Thread: Energy upgrades

I had a call from a new home 1 yr. customer stating that a local energy company, [ that is doing some big time radio ads] claimed he could save 40-50% on his bills by reducing the attic temp by 15-20 degrees by adding a thermal energy barrier, adding additional insulation and more attic venting. For a fee of $2200.
He already had R38 insulation, eave, gable vents, and ohagin roof vents.
On the attic venting the company told him he needed more, after he told them that I had stated it looked addiquate, the rep then stated that it looked that it may have enough to pass code, and offered to give him a free solar fan instead of adding vents.

My reply to the customer was.. it would take forever to see a return on that amount of investment, if he wanted to save some $s it may benifit him to add some insulation to the existing flex ducting.

If this was your home would you spend the $2200?
How much would it save by adding insulation to the ducting.??

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DH: This is a good place to start:

Insulation Fact Sheet

And here for radiant barrier information
Radiant Barrier Fact Sheet

Does the "energy company" have data or a report to back up their claims?
How about 5 customers that can vouch for their claims?

A lot of the energy cost savings data out there is "modeled" and re-gurgitated over and over by "energy specialists".

EEI - Top 10 Energy Saving Tips—Fact or Fiction?

Easy, Low Cost Energy Saving Tips

Adding a programable thermostat and reducing "air infiltration" are touted as a couple improvement with the least cost and fastest paybacks

Even cheaper... manually adjust it!!

Example from Home Energy Tune-UP® ©CMC Energy Services, Inc. 2006

home in Virginia

Date built (est.): 1961
# of bedrooms: 4
House size: 2,200 sq. ft.
House volume: 17,600 cu. ft.
Primary Heating fuel: Natural gas
Price of heating fuel: $2.06 /therm
Price of electricity: $0.081 /kWh

Insulation
Ceiling Insulation Add Insulation
Annual Savings $51 – Cost $731 - Payback in Years = 11

Outside Wall Insulation Add Insulation
Annual Savings $350 – Cost $1,960 - Payback in Years = 6

Knee Wall Insulation Add Insulation
Annual Savings $43 – Cost $77 - Payback in Years = 2

Basement Wall Insulation Add Insulation
Annual Savings $120 – Cost $1,912 - Payback in Years = 16

Air Seal-Up Obtain Seal-uP (air infiltration)
Annual Savings $179 – Cost $624 - Payback in Years = 4

Heating System 15/20 Replace with ENERGY STAR® model
Annual Savings $266 – Cost $2430 - Payback in Years = 9

Programmable Thermostat Install
Annual Savings $381 – Cost $190 - Payback in Years = less than 1

Water Heater Age 16 / life 12 Replace
Annual Savings $144 – Cost $657 - Payback in Years = 5

Appliances
Refrigerator Age 20 / life 10 Replace with ENERGY STAR® model
Annual $61 / cost $630 / payback 10 years

Refrigerator Age 10/ life 10 Replace with ENERGY STAR® model
Annual $26 / cost $810 / payback 32 years

Freezer Age 22 / life 12 Replace with ENERGY STAR® model
Annual $34 / cost $510 / payback 15 years

Clothes Washer age 13/ life 10 Replace with ENERGY STAR® model
Annual $45 / cost $555 / payback 12 years


* Simple payback = Cost ÷ annual savings

CS: Some of Edison's info is tainted, vis a vis the recommendation to use an insulative blanket on water heaters. This will void some manufacturers' warranties.

Originally Posted by Dan Harris

I had a call from a new home 1 yr. customer stating that a local energy company, [ that is doing some big time radio ads] claimed he could save 40-50% on his bills by reducing the attic temp by 15-20 degrees by adding a thermal energy barrier, adding additional insulation and more attic venting. For a fee of $2200.
He already had R38 insulation, eave, gable vents, and ohagin roof vents.
On the attic venting the company told him he needed more, after he told them that I had stated it looked addiquate, the rep then stated that it looked that it may have enough to pass code, and offered to give him a free solar fan instead of adding vents.

My reply to the customer was.. it would take forever to see a return on that amount of investment, if he wanted to save some $s it may benifit him to add some insulation to the existing flex ducting.

