I looked at my thermostat last night, and it read 75˚. To me, it means we're officially getting away from the last bits of the summer weather. I live in a rowhouse with neighbors on either side, so it takes a while for the weather to really change my indoor temperature. In fact, my heating and cooling bills are significantly lower than my friends who live in detached houses, despite the fact that my old house has little to no insulation in the walls.
A major source of heat loss in any house, however, is through the roof. Many of us have too little insulation up there, or poorly installed insulation. The current energy code requires insulation levels of R-38 in attics, and it may be higher depending on where you live. You can achieve this by using 12" of fiberglass batt insulation (the yellow or pink cotton-candy-like stuff), 13" of loose-fill insulation (the loose, cottony stuff), or 6"-10" of expanding foam insulation (the rigid stuff that fills cracks).
(top) Fiberglass batts; image from http://insulation.owenscorning.com
(middle) Loose-fill; image from http://www.northerninsulation.biz
(bottom) Spray-foam; image from http://www.innovativeairsolutions.com
Now, I could go on and on about all the reasons why you'd choose one of these products over another, but I'll just give you the main reasons and leave the details for another day. The main factors you'll consider are:
- Accessibility of the space that needs insulating,
- Space available to accommodate the desired insulation thickness,
The most important thing, in any case, is to make sure that the insulation is installed properly. Otherwise, it's a waste of money and effort. The goal is to have a continuous layer of insulation, with a minimum of gaps and breaks where heat can escape. A major culprit is recessed lighting, so I want to give a brief description of the ideal situation.
Ideally, your recessed lights are IC-rated. You can find out whether they are by looking at the sticker inside the light (see below). If the sticker has been removed, it's best to assume the fixture is NOT IC-rated, and contact an electrician for verification. "IC-rated" means that the fixture is designed for "insulation contact". This is good, because it means that the insulation can come all the way up to--and over--the fixture without creating a fire hazard. Non-IC-rated fixtures require a three-inch gap between the fixture and any surrounding insulation, leaving lots of room for heat to move.
Recommended lamp table with IC requirements; image from http://www.iaei.org
The other thing to see is whether your fixture is gasketed. The gasket is a rubber ring or fin that goes around the fixture (under the trim), closing up the gap between the fixture and the ceiling around it. It acts the same way weatherstripping does on a door, keeping air from passing through the gap.
The final culprit for energy loss is the attic access itself. In my house, I have a hatch that I lift and slide over. The top of the hatch has fiberglass batt insulation glued to it. Not a perfect solution, but better than nothing. If you have a pull-down stair to your attic, you can get an insulation cover like this one on amazon.com. If you have a stairway up to your attic, you should have insulation in the walls and weatherstripping around the door.
If you find that your attic insulation is sub-par, you can often remedy it yourself by heading to your local home improvement store. Many insulation products are easy to install yourself. When it comes to lighting, it's best to leave it to the pros.