulation is a fiberglass bat, and will allow for heat loss from the conditioned space. This warm air will condense as it cools. A normal family of five will deposit up to 5 quarts of moisture into the air every day from bathing, breathing, cooking, etc. Spill 5 quarts of water onto your floor and get a visual of how much moisture is involved. Without venting this warm moisture laden air out of your attic where else does the moisture have to go. At this point you have a moisture source, a wood cellulose sheathing, and an attic temperature which will support mold growth (not to mention the billions of mold cells common to all air sources. I suggest you control indoor moisture sources as well as possible, your 25 to 45 % RH is not considered high. I suggest that you properly vent the soffits and ridge line of the attic space. Additional insulation tightly installed to an R-38 or more will also make some difference. A good test will check your window surfaces in the home. If you are not showing excessive frost buildup in the windows or aluminum sliding door or window frames, this is simply a lack of ventilation in the attics in a normal home.

Prior to becoming a home inspector my father in Law and I operated an insulation company, and I have personally insulated hundreds of attics, and as a home inspector have been in thousands of attics. This attic is simply under ventilated. Ideally you want the interior attic temperature above the thermal insulation level to be the same temperature as the exterior. With heat loss from the conditioned space this obviously will never occur. Hope this helps.

[Ernie Tate]

Sorry! I ment to address the last post to Gerry.

[Roy Cooke sr]

Being Calgary and it is cold I do not think you need to worry about Black mould.
Stopping the warm moist home air to the attic is what you need to do .
Adding more ventilation can just increase the air from the house.
The first warm sunny day will get the frost gone from the sheating.
Go to some of the CMHC places I have posted and see.
I can send you more information if you want.
Look for elect boxes or flush ceiling lights that could be leaking air .
Stop the air leaks and concirns will be gone .
Roy Cooke ... Royshomeinspection.com

[Jerry Peck]

I've read in the past, but no longer can find that information or link to it, that Minnesota had testing done which showed that fiberglass insulation, especially loose fill, but fiberglass batt to a lesser degree also, suffered a loss of R-value of up to 50% in extreme cold climates such as the winter temperatures in Minnesota.

I imagine that Canada would be a similar, and possibly worse, environment as to cold temperatures.

That R-value loss could be coming into play with frost in the attics as it allows for a greater air attic air temperature in the attic air which is closer to the ceiling, with the temperature falling more rapidly the closer to the sheathing you get.

That means the air in the attic could contain more moisture escaping from within the living space below, then condensing out (which causes the frost) on the colder sheathing.

Regardless, though, the cause is the moisture in the air, and the most likely source for that moisture is from inside the living area, and the reason that moisture is in the attic is excess leakage - air exfiltration - from the living space into the attic.

The first solution I would recommend would be to have a contractor go into the attic and move the insulation away from all the wall top plates, ceiling lights, etc., anything which penetrates into the attic from below, sealing up ALL gaps and spaces around EVERYTHING, then moving the insulation back into place. That would be the first step in reducing the moisture load in the attic, which may well bring the condition under control, but this will still solve and reduce many other problems, and save energy as every gap and space sealed is one less gap or space where conditioned air - which costs money to condition - can escape to the attic and be lost as wasted energy.

[Jerry Peck]

Being Calgary and it is cold I do not think you need to worry about Black mould.


Some people always jump onto that mould wagon as the first thing to worry about, when there really is no, or very little, to worry about with regards to mould in the house, especially when in the attic.

[Roy Cooke sr]

Some people always jump onto that mould wagon as the first thing to worry about, when there really is no, or very little, to worry about with regards to mould in the house, especially when in the attic.
Thanks Jerry .
Exactly every home has Mould . I just removed some pudding from my Fridge and it had some on top.
Fiberglass is just a big filter

Some interesting reading below ... Roy

http://www.buildingscience.com/documents/reports/rr-0209-mold-testing/view?searchterm=mold (http://www.buildingscience.com/documents/reports/rr-0209-mold-testing/view?searchterm=mold)

http://www.cdc.gov/mold/dampness_facts.htm (http://www.cdc.gov/mold/dampness_facts.htm)

http://www.epa.gov/mold/moldguide.html (http://www.epa.gov/mold/moldguide.html)

[Cobra Cook]