If this was your home would you spend the $2200?
How much would it save by adding insulation to the ducting.??

I read somewhere that depending on your climate installing thermal energy barriers could reduce the roof tile life causing them to deteriorate quicker, I don't know if there is any truth to that claim.
I'm trying to remember where I read that statement.

Radiant barrier

I do believe a barrier does lower the attic temp up to 20 degrees. All that heat around the duct work and air handler at that 20 degrees hotter takes a big toll on energy. The best way to handle ventilation with a radiant barrier is with ridge vents when possible.

I do believe that the spray on would be better but the companies that do both say the foil barrier below the rafters is better. To create a barrier between the sheathing and barrier with six inches between makes no sense. Now you have all that heat build up in that pocket instead of getting reflected back out at the sheathing.

Now lets mention a roof leak. How do you find it if the water is running down the back side of that applied barrier under the rafters to the eves.

Insulation, ventilation, radiant barrier, taped with mastic duct connections along with an upper insulation R factor for the duct insulation makes a huge difference along with all the air leaks around the air handler.


Does a radiant barrier have a big affect on efficiency alone???? I think so and everyone I inquire to thinks so. 2,200.00. A spray on will cost less if one shops around. Does it break down before an applied barrier??? Maybe. Can you still catch a leak with the spray on. Yes. Is it worth it?? I think it will pay for itself over a short period of time and as for a resale, I don't think you will lose money. That cost is usually gladly accepted by buyers.

Seems that everyone is now concerned with energy consumption.

I have been asked numerous times about spray-on insulation in the attic (and side walls) as to their real effectiveness. There are a couple types (closed & open cell). I have heard that open is superior because it allows any roofing deck leaks to appear. Which is better?

Does this method really reduce the temperature in the attic. What about an outlet for natural water vapor within the home?

Also, if you have the spray on, do you remove all venting and what about the existing insulation?

If it's a new construction, would you also add blown in (or batt) insulation?

Is there any definitive reports from any organization that evaluated and tested this method?

Your experienced opinion is valuable to me.

Thanks,
CJ Morris

Originally Posted by CJ MORRIS

Seems that everyone is now concerned with energy consumption.

I have been asked numerous times about spray-on insulation in the attic (and side walls) as to their real effectiveness. There are a couple types (closed & open cell). I have heard that open is superior because it allows any roofing deck leaks to appear. Which is better?

Does this method really reduce the temperature in the attic. What about an outlet for natural water vapor within the home?

Also, if you have the spray on, do you remove all venting and what about the existing insulation?

If it's a new construction, would you also add blown in (or batt) insulation?

Is there any definitive reports from any organization that evaluated and tested this method?

Your experienced opinion is valuable to me.

Thanks,
CJ Morris

CJM: This may help:

http://www.jlconline.com/cgi-local/v...170a32100a060b

AD Posted a good post on savings.
Considering that in just a few short years I will be required to go to my
"end of life counseling classes" I'm thinking just do the short term items, spend my money at vegas, and let the next home owner worry about the long term expenses.

Good article, Aaron. Would anyone care to comment on this?
I have been concerned on this for the last few years, first thinking it was ok, then that conditioned attic would require the coverage of foam for fire resistance, then it seemed to be ok.

Fire Resistance
When the unvented assembly is a cathe-
dral ceiling, the foam will be covered
with drywall, which is a code-approved
thermal barrier. In an attic, though, the
rafter bays are not normally covered by
drywall, so the issue of fire-resistance
comes into play (Figure 8, page 8).
This can be a gray area in the code, so
be sure to check with your building
department before building an unvented
attic space. Most codes state that if
the attic is accessible for the service of
utilities, the foam must be covered with
an ignition barrier. Certain water-based
intumescent coatings qualify as ignition
barriers.
If the attic area is not accessible or is
not “accessed for the service of utilities,”
it may be possible to leave the SPF ex-
posed. Many contractors are confused
about how to treat this enclosed attic
space. Providing access through a ceiling
hatch is okay but not necessary; venting
to the room below is prohibited by the
fire code.

