# crawlspace walls



## joelowrider (Dec 29, 2011)

So I have a 3 foot crawlspace that is very damp We are thinking of putting a dehumidifier in it and insulating the outer walls. 

Right now we have the floor joist insulated with the reflex reflective bubble wrap. Should this be pulled down left up or what


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## AGWhitehouse (Jul 1, 2011)

Please post useful information if you expect any answers....

Do you have plastic or some other kind of vapor retarding system on the floor now? On the walls? Is the crawl space vented? Where are you on this big blue marble? Is bubble wrap your only insulation?


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## Windows on Wash (Aug 30, 2011)

Reflectix is not insulation and is barely effective as a radiant barrier...neither of which is proper in this application.



Where is the home located
What is the drainage/grade around the property like
What is the relative humidity in the crawlspace in the summer
Any utilities in the crawl
any additional details are useful here as are pictures.


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## joelowrider (Dec 29, 2011)

I have a 6 mill black vaper barior on the floor. tapped and overlaped

I live in Evansville IN about 30 foot off the Ohio River.

The Grading is bad due to the fact I have a hill behind the house My house is on the low side.

We have a french drain system aroun the back side of the house (drains water 365 days a year)

We also have a tile system under the house to a sump pump That mainly runs on very rainy days.

The Crawlspace is vented and humidity can get to 90 in the summer we put a power fan on it and we can get it to 60.


All of the houses around here have sealed crawlspaces now.

So we have ordered a 20 mill vapor barior and the foam insulation we are going to close off vents and condition the space my only question is to leave the radiant barior or take it down


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## Windows on Wash (Aug 30, 2011)

joelowrider said:


> I have a 6 mill black vaper barior on the floor. tapped and overlaped
> 
> I live in Evansville IN about 30 foot off the Ohio River.
> 
> ...


Neither.

Leave the space as unconditioned in my opinion and apply a continuous vapor barrier across the underside of the framing of the floor. 

Batts in between the joist with a healthy layer of rigid foam (seams staggered and taped/sealed) would be my best approach. 

With that high a moisture content and fundamental drainage issues, I would leave the crawl as vented and continue to manage the moisture diversions/ejections.


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## Bob Mariani (Dec 1, 2008)

Vented crawlspaces are a no-no. To remove the moisture use exhaust only ventilation. Check out EZ-Breathe, works about 10 times better and much cheaper to run than a dehumidifier. The poly of the floor is the right thing. The reflective bubble wrap can come down.


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## Gary in WA (Mar 11, 2009)

The radiant barrier is ½ correct, it will stop the radiative coupling to the cold earth, but doesn’t warm the joist ends: http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/

Gary


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## Windows on Wash (Aug 30, 2011)

Bob Mariani said:


> Vented crawlspaces are a no-no. To remove the moisture use exhaust only ventilation. Check out EZ-Breathe, works about 10 times better and much cheaper to run than a dehumidifier. The poly of the floor is the right thing. The reflective bubble wrap can come down.


How do you figure in this case?

Vented crawl spaces have been used for 100's of years successfully and what difference does it make in this case if the insulation and air barrier are intact at the floor joist level.

I would agree with you that converting a crawl to conditioned is applicable in most cases, however, the homeowner in this case has noted that he has poor grading and high water table. Most moisture/rH control measures in crawl spaces are designed at handling minor moisture issues. If he has a sump and french drain combo that runs pretty continuously, I would prefer to rely on a system that just manages the bulk moisture and control humidity via insulation and air barriers.

With that high and continuous moisture issues, that EZ breathe will be running constantly as compared to the occasional cycling of the sump pump. Which one is going to be using more energy at that point?


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## Bob Mariani (Dec 1, 2008)

the EZ-breathe will still use less energy. Bulk water however should be treated as a separate issue. vented crawlspaces have been used for years... another thing done wrong. In humid months more moisture is brought into the space, which creates a problem. The new code and informed building practices now understand that vented crawlspaces are wrong.


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## Windows on Wash (Aug 30, 2011)

I realize that EZ Breathe quotes $2-4 per month in usage but I would be very interested in seeing what the current draw is and what the electrical usage would be under very humid conditions. I suspect that $2-4 is under very low cycling conditions.

I think we are debating and accepted point here. I agree that conditioned crawls are ideal and when building a home, crawls should be engineered as conditioned vs. vented.

That being said, the grading issues, the fact that this is existing construction, the high water table, and considerable moisture issues make this a good candidate to remain a vented crawl. If the grading were better, not such much bulk water, etc I would be more inclined to encourage the poster to make it conditioned.

If the insulation and air barrier details are correct across the underside of the floor, I see no additional benefit to treating this as conditioned crawl and if done right, I also don't see any energy offset benefit to the conditioned crawl.