Put in a ridge vent, make sure there are no exhaust fans exhausting into the attic, make sure the attic floor is fully insulated with a vapor barrier facing the sheet rock on the attic floor not on the outside, other than that not much more you can do. If the humidity is high outside and the temp is below freezing what do you expect the moisture in the air to do, it is just like when it frosts in your yard, no difference

[Roy Cooke sr]

Put in a ridge vent, make sure there are no exhaust fans exhausting into the attic, make sure the attic floor is fully insulated with a vapor barrier facing the sheet rock on the attic floor not on the outside, other than that not much more you can do. If the humidity is high outside and the temp is below freezing what do you expect the moisture in the air to do, it is just like when it frosts in your yard, no difference
0°F here this morning No way do I want to put in a ridge vent now.
Vapour Barrier is code now .
Old home I would not be to concerned as two or more coats of paint do the job . My attic has no frost this morning but my car is covered .
I do not think outside humidity effects the attic much .
We had big fog yesterday morning .
I am also of the feeling to much attic ventilation is not a good thing.
Royshomeinspection.com

[David Bell]

I saw no obvious venting at all,,if ridge vent is not possible at least cut in some high gable louvers on opposite sides

[Bert de Haan]

I've read in the past, but no longer can find that information or link to it, that Minnesota had testing done which showed that fiberglass insulation, especially loose fill, but fiberglass batt to a lesser degree also, suffered a loss of R-value of up to 50% in extreme cold climates such as the winter temperatures in Minnesota.
Do you mean because of air infiltration because of windwashing or some thing that just applies to Fiberglass?

[chris mcintyre]

This thread makes a pretty good argument for the sealed, insulated, spray foam (directly to the roof deck) attics.

[Bert de Haan]

This thread makes a pretty good argument for the sealed, insulated, spray foam (directly to the roof deck) attics.
I was asked to assess some relatively minor repairs to be made to a roof structure. (Not as HI but as contractor.) This was in a livestock housing facility so moisture is more of an issue than in attics.
Anyways, the -minor repair- turned into -not worth repairing.-
Everything from the foam insulation on up was rotten, sometime so badly rotten that all there would be left of the purlins spanning the trusses was a small pc stuck on a nail or something. Every thing below the insulation was still fine.
Obviously the foam absorbed the moisture and the wood work stayed moist continuously. Sealed, closed-cell shouldn't do this but it scared the bejeebies out of me. I have seen foam insulation around windows that had enough water in it, it could be squeezed out so some foams do absorb moisture.

[chris mcintyre]

....that all there would be left of the purlins spanning the trusses....


I'm assuming this was a metal roof. On a roof with OSB and fiberglass shingles where the foam is sprayed against the roof deck at least 8" deep(with open cell) and the felt and shingles are on the other side, I would think that without an irrigation system installed in the attic that it would be nearly impossible to get enough moisture in the attic to rot the sheathing. Just my opinion.

[Roy Cooke sr]

I
Anyways, the -minor repair- turned into -not worth repairing.-
Everything from the foam insulation on up was rotten, sometime so badly rotten that all there would be left of the purlins spanning the trusses was a small pc stuck on a nail or something. Every thing below the insulation was still fine.
Obviously the foam absorbed the moisture and the wood work stayed moist continuously. Sealed, closed-cell shouldn't do this but it scared the bejeebies out of me. I have seen foam insulation around windows that had enough water in it, it could be squeezed out so some foams do absorb moisture.
I do not know I would say obviously ,
I have seen foam under the sheating and every thing was fine I have also seen Rotten sheating where there was no foam .
It to me might have been worn out shingles alowing water to penetrate and the foam stopped the water from getting into the space under the roof.
Roy Cooke

[Bert de Haan]

I'm assuming this was a metal roof. Yes it was.
On a roof with OSB and fiberglass shingles where the foam is sprayed against the roof deck at least 8" deep(with open cell) and the felt and shingles are on the other side, I would think that without an irrigation system installed in the attic that it would be nearly impossible to get enough moisture in the attic to rot the sheathing. Just my opinion.You may be right.


I do not know I would say obviously ,
I have seen foam under the sheating and every thing was fine I have also seen Rotten sheating where there was no foam .
It to me might have been worn out shingles alowing water to penetrate and the foam stopped the water from getting into the space under the roof.
Roy Cooke
The roof covering wasn't in good shape but it wasn't in such bad shape to have this effect over the whole roof. Maybe I'm being a little quick with my -obviously- conclusion but it did scare me off enough to not put spray foam in my attic just yet.