Jim,

From the 2006 IRC.
- R314.3 Surface burning characteristics. Unless otherwise allowed in Section R314.5 or R314.6, all foam plastic or foam plastic cores used as a component in manufactured assemblies used in building construction shall have a flame spread index of not more than 75 and shall have a smoke-developed index of not more than 450 when tested in the maximum thickness of 4 inches (102 mm), provided the end use is approved in accordance with Section R314.6 using the thickness and density intended for use.
- - Exception: Foam plastic insulation more than 4 inches thick shall have a maximum flame spread index of 75 and a smoke-developed index of 450 where tested at a minimum thickness of 4 inches, provided the end use is approved in accordance with Section R314.6 using the thickness and density intended for use.
- R314.4 Thermal barrier. Unless otherwise allowed in Section R314.5 or Section R314.6, foam plastic shall be separated from the interior of a building by an approved thermal barrier of minimum 0.5 inch (12.7 mm) gypsum wallboard or an approved finish material equivalent to a thermal barrier material that will limit the average temperature rise of the unexposed surface to no more than 250°F (139°C) after 15 minutes of fire exposure complying with the ASTM E 119 standard time temperature curve. The thermal barrier shall be installed in such a manner that it will remain in place for 15 minutes based on NFPA 286 with the acceptance criteria of Section R315.4, FM 4880, UL 1040 or UL 1715.
- R314.5 Specific requirements. The following requirements shall apply to these uses of foam plastic unless specifically approved in accordance with Section R314.6 or by other sections of the code or the requirements of Sections R314.2 through R314.4 have been met.
- - R314.5.1 Masonry or concrete construction. The thermal barrier specified in Section R314.4 is not required in a masonry or concrete wall, floor or roof when the foam plastic insulation is separated from the interior of the building by a minimum 1-inch (25 mm) thickness of masonry or concrete.
- - R314.5.2 Roofing. The thermal barrier specified in Section R314.4 is not required when the foam plastic in a roof assembly or under a roof covering is installed in accordance with the code and the manufacturer’s installation instructions and is separated from the interior of the building by tongue-and-groove wood planks or wood structural panel sheathing in accordance with Section R803, not less than 15/32 inch (11.9 mm) thick bonded with exterior glue and identified as Exposure 1, with edges supported by blocking or tongue-and-groove joints or an equivalent material. The smoke-developed index for roof applications shall not be limited.
- - R314.5.3 Attics. The thermal barrier specified in Section 314.4 is not required where attic access is required by Section R807.1 and where the space is entered only for service of utilities and when the foam plastic insulation is protected against ignition using one of the following ignition barrier materials:
- - - 1. 1.5-inch-thick (38 mm) mineral fiber insulation;

- - - 2. 0.25-inch-thick (6.4 mm) wood structural panels;
- - - 3. 0.375-inch (9.5 mm) particleboard;
- - - 4. 0.25-inch (6.4 mm) hardboard;
- - - 5. 0.375-inch (9.5 mm) gypsum board; or
- - - 6. Corrosion-resistant steel having a base metal thickness of 0.016 inch (0.406 mm).
- - - The above ignition barrier is not required where the foam plastic insulation has been tested in accordance with Section R314.6.

-

R314.6 Specific approval. Foam plastic not meeting the requirements of Sections R314.3 through R314.5 shall be specifically approved on the basis of one of the following approved tests: NFPA 286 with the acceptance criteria of Section R315.4, FM 4880, UL 1040 or UL 1715, or fire tests related to actual end-use configurations. The specific approval shall be based on the actual end use configuration and shall be performed on the finished foam plastic assembly in the maximum thickness intended for use. Assemblies tested shall include seams, joints and other typical details used in the installation of the assembly and shall be tested in the manner intended for use.

The Icynene foam insulation I looked up rates as follows:
- flame spread:
- - allowed: 75
- - tested: 15 at 5" thick; 20 at 3" thick; 20 at 2" thick
- smoke developed:
- - allowed: 450
- - tested: 400 at 5" thick; 350 at 3" thick; 180 at 2" thick

Which means that Icynene DOES NOT require being protected.

Originally Posted by Jim Luttrall

Good article, Aaron. Would anyone care to comment on this?
I have been concerned on this for the last few years, first thinking it was ok, then that conditioned attic would require the coverage of foam for fire resistance, then it seemed to be ok.

