Energy Efficiency: Insulation #2
How much insulation do you need?
It depends on the severity of your winters, the intense heat of your summers, how you heat or cool your home and how much you can get into the area you want to insulate. You will probably want at least R-30, which is equivalent to about ten inches of insulation, in your attic.
What else do you need to know before you insulate?
Don’t forget about