Thread: Attic Problems moisture.....

Michael,

You have done quite a bit. I think it may be advisable to wait a few more days to see if the attic climate has changed for the better.

Cheers,

I second that opinion, Raymond. There will be quite a bit of moisture in that insulation and lumber; it will take some time to dry out.
If you have a week to wait, you might be surprised how much good you have done. If you have access to a moisture meter, that would tell you a little more about the moisture content of the building materials rather than just the RH of the air.

I didn't read every response so if this is redundant I apologize.

Block off the gable the gable vents. Air enters the gable and almost immediately exits the ridge...or worse, air moving past the the house creates a low pressure area on a gable end and uses the ridge vent as an intake.

Ridge venting works well but only when there is a balanced (at least equal in area ) intake vent at the eave.

In most cases, perforated soffit material needs to be continuous (not a piece every two feet) to be effective as an intake.

The last consideration is whether you're measuring relative humidity or absolute humidity. 40% relative humidity at70 degrees will yield nearly 100 % relative humidity at 30 degrees.

Well every day it seems that I find something that needs to be fix with the attic and its problem. I stated that my soffit P vents were open, that is I could see light throught them. Its seems that I was not alone in this assumtion. Well somthing told me to check from the outside, so here is what I found on the front of the house above the farmers porch. It looks like the vents were pushed down to the roof board that runs horizontal. Also on the gable end a 2 x 4 board was extending into the soffit blocking air flow. Here are some pictures......

I can't beleive this...... soon or later this will get corrected......I have made the most progress since I sent this thread. I can't believe I spent $1700 and had guys in person try and figure this out....

thank you

Ahhhhhhh.........grasshopper.........youve done well.

I am not sure if this is the cure all, I believe this insulation has been compromised but at least I am heading in the right direction.....

Michael,

Some of the following has been said above, some has not, some you have stated you have corrected, some you have not stated that.

- Seal off all openings from the house. You've sealed off around the ceiling light boxes, however, have you pulled the insulation back where the walls are and sealed where the wiring, plumbing, etc., is coming up out of the top of the walls (coming up through the top plate)? While not as great of an issue the air around the light boxes regarding moisture from inside, there will be moisture in the walls which will come up through those unsealed openings, but, the more important issue regarding these openings and spaces is that sealing around these items coming through the top plate will also reduce the speed of spread of fire (and one of the two reasons - the main reason - these are required to be sealed anyway, energy air infiltration and exfiltration is the other reason - which also includes moisture traveling within that air).

- Exhaust all air from exhaust devices (exhaust fans, etc.) to the outdoors, not into the attic. This I think you have already done.

- Make sure (with a ventilated attic) that you have proper ventilation - and you just discovered the soffit vents were effectively blocked by the vent channels being pushed down to the fascia/sub fascia. These are just foam and can easily be cut or broken off.

- With soffit vents and ridge vents, and with the soffit vents actually working (looks like yours were not working), when the ridge vent gets covered with snow, the soffit vents work through cross ventilation soffit vent-to-soffit vent. With the soffit vents working properly, you should not need a gable vent. Now, if the gable vents are up at the very top of the gables, the gable vents would just act as extensions of the ridge vent and not really create a problem with the gable vents being there.

- Your loose fill cellulose insulation will be wet for quite awhile, if you remove it, you should be able eliminate a source of retained moisture, causing high relative humidity levels in the attic compared to outdoors.

- Your wet sheathing will take a while to dry out, also causing the attic relative humidity to be high.

- If your gable vent is not all the way up to the top of the gable, you may want to close it off and move it up to the top of the gable.