To take all that square footage in an attic and condition the space at the cost of what it would take to do and the cost of keeping it conditioned would be enormous over a period of time. That would be like adding at least a third more to the homes footage or more. Turning it into a condition space by permit will increase your taxes substantially. You are only taxed on the hab itable squre footage of the home as well as price but price increases as footage is added.

On the other hand a tax credit is in order by adding ventilation, insulation, radient barrier etc. Also the savings over time and I do mean forever will certainly pay you back and if you sell you may have other concerns with the home but then you throw the price on the home for all these upgrades and no one will complain.

Thanks for the code, Jerry. That addresses my specific concerns. I have seen several of these and have been a big fan of the idea for years due to the energy savings, but the possibility of having to cover the interior of the foam had me confused.
I guess it all depends on the listing of the product used.

Ted, this would add to the interior volume but it would not change the habitable square footage or taxes. While the attic does move into the thermal envelope, nothing else changes, not even flooring to in the attic. It may add to the taxes because of the higher construction costs but then so would a higher efficiency A/C unit.

One thing that is worth mentioning is that radiant barriers would not be appropriate on these interior foam covered roof decks.

One point w/respect to energy efficency that seems to be overlooked is the consumer's ability to verify the efficency data presented.
Point - when reading an EPA appliance tag, how many people know what they are paying per kilowatt hour, or per therm of gas. How many people on average know what a therm of gas is?
Additionally, with an energy star certified house, is there any incentive by the utility. I was recently, involved with a new construction house the owner wanted certified as energy star. It took a lot of effort, but as an example, the electric company offered a ES discount of $0.005 cents per kilowatt hour after the 1st 350 kwhrs consumed per month. I really had a tough time with that considering the cost per kilowatt w/o ES was $0.078
It seems there is a lot of sales hype and not much substance to back it up.

Consumers can easily compare the approximate impact of one upgrade measure vs. another using "rate calculators" available through electric utiliy company web sites ... AEP has an excellent "rate calculator".

Contact a professional insulator experienced with retrofit strategies who offers multiple types of insulation e.g. foams, loose-fill, batts, foils etc. A good place to check is the web site of the Insulation Contractors Association of America ... ICAA (Insulation Contractors Association of America).

The attic insulation of a 1 year old house should be at or near current code levels; thus, additional insulation may produce marginal results vs. other measures e.g. air sealing, additional attic ventilation, etc.

These reccomendations seem alittle excessive. Attic insulation at R-49,in this area, wow. The code requires R-30 and the one I just certified as ES had R-38 in it. I also wonder how they proposed adding the R-30 around the band before installing a floor system as they recommend. Frame carpenters are not very good insulators.
Also they again don't answer the question, how much money will it save or cost the consumer using what numbers for cost.

I don't recall recommending any specific R-values. I only mentioned sources of information available at no cost that provides provides property owners, as well as home inspectors, with quick confirmation re: priorities and potential for payback.

Prescriptive code measures under current energy code standards reflect a lot of industry input. At some level, the point of diminishing return is reached with respect to the impact of an individual measure. Building scientists refer to houses as systems. Recommendations should be prioritized taking a systems approach.

I've been at this since 1965. Cast your lot with what "seems" correct to you if your experience and inclination leads elsewhere.

Sorry Bob, I should have mentioned I visited the site linked in your post. Using their calculator I input the first 3 zip digits and answered a few questions for a generic recommended insulation.
After getting my feet wet with an ES house I really became very interested in housing energy consumption.
I realized I could not count on my HVAC contractor to always do the right thing. They really like to oversize. By utilizing the 3rd party certification , the cooling was downsized by 2 tons. It really made me wake up.
As a result I'm starting to look at home inspection in a much different way.

Jim,

Among the best publications for recommending best energy efficient building practices are the Builder Guides available from the Energy Efficient Building Association (EEBA || Energy and Environmental Building Association). Guides are available for each of 4 climate zones. Pick the one that covers your service area.

Houses are systems composed of sub-systems: envelope and HAVC. Each sub-system has its own complex components. Building science is facinating. These books boil is down and illustrate the principles so that lay persons, including home inspectors, are able to understand and convey them to others.