[Jerry Peck]

Do you mean because of air infiltration because of windwashing or some thing that just applies to Fiberglass?

Because the cold air settles down into the insulation, slowly, but it does, and as it does settle down into the effective insulation thickness is reduced, which results in a respectively lower R-value.

In climates which are not as cold (and not for as long) the temperature of the air in the attic and in the insulation has a chance to be re-warmed, which delays the settlement of the cold air.

This effect is most pronounced in the much looser packed fiberglass of loose fill, however, fiberglass batt still allows for that process due to the air spaces between the fibers.

Cellulose and other more dense insulation does not suffer from that same condition, or if they do the effect is negligible.

[Ernie Tate]

Roy and Jerry

With all due respect to your knowledge. I have read you posts for several months now and I do have respect for most of your opinions. This frost in the attic thing and your apparent lack of acknowledging the importance of attic ventilation in a cold heating climate is absurd. Yes moisture in the attic is coming from within the conditioned area's of the home. Yes a home owner should vent bathroom, kitchen and clothe dryer exhauststs fully to the exterior of the home. We went through a period of construction in the 70's and early 80's where builders were told the tighter you can seal up a home the better off you will be. Well it didn't work then either. Air exchanges in a home are important (don't confuse that statement with thinking I mean sealing ceiling light boxes and attic access's is not important, because it is).

There is no difference in the mold on your pudding and the mold that is going to grow in Gerry's attic if it is not properly vented. It's easy to throw the pudding away. What's your answer for his attic when he goes to sell and Mr. Home Inspector comes along and says " gee what a nice home, with the exception of the black attic mold". It's time to either get off the high horse about not installing ventilation in an attic, or explain why it's just the rest of the world that is wrong. Mold propagation in an attic needs three things (just like your refrigerator) food source, moisture and the correct temperature. All three are present in an attic. The mold cells floating in the attic are simply waiting for a reason to propogate.

You guys can run around with your caulking guns and tell everybody things will be fine. Personally I am going to wait for that special day and install some attic ventilation in my homes.

Nobody else has denied that moisture comes from within the home, and that it can be some what controlled (but not 100%). Insulation R values are resistance to heat loss, which is greatest through a ceiling. Even R 60 insulation will eventually allow warm moisture laden air into an attic.

Lets give these guys reading these posts the benefit of our combined experience and recognize the value of ventilation for what it really is.

[Jerry Peck]

Lets give these guys reading these posts the benefit of our combined experience and recognize the value of ventilation for what it really is.


Ernie,

I believe that if you go back and re-read my posts, you will see that *I* *DO* state that insulated attics required proper insulation.

I believe you will also see that Roy and I have stated that there IS moisture in the attic (otherwise there would not be any condensation, which is what lead to the frost).

You will also find that I said that all openings LEADING INTO THE ATTIC need to be sealed ... not about sealing of the attic vents - but that is another topic of itself.

On that other topic of itself ... there is nothing wrong with having SEALED attics which have NO ventilation.

The problem comes in when there is a VENTED ATTIC which does not have adequate ventilation, and the moisture in the attic becomes a problem when EXCESSIVE amounts of moisture enter the attic from the living space below. Those EXCESSIVE amounts are from air leaks which ARE REQUIRED TO BE SEALED, but are most often not sealed. There will always be some air and moisture transfer from the living space into the attic through the drywall itself.

For the benefit of all who read these posts, it is of importance that you READ THE POST CORRECTLY and not change that information around and try to say that it says something else.

What Roy and I were commenting on was the reference to being concerned with mould in the attic, when that is of no concern - deal with the cause of the moisture and the mould which is of no concern will disappear - the mould DOES NOT need to be tested as to what type it is or what the spore count is.

[Roy Cooke sr]

Roy and Jerry

With all due respect to your knowledge. I have read you posts for several months now and I do have respect for most of your opinions. This frost in the attic thing and your apparent lack of acknowledging the importance of attic ventilation in a cold heating climate is absurd. Yes moisture in the attic is coming from within the conditioned area's of the home. Yes a home owner should vent bathroom, kitchen and clothe dryer exhauststs fully to the exterior of the home. We went through a period of construction in the 70's and early 80's where builders were told the tighter you can seal up a home the better off you will be. Well it didn't work then either. Air exchanges in a home are important (don't confuse that statement with thinking I mean sealing ceiling light boxes and attic access's is not important, because it is).

