Unvented Crawl Space

[Bama dav]

Does a dehumidifier meet the requirements of 408.3 2012 IRC? Would you allow it? Thanks for your opinion.

 

[jar546]

Does it meet the intent may be a better way to look at it.

A properly sized dehumidifier that properly disposes of condensate and is protected from freezing may just be the best way to go providing the crawlspace is set up unvented. The dehumidifier would have to have a setting that is conducive to keeping the wood dry and it would be nice to know when it fails there is some sort of indication to the occupants.

From a prescriptive code standpoint, I am unsure until I read the section again.

 

[Francis Vineyard]

Though heavy duty dehumidifiers are advertised for this purpose to operate at lower temperatures this system is not recognized for new construction.

From an energy conservation standpoint it may consume more power than conditioning with the home HVAC system.

Francis

 

[jar546]

Though heavy duty dehumidifiers are advertised for this purpose to operate at lower temperatures this system is not recognized for new construction.From an energy conservation standpoint it may consume more power than conditioning with the home HVAC system.

Francis

Excellent point. I would recommend extending the thermal barrier into the crawlspace.

 

[Sifu]

I don't think it does. Also depends on the owner to maintain, which could lead to problems. Here we have heard just about every idea you can imagine to get around the air transfer pathway to the common area. Prescriptively speaking, I don't know of one.

 

[Rider Rick]

Would the crawl space be heated with the house?

I have inspected an insulated crawl space that only had vents to the living area in Washington State. The owner said that is the way it is done in Alaska State.

 

[jar546]

A dehumidifier would not be code compliant for a crawlspace. Read 408

 

[peach]

where would the condensate go?

 

[Francis Vineyard]

If it where an existing crawl space converted to unvented with a dehumidifier good pratice would have the floor sloped towards a sump pit provided with drainage or pump to discharged any water that may accumulate to an approved location.

As a reminder new construction also requires that drains be provided around foundations perimeter that retain habitable or usable spaces located below grade and that the foundation walls be waterproof or dampproof for conditioned crawls (interior enclosed spaces).

Francis

 

[peach]

Doesn't sound like good practice is what they are going for....

 

[Bama dav]

Thanks for the replies, It is a new house with spray foam on the foundation walls. The ESR(1826) requires foundation vents per 408.1 (2012). If you put in foundation vents it would no longer be a conditioned space so you would need to insulate the floor joist. So then on to enclosed crawlspace, It requires a pathway to the common area which not allowed per the ESR report on foam insulation. So I thinking it will require a prescriptive ignition barrier with a pathway to the common area. It doesn't seem to be a good way to meet the code and the ESR report.

 

[peach]

once you insulate and condition it, it's conditioned space. It bumps you into R408.3 "unvented crawl space"

 

[Francis Vineyard]

As a reminder there are the prescribed barriers listed in the code and exceptions that meets the listings under the specific approval section; this is the ESR document.

ESR-1826 section 4.4.2 Application without a Prescriptive Ignition Barrier installed with one of the following conditions that air from crawl does not circulate to other parts of the building. This section also refers to section 4.4.2.3 for crawl spaces that the prescribed ignition barriers or coating is not required when the foam does not exceed 3½ inches.

It is my interpretation that an ignition barrier is not required for unvented crawl spaces with up to 3½ of this product.

Should contact the manufacturer or ICC if you are a member for clarification.

Francis

 

[Bama dav]

Francis, you correct its the pathway to the common area in the unvented crawlspace that's got me curios how you do that when the ESR report says you cant communicate with the other areas. I will call ICC tomorrow to get some clarification. Thanks for your help.

 

[Daddy-0-]

I think you are wise to question the install. Some of these products need a thermal barrier and protection from termites while others have it built right in. Contacting the tech support at the manufacturer usually clears away some of the mud from the water.

 

[Rider Rick]

Why not build it like a heated basement.

 

[Sifu]

I am in the middle of this very battle. There are some, though very, very few spray foams that you can use without the prescriptive ignition barrier when the air circulates to the common area, and then only when they are covered with an approved alternate thermal barrier. Most ES reports contain the restrictions already mentioned. What I have found is that those restrictions are the same criteria use in ACC 377, appendix X (acceptance criteria for spray foam) and the foams were tested under those criteria, therefore the ES reports must limit the use to those criteria. I have found at least one product that does not contain those restrictions but only when their intumescent thermal barrier is applied. That thermal barrier is a two step process, which must be installed in specific conditions which IMHO wouldn't be easy to accomplish or verify in a 2' crawlspace full of ducts and pipes.

So on the one hand prescriptive code requires circulating air from the crawl to the common area, and on the other hand prescriptive code prevents most foam plastics from being exposed in those crawls. For my part, I have been successful with a few builders in getting them to circulate the air properly and use insulation other than surface applied foam, I have been less successful getting my bosses to back me up on it.

It should be noted that I have spoken to several reps from the chemical corps that make these foams and they have provided (sometimes reluctantly) information and confirmation of my findings. I get the impression they realize there are some issues with prescriptive code compliance but that not enough inspectors have caught on to it yet for them to worry much about it. JUST MY IMPRESSION.

 

[Bama dav]

I spoke with an engineer with ICC today and he said that crawl space must be vented by foundation vents or by circulating air from the unit in the house (unvented crawlspace). While a dehumidifier was allowed in the crawlspace in no way would it be considered ventilation. So the ESR report doesn't allow circulation from the crawlspace with foam insulation and the code requires it, what I supposed to do? He didn't have an answer.

 

[Francis Vineyard]

Would be best to speak with the person that wrote the ESR.

Contacted Icynene for clarification and waiting for a reply.

Francis

 

[Rider Rick]

I spoke with an engineer with ICC today and he said that crawl space must be vented by foundation vents or by circulating air from the unit in the house (unvented crawlspace). While a dehumidifier was allowed in the crawlspace in no way would it be considered ventilation. So the ESR report doesn't allow circulation from the crawlspace with foam insulation and the code requires it, what I supposed to do? He didn't have an answer.

Could you install rigid insulation to the outside of the foundation wall?

 

[Sifu]

So the ESR report doesn't allow circulation from the crawlspace with foam insulation and the code requires it, what I supposed to do?

Don't use the foam. Or use the foam with prescriptive ignition or thermal barrier. There are other ways to insulate. I have had that conversation and emails with ICC. I think it boils down to the fact that either the code hasn't caught up to the industry or the industry got ahead of itself.....or a little of both.

 

[Bama dav]

Could you install rigid insulation to the outside of the foundation wall?

Yes, that is what the fiberglass guys do. They use a rigid fiberboard insulation (r5).

 

[Daddy-0-]

Have them apply for a modification or follow the IRC. All you can do if they will not bend on the install. Time for them to do the homework in my opinion.

 

[Rider Rick]

2 inch is R-10 and I think this will meet code for basement stem walls and under slab with 6 mil vapor barrier.