- Continuous soffit vents really have very little net free vent area (even if they were not blocked off, as yours were), you simply may not have enough net free vent area in the soffit vents to be sufficient for your attic ventilation needs. If your soffit is "fully vented", i.e., it has no 'non-vented' areas, then you might (at best) have 4-6 square inches of net free vent area per linear foot of soffit vent, with the minimum required net free vent area being 1 sf vent area to 300 sf attic area with soffit and ridge/or/gable vent, or 1 sf vent area to 150 sf attic area with only soffit vents. With soffit and ridge/gable vents, you would want approximately 50% of the area at the ridge/gable and 50% at the soffit. Approximately measure you attic area to determine the minimum require ventilation, then measure your soffit length and approximately determine the net free vent area provided by the soffit. With a ridge vent you might get as much as 18 square inches of net free vent area per linear foot of ridge vent.

As you can see, the restriction is more easily going to the the soffit vents as even if the ridge vent was accompanied with 2 soffit vents, the soffit vent area would still be about 1/2 of the ridge vent area. All you can do is run the numbers.

This post is getting long and long posts are harder to follow, so I will stop here.

Originally Posted by Jerry Peck

Michael,

Some of the following has been said above, some has not, some you have stated you have corrected, some you have not stated that.

- Seal off all openings from the house. You've sealed off around the ceiling light boxes, however, have you pulled the insulation back where the walls are and sealed where the wiring, plumbing, etc., is coming up out of the top of the walls (coming up through the top plate)? While not as great of an issue the air around the light boxes regarding moisture from inside, there will be moisture in the walls which will come up through those unsealed openings, but, the more important issue regarding these openings and spaces is that sealing around these items coming through the top plate will also reduce the speed of spread of fire (and one of the two reasons - the main reason - these are required to be sealed anyway, energy air infiltration and exfiltration is the other reason - which also includes moisture traveling within that air).

- Exhaust all air from exhaust devices (exhaust fans, etc.) to the outdoors, not into the attic. This I think you have already done.

- Make sure (with a ventilated attic) that you have proper ventilation - and you just discovered the soffit vents were effectively blocked by the vent channels being pushed down to the fascia/sub fascia. These are just foam and can easily be cut or broken off.

- With soffit vents and ridge vents, and with the soffit vents actually working (looks like yours were not working), when the ridge vent gets covered with snow, the soffit vents work through cross ventilation soffit vent-to-soffit vent. With the soffit vents working properly, you should not need a gable vent. Now, if the gable vents are up at the very top of the gables, the gable vents would just act as extensions of the ridge vent and not really create a problem with the gable vents being there.

- Your loose fill cellulose insulation will be wet for quite awhile, if you remove it, you should be able eliminate a source of retained moisture, causing high relative humidity levels in the attic compared to outdoors.

- Your wet sheathing will take a while to dry out, also causing the attic relative humidity to be high.

- If your gable vent is not all the way up to the top of the gable, you may want to close it off and move it up to the top of the gable.

- Continuous soffit vents really have very little net free vent area (even if they were not blocked off, as yours were), you simply may not have enough net free vent area in the soffit vents to be sufficient for your attic ventilation needs. If your soffit is "fully vented", i.e., it has no 'non-vented' areas, then you might (at best) have 4-6 square inches of net free vent area per linear foot of soffit vent, with the minimum required net free vent area being 1 sf vent area to 300 sf attic area with soffit and ridge/or/gable vent, or 1 sf vent area to 150 sf attic area with only soffit vents. With soffit and ridge/gable vents, you would want approximately 50% of the area at the ridge/gable and 50% at the soffit. Approximately measure you attic area to determine the minimum require ventilation, then measure your soffit length and approximately determine the net free vent area provided by the soffit. With a ridge vent you might get as much as 18 square inches of net free vent area per linear foot of ridge vent.

As you can see, the restriction is more easily going to the the soffit vents as even if the ridge vent was accompanied with 2 soffit vents, the soffit vent area would still be about 1/2 of the ridge vent area. All you can do is run the numbers.

This post is getting long and long posts are harder to follow, so I will stop here.

Jerry

Here are where my gable vents are located....

Michael,

This would have been much better, as far as gable vent location goes.

Just make sure the net free vent area total (of one or two gable vents) meets at least minimum requirements).