There is no difference in the mold on your pudding and the mold that is going to grow in Gerry's attic if it is not properly vented. It's easy to throw the pudding away. What's your answer for his attic when he goes to sell and Mr. Home Inspector comes along and says " gee what a nice home, with the exception of the black attic mold". It's time to either get off the high horse about not installing ventilation in an attic, or explain why it's just the rest of the world that is wrong. Mold propagation in an attic needs three things (just like your refrigerator) food source, moisture and the correct temperature. All three are present in an attic. The mold cells floating in the attic are simply waiting for a reason to propogate.

You guys can run around with your caulking guns and tell everybody things will be fine. Personally I am going to wait for that special day and install some attic ventilation in my homes.

Nobody else has denied that moisture comes from within the home, and that it can be some what controlled (but not 100%). Insulation R values are resistance to heat loss, which is greatest through a ceiling. Even R 60 insulation will eventually allow warm moisture laden air into an attic.

Lets give these guys reading these posts the benefit of our combined experience and recognize the value of ventilation for what it really is.

I tyr to not let my opinions Influance my knowledge.
Usuall when I say some thing I have information to back up my statements .
If I have a small amount of dought you will see my words could or might and other words.
I see too much of amatures teaching amatures to be amatures in this industry.
Now to you I say try Google and see what you find .
They have been building unvented attics in other colder parts of the world and it seems to be great .
Try this (Unvented attics - Google Search (http://www.google.ca/search?hl=en&source=hp&q=Unvented+attics&meta=&aq=f&oq=))

I expect you might need to cut and paste it . Jerry and I just might have a little more knowledge then you give us credit for .

Royshomeinspection.com

Please post your web site so we can see it .

[Ernie Tate]

Gee Jerry

You sure took the long way around to continue to deny ventilation in an attic in a cold, heating climate is important. I realize after looking at your web site and finding out that you live in florida why you havn't witnessed first hand what a lack of ventilation can do in an attic.

For those of you following this exchange of idea's from a bunch of old bull headed home inspector's there is a difference between venting attics in a cold, heating climate, and a warm predominantly cooling climate.

Ventilation in an attic (any attic) in a heating climate will prevent ice damming, gutter freeze ups, attic mold, premature shingle deterioration, possible roof edge rot, loss of ceiliing due to moisture saturation (yes I have seen this), and lord know what else.

I live in south eastern Idaho where is not uncommon to see temperatures 20 to 40 below zero.

I love this exchange of idea's. Keep up the good work.

[Ernie Tate]

Roy

I did google the link, nothing I have not seen before but was worth mentioning for some of the other ameteurs. The only thing is you are missing the entire point of my criticism of your advice to Gerry who happens to have an attic full of frost. His attic is obviously not a candidate to be considered an unvented attic. The problem as I see it that you guys have bullied this website so long you think your gods gift to home inspectors. I have probably forgotten more about construction than you will ever know.

Can we not be sensible and agree in this particular attic that it would be reasonable to install some ventilation.

Gerry asked for our help and advice, telling him to tune up the caulking gun and not worry about the frost in the attic is not very nice. :)

[Jim Luttrall]

Forgive me, but we here in Seattle don't see many freezing temperatures (until this week) and I haven't seen frost buildup in the attic space. How concerned should I be about this?? The situation is a 2000 build, the North side of the sheathing (from the attic) had a layer of frost. I had adequate ventilation and adequate insulation (aside from a few areas where there were footprints). Is this "normal" for freezing temps or should I never, under any circumstances have frost buildup on the sheathing?? Thanks in advance!

Ernie, The OP says he had adequate ventilation and insulation. That is the premise of all of the respondents.
NO ONE that I have read here has said anything about not ventilating the attic, that is something every amateur knows. Before you criticize everyone in sight like you know more and have forgotten more than anyone else on earth, try to read what was written rather than inventing your own story line.

[Roy Cooke sr]

Roy

I did google the link, nothing I have not seen before but was worth mentioning for some of the other ameteurs. The only thing is you are missing the entire point of my criticism of your advice to Gerry who happens to have an attic full of frost. His attic is obviously not a candidate to be considered an unvented attic. The problem as I see it that you guys have bullied this website so long you think your gods gift to home inspectors. I have probably forgotten more about construction than you will ever know.

Can we not be sensible and agree in this particular attic that it would be reasonable to install some ventilation.