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## CrawlSpaceMoist (Nov 24, 2011)

I definitely agree it sounds like a sealed/conditioned crawl space is the way to go here.
With an exterior french drain and an interior tile to a sump pump, it sounds like you're handling the 'bulk' water. You don't really clarify what about your crawl space is 'moist' - the ground or what.
A fan that pulls humidity from 90 to 60 is amazing, but 60 is still high, depending on the temperature of the crawl and it's components. Have you taken any moisture readings in the wood of the joists?
Honestly, think about it. If you have a VB on the floor, you're handling the moisture (humidity) eminating form the floor - you're left with a circulation/humity issue. Unless it's muddy under the plastic?
I'd stay away from putting any poly on the underside of the joists. You could likely trap moisture between the poly and the floor and allow tremendous condensation issues, especially during the summer when the a/c is running.
Seal is, run a quality dehum to control the humidity in the crawl. Remember, once the humidity is controlled, the dehum will only run as-necessary.


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## Earnie (Jan 24, 2008)

When I moved into my house the crawlspace was like a rain forest. No poly on the floor, open foundation vents, plumbing, electrical, ducting, and HVAC air handler were dripping water. So I did some reading.

I placed 6 mil poly on the ground as required by code. A week or so later I looked in the crawlspace to now find a lake. Dripping water was now standing on the poly. Did more reading.

Next I closed and sealed the foundation vents and installed a cheap dehumififier. It took over a week of constant dehumidifier operation but the water on the poly dried. So did the insulation, electrical, plumbing, and HVAC. Did even more reading.

Next was placing foam board in the rim joist area and sealing around it. The cheap dehumidifier lasted a year. The new one is a SantaFe Compact. Right now the humidity level in the crawlspace is 54%. This is without sealing the poly to the walls, at seams, or around pillars. Found a site selling 16 mil poly. Started replacing the 6 mil. 

Last project is to install foam board on the block walls. Still need to find a suitable way to cover the foam board. I will not use drywall.

So for my situation, closing the vents and starting to encapsulate the crawlspace has made a huge difference in the Rh.


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## CrawlSpaceMoist (Nov 24, 2011)

If I may ask, why are you planning on covering the foam board?

And thanks for the post. one thing that's often forgotten with a crawl space SYSTEM is that the air is in balance with the dirt. Normally, especially in the South, sub-surface moisture 'breathes' out from the soil as humidity into the craw where the vents are supposed to help clear it out. HOWEVER, in crawl spaces where the humidity entering is extremely high and (typically) with poor circulation, the soil can absorb moisture from the air.
When you place a poly, you 'break' that absorption zone. it's pretty rare (in my experience), but you can have people with poor crawls, they place a poly, and it gets worse!  You've just isolated your problem as primarily from the venting.
Sealed crawl is the way to go! thanks for sharing.


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## Earnie (Jan 24, 2008)

Why will I cover the foam board? 2009 NC Residential Code Section R314 Foam Plastic.

Specifically, R314.5.4 Crawlspaces. 

"The thermal barrier specified in Section R314.4 is not required where crawlspace access is required by Section R408.4 and where entry is made only for service of utilities and the foam plastic insulation is protected against ignition using one of the following ignition barrier materials:

1. 1.5 inch thick mineral fiber insulation
2. .25 inch thick wood structural panels
3. .375 inch particleboard
4. .25 inch hardboard
5. .375 inch gypsum board or;
6. Corrosion-resistant steel having a base metal thickness of .016 inch.

The foam plastic ignition barrier is not required where the foam plastic insulation has been tested in accordance with Section R314.6."


I read it that the foam board must be covered unless tested and approved. Help me understand why protection is not required for the foam board.


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## Bob Mariani (Dec 1, 2008)

I use Dow Tuff R for crawlspaces.. even their site explains it is the best way to fix a crawlspace and vents should be closed off. Also if you look it does not require a thermal or ignition barrier. http://building.dow.com/na/en/applications/building/foundations/foundationscrawl.htm


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## Earnie (Jan 24, 2008)

I don't want to take away from the original poster question. Just adding my experience.

Bob, I don't see where the link states no thermal or ignition barrier required. Dow can state whatever it wants. The building code says different unless Dow has provided testing data and the product has been approved.


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## Bob Mariani (Dec 1, 2008)

In any case you need to follow you local codes. Unfortunately they are very outdated and flat out wrong when it comes to energy efficiency retro-fits. Codes will be changing for 2012 when local officials adopt them. big changes. 
1) vapor barriers are not to be used in mixed climates
2) exterior foam insulation is required to stop thermal bridging
3) air sealing and a blower door test are required
4) vapor retarders over dense packed cellulose are not required
5) Mechanical ventialation (HRV) will be required


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## Earnie (Jan 24, 2008)

Yes, I agree with your statement about the code being outdated. But as we know, what's in the current and local code is what we have to comply with, like it or not. Or do it as we want to do in OUR house and hope it never becomes and issue.


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## Bob Mariani (Dec 1, 2008)

if it not to be inspected and building science shows it is the right way, I would go with the right way. Poly on warm side of walls for mixed climates is an excellent example.. By code grow mold. As a contractor I install the poly get inspections and rip it out. Inspector knows this is being done and agrees with it. If fact it was his recommendation. code here still wants cross vents in a crawlspace. yet when doing a fix we immediately seal these off. (note DOW says to do the same thing) Building Science is relatively new. And codes were not built to local conditions. Our housing stock is built horribly as a result.


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## Earnie (Jan 24, 2008)

I have no problem with what you wrote but there are limits. Yes?

To the issue of covering foam board, my understanding is protecting the foam from fire and the potential gases it produces when burning. 