Remember, you cannot just measure the 'opening area', you have to deduct for the 'louvers', on wood louvers, that typically only equates to about 25% of the total opening area as net free vent area, maybe less. Metal louvers are typically around 70% (if I am remembering correctly without looking it up).

Don't sweat the gable vents;;;;;;;;;;; But fix the baffles

Stop the humidifier, seal things up. Insulate well and be done.

On my home I have soffit and ridge and attic fan. During the summer months the attic fan pulls from the soffits and during the winter when it's off the natural occurrence of the soffit and ridge combo takes over.

The playing in of cross ventilating from your new gable vents won't factor much in the soffit/ridge flow. You have quite a bit of height and heat rising to either gable or ridge vent is still going to pull from the soffit.

check your soffit According to a roofing contractror I deal with There was a batch that did not work(Brand) I did a partial inspection and found what you are talking about. Turned out the soffit was bad

Originally Posted by Mike Schulz

Don't sweat the gable vents;;;;;;;;;;;

On my home I have soffit and ridge and attic fan. During the summer months the attic fan pulls from the soffits and during the winter when it's off the natural occurrence of the soffit and ridge combo takes over.

Er ... ummmm ... Mike, until his ridge vents are snow covered ... you know, like shown in his photos.

The playing in of cross ventilating from your new gable vents won't factor much in the soffit/ridge flow.

Possibly, until the ridge is ... ... *snow covered*.

Originally Posted by Timothy M. Barr

check your soffit According to a roofing contractror I deal with There was a batch that did not work(Brand) I did a partial inspection and found what you are talking about. Turned out the soffit was bad

Timothy,

Not quite following you there.

You are referring to the continuous soffit vents?

"There was a batch that did not work(Brand) I did a partial inspection and found what you are talking about. Turned out the soffit was bad"

Did not work / bad how?

The perforations where not all the way through?

All continuous soffit vents are are (boy, that sounds strange "are are") continuous sheets of vinyl or aluminum with holes or raised perforations in them. About the only thing I can think of which 'would not work' and cause them to be 'bad' would be defective perforations.

Michael,
Looking at your photos where you seal-foamed around the light fixtures... it may be hard to see but I didn't see a poly vapor barrier. Is there one ?

Holes were not all the way thru looked good just didn't work

Ahhhhhhhhhhhh.....Oh great one.

If the peak is covered with snow then the gable ends will take it's place.
Either way hot air rises and pulls air into the soffit and out the gable ends or ridge.

But the problem was solved by removing the water hose........I mean humidifier.

Gable vents will only work with wind moving parallel with the ridge.

Originally Posted by Raymond Wand

Gable vents will only work with wind moving parallel with the ridge.

True only if that is all there is for vents!


Gable vent intent was cross wind design because there was no other ventilation typically in the attic but end vents. Air will flow from soffit to gable, ridge vent, roof mounted caps, turbines, attic fans. etc.

Originally Posted by Mike Schulz

Ahhhhhhhhhhhh.....Oh great one.

If the peak is covered with snow then the gable ends will take it's place.

*I* am aware of that.

YOU sounded as though YOU were proposing to *do away with* the gable vents.

And that would not necessarily be a good thing with snow covered ridge vents.

Mike,

Many attics have some condensation (especially on nails) in certain weather conditions and can be difficult to eliminate completely. Do you know how often and under what weather conditions there is high moisture in the attic? Is the attic dry most of the time?

If the moisture problem is as bad as you think it is there would be fungal/mold growth in the attic. I don't see any evidence of that in the pictures. Maybe there's no big problem. The attic looks pretty good to me.

I inspect many homes with ridge vents and gable vents. While it is recommended to use ridge vents with soffit vents alone, most of these homes do not have any ventilation problems (no ice damming, condensation or mold/mildew).

Maybe it is best to do further monitoring and logging the dampness and humidity levels over a period of time. I don't see any need to be in a hurry. The house is 7 years old and I don't see any mold in the attic.

Good luck.