Bob

Bob, I agree on all points, the problem I see most often is a fix for one area having a negative impact in another. Kinda like failing to see the forrest for the trees.

Now I hate to admit it but the guides you mentioned sound interesting but I could not find them when I visited the link. Would you mind helping me find it, I assumed the bookstore but didn't see it,

Jim,

Try these web sites:

Building Science Corporation

www.joelstibureck.com

Joe Lstiburek is a Massechusetts based building scientist and a very popular speaker who advocates the "house is a system" approach to building science. How one designs or alters one sub-system has ramifications upon all of the other sub-systems.

Best practice requires balancing sub-systems for maximum benefit of the overall system ... e.g. optimum whole house performance and efficiency.

Be wary of peddlers hawking energy saving gizmos and widgits. Instead, look at the whole house as a system from a building science perspective.

If EEBA holds one of their Building America symposiums in your area, take a day to go learn, mix and mingle with knowledgible folk.

Bob

I probably wouldn't spent the $2200 but I have seen good results with the solar attic fan. It works really well. It can significantly reduce attic temperature and that just makes good common sense.

Originally Posted by Russell Palka

the solar attic fan. It works really well. It can significantly reduce attic temperature

However, it also does some things which are not wanted.

For example, if the attic fan is an exhaust fan, it will depressurize the attic and draw conditioned air from the house into the attic, which then needs to draw unconditioned outside air into the house to make up for the conditioned air sucked out through the attic, resulting in not only a net loss of energy but potentially ill effects for the living environment.

Or, if the solar attic fan were to run as an intake and pressurize the attic to avoid the above negatives, the now pressurized attic would drive hot unconditioned attic air into the house, along with any and all pesticide applications made in the attic, and do the same thing as above only in reverse and probably end up being worse than that stated above.

An attic fan is not a good idea, even if it costs nothing to run because it is solar.

OK Jerry, what is your take on crawlspace venting?

Originally Posted by James Skinner

OK Jerry, what is your take on crawlspace venting?

In many climates crawlspace venting works.

In some climates crawlspace venting may not work and the crawlspace may need to be sealed.

If you have a vented crawlspace and need to add mechanical ventilation ... you don't need to add mechanical ventilation, you simply have insufficient vent area and / or vents not in the correct locations (or the vents are blocked).

If a crawlspace is being mechanically exhausted out because of excessive ground moisture, then exhaust out from UNDER the moisture barrier, not above it. I.e, don't negatively pressurize the crawlspace, negatively pressurize what you are trying to - the area under the moisture barrier where the excess moisture it - then vent the area above the moisture barrier.

Originally Posted by Jerry Peck

In many climates crawlspace venting works.

In some climates crawlspace venting may not work and the crawlspace may need to be sealed.

If you have a vented crawlspace and need to add mechanical ventilation ... you don't need to add mechanical ventilation, you simply have insufficient vent area and / or vents not in the correct locations (or the vents are blocked).

If a crawlspace is being mechanically exhausted out because of excessive ground moisture, then exhaust out from UNDER the moisture barrier, not above it. I.e, don't negatively pressurize the crawlspace, negatively pressurize what you are trying to - the area under the moisture barrier where the excess moisture it - then vent the area above the moisture barrier.

If you have adequate ventilation on one side of the crawl and put an exhaust fan on the other that operates on a humidistat I seriously doubt that the exhaust fan is adding negative pressure at all.


Same the with the above mentioned solar roof fan. From what I have seen in attics with the solar fans they are doing nothing but helping to slowly move the air thru the attic and get rid of that hot stagnanty air.

These are not jet engines. If you have adequate eve vent or crawl vents for that matter you are not doing anything to add negative or positve pressure with these fans.

Maybe the electric power fans. These are big fans and they move a lot of air in and attic.

The crawl fans are smal and not that powerful. I can not see them being a negative at all.

All opinions vary. All attics ans crawls should be evaluated on an individual basis.

I am an absolute fan (no pun intended) of solar fans for attic and crawl space ventilation fans to get rid of that moist air in the crawl.

Should all attics or crawls have fans venting them. I am sure there are a few out there where the answer would be no.

Originally Posted by Ted Menelly

These are not jet engines. If you have adequate eve vent or crawl vents for that matter you are not doing anything to add negative or positve pressure with these fans.