Will those gases make it into my living space before I know there is a fire in the crawlspace? I have no idea. A smoke detector in the crawlspace (and attic) might be a good solution.


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## Bob Mariani (Dec 1, 2008)

yes a good solution. Crawlspace ceiling should be as air tight as you can get it. The smoke is bad, but you couch cushions, OSB, flooring, paint and much more are much worse.


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## Gary in WA (Mar 11, 2009)

Crawlspaces and attics and published information to pass inspection: http://www.diychatroom.com/f103/knee-wall-insulation-help-129363/index2/

Gary


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## websnooper (Jan 16, 2012)

Bob Mariani said:


> yes a good solution. Crawlspace ceiling should be as air tight as you can get it. The smoke is bad, but you couch cushions, OSB, flooring, paint and much more are much worse.


Why would a crawlspace ceiling need to be air tight if it was being treated as sealed/conditioned?

I guess you could stomach cancer is worse than lung but that doesn't mean I want either.

Code is code....and the foam is supposed to be covered. Random dismissal of a tenant in the code is not exactly advisable. :whistling2:


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## Bob Mariani (Dec 1, 2008)

a crawlspace is normally not intentionally conditioned living space. As such it is considered outside the building envelope. The insulation (thermal boundary) and air sealing (pressure boundary) should be aligned. Also air in the crawlspace would rise due to stack effect and it is not the quality of air you wish for your family


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## Windows on Wash (Aug 30, 2011)

If you turn it into a sealed crawl, isn't the pressure and thermal boundary the crawlspace stem wall at that point?

If that is the case, why is the pressure boundary required at the ceiling? At that point you are mixing layers. Air and insulation, in the same plane, is the outside wall. 

As part of any crawl space sealing protocol, the floor is going to be covered an with Poly and sealed at the stem wall so there should not be any issues with dirt smells/odors.


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## CrawlSpaceMoist (Nov 24, 2011)

If you're sealing and conditioning the crawl space, the air quality shouldn't be an issue.
Per the building science RR-0401:
"Crawl spaces should be designed and constructed as mini-basements, part of the house – within the conditioned space."

Since the code allows/requires conditioning, including the exchange of air between the occupied space and the crawl space, it appears the issue is not that the crawl should not be considered outside the building envelope, but part of the functioning system of the home.


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## Windows on Wash (Aug 30, 2011)

CrawlSpaceMoist said:


> If you're sealing and conditioning the crawl space, the air quality shouldn't be an issue.
> Per the building science RR-0401:
> "Crawl spaces should be designed and constructed as mini-basements, part of the house – within the conditioned space."
> 
> Since the code allows/requires conditioning, including the exchange of air between the occupied space and the crawl space, it appears the issue is not that the crawl should not be considered outside the building envelope, but part of the functioning system of the home.


This is my point exactly. Thanks.

It is either sealed (i.e. conditioned) or vented. Not a mixture of the two.


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## CrawlSpaceMoist (Nov 24, 2011)

Doesn't the Thermax Sheathing meet the requirement of r314?


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## Windows on Wash (Aug 30, 2011)

Some say yes and some say no. My only point in this discussion to make sure you get approval from your local inspector before you take chances of falling on the wrong side of the code.


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## Earnie (Jan 24, 2008)

We should be commenting on old construction not new. See original posters question.

In a perfect world if I were designing a new house and needed a crawlspace I would desing and build a mini-basement or "basement for trolls" as I remember it being described.

I would not overlook the HVAC requirements (heat gain/heat loss) if I planned to condition my crawlspace. So I won't be installing a new HVAC system to accomodate a conditioned crawlspace. Please don't write that the crawlspace load would be of no concern and tapping into the existing HVAC would be ok. 

As to Thermax, or any other glass-fiber-reinforced polyisocyanurate, that product was my orginal choice until I read that it absorbs water. Also, the foil would not allow any moisture that enters the brick/block wall to dry to the inside. Not sure why I want that, but that was needed. 

I do not have a Phd in building science. I'm a home owner who wants to know what is being done to my house and why. It's my money, my house and I live in it.


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## Earnie (Jan 24, 2008)

Copied from Building Science.com Info-512 Crawlspace Insulation May 14, 2009.


Crawlspace walls should be insulated with non-water sensitive insulation that prevents interior air from contacting cold basement surfaces—the concrete structural elements and the rim joist framing. Allowing interior air (that is usually full of moisture, especially in the humid summer months) to touch cold surfaces will cause condensation and wetting, rather than the desired drying. The structural elements of below grade walls are cold (concrete is in direct contact with the ground)—especially when insulated on the interior. Of particular concern are rim joist areas—which are cold not only during the summer but also during the winter. This is why it is important that interior insulation assemblies be constructed as airtight as possible.

The best insulations to use are foam based and should allow the foundation wall assembly to dry inwards. The foam insulation layer should generally be vapor semi impermeable (greater than 0.1 perm), vapor semi permeable (greater than 1.0 perm) or vapor permeable (greater than 10 perm) (Lstiburek, 2004). The greater the permeance the greater the inward drying and therefore the lower the risk of excessive moisture accumulation.