Food for thought, here in Alaska builders seem to have caught on to the fact that roof penetrations lead to moisture problems in the attic maybe 4-5 years ago, that means we have a few hundred thousand homes with plenty of unsealed roof penetrations. Most of these homes (even the older ones, which would be pre-1960) have some kind of vapor barrier. It seems the house in question suffers directly from the lack of a vapor barrier even if most of the excessive moisture in the home is dealt with, you will always have the potential for freezing between the layers of insulation. Isn't the idea limiting the amount of moist air into the attic to the bare minimums as suggested (sealing all the penetrations, turning off the humidifier, etc.) somewhat of a moot point w/o installing a vapor barrier?

I'm guessing it would depend the area you are from. Around here there's no barrier and predominately loose fill cellulose or fiberglass

That's true, it definitely seems to be a "problem" when there isn't a vapor barrier installed in Alaska homes.
I'm curious why there is not more of a problem during freeze/thaw periods for the homes you inspect. W/O the attic being conditioned space of course...

There are interior paints that will function as a vapour barrier.

I have heard of those paints before and a large subdivision has been given the Municipality blessing to build w/o vapor barriers if they use these paints, but it seems that due to the frequent earthquakes we have, cracks will develop in the paint rendering it useless over time (might be a lot of time). So most, if not all, of the homes you inspect w/o a vapor barrier do not get commented on regarding the lack of a vp? Another locality difference...

Hello

Thanks again for all the input. Here is what I have done in the last week.

I sealed off a pipe I found that had some foam around it but it wasn't completly sealed. The wall that separates the bathroom and a closet had aluminium tape on the seam, I sealed it up with foam. Also I fixed the P vents that were to far down.

Tommorrow I am having the blower door scan test to see if I have more leaks in the ceiling. The humidity readings in the attic during the day has been down to 55% when the humidity outside has been around 40%. The roof has been covered with snow for a week now, with some melting in the front side but not much in the back. The humidity was 77% last night, but the humidity outside was 83%. This morning is was about 68%.....

I think I am making progress without removing all that insulation. Here is a picture of what I sealed up..... the sliver duct is for the bathroom fan that was sitting in the soffit but now is exhausting outside the gable wall.

thanks

Michael,

Does sound like you are making progress. Keep it up, you might get to where the level is acceptable without going the full distance.

Well I had the blower door test and we found some leaks in the attic. most of them from interior walls, so I am going to have them sealed up. Also along the gable walls.

So after the attic floor is sealed it should solve my humidity and sheathing condensation problems?

It will definitely improve the situation, however, a lack of continuous vapor barrier will still allow for a certain amount of humidity to permeate through. If you find you still have higher than acceptable levels of humidity in the attic, you may consider using one of those vapor-barrier type ceiling paints on you next painting project.

Originally Posted by Joe Klampfer

It will definitely improve the situation, however, a lack of continuous vapor barrier will still allow for a certain amount of humidity to permeate through. If you find you still have higher than acceptable levels of humidity in the attic, you may consider using one of those vapor-barrier type ceiling paints on you next painting project.

Joe

What is considered acceptable humidity level in the attic?

Originally Posted by Michael

What is considered acceptable humidity level in the attic?

Michael,

I don't know of any 'hard and fast' relative humidity number for the attic, however, if the attic is well ventilated, then the level should be similar to that of the outside air relative humidity (assuming that the outside air and the attic air is being exchanged sufficiently to provide adequate ventilation, making them one and the same, or thereabouts) only slightly lower.

While there may be some RH gain in the attic from interior moisture migrating up into the attic, the attic is typically warmer than the outside air, which makes the RH in the attic lower than the outside air (same amount of moisture in the air, but the air takes up more space being warmer, which drops the RH - warmer air holds more moisture than cooler air).

I.e., if it is raining outside, it should not be raining inside the attic because the RH is lower in the attic.

