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Going against recommendation on our crawl space insulation?

11 years ago

We are in the process of building a large home. It will now have to have a crawlspace, and therefore we are doing an enclosed crawl space underneath. That being said, this means there will be spray foam insulation in the crawlspace and I am requesting that it also be sprayed underneath the floor boards above - in other words, spray foam up underneath what is the hardwood floor of the first floor.

The recommendation is NOT to do this, because of the temperate body of air that will enhance the energy concept of the house, which is being built with ICFs. Not to mention everyone deems it highly unnecessary.

HOWEVER, our reasoning has nothing to do with that. We had a brown recluse infestation previously in our last home, and admittedly have an extreme view now on "tight" construction. We own up to our irrationality on this but until you have been through that, you cannot fathom that experience. We look at the spray foam under the floorboards as yet another barrier we can do in an effort to not have that horrific problem ever, ever again. If it means paying a few more dollars in heating/cooling bills each month, so be it.

My question is this - my HVAC guy, energy guy and builder are not recommending this. I would love to hear pros and cons of the true impact of spray foaming under the floorboards. I will have solid hardwood on the first floor (some carpet, not much) and the enclosed crawlspace will have a dehumidifier and not be part of the HVAC system. The entire crawl will be ICF construction with no vents/holes to the outside other than the lone access entrance.

Thanks very much for any discussion that will enlighten me on this!

Featured Answer

User

11 years ago

If you have ICF construction, you have a SOLID CONCRETE BARRIER to keep the spiders out. With rebar! Extending under ground! They don't burrow and can't chew through concrete.

If your "HVAC guy, energy guy and builder are not recommending this" it's for a really good reason.

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Comments (8)

worthy
11 years ago
The more you think about crawlspaces, the worse the idea sounds, no matter what the variation.

It would seem the spf would not be the only--let alone the best--insect barrier. Why, for instance, not just tight screening against the crawl ceiling?

I saw Billy fighting br. Nasty!
LOTO
11 years ago
I just started a topic this morning that is similar and also will be installing hardwood flooring over my crawl space foundation and am getting 2 very different opinions on how to foam the crawlspace...I am not worried about spiders 'cause I spray my own home but the moisture buckling my wood floors is my biggest concern..conditioned crawl or not to condition?
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I corrected your URL and put it in the link box below. In that article Joe Lstiburek recommends conditioning the crawl space which would avoid the problems you are concerned about. He says: "Photograph 5: Conditioned Crawlspace - The way all crawlspaces should look. Dry, warm, part of the house, not part of the outside or part of the ground. Insulated on the perimeter not in the floor. Beautiful." Here is a link that might be useful: link
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rollie
11 years ago
Heat it, cool it, treat it like it is part of your house,(which it is) and you both will be fine. Doesnt matter if you are in a heating.. or cooling climate.. Condition it for best results..

If you dont want to condition it, then build an airtight floor system and put it on piers..
NewToGreen
Original Author
11 years ago
Thanks all. We were originally supposed to have a slab but can't now because of soil conditions. A basement isn't an option. I will research a bit more on the conditioned vs. dehumidifier pros & cons.

and just a note that as a general rule spraying doesn't do anything for BR spiders unless it's directly to the source, which is why infestations become so problematic.

lazygardens, my husband and I had to laugh at your "concrete barrier" in caps, comment. We know you are right! And know we are a bit irrational on this, but until you are sleeping with them and taking apart your toasters and couches with mirrors and flashlights before moving, you can't appreciate the reason behind our insanity :-)
User
11 years ago
NewToGreen ... I'm really looking forward to having an ICF house built because of the lack of spots for infiltration of air and bugs.

I live in Arizona and also have a house in New Mexico. We have scorpions, black widows, rattlesnakes, mice with Hanta virus, prairie dogs with bubonic plague, skunks with rabies, tree rats with an appetite for wiring insulation, several native cockroach species, several cricket species, native and imported fire ants, Africanized honeybees, and some humongous non-venomous spiders.
DLM2000-GW
11 years ago
Wow - hope you're not on the Arizona relocation committee, lazygardens ;-)
PRO
Epiarch Designs
11 years ago
New- you are going ICF for your shell (as am I). Have you also consider ICF for the floor structure? The cost of the floor plus spray foam would probably be higher than an ICF floor. It would also not be made of concrete....and be insulated and most likely not as air tight.
The other option is a SIPs floor. Again, strong, air tight, and insulated.

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