Floor insulation, cellulose vs hard foam

[Arky217]

The house I'm building is 24' x 48' on a crawl space with a trussed roof.
The floor has 2x8's for floor joists on 19.2" centers. The sub floor is 3/4" T&G Avantech sub floor panels. On top of the sub floor, I am planning to use solid bamboo snap together wood flooring throughout the entire house.

I originally planned to insulate the floor with cellulose by blowing it in from the crawl space after the sub floor is down, using the glue-on mesh made for that installation method. Then I would sheath the bottom of the joists with preforated pegboard followed by 1/4" hardware cloth for rodent prevention.

Now, I'm wondering if maybe I could just glue hard foam sheets over the sub floor and then the bamboo flooring over the foam.
It seems this would be a lot easier and simpler, but perhaps quite a bit more costly.

Would this be feasible ? And, if so:

What thickness of foam would equal the insulation value of 7.5" of cellulose ?

What kind of foam should I use; any suggested sources ?

And finally, would the foam need to be thick enough to where I would need to use a double bottom plate for the interior walls so that I would have something to nail the bottom of the drywall to ?

Or would it be feasible to just build the interior walls after the bamboo flooring is down (don't know how much that would interfere with the flooring's ability to 'float') ?

Thanks,
Arky

[JRR]

Another option is to sealed/insulate/warm the crawl space.  This keeps the floor structure away from cool/wet zones.  Makes floor penetrations less of a concern.  Just another way to skin the proverbial feline.

[MountainDon]

What is the climate zone or state the building will be in?  Climate can make a difference as to what works best or what is needed.

[Arky217]

What is the climate zone or state the building will be in?  Climate can make a difference as to what works best or what is needed.

Central/western Arkansas

[MountainDon]

Thanks, and pardon my ignorance, but is the structure already built or is this a question in the design stage. (There is so much going on I loose track of what's what at times. Sorry.)

[Arky217]

Thanks, and pardon my ignorance, but is the structure already built or is this a question in the design stage. (There is so much going on I loose track of what's what at times. Sorry.)

Pier/post foundation done, floor joists done (subfloor will go on after roof is on), exterior walls done, in process of setting trusses.

[MountainDon]

I'm not sure but I believe being in what is classed as a mixed humid climate complicates this.

I wonder if the rigid foam board could be applied to the underside of the floor joists and the seams sealed with tape or foam compatible caulk?  I believe I've seen this someplace (building science?) but can not put my finger on it. I think the joist bays were left empty, not filled with anything. And I think the rim joists were insulated with foam as well.      

The ideal insulation is likely something like sprayed on closed cell foam at least 2 inches thick against the underside of the subfloor and joists.

Try searching the buildingscience website for methods to insulate a raised floor in a mixed humid climate.


I had thought of doing rigid foam board on top of the subfloor with cement board then porcelain tile for our cabin. I didn't like the extra thick bottom wall plates, or whatever, that would be needed to secure drywall etc around the floor. It still has some appeal.... 

[cmsilvay]

We have rigid 1" foam board screwed to the joists and batt insulation in the joist cavaties. My location is is similair to the Arky OK/AR border.

[Grouseman]

Are you on piers or have a typical crawl space area?  If possible I would have foam sprayed at the subfloor level if on piers or spray foam on the concrete block foundation.  Only way to go in my opinion.

Grouseman

[Ndrmyr]

I'm in the process of insulating my walls, 2 x 6 infills for post and beam on 16" centers and I am using 3" closed cell foam board to insulate.  The short story is that I secured a bunch of vented nailboard at auction which is 4 x 8 sheets of 3" foam with 7/16 OSB stapled to furring strips that are glued to the foam which has firberglass cloth on both sides.  I used them on the roof and had extra so am separating the osb from the foam and using the foam for insulation.  It is easy to cut on a tablesaw although a jobsite saw will not raise the trunnion high enough to cut all the way through where a good 10" tablesaw would do so.  It is remarkably easy to rip them into strips which will fit so snugly that caulking doesn't appear neccessary.  If used on floor joists, I would cut some furring strips to act as cleats and air nail them in to hold the foam tight.  No worry about moisture, I would do it in an instant.  In my location, N. IL. there are two factory seconds foam distributors and I would suspect there may be some in your area also.  Truly worth considering.