Floor insulation required?

[Sifu]

Trying to apply some critical thinking here. If a house has a sealed and "conditioned" crawlspace with insulated walls under a "basement" floor system there is no floor insulation. The room above also has some unconditioned spaces with fully insulated walls, interior and exterior. The spaces are not within the conditioned space. Contractor has not installed floor/ceiling insulation above these spaces. I contend they should be insulated. The crawlspace "gets away" with not insulating the floor because of the thermal mass of the earth which is contained by the insulated walls. The story above does not benefit from the thermal mass (at least not near as much)of the earth, therefore the insulation would not have any heat to retain which would cause a cold floor above.

When I type this stuff out it seems pretty confusing. The house is on such a slope the basement floor is wood framed with a sloped crawl under it from 2' to 7'. They poured the foundation/basement walls without any provisions for ventilating the under-floor space so I told them at frame they needed to figure something out.

Following me? Insulation in the floor above the unconditioned spaces or not?

 

[SCBO1]

If the question is: Insulation in the floor above the unconditioned spaces or not?

IMO, The unconditioned area above a conditioned room would need insulation in the floor/ceiling and would require insulation even if that space does not have floor sheeting attached to the FJ/CJ above the conditioned space below. (Like a knee wall area where the floor and wall gets insulated but not the roof line).

pc1

 

[Sifu]

The more I think about it the more I think its a no brainer. If an unheated basement requires insulation in the ceiling to separate the conditioned rooms above why wouldn't the same go for an unvented crawlspace situation like this. I've just never had this situation so I've never had to think about it. It boggles my mind why someone wouldn't want a warmer floor versus a colder floor anyway.

 

[mtlogcabin]

CONDITIONED SPACE. An area or room within a building being heated or cooled, containing uninsulated ducts, or with a fixed opening directly into an adjacent conditioned space

If there is a fixed opening between the basement and the conditioned space above then the basement is considered "conditioned" like wise for the space you are concerned about. What is the use of the "space" you are concerned about?

 

[Sifu]

The condition is this:

A basement which is 1/2 finished, heated and thermally isolated from the outdoors and from the portion that is unfinished and unheated. The unfinished and unheated spaces contain insulated ducts, exterior walls, windows with insulation and are used for mechanical equipment and storage. There are two or three isolated rooms like this leading off of the finished space and they are separated by insulated, weatherstripped doors. The entire story is over a "sealed" crawlspace with insulated walls. Some of these areas will undoubtedly be finished in the future. I contend those rooms will be cold rooms, unconditioned and outside the thermal envelope, all according the definitions contained in the IRC, which are a little different than the definition by mt.

 

[mtlogcabin]

I see your problem now that I looked at the definitions in the IRC in lieu of the energy code that I quoted and we use.

I will have to agree with you, condition the spaces or insulate (floors)between the conditioned and non-conditioned space as defined in the IRC that you are using

 

[jj1289]

If the structure was deisgned to the prescriptive requirements of Chapter 11 of the IRC then insulation is required. If the house was designed using the REScheck it is possible to pass without insulation the floor.

 

[Sifu]

They insulated. I don't think it could have even passed a rescheck if you entered in the spaces as unconditioned, but it doesn't matter, they ended up seeing it my way.