Up to two inches of unfaced extruded polystyrene (XPS) (R-10), four inches of unfaced expanded polystyrene (R-15), three inches of closed cell medium density spray polyurethane foam (R-18) and ten inches of open cell low density spray foam (R-35) meet these permeability requirements.
In crawlspaces where the insulation material will need to be covered by a fire/ignition barrier, it may be acceptable to use fire-rated foil-faced insulations. However, such requires careful attention to supplemental moisture management strategies. With vapor impermeable facings on interior insulation, it is possible that water may accumulate between the insulation facing and the inside surface of the foundation wall. The airtightness of the assembly is, therefore, extremely important to prevent the exchange of air between this damp interface and anywhere else in the building.


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## AGWhitehouse (Jul 1, 2011)

FYI on foam exposure:

If you do not provide the thermal and ignition barriers specifically mentioned in the code then you will need to get specific written approval from your local code official. Sprayed on intumescent paint, manufacturer claims, special foil facings, etc. are an exception to the code and need written approval to be considered acceptable.

Here's the exact code exerpt. Notice how it does not allow it to be left uncovered and/or painted without said approvals. Also note that the foil facings on the foam are not considered approved thermal/ignition barriers as they are not listed in the approved methods noted below.

*SECTION 2603 - FOAM PLASTIC INSULATION*

*2603.4 Thermal Barrier.* Except as provided for in Sections 2603.4.1 and 2603.9, foam plastic shall be seperated from the interior of the building by an approved thermal barrier of 1/2-inch (12.7mm) gypsum wallboard or equivalent thermal barrier material that will limit the average temperature rise of the unexposed surface to not more than 250degF (102degC) after 15 minutes of fire exposure, complying with the standard time-temperature curve of ASTM E 119 or UL 263. The thermal barrier shall be installed in such a manner that it will remain in place for 15 minutes based on FM 4880, UL1040, NFPA 286 or UL 1715. Combustible concealed spaces shall comply with Section 717.

*2603.4.1 Thermal barrier not required.* The thermal barrier specified in Section 2603.4 is not required under the conditions set forth in Sections 2603.4.1.1 through 2603.4.1.13.

_(Sections 2603.4.1.1 -> 2603.4.1.5 and 2603.4.1.7 -> 2603.4.1.13 don't pertain to this topic)_

*2603.4.1.6 Attics and Crawl Spaces.* Within an attic or crawl space where entry is made only for service of utilities, foam plastic insulation shall be protected against ignition by 1 1/2-inch-thick (38mm) mineral fiber insulation; 1/4-inch-thick (6.4mm) wood structural panel, particleboard or hardboard; 3/8-inch-thick (9.5mm) gypsum wallboard, corrosion-resistant steel having a base metal thickness of 0.016 inch (0.4mm) or other approved material installed in such a manner that the foam plastic insulation is not exposed. The protective covering shall be consistent with the requirements for the type of construction.

*2603.9 Special approval.* Foam plastic shall not be required to comply with the requirements of Sections 2603.4 through 2603.7 where specifically approved based on large-scale tests such as, but not limited to, NFPA 286 (with the acceptance criteria of Section 803.2), FM 4880, UL 1040 or UL 1715. Such testing shall be related to the actual end-use configuration and be performed on the finished manufactured foam plastic assembly in the maximum thickness intended for use. Foam plastics that are used as interior finish on the basis of special tests shall also conform to the flame spread requirements of Chapter 8. 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.


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## Earnie (Jan 24, 2008)

Exactly, and that is why the Code in some respects is wothless.

It would rather me place wood structural panels (food for termites) particle board (food for termites), hardboard (food for termites), gypsum board (food for mold) inches from a dirt floor. 

Also, the foam must be covered by one of those materials so none of the foam is exposed. That means all sides, ends too, not just the front surface, 

Only viable materials are mineral fiber insulation and corrosion resistant steel. I wonder how expensive it would be to place .016 inch steel panels in a crawlspace? No, I won't be doing that and I have no idea where to get 1.5 inch thick mineral fiber insulation.


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## Bob Mariani (Dec 1, 2008)

Another way I insulate crawlspace walls is to glue pins to the wall. Then push on Roxul (rock wool insulation) and apply a cap over the pin. It is sort of like a large pop rivet application. The contact glue used for the pins smells and needs good ventilation and 24 hours to cure. So it is a two day application. But meets codes, does not attract mold, pests and insects. And is an inexpensive method. You can either go with 3" Roxul or two layers to get 6" depth.


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## Gary in WA (Mar 11, 2009)

The Roxul is vapor-permeable and would not slow vapor-drives, the whole point of foamboard (insulates/ Class 2 vapor retarder) to control it to a manageable level.

If the board manufacturer has an Evaluation Report for the product, it may not require a thermal/ignition barrier covering *when meeting their requirements*; http://www.ncfi.com/Insulation/uploads/Evaluation%20Reports,%20Acceptence%20Criteria%20and%20the%20Building%20Codes%20SF0608L.pdf

Earnie, most from the link I sited: 

Owen Corning pink board in attics: #4.2.1: http://commercial.owenscorning.com/a...79af27e5d.pdfI 

I am merely showing the reason spray foam professionals may not cover it, and if you are under an “I” Code, there is information you may be missing. I would cover it whenever convenient to do so, just for the fire safety issue.