Here is a link concerning saturation vapor pressure and temperature which shows the degree to which warmer air holds moisture than cooler air. Relative Humidity of Air

As it says "Relative humidity by partial pressure", the chart is for "saturation pressure", but should be a good visual for the purpose to show the difference in RH also.

Note that the air can hold much less moisture at 10 degrees F than it can at 40 degrees F, approximately 1/4 as much.

(Note that the air can hold much less moisture at 10 degrees F than it can at 40 degrees F, approximately 1/4 as much.)

Jerry

So why am I insulating so much, maybe I need some heat up there......

(So why am I insulating so much, maybe I need some heat up there......)

No just don't use that humidifier or adjust it down (get rid of it). Make sure family is using exhaust fans when bathing and cooking.

Since you turned it off you said the attic is getting close to outside air Right?

It's not rocket science

Originally Posted by Michael

So why am I insulating so much, maybe I need some heat up there......

That answer lies in why the recommendation to insulate at the underside of the roof sheathing instead of at the ceiling / attic floor was made.

Making that 'conditioned' or even 'semi-conditioned' space solves many problems, however, the reason for insulating as you are has nothing to do with 'moisture in the attic' but has to do with 'comfort in the house'.

If you were to remove the insulation entirely, you 'could' still heat the house, but at great expense, so, instead, the insulation is laid at the floor of the attic (it's the old fashioned and long acknowledged way to do things).

If you were to remove the ceiling / attic floor insulation and insulate at the underside of the roof sheathing AND (this would be critical then) seal up all ventilation between the attic and outside (you want no air exchange between the two), you would have similar energy considerations as you would if the insulation were down on the ceiling.

Originally Posted by Mike Schulz

(So why am I insulating so much, maybe I need some heat up there......)

No just don't use that humidifier or adjust it down (get rid of it). Make sure family is using exhaust fans when bathing and cooking.

Since you turned it off you said the attic is getting close to outside air Right?

It's not rocket science

Mike

I don't think it is rocket science but something just doesn't make sense to me. This morning before sunrise, the attic readings were 78% RH and 29 degrees, and outside reading was 77% RH and 29 degrees. Most of the snow on the front of the house is gone and NO frost on any nails. But the last time I had these readings with the same roof conditions I have frost on the nails on the side of the sheathing where there is no snow.
I guess the humidity level is not an accurate measure for moisture?
I don't think I should condition the attic space at this point since I have spent money on venting the attic. I should continue to seal the ceiling?

This is a real headache........

I don't think it is rocket science but something just doesn't make sense to me. This morning before sunrise, the attic readings were 78% RH and 29 degrees, and outside reading was 77% RH and 29 degrees. Most of the snow on the front of the house is gone and NO frost on any nails. But the last time I had these readings with the same roof conditions I have frost on the nails on the side of the sheathing where there is no snow.
I guess the humidity level is not an accurate measure for moisture?

Michael, it sounds like you have made it just about as good as it can be from the readings. You can't make the attic any drier than the outside air when venting with outside air. You have sealed the attic floor tight and have provided plentiful outside air to vent. Relax. There may be days when you have close to 100% RH in the attic when it is raining outside, but it will pass. If you have ever been outside on a foggy day you know how the moisture sticks on everything, there is just too much water for the air to hold, but as soon as the sun comes out and heats the air the fog goes away. The moisture is still there, but the RELATIVE humidity goes down because the air is warmer and has the ability to hold more moisture. Relative humidity can be a tricky thing. Give it time and watch for symptoms of problems without worrying about the specific readings.

Well I had the attic floor sealed today. A energy company came and sealed all walls to include the gable end walls.

I think it is as good as it is going to get, the RH in the attic went down to 31% which matched the outside RH.

I wanted to thank you all for helping me get this problem under control. The place where I am headed doesn't have any humidity problems but tempertures at 130 degrees is no treat.


One last thing, my sheathing has some splitting ( no leaking), can I put some kind of sealer on the sheathing so it will not get any worse, just like when you seal a outside deck? Or is it ok?

Thanks again
Michael