Our 22 year old house has a stand up crawl space that is vented. We were advised to keep the vents open year round (here in central North Carolina), and to close just the one vent near the boiler in the winter. The floor in the crawl space is mostly dirt and it is covered with a thick plastic sheet which I think is supposed to prevent moisture from permeating the crawl space.

The ceiling of the crawl space (which is the floor of the living space -- it's a one story house) is insulated with batting, and the HVAC ducts in the crawl space that provide for heating and AC are well insulated.

I am unaware of any new guidelines of the type you mentioned, but I will certainly look them over closely.

Fungus and mold grow in dark, warm, damp, poorly ventilated spaces so venting is often required during the summer. But venting the crawl space usually only allows enough humid air to enter the crawl space to cause problems with the framing and not enough to provide proper ventilation. If you seal the crawl space and make it part of the conditioned space of the house the problem is eliminated.

Give the linked report to you contractor. If he doesn't understand it or agree with it, find one who does.

Here is a link that might be useful: Joe tells you how

It is a debatable depending on your local climate, but all the latest research agrees with your findings. I would find a builder who is more up to date if your current builder wants to do it the "good ol' way".

Concrete is more effective than poly for stopping the radon. You can get a test kit to find if it's really a problem in your house. If it is, then you probably want to build radon mitigation now. You basically install a pipe into the concrete that vents any gas out the roof. It's worth getting an estimate if you have radon.

mightyanvil - Thank you for the link to "Joe tells you how". What a great article, I read every page. I will definitely give a copy to my contractor.

twalkman - Thank you for your advice about the "good ol' way" and I will certainly get a radon kit to test out our basement in our house. I should have done so years ago but never really thought about it.

Thanks again!

This was very interesting and informative. I wonder if there is a way to retrofit a closed conditioned crawlspace on an older structure with the traditional passive ventilation?

Guess what, as it turns out NY State requires that a crawlspace must be ventilated. The codes were updated in 2008 and have this requirement even though it doesn't agree with the Federal Gov't. (Probably it was not even taken into consideration by the state when it was updating code.) My architect has suggested that we could close off and insulate the vent since it will have an access through our heated basement. This is of course after the inspection. Ridiculous isn't it! That is what we will probably do.

Thanks everyone for your help!

Rather than just cheating the code, you should take your architect's plans, the Federal Government documents and the article mightyanvil posted and ask for a VARIANCE when you submit your plans for approval. This would serve two purposes: (1) you won't be out of code if you ever have to sell; (2) you might convince someone on the code/planning committee to review the existing code and modify it to adopt the federal standard for future building projects.

sarschlos_remodeler is right for another reason. If you ever have a fire or plumbing leak or other insurable damage, the insurance company will not honor your claim if they establish that the local building codes were not followed.

Thank you sarschlos_remodeler and haus_proud for your suggestions on obtaining a variance. Hopefully they will review the existing code and modify it to adopt the federal standard for future building projects.

Somebody might be pulling your leg. The 2007 New York State Residential Code is based essentially word for word on the 2003 International Residential Code (issued in 2000, 2003 & 2006) that requires crawl spaces to be vented but allows five exceptions, #5 being is a sealed, insulated conditioned crawl space (as recommended by Lstiburek and the Department of Energy).

I find it highly unlikely that New York State has issued a mid-revision-cycle supplementary code revision to prohibit conditioned residential crawl spaces. But I could be wrong. Where are you getting the code information?

Insurance companies cannot refuse to honor their obligations if the code violation did not lead directly to or increase the severity of the property loss although they would love for you to think so and therefore not make a claim. I don't think an unvented crawl space would be considered an increased insurance risk whether it was legal or illegal.