Here is one from Dow, follow the other links/questions to learn more;
http://dow-styrofoam.custhelp.com/ap...KkNueDl5R2s%3D

You can check the certain type listing: http://dow-styrofoam.custhelp.com/app/answers/detail/a_id/3891/~/what-are-the-astm-c578-classifications-for-styrofoam%E2%84%A2-brand-extruded 


Thermal and ignition barrier Code understanding: http://www.biobased.net/architects/White Paper Thermal and Ignition Barriers for SPF.pdf

RMAX foam boards in attics/crawlspace with no covering 1. if vented space; 2. combustion air provided; 3. board max. density 2#c.ft., max. thickness of 4-1/2” : http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1864.pdf

Hardi meets CA Building Code with this report, otherwise you couldn’t install Hardie there: http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1844.pdf

If the manufacturer has an Evaluation Report on that specific product, follow the installation guidelines and usage listed therein. ESP used in attics/crawls; 1. entry only for service, NO storage; 2. no interconnecting attic or crawlspaces; 3. air in attic/crawl NOT circulated to parts of building; 4. attic venting as per code; 5. crawlspace venting as per code: http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1788.pdf

AdvanTech roof and wall panels meet code-prescribed water-resistive barrier without one; http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-1785.pdf 

Handi-Foam Class 1, SPF *does* require an ignition barrier in attics/crawls; http://www.icc-es.org/reports/pdf_files/ICC-ES/ESR-2717.pdf

List of products/manufacturers, watch the code colors for year they apply, found at the end of list; http://www.icc-es.org/reports/index.cfm?list=list

Obviously all foam/boards cannot be left uncovered and the air cannot exchange to a living space, products vary, read the report, if none is given- follow the Code (thermal or ignition barrier) in use along with your Building Inspector. Many jurisdictions have local amendments to the prescriptive “I” Codes. You may be in a State that does not use an I-Code, follow the AHJ. 

Gary


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## Bob Mariani (Dec 1, 2008)

The vapor barrier is already addressed since you should always have the poly on the floor and up to the sill plate.

as far as foam this from code in NC
Fire Safety
A key element in residential fire safety is
fireblocking between different levels in a home.
Fireblocking requirements already exist in the
residential building code, but allow the use of
porous materials like fiberglass or rock wool
insulation. North Carolina has improved these
requirements to require the use of non-porous
materials for fireblocking in crawl spaces.
Foam plastic insulation receives special
scrutiny in residential building codes because
some foam insulations have the potential to
release toxic or flammable gases when heated,
or they can accelerate the spread of a fire if
they ignite. To reduce these risks, most codes
require a thermal barrier (typically 1/2 inch
[13 mm] gypsum board or equivalent) or an
ignition barrier (typically 3/8 inch [10 mm]
gypsum board or equivalent) over foam
insulation. However, several foam insulation
products have been designed and tested to
reduce or eliminate those risks. Such products
can be installed without a thermal barrier or
ignition barrier with the appropriate
documentation.
Seal all plumbing, electrical, duct,
plenum, gas line and other wiring
penetrations through the subfloor
with non-porous materials. Rock
wool or fiberglass insulation alone
is not sufficient.
Provide documentation of product fireratings
(in the International Code Council
National Evaluation Report (ICC NER) for
the product) to allow installation of
exposed foam insulation without a thermal
barrier or an ignition barrier, if applicable
Provide documentation of fire-rating to
allow installation of exposed facing
materials on batt insulation in the band
joist or pony walls, if applicable
Do not use a crawl space to store
gasoline, solvents, or any tools or
materials that present a fire hazard.


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## Earnie (Jan 24, 2008)

"The vapor barrier is already addressed since you should always have the poly on the floor and up to the sill plate."

Sorry, but I won't be doing that either. NC, and probably most of the South, has termites. I would never install plastic vapor barrier from the dirt floor up to the sill plate. I don't recall the reference, but I believe there is a requirement to have a 3 inch inspection area below the sill plate to check for termite activity if the wall is covered. 

Maybe I'm ignorant of the facts (and I have asked this before), but why would I want a plastic vapor barrier covering the block wall? Isn't that trapping moisture between the block wall and the plastic?

Here is an easy way to remedy this issue. Does anyone have the name of a company that makes a code compliant and fire rated foam board that can be used to cover crawlspace walls? Specific product name will be helpful. What I mean is, something more than "check Dow or Owings Corning".


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## AGWhitehouse (Jul 1, 2011)

*I love how GBR deletes my post and continues on giving vague mis-leading responses. Bob Mariani posted the code for NC and it says the same as what I posted. YOU NEED BUILDING OFFICIAL APPROVAL TO LEAVE FOAM EXPOSED. No exceptions! I can't say it in any plainer english...please stop the vague information when dealing with life safety issues. It's misleading and life threating.*


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## Bob Mariani (Dec 1, 2008)

AGWhitehouse said:


> *I love how GBR deletes my post and continues on giving vague mis-leading responses. Bob Mariani posted the code for NC and it says the same as what I posted. YOU NEED BUILDING OFFICIAL APPROVAL TO LEAVE FOAM EXPOSED. No exceptions! I can't say it in any plainer english...please stop the vague information when dealing with life safety issues. It's misleading and life threating.*


