Should I Insulate Between Floors?

Duringenergy audits, we get into a lot of building shell discussions. Should Iinsulate my basementor should Iinsulate my interior wallsto pick two completely random questions that I totally haven’t written about.

The question of whether you should insulate between floors is remarkably similar to that of insulating interior walls. At first blush, it makes some kind of sense. Heat is escaping everywhere, addinginsulation slows heat lossso why not? So should you insulate between floors?

To repeat from the interior wall post:
Short answer: No.
Long answer: Nooooooo.
Longer answer: Maybe, sometimes.

Should I Insulate Between Floors – The No Part

The reasons for not insulating are real straightforward. Thebuilding enclosure是一个分界线between your OPEC warmed house and New England’s annual winter trick or treat (but, but autumn was so awesome why couldn’t it stay like that). Everything including both sides of the flooring are inside the building envelope so both sides would be warm.

So simple answer: unless you have an extra $10,000 and a big hearted desire to create jobs in the insulation industry, it makes no sense to insulate between floors.

Doing so can even cause problems. Sticking yourvapor barriersthermal resistanceinto places besides the exterior building shell can create odd interior dynamics.

I’ll relate a story I told previously in the interior wall post. During a Maine Housing training program, we toured a state-owned building which included an indoor pool. The indoor pool had been filled in with loam. I have no idea why either.

The space was not piped for heating, as the pool had heated the space while in use. The interior walls and ceilings were insulated, eliminating a lot of heat radiating into the pool room.

This insulation inadvertently reduced room temperatures below the dew point. There wasa dehumidifierthat didn’t even come close to handling the room’smoisture load. Final tally: mold just about everywhere. Hoo…ray.

我应该隔离层-和吗Sometimes Yes

Because during these hard economic times, your generous doubling of the size of your insulation project is greatly appreciated. That said, there are scenarios where insulating between floors is done. If you have an indoor pool, sauna or similar high temperature, high moisture environment, it makes sense to have full vapor, thermal andair barriersin place.

Homes which have full home theatres or other sound equipment may desire sound proofing.Cellulose, fiberglass androck woolare excellent sound retardants and can greatly deaden sound when installed between floors.

Sometimes buildings are construction with first floor eaves and soffits. If the first floor soffits open into the joist bays, these should be air sealed and insulated.

Insulated between floors have very little if not quite no insulating benefit. However there are certain scenarios and reasons like sound proofing to insulate between floors.

5 thoughts on “Should I Insulate Between Floors?”

  1. So, what’s your verdict on the fact that some 25 to 30 years ago we insulated between our 2nd and 3rd floor? Love, Mom

  2. Hi, The information you posted s exactly what I need. I am building out an in-law apartment in the lower level of a split level house. I was going to use 2 inches of spray Tigerfoam insulation (designed for thermal but also is soundproofing) and then Rock Wool. The objective is to heavily reduce sound / noise.

    Are there any problems with this application?


    • Kelly,

      Thats for the compliment. Generally the approach you mentioned would work well except that I’m unclear how it is being used. Walls? Ceiling?

      In any case, remember that the Tiger Foam is closed cell foam and will act as an air and vapor barrier. When finishing, don’t add additional plastic sheeting to act as a vapor barrier or use latex based paint (also a vapor barrier).

      I don’t know your local building codes but odds are that the spray foam will require an ignition barrier. Finishing with drywall usually meets that criteria.

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