Gerry asked for our help and advice, telling him to tune up the caulking gun and not worry about the frost in the attic is not very nice. :)

Sorry you seem to lack some compresion My total of 33 posts is far from Bulling .
I am sorry to hear you forgotten so much of what you learned .
I looked for your web site please correct me if I am wrong .

(" http://tcshomeinspections.com/about.html')

To ridicule Jerry for living in Florida sounds like jealousy,
Well I am glad for Jerry and wished I too could live in the South.
, I understand most people who live in Florida are from away.
I expect Jerry and I just might have a few more years in construction then you.
Years in Construction does not make an expert I am still learning.
To ignore Google is unfortunate as it has much information to help all.
No I do not know if it needs more ventiliation All I know is it has frost in the attic and I see it frequently .
Simple fix is stop warm moist air from entering the attic .

Royshomeinspection.com

[Jerry Peck]

Gee Jerry

You sure took the long way around to continue to deny ventilation in an attic in a cold, heating climate is important.

Ernie,

Are you actually reading my posts? I mean, reading the words I am writing?

Or are you simply imagining words so you can try to say I said something different?

(for your reading skill improvement I have made red and bold the part you seem to be missing)

Reis,

Whenever you see things like in your photo, I would hesitate before stating there was "adequate" ventilation as better ventilation may well hep prevent that, which would mean that what is there is no "adequate".

Now, if by "adequate" you mean 'the code required' amount of ventilation, then I would stay away from the term "adequate" anyway.

Like others (or so it seems as I read the above), I suspect two things:
- too much air exfiltration from the living space into the attic
- the humidity may have already been in the attic and a sudden and dramatic temperature drop simply freezes the moisture in place
- which gets back to 'too much air exfiltration from the living space into the attic'

Which indicate inadequate ventilation (allowing air exfiltration from the living space into the attic means that more ventilation is needed to off set it). Which is not so much of a ventilation problem as much as an air exfiltration problem.

I do see where I left off a close parenthesis, but I would think that a person reasonably proficient in reading would recognize that and understand where it was supposed to be, but I have added it in blue ")".

I then went on to explain that, in the case being asked about, the cause is excess moisture in the attic, and that the most likely cause of that excess moisture is from the living space inside the house.

[Bert de Haan]

... I have probably forgotten more about construction than you will ever know.


I also might have forgotten more than they will ever know but it is exactly this forgetting that makes me so vulnerable to mistakes.:) I might not need to listen (to both sides of this argument) if I had not forgotten all that. Too bad this ended up as argument (arguing) rather than an argument (argumentation.) In spite of all that, I believe most of us amateurs will be able to weed through this and still be able to learn.

[Ernie Tate]

Hello Jim

Please look at GerryM's post, I failed to see where he stated he had adequate ventilation. I believe we are talking about two different homes, and posts.

I think its time to start over. I am very passionate about black attic mold and its cause's. Moisture in an attic can come from many many sources, I believe we all agree with this. What to do with when it gets there, as is the case in GerryM's attic is important. I am trying to make a simple point that venting unwanted moisture out of an attic space in a heating climate is important. End of my story. :)

[Jerry Peck]

I am trying to make a simple point that venting unwanted moisture out of an attic space in a heating climate is important. End of my story. :)


And I don't recall anyone who has disagreed with that. :rolleyes:

[Cobra Cook]

Just curious? We are talking about too much moisture penatrating through the attic from the living space below in a cold climate with some sort of heat inside of the house, arn't we? Where is all of this excess moisture coming from? In the winter time with the heat going you are actually lowering the humidity in the air by heating it up. Shoot even baseboard electric heaters dry the air. If the house has a humidifyer maybe its just set too high or if maybe you have a ventless gas heater that is providing heat, then they do put moisture back into the air through the burning process. You really do not need too much venting in the attic in the winter time and that is why turbin vents come with a styrofoam blocks you put in the hole to prevent too much venting in the winter, just like a thermostat on a power vent. The summer time is where venting plays the most important part. Do Eskamos put vents in their eggloos? I wonder?

[H.G. Watson, Sr.]