 The most commonly used rigid foam board used on crawlsapce walls is probably Thermax Sheathing and it has passed FM 4880 which means it does not require ignition barrier protection. You can look it up by going to dowbuildingsolutions.com


And almost all professional spray foam does not need an ignition barrier. Where do you get this info? I do this for a living! And I pass inspections every day in many many towns both in CT and NY


Many closed cell foam manufacturers have passed testing that shows their materials do not require an Ignition Barrier in applications where an Ignition Barrier is required because those materials pass the ignition barrier test without any protection and comply with AC377 Apendix X. An ignition barrier is the only protection required in many interstitial space applications of foam chracterized by limited or no access, containing wires, pipes, ducts, or mechanical devices, air from this space cannot communicate with other spaces


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## CrawlSpaceMoist (Nov 24, 2011)

Earnie said:


> "The vapor barrier is already addressed since you should always have the poly on the floor and up to the sill plate."
> 
> Sorry, but I won't be doing that either. NC, and probably most of the South, has termites. I would never install plastic vapor barrier from the dirt floor up to the sill plate. I don't recall the reference, but I believe there is a requirement to have a 3 inch inspection area below the sill plate to check for termite activity if the wall is covered.
> 
> ...


NC Code requires a 3" termite inspection zone below the top of the foundation wall yes.
So what if you 'trap' moisture between the poly and the wall? Pratically the only time I don't spec poly up the walls is if it's poured concrete and largely impervious.
Block and Brick walls absorb moisture and release it (typically) as humidity into the crawl. Varies based on depth below grade, waterproofing, etc.
But the poly isn't stuck to the wall to create a back-side waterproofing. Fastened and caulked at the top, it would allow the vapor to condense and run down to the dirt. You know, like a vapor barrier.
Then, put your insulation on the poly and it's protected.


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## Earnie (Jan 24, 2008)

CSM,

I understand what you are doing and how you are applying the poly. Is there tested and documented proof that installing the poly to the brick will not cause a problem long term?

That's great poly can be used but I need to be sure I'm not fixing one problem and creating a bigger one.

I'll search and see if I can find where I read placing poly on the crawlspace was wrong.


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## CrawlSpaceMoist (Nov 24, 2011)

Hmmmm, a study that proves something doesn't cause a problem... let me look. I'm thinking the advanced energy studies address it.
If nothing else, NC codes specifies for sealed crawls a 100% wall to wall poly, OR it's to run up the wall to 3" from band sill.
Curious, what problem(s) do you think it would cause? I've read that up north spray foam on the foundation walls can cause the moisture to stack until it reaches the band sill and rots it. Poly on the wall doesn't do that, as it doesn't seal the material.


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## Earnie (Jan 24, 2008)

CSM,

I read your reply to imply that you have no hard data. The "advanced energy studies"? What advanced energy studies? Sources please.

Where exactly did Raleigh get the data to support what they currently have in the code regarding sealing crawlspaces? Remember, this is the same organization that required crawlspace vents which draw in hot humid air into a cool dry crawlspace.

I called Raleigh yesterday and left a message about this exact issue. So far no reply. They were in a training class. 

Sorry, but you're not convincing me that the plastic won't cause a future problem.


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## CrawlSpaceMoist (Nov 24, 2011)

I'm not here to convince you of anything. It's your house - do what you want within state code requirements. Like any other system within your house, monitor it, be aware of what's going on. I don't care what you do, but vented crawl spaces leave the underside of the home bathed in humidity.
Advanced Energy studies - crawlspaces.org. They've done I think 3 studies now on sealed crawl spaces, the first here in NC. You could have just done a google search.
They didn't require vents to 'draw in' moisture from outside. Back in the 'old days' vents weren't required, and they started requiring them to help clear OUT the humidity and moisture that will build in a crawl space. Still lunacy in my opinion, but a lot of crawls work okay with it. Others are horrendous.
If you think poly on the walls will cause a problem, which you still left unstated, then by all means don't do it.


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## Earnie (Jan 24, 2008)

No problems with what you just wrote. 

I have no idea what might happen over time with poly on the walls. That's why I'm asking. I'd like to read a study or report on testing that has been done. From there I can make an informed decision.

Thanks for the link to crawlspaces.org.


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## CrawlSpaceMoist (Nov 24, 2011)

No problem. I just can't remember any information or study on sealed crawls where the poly on the walls was ever questioned as a potential problem. Personally, I don't see what issue it would cause. any moisture through the walls would still come through, but condense and run down the poly. There no organics to grow a mold...
just don't have anything official to share to 'prove' it... I'll be looking though, now that I'm curious!


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## Windows on Wash (Aug 30, 2011)

Poly on the walls should be fine.

Issues with closed cell foam on older brick and block homes have been noted to create spawling issues of the brick by not allowing the moisture to dry to the warm side, but I have never heard of anything as it pertains to poly.


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## Earnie (Jan 24, 2008)

"Poly on the walls should be fine" just won't work for me. "Should be" means maybe, maybe not.

