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I'm learning many things about our new home. This winter I learned that a room directly above a garage stays much colder than the rest of the house (up to 10+ degrees colder in our case). What options exist to eliminate or reduce this problem? Is there some way I can easily increase the insulation without having to tear floors up, or open up ceilings - or is that the best option available to me?

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Is the garage insulated? –  msemack Jan 14 '11 at 13:49
    
@msemack I'm not so sure the ceiling is, but I believe the walls are. –  Jonathan Sampson Jan 14 '11 at 15:53
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Mike Holmes did an episode about this in season 3 of "Holmes on Homes", the episode was called "Cold Feet". If you can find it on the net, it might give you some ideas on how to tackle the project. –  Tester101 Jan 14 '11 at 20:01
    
Mike Holmes is my mentor. I have incorporated a lot of the tougher Canadian practices here in Maine with my customers. –  shirlock homes Jan 14 '11 at 20:57

3 Answers 3

up vote 18 down vote accepted

Jonathan, your problem is very common. Do you know what is in the floor for insulation now? Assuming there is some f/G batts or something similar, it would be hard to try to add anything else, such as high density cellulose directly into the cavities. As much as you probably don't want to hear it, the best way is going to remove the sheetrock from the garage ceiling and remove the existing insulation. With the framing completely open, be sure to seal all holes through joists and floor areas where wires or other components may pass thru with foam. The absolute best insulation would be to have a high density foam sprayed into each bay and into any voids along garage door headers etc. This would give you the maximum R value and absolutely stop any cold air infiltration to the bedroom above. The goal would be to achieve an R value of 30 or more. The alternate method for DIY would be to again, seal any air passage ways and door headers with spray foam, then carefully install the max amount of f/g blanket and cover entire field with 4 mil poly and tape all seams and edges with tuck tape before reinstalling your fire rated sheetrock. This is not the best solution as the r value of the f/g is going to be limited by the size of the joists. 2X8 for example will limit you to about an R 23. A slightly higher R value could be achieved with blown in high density cellulose after sheetrock is installed, in place of the blanket f/g insulation. The spray foam is definitely the best overall, but the most expensive as well.

In response to Sharp Tooth's answer, too long for comment section: I have seen 2 to 4 inches of rigid foam insulation added to garage ceilings in this situation. The only drawback of this method is the problems it causes with garage door openers and suspension hardware. It also can cause issues with overhead lighting and overall head space. I hate to be a nay sayer, but I have to negatively comment on your other suggestions. Insulating a garage that does not have new style insulated, airtight doors is a total waste of money. Likewise, trying to heat a garage that is not build to be energy efficient can be extremely expensive to install and fuel, especially if a separate zone or plumbing needs to be added. This is not a viable solution as every time the garage door opens, out goes all that expensive heat. Carpeting, even over a thick foam pad will not help much either, maybe a gain of 2 to 4 "R", quite negligible. I hope you were not serious about heat tape under the ceiling. Other than electric or forced hot water radiant heat grids that would be installed under the floor, not under the ceiling, there is no safe product to do what you decribed. It would not work anyway, since the source of heat would be on the wrong side of the insulation and the vast majority of the heat would be wasted into the garage air. Sorry to shoot down your suggestions, but I truly believe questions should have informed, proven solutions, not wishful guesses.

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You'll also want to make sure that the garage is sealed off from the room above, you don't want any fumes that may accumulate in the garage to infiltrate the living space. The best option here is to remove the garage ceiling and properly spray foam the entire area, then install vapor barrier to prevent any moisture or fumes from leaving the garage. The cost may be high upfront, but you will save on your heating and cooling cost after. –  Tester101 Jan 14 '11 at 13:03
    
Thanks Jeff for combining my answers, definably reads better now. –  shirlock homes Jan 15 '11 at 11:50

Surely the most direct way is to open up the ceiling or the floor and add the insulation there. Other than that you could try the following:

  • put a thick carpet onto the bedroom floor so that it covers the entire floor, however this won't help much since carpets are quite thin
  • add another ceiling and install insulation above it (or just install insulation onto existing ceiling and leave it uncovered, which might be okay for the garage) - will work, but will consume space under the existing ceiling
  • insulate the garage so that it doesn't cool that much
  • install a heat source in the garage to compenstate for the heat lost by the garage
  • install a heating cable under the ceiling to compensate for heat lost by the bedroom (this should be well thought so that you don't set the house on fire).
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I wouldn't install a heat source in the garage, or heating cable. This should be done purely by insulating below the ceiling of the garage or the floor of the upper room. –  Mark Robinson Jan 14 '11 at 15:26

Firstly remember that it is the first bit of insulation that has the best payback, so don’t overlook the option of putting down a thick carpet – not the best solution, but it may cut down heat loss in the short time for very little effort.

Another option that not the best solution but will help if you don’t mind the down sides. In the UK (and I assume the USA) you can get insulated boards for boarding lofts, these have a chipboard top that is fixed to solid insulation. You could lay these over the floor in the room, sealing any gaps. However:

  • The floor height will be increased, so you will have a step up into the room and the doors may no longer fit.
  • You may get problems with condensation forming in the floor.
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