Just curious? We are talking about too much moisture penatrating through the attic from the living space below in a cold climate with some sort of heat inside of the house, arn't we? Where is all of this excess moisture coming from? In the winter time with the heat going you are actually lowering the humidity in the air by heating it up. Shoot even baseboard electric heaters dry the air. If the house has a humidifyer maybe its just set too high or if maybe you have a ventless gas heater that is providing heat, then they do put moisture back into the air through the burning process. You really do not need too much venting in the attic in the winter time and that is why turbin vents come with a styrofoam blocks you put in the hole to prevent too much venting in the winter, just like a thermostat on a power vent. The summer time is where venting plays the most important part. Do Eskamos put vents in their eggloos? I wonder?

You seem to confuse the difference between relative humidity and absolute humidity.

There is more than one way to heat a home, other than dry heat forced air.

Occupied homes with living beings respirating and engaging in life activities produce copious amounts of moisture.

Colder air can "hold" less "moisture". Hence the condensation/frost on the coldest surface.

[Ernie Tate]

Well said

Thank you Mr. Watson:)

[Roy Cooke sr]

Do Eskamos put vents in their eggloos? I wonder?
Yes they did they had to get the smoke out from The seal oil lamp they used for light heat and cooking . Temp inside was about 33°F

Story from google here ( (http://www.primitiveways.com/igloo.html) http://www.qia.ca/i18n/english/pdf/Igloo%20June%203%20outlined.pdf )

Roy Cooke

[Cobra Cook]

Well i do admit that when y bride and i do have wild and crazy hot sex we do give off quite a bit of moisture but, to mosturize an entire house no chance of that, hot showers, cooking, ect still the same since they are both vented to the out side, relitive or absoulote humidity are the same animal, one is the relationship between the temp and weight of the air and the other is simply moisture. humidifiers simply give off moisture based on what the humidistat tells it to do by what the occupants set it at. I don't care what type of heat you use it all will dry the air thus lowering the moisture in the air it is heating, just like a dryer heats up your clothes to remove the moisture, hair dryers do the same. While warmer air can hold more moisture and have lower RH the lower temp air still contains the same amount of moisture but at a higher RH. Take the temp in you refrigerator and see how much the rh is to compare it to the humidity in your house is. Wood, coal , electric base board , radiators, heat pump, gas, kerosen heators, oil circulators, oil burners, did i miss any, will more than dry what the occupants can produce which is why you get dry skin in the winter and oily skin in the summer.

[Jim Luttrall]

Cobra, your missing the boat on your understanding of moisture movement from what you are posting.
Your whole house does turn into a big dryer in the winter heating up all the moisture inside, turning it into steam (water vapor) which then leaks through the holes, some of which are in the attic. (It also leaks into the walls, but that is another story.)
What happens to that warm moist air in the attic? It cools down which raises the relative humidity and if the temperature difference is great enough, the water vapor condenses into liquid and you have wet attic materials, just like fog condenses on every cold surface.
What is the solution? Either add heat to the attic (not very practical in today's homes), reduce the amount of moisture that goes to the attic ( vapor barriers and air sealing), or ventilate to reduce the amount of water vapor in the attic space before it has a chance to reach dewpoint. Or use a combination of the above.
Contrary to your hypothesis, Ventilation is even more important in vented attics in the winter than in the summer.

[John Kogel]

Do Eskamos put vents in their eggloos? Just a splash of rum in mine, thanks. :)

[H.G. Watson, Sr.]

Well i do admit that when y XXXXX XXX X XX XXXX XXXX XXX XXXXX XXX XXX XX XX XXXX XXX XXXXX X XXX XX XXXXXXXXX but, to mosturize an entire house no chance of that, hot showers, cooking, ect still the same since they are both vented to the out side, relitive or absoulote humidity are the same animal, one is the relationship between the temp and weight of the air and the other is simply moisture. humidifiers simply give off moisture based on what the humidistat tells it to do by what the occupants set it at. I don't care what type of heat you use it all will dry the air thus lowering the moisture in the air it is heating, just like a dryer heats up your clothes to remove the moisture, hair dryers do the same. While warmer air can hold more moisture and have lower RH the lower temp air still contains the same amount of moisture but at a higher RH. Take the temp in you refrigerator and see how much the rh is to compare it to the humidity in your house is. Wood, coal , electric base board , radiators, heat pump, gas, kerosen heators, oil circulators, oil burners, did i miss any, will more than dry what the occupants can produce which is why you get dry skin in the winter and oily skin in the summer.