If you have adequate eave vents and adequate crawlspace vents, why do you even need to add ANY TYPE of exhaust fan?

Originally Posted by Jerry Peck

If you have adequate eave vents and adequate crawlspace vents, why do you even need to add ANY TYPE of exhaust fan?

It moves the air instead of it just sitting there and slowly rising up and out some turbine vent. It cools it quicker and by slightly moving the air it keeps it cooler all day.

Those dead hot absolutely no air days is always when those attics are the hottest. Move the air a little and it cools right down.

You have been in many an attic where it is stfling even thought there was plenty of ventilation. Get a breezy day and go into the same attic and it is much cooler because the air has been moving, even though it it is still 102 outside.

Same in a crawl. You can go into the crawl and see the vents all around you. No moving air outside and you can't breath in that dead air slightly damp musty smelling crawl. Move the air slightly and it is actually refreshing down there.

Originally Posted by Ted Menelly

You have been in many an attic where it is stfling even thought there was plenty of ventilation. Get a breezy day and go into the same attic and it is much cooler because the air has been moving, even though it it is still 102 outside.

And any fan capable of simulating that CFM is going to negatively effect the pressure differences.

The breezy days work because the air movement over the ridge creates a negative pressure and the air movement at the eaves creates a positive pressure, it is that pressure difference which moves the air in the attic.

Similar for houses with all soffit vents, air movement increases pressure on one (or more) sides and decrease pressure on one (or more) sides, which creates air movement within the attic.

With a fan, you are only decreasing the pressure (with an exhaust fan) or increasing the pressure (with an intake fan) with no accompanying change in pressure at the other areas.

Originally Posted by Jerry Peck

And any fan capable of simulating that CFM is going to negatively effect the pressure differences.

The breezy days work because the air movement over the ridge creates a negative pressure and the air movement at the eaves creates a positive pressure, it is that pressure difference which moves the air in the attic.

Similar for houses with all soffit vents, air movement increases pressure on one (or more) sides and decrease pressure on one (or more) sides, which creates air movement within the attic.

With a fan, you are only decreasing the pressure (with an exhaust fan) or increasing the pressure (with an intake fan) with no accompanying change in pressure at the other areas.

Just all technicalities

Yes I understand pressure and what may cause it in an attic or crawl.

Fact is if you are in a bedroom and the only outlet for air return is under a door then when you try to close that door you go only so far and it sucks shut. That is to much pressure on the room and you are infact prssurizing the room with the supply vents and no return other than under the door.

Put a jumper duct over that door so the room does not pressurize and has good airflow thru the room and you take that pressure buildup out of the room.

Same thing in an attic. If you have little to no eve vents then when you put a fan in you are sucking against the entire attic floor area to the home. Add soffit vents and that fan in the roof is not sucking against the attic floor but is drawing air thru the soffit/eve vents cooling the attic.

That slight pressure created is not goiung to adversly affect the home with pressure more than it will cause a good effect by removing the hot air in the attic thus cutting back on energy cost. Plus the solar fan draws no power to use thus saving money on the home cooling bills over time for years.

Jerry, I'm curious so I going to provide a situation I'm currently working with. I'm looking for some input, cause this one is baffling me.
1) Crawl space is approx 2000 sqft. with automatic foundation vents spaced I guessing every 6-8 ft. with exception of garage on one corner.
2) Some time ago, a perimeter french drain was installed inside the crawlspace with a sump pump at the low point.
3) crawlspace floor is dry, I mean rock hard dry & cracked, Lots of clay.
4) some plastic down but not a lot. mainly over the french drain.
5) Issue is condensation forming in the insulation. You can see moisture drops formed on the fiberglass fibers.
6) Only one vent is closed and it is located at two propane bottles connected to house gas piping. Figured it better to leave it closed to ensure any extra gas stays out side.
7) Intend to install a vapor barrier, and add forced ventilation. Think there is a problem with humid warm air condensing inside cooler crawlspace. Hopfully will warm crawlspace to match exterior air temps and change dewpoint temp. Intentions are to pressurize the crawl.
8) Forgot to mention, house sits on a well wooded lot and stays in the shade a good bit of the time. Also lots of vegetation all around. Part of the plan is to remove that also.

