We just moved into an apartment above a garage, and have had some exorbitant heating fuel bills. To our dismay, we just noticed that the garage ceiling (apt floor) has no insulation. After we complained to the landlady about the heating bills, she offered to reduce our rent throughout the winter months to help defray the cost of heating. We were considering asking her, instead, to buy insulation that we could install ourselves. So, I'm wondering whether or not it is possible for us to do this kind of job (the rafters in the garage are covered by some flimsy particleboard); what kind of insulation to buy (given that the heat flow is downward); and how much we will have to ask her to fork out for this (the apartment is about 950 sq. feet).

Thanks a lot!

 

There's more going on here than you realize. First, insulation or no, THAT GARAGE CEILING IS ILLEGAL!!! If you have living space above the garage, the garage ceiling HAS to be a firewall! That means 5/8" Type "X" sheetrock, not "some flimsy particleboard".

Once you take the particle baord down, you'll know what size joists (2X6's, 2X8's or whatever) you are dealing with between the garage and the apartment. That will determine the proper insulation you need to install. (2X6's = R-19, 2X8's = R-25, etc.) After the insulation is in place. install the 5/8" 'rock, and tape the joints. I would make sure that the landlady has a bldg. permit for all this work, just to insure that the 'rock is hung properly, if for no other reason.

 

Lefty is correct, and if I may make an addition to his reply, I looked up the code for your area. It says the floor must be R-19, however, it also says that a ceiling must be R-38. Which will present another problem. The local building board may very well say use the R-38 for the garage ceiling.
What you want to do will definetly require a building permit.

 

I agree with much of the previous answers with the exception that I would do the ceiling then have cellulose installed. It will be somewhat more expensive but the benenfits are worth it. It has a better R-value, a tighter seal, and better sound deadening characteristics. More than this, considering it is over a garage, the fire retardency is much better. Note: Make sure that vehicles are never "warmed up" or left idling in that garage, even with the door open!