"Cobra Cook",

You have proven in the past that you use a term, abbreviation, etc. with absolutely NO COMPREHENSION as to what it means (such as SoP in numerous posts, then claim it means Standard Operating Procedure - not Standards of Practice, and still have no idea what the SoPs are).

It is obvious you have no idea what you are trying to talk about in this topic thread.

1. The same amount of actual (absolute) moisture (measurable water volume/content) but a lower RH all things being equal when you warm a selected sample of "air". RH stands for Realitive Humidity.

2. Most modern refrigerators employ a dryer/heater function - all part of the defrost cycle; Even "ice boxes" employed a drain and a means to catch run off and condensation - thus the "drip pan". Newer zero clearance appliances still have a "drip pan" and direct the heat from the condensor fan to blow on and evaporate the "dripped" collection. Therefore both your example making whatever your point was, is faulty; and your refrigerator example is yet another source of MOISTURE to the conditioned space.

3. Apparently you have limited experience with hydronic or radiant heating, the concept of evaporation, what happens during animal respiration, the combustion process, and science in general.

4. Your oily skin references indicate an ignorant and bigoted unfamiliararity with the body human.

5. You often make wild and inaccurate statements and claims filled with with spelling errors, factual errors, and ignorant claims: one wonders what is your purpose or motive drives your participation on this message board.

[Steven Stafford]

Ouch!

[David Bell]

Section 406.1 of the IMC states that Uninhabited spaces, such as crawl spaces and attics, shall be provided with natural ventilation openings as required by the IBC or be provided with a mechanical exhaust and supply air system.

[Jerry Peck]

Section 406.1 of the IMC states that Uninhabited spaces, such as crawl spaces and attics, shall be provided with natural ventilation openings as required by the IBC or be provided with a mechanical exhaust and supply air system.

The IMC doe not apply to one- and two-family dwellings or townhouses.

The IRC does allow the use of the other codes if one so choses, but the IMC is not enforceable to the structures covered by the IRC ... unless the plan calls for the (whatever system) to meet the IMC, in which case the IRC calls for meeting the construction documents (one of which is the plan) and thus the IMC would be included by reference.

[Cobra Cook]

Jim, HG ,go s---w your selves, while I do not spell check every one of my words, I do think out every thing I post, you two are the ignorant ones in that it appears you expect every one to agree with your posts are the only answer that can be achieved with a questions, one point is that when a refrigerator or freezer defrosts, the condensate goes to the drain pan of which the discharge line from the compressor is laying in to help lower the head pressure for a more efficient operation. This does not raise the moisture in the house as it was already their in the first place, it is merely recycling it to where it came from, the inside air and a very little amount at that.
SOP Standard Operating Procedure is what any business is supposed to operate under, SOP's, Standards’ of Practice may only relate to you as a Home Inspector to follow certain guidelines of what an inspector should follow, but each organizations are a little different, I go one step further to also incorporate them into how to successfully stay in business. I strongly suggest you read up on that subject. You apparently do not have the intellect to think for your self which is evident in the way you cut and paste in most of your post. If that is ignorant in your mind then I feel sorry for you, your wife and kids if you have any that is, if anyone would have you.
You dare call me a bigot, just be careful to not slip and divulge the location of your business. If your skin does not feel different in the winter when the humidity is lower in a heated environment than in the summer when the humidity is balmy then you apparently are not human but merely a sack of blubber who has no intellectual ability to think before you open that big mouth and what ever you use to write on this post. :confused:
I read this post because sometimes people just want a simple answer to what may seem like a complicated question to them but could just a simple answer to an experienced home inspector or other professional person who reads this site.What they choose to do with that answer is up to them. I do not cut and paste articles that I have seen numerously from your posts to attempt to prove my point and best of all I do not preach Code as U do either as it is not within the "Stanards of Practice" of any home inspector. I would be interested in knowing what school certified either of you to become a home inspector. The end, Cobra:)

[Bert de Haan]