Originally Posted by James Skinner

1) ... with automatic foundation vents ...

Describe and define "automatic" foundation vents.

I am envisioning "flood resistant" vents which are supposed to be open all the time and automatically close when flooding reaches their level.

Oh and Ted don't be bashful, jump in there too. I am looking for idea's/ guess's. Please keep in mind money is an issue so I cannot get too crazy or I 'd get a dehumidifier. Currently, guessing the plastic and fan should be a couple of hundred. Totally, sealing the crawl would run a couple 1000.00.

Also, this house is 20+ years old.

Gee, Jerry, you've got me on that one, I haven't seen those. In this case I'm referring to thermally controlled vents. They open/close automatically in response to temperature. No power involved, just a expanding/contracting spring controlling the louvers.

As I keep adding all the time. All crawls need to be individually evaluated.

Cooler in the crawl most of the time than the temp outside, yes. Water droplets forming on the insulation. Then you have to move air to keep this from happening. I would say the moisture is already in your crawl but of course I am not there to see it. The bottom of the insulation is the same temp as the crawl. I would say moisture in the crawl keeps rising up into the insulation and so much gets into it it actually is now water. Move the air in the crawl. Have the fan operated by a humidistat. Moisture level rises, fan kicks on and does not shut off till moisture level drops.

It sounds to me that you have more than the cost of sealing the crawl. It sounds like if you are going to do that there is a whole slew of things to take care of first. If there is that much moisture in the crawl then there must be considerable moisture in the soil of the crawl.


Do not. I repeat. Do not just read the books of the "pros" and seal your crawl space. You know what. I can go on forever here but it is all speculation.

Test the soil under the home and see how deep it goes and where it may be coming from. Gutters come to mind. Grading comes to mind. If there is a lot of moisture getting down into the soil under the home and you can do nothing abouit it then I would suggest sloping the crawl and adding a sump dug down into a hole. All the moisture will go into that direction.

Again, I have to stop because I am throwing possible gabage around that means nothing to your crawl situation.

Frankly that is how I feel about all the "pros" and there books.

Every crawl needs to be evaluated individually.

Originally Posted by James Skinner

Gee, Jerry, you've got me on that one, I haven't seen those. In this case I'm referring to thermally controlled vents. They open/close automatically in response to temperature. No power involved, just a expanding/contracting spring controlling the louvers.

Okay, bi-metal spring which operates the louvers as the temperature changes.

With your semi-vented crawlspace (I used the semi-vented term as it is neither vented nor unvented) there is a good possibility that your crawlspace is not "vented properly", possibly with those vents closing when in fact they should be open.

To my knowledge, the code does not allow those. The crawlspace is either "vented" or "sealed" (non-vented), not "vented some of the time".

Also, there may be insufficient venting caused by those louvers themselves. Have you done a calculation of the net free vent area you have as regards the net free vent area required?

2,000 sf crawlspace requires 2000 / 150 = 13.34 sf net free vent area

If metal louvers are in the vents, the reduction of each vent is at least down to a factor of 70%, potentially even less, which means you need vent opening sizes of 13.34 x 1.43 = 19.1 sf absolute minimum, and probably closer to 25 sf for those vents.

How many vents of what size do you have? Take you number of vents x height inches x length inches / 144 = ?? sf (should be at least 20, probably even at least 25).

Ted- there has been quite a bit done to this crawlspace over the years. My involvement started one week ago. The total amount expended will probably exceed the cost of sealing the crawlspace originally. It seems there has been progress but they have not totally solved the problem.
Currently, am looking for a more conservative approach, where I can progressively work toward the final solution, building upon each step, in the hope of discovering a less expensive solution for the owner and seeing the results for myself.
I think Jerry may have hit on a possible issue with the total vent space available. It may be a good idea to start at the beginning with the basics and calculate the vent space needed vs. the actual available. To date have been making some assumptions based upon observation. I hadn't considered the amount lost as a result of the louvers.
There are alot of factors that come into play here. All of which contribute to the problem. The site placement and drainage are definitely big contributors here. I will gather some info and pass on after I return to site on Monday.