Here are two studies with pictures that show no plastic on the block walls. 

http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11480

http://www.buildingscience.com/documents/information-sheets/crawlspace-insulation



Here are a few definitions from Building Science.com

Vapor Impermeable: Materials with a permeance of 0.1 perm or less (rubber membranes, polyethylene film, glass, aluminum foil). A Class I vapor control layer.


Vapor Barrier: A material that has a permeance of 0.1 perm or less. A vapor barrier is a material that is essentially vapor impermeable. A vapor barrier is a Class I vapor control layer. The test procedure for classifying vapor barriers is ASTM E-96 Test Method A—the desiccant or dry cup method.


Vapor Retarder: A vapor retarder is a material that has a permeance of 1.0 perm or less and greater than 0.1 perm. A vapor retarder is a material that is vapor semi-impermeable. A vapor retarder is a Class II vapor control layer. The test procedure for classifying vapor retarders is ASTM E-96 Test Method A—the desiccant or dry cup method.


From Advanced Energy.org

http://www.advancedenergy.org/buildings/knowledge_library/crawl_spaces/pdfs/Closed%20Crawl%20Spaces_An%20Introduction%20for%20the%20Southeast.pdf

"Cover the masonry perimeter walls with minimum 6-mil polyethylene vapor retarder, leaving at least 3 inches (76 mm) of exposed masonry at the top of the wall. Mechanically attach the vapor retarder material and seal it to the wall with duct mastic."​


How can 6 mil polyethylene plastic be described as a vapor retarder when its actually a vapor barrier based upon its permeance?

Who is correct?


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## Windows on Wash (Aug 30, 2011)

Both are correct in this case.

There is a mixture of definitions out there in the market right now and the industry is moving away from the Vapor barrier designation.

All of them are vapor retarders, it is merely a case of what class of vapor retarder they are.

Poly plastic (perm rating of less than 0.1) is a Class I vapor retarder.

I appreciated your research intensive approach to this process but you will soon find out (if you haven't already) that is you look around long enough that you will find a dissenting opinion. 

As most of the folks on here, many of whom have done this quite a few times, have indicated, poly going up the stem wall and foam on the walls should be fine.

Several of the Building Science papers on crawls are best case scenarios and apply to the design aspect of it. Many factors involved in retrofitting an existing crawl cannot meet the design guidelines in their best practices layout because of existing construction.

Sealed crawls, in about 95% of the cases, are the way to go. How to get there depends on the application and construction.

Poly on the floor and sealed to the stem wall is probably one of the universals followed closely by a rigid foam on the walls.

Do you have a picture of the crawl and can you summarize your construction or your concerns as a result of your construction.


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## Earnie (Jan 24, 2008)

Thank you for the detailed reply. 


I'm not promoting BSC, but I do find their information science based vs. a guess or "that's how its been done for years". Maybe time will prove BSC's data wrong.


My issue involves sealing and insulating a 3 foot high x 1,200 sf crawlspace which contains the HVAC air handler and bottom floor ducting. Along with other utilities.


I need to insulate the block foundation wall especially for Winter since the HVAC (heat pump) is struggling with the 60 degree crawlspace temperature. All other sealing measures have been finished except for the foundation walls, though I do plan to upgrade the 6 mil ground poly in the future.


The conflicting information on how to insulate the walls have the project on hold.


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## Gary in WA (Mar 11, 2009)

AGWhitehouse said:


> *I love how GBR deletes my post and continues on giving vague mis-leading responses. Bob Mariani posted the code for NC and it says the same as what I posted. YOU NEED BUILDING OFFICIAL APPROVAL TO LEAVE FOAM EXPOSED. No exceptions! I can't say it in any plainer english...please stop the vague information when dealing with life safety issues. It's misleading and life threating.*


Your post was deleted to our staff-saved "trash bin" because it did not treat the OP with respect as per our forum rules: "Users shall treat each other with respect at all times on DIYChatroom.com. Name calling, personal attacks, or other inappropriate behavior will not be allowed and may cause your account to be banned". Found at the bottom right-hand corner of every page.
You agreed to this upon your membership, any other concerns, contact a moderator, or Nathan, by private messaging. Thank you, Gary


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## Windows on Wash (Aug 30, 2011)

Earnie said:


> Thank you for the detailed reply.
> 
> 
> I'm not promoting BSC, but I do find their information science based vs. a guess or "that's how its been done for years". Maybe time will prove BSC's data wrong.
> ...


There is not a whole bunch of conflicting information.

Rigid foam is great and works quite well.

You should call you code enforcement officials and check to see what requirements are necessitated for whatever foam you go with.

You can quite easily use foam and cover it with a JM spider insulation or rockwool batts if need be.


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## AGWhitehouse (Jul 1, 2011)

Bob Mariani said:


> The most commonly used rigid foam board used on crawlsapce walls is probably Thermax Sheathing and it has passed FM 4880 which means it does not require ignition barrier protection. You can look it up by going to dowbuildingsolutions.com
> 
> 
> And almost all professional spray foam does not need an ignition barrier. Where do you get this info? I do this for a living! And I pass inspections every day in many many towns both in CT and NY


Please show me the code section that allows for foam to be left exposed *without building official involvement.* That is the issue here. It needs to be made clear that you can leave *CERTAIN* assemblies exposed, but they *MUST HAVE PRIOR APPROVAL*. I've posted the code governing the design side in CT and it does not allow it to be left exposed without building official approval. The contractor side has always assumed their own way of things, hence the reasons for all the WTF moments when buildings get inspected by true professionals....


