Hello: Should I use Tiger Foam to spray the entire bedrock floor of my crawl space and insulate the crawl-space walls to create a 'conditioned' space? I would have ducts from the air/heat exchanger in this space as well. Or, just insulate the floor above the crawl-space? It is going to be a retirement house so keeping the future heating costs low is important. Here is a Youtube link to the site excavation: http://youtu.be/Sal6hLuVlJQ Thanks for any suggestions.

The most important question is where is your new home going to be located?

If you insulate the floor of the crawl space with foam and have duct openings in that space to condition it, what do you plan to use to cover the foam to address potential fire issues? In general, you shouldn't leave ignitable foam exposed in conditioned spaces.

That spray foam is expensive (>$1/inch per square foot). Another option would be to fill the crawl space with sand or gravel with just enough material to get it level, then lay down a plastic vapor barrier with taped seams, then lay down sheets of rigid insulation, either XPS or less expensive EPS (you might look into finding reclaimed insulation to save even more), 2" to 4" thick. Then pour a 2" thick concrete slab over the insulation. This is often referred to as a "rat slab". Then you could use your entire crawl space as either a supply or return plenum and possibly forgo some duct work costs.

Is radon a concern in your area? If so, you should place perforated plastic pipe in the sand/gravel fill and provide an exit duct to get any potential gasses out of the area.

Here is a link that discusses sealed conditioned crawl spaces and the issues of using that area as a plenum:

http://www.buildingscience.com/docu...-and-codes

Thank you. :) My problem is that the bedrock is too uneven to cover with rigid insulation and then cement rat slab. See: http://www.youtube.com/watch?v=Sal6hLuVlJQ&feature=plcp The house will be located north of Montreal, QC Canada. Radon is not an issue in the area.

In order to use sheet foam the sand would not need to be level, only flat. Spray foam, while more expensive would also work well, so if you go that route, use a minimum of least 2", but preferably at least 4". For the best bond, clean the rock off well. On the uphill side you'll need to be careful to insure that water cannot leak in under the concrete. Hydraulic cement can be sued to seal the joint. A very high portland cement mix will help on the footing. There it is critical that the footing be bonded directly on rock, without any sand or dirt.

Thanks Bob! :)

Given the unevenness of the bedrock, I was thinking that I would create a un-insulated 'closed in' crawl space and use R-54 SIP's as my floor. I would cover the bedrock with a 'pool liner like' vapor barrier up to the sill plate. I would 'manage' any water behind the vapor barrier with a sump pump. The vapor barrier should protect my beams that support the SIP floor. I might slightly heat the area on the inside of the vapor barrier to just above the freezing point, if anyone thinks to do that would be a good idea. Would the R-54 SIP's provide a warm floor? Does this whole idea have flaws? Thanks for any advice on this. See picture: https://www.dropbox.com/s/001adfmij4byctv/111.JPG Rob

If I were able to make the crawl space 'waterproof', could I use cellulose over the vapor barrier, just like attic insulation, to insulate the 'floor' of the crawl space? Is there a better choice of inexpensive insulating material to accomplish this? Thanks, Rob.