I'll have a try; The low moisture content in the air during the winter is not really due to the heating of the house but due to the cold temperature outside. The cold air can't hold as much water so it condenses and leaves the air. That's why there is hoar frost. That is also why drywall in an unheated garage becomes soggy; it is absorbing the moisture that the air cannot hang on to anymore. When this air with the low moisture content (even though it is almost saturated i.e. high relative humidity, low absolute humidity) leaks into the house, our heating system warms it up and all of a sudden it is able to absorb more moisture again. It absorbs this moisture from all the things you mentioned; showers, perspiration, cooking and yes, also from our skin. So the absolute humidity in the house air goes up but the relative humidity is still way lower than the outside air. (They are not the same animal.) When this air gets cooled enough, the moisture will condense. That is why you get moisture on the inside of your windows and not on the glass door of the china cabinet. That is also why the drywall in the house doesn't get soggy even though there is more total moisture inside compared to in the unheated garage.
In the event the house air leaks into the attic when it is very cold, it may get cool enough to let go of whatever moisture it picked up out of the house. You wrote
Take the temp in you refrigerator and see how much the rh is to compare it to the humidity in your house is. My guess is the absolute humidity will be considerably lower in the fridge than in the house but the relative humidity in the fridge will likely be much higher in the fridge than in the house.

[Jim Luttrall]

Jim, HG ,go s---w your selves, while I do not spell check every one of my words, I do think out every thing I post, you two are the ignorant ones in that it appears you expect every one to agree with your posts are the only answer that can be achieved with a questions, one point is that when a refrigerator or freezer defrosts, the condensate goes to the drain pan of which the discharge line from the compressor is laying in to help lower the head pressure for a more efficient operation. This does not raise the moisture in the house as it was already their in the first place, it is merely recycling it to where it came from, the inside air and a very little amount at that.
SOP Standard Operating Procedure is what any business is supposed to operate under, SOP's, Standards’ of Practice may only relate to you as a Home Inspector to follow certain guidelines of what an inspector should follow, but each organizations are a little different, I go one step further to also incorporate them into how to successfully stay in business. I strongly suggest you read up on that subject. You apparently do not have the intellect to think for your self which is evident in the way you cut and paste in most of your post. If that is ignorant in your mind then I feel sorry for you, your wife and kids if you have any that is, if anyone would have you.
You dare call me a bigot, just be careful to not slip and divulge the location of your business. If your skin does not feel different in the winter when the humidity is lower in a heated environment than in the summer when the humidity is balmy then you apparently are not human but merely a sack of blubber who has no intellectual ability to think before you open that big mouth and what ever you use to write on this post. :confused:
I read this post because sometimes people just want a simple answer to what may seem like a complicated question to them but could just a simple answer to an experienced home inspector or other professional person who reads this site.What they choose to do with that answer is up to them. I do not cut and paste articles that I have seen numerously from your posts to attempt to prove my point and best of all I do not preach Code as U do either as it is not within the "Stanards of Practice" of any home inspector. I would be interested in knowing what school certified either of you to become a home inspector. The end, Cobra:)

Cobra, sorry if my trying to explain something offended you enough to lump my name in with another to tell us to go s---w ourselves. I have no idea what the other poster said since he is on my ignore list. Since you seem to know it all and do not seem to be interested in give an take, you will be on the same list too. Have a nice life.

[Richard Reynolds]

I have seen this problem in Wyoming and after further inspection I find there are no soffit vents or they are covered up. This will cause the attic to draw warm moist air up from the hous.

[Rick Bunzel]

To All

Great Post except for the thread drifts.

OK OK I get how this happens - How should we write it up? What type of contractor is best to refer this out too?

Thanks

//Rick

[Roy Cooke sr]

To All

Great Post except for the thread drifts.

OK OK I get how this happens - How should we write it up? What type of contractor is best to refer this out too?

Thanks

//Rick
('Recommend immediate repair by qualified person.")

This gets the home Inspector ( you?) off the hook and lets the client know they should do somthing .

Just about any reasonable handy Man ( person ) should be able to find and fix the air leaks from the home .

Roy Cooke

[Jerry Peck]

What type of contractor is best to refer this out too?


Just about any reasonable handy Man ( person ) should be able to find and fix the air leaks from the home .


Very few, if any, "handyman' type people, be they he or she, will be properly licensed and insured.

What if something happens to them? What if they do something they should not?

[Richard Reynolds]

Further inspection and repair should be conducted by a licensed contractor.

[Roger Hankey]

1. Have a qualified energy auditor or building scientist quantify and locate the air leaks using a blower door and IR thermography. 2. Have a qualified insulation firm seal all air leaks as ID'd by the energy audit. It may be possible to skip step one if the insulation contractor deems that it is cost effective to REMOVE all existing attic insulation to reveal the air leaks and facilitate sealing the leaks. The insulation contractor would re-insulate after sealing all leaks. This is NOT a job for a handyman.