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## Earnie (Jan 24, 2008)

AGW,

From your experience and educational background, do you advocate installing polyethylene film (6 mil plastic) from ground level all the up (in my case to within 3 inches of the rim joist) block crawlspace walls? 

Also, if insulating a block crawlspace wall, would you specify extruded polystyrene (XPS) rigid foam board or foil faced polyisocyanurate foam board?

I understand local code is the final word but just interested in your point of view.


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## Bob Mariani (Dec 1, 2008)

Code states the foam must have an ignition barrier. Almost all commercial closed cell foam now meets this requirement. I do this work every day and jobs are passed every time. I already stated the manufacturer's reference to this fact... fortunately building inspectors here get BPI certified so they are a up to the new products and specifications of those products.


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## Earnie (Jan 24, 2008)

Bob,

Would you mind placing a link to a fire rated foam board that is code compliant? Or can you get me the manufacturer's name and specific product name?


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## Earnie (Jan 24, 2008)

I just called Dow. Here is what was emailed to me:

http://building.dow.com/ee/pdf/ESR-2142.pdf

Section 4.2.2 specifies the types of foam board, X and IV, that can be installed without a thermal or ignition barrier.

Table 1 lists specific product names by their type (X, IV, etc).

ILocal building department may want to see this document.

I suspect there is some hidden catch which prevents leaving the foam uncovered.


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## Gary in WA (Mar 11, 2009)

Er, that would be in the link I gave you in my post #22, linking to Dow and that ER in my #22 (there also)--- the last one listed....

"I suspect there is some hidden catch which prevents leaving the foam uncovered. " ---- yes, you have to meet their conditions of use and present it to the building official before you start as I said earlier.

Gary


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## Gary in WA (Mar 11, 2009)

The plastic alone is fine on the walls unless it is a conditioned crawlspace. You want conditioned if the HVAC ducts are down there. To condition---- insulate the walls, otherwise, insulate the floor. I would mastic or asphalt emulsion the plastic as it has to be air tight. You will still have problems with the joists getting wet from any other moisture source under there, along with radiation because the walls are not insulated, only plastic covered, leaving a cold crawlspace: http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/

http://www.buildingscience.com/documents/insights/bsi-049-confusion-about-diffusion

Gary


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## Earnie (Jan 24, 2008)

GBR in WA said:


> Er, that would be in the link I gave you in my post #22, linking to Dow and that ER in my #22 (there also)--- the last one listed....
> 
> 
> Gary


 
Yes, I see that now. I did look through the earlier replies but overlooked the link to the other post's link.


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## Earnie (Jan 24, 2008)

GBR in WA said:


> The plastic alone is fine on the walls unless it is a conditioned crawlspace. You want conditioned if the HVAC ducts are down there. To condition---- insulate the walls, otherwise, insulate the floor. I would mastic or asphalt emulsion the plastic as it has to be air tight. You will still have problems with the joists getting wet from any other moisture source under there, along with radiation because the walls are not insulated, only plastic covered, leaving a cold crawlspace:
> 
> 
> Gary


 
But is it wise to do both? Cover the walls with plastic, then put rigid foam board on top of the plastic.

If yes, why couldn't I just use something like Dow's Thermax which is a glass-fiber-reinforced polyisocyanurate insulation board with a foil covering? Foil for the air seal and the core for insulation.

That is the question I have been trying to get answered.

Update: I found this at Dow. http://msdssearch.dow.com/Published...foam/pdfs/noreg/179-07259.pdf&fromPage=GetDoc


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## Gary in WA (Mar 11, 2009)

Sorry, I guess I made it confusing to understand. 

NO plastic if using foamboard.

Tape to joints with foil tape. Check with local AHJ for air exchanges.

Gary


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## AGWhitehouse (Jul 1, 2011)

Earnie said:


> AGW,
> 
> From your experience and educational background, do you advocate installing polyethylene film (6 mil plastic) from ground level all the up (in my case to within 3 inches of the rim joist) block crawlspace walls?
> 
> ...


I'd recommend either the plastic or the XPS foam, depending on your budget. There is no need to use both.


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## Earnie (Jan 24, 2008)

Thank you for the reply Gary and AG.


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## Windows on Wash (Aug 30, 2011)

Earnie said:


> Thank you for the reply Gary and AG.


What...I get no love


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## Gary in WA (Mar 11, 2009)

Well, I've been home sick for 3 days, and I answered one right, and got a thanks! I'm feeling pretty good, I'll give you one of mine; take your right hand, reach over the left shoulder........
I'm staying out of the staff break room, think I picked up a virus there...

Gary

PS- For WW: :thumbup:


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## Earnie (Jan 24, 2008)

Hey, I gave you one in post 50. But it I can make your day better ............

Thank you Wash for your helpful replies to my questions.


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## Windows on Wash (Aug 30, 2011)

Earnie said:


> Hey, I gave you one in post 50. But it I can make your day better ............
> 
> Thank you Wash for your helpful replies to my questions.


I'll take it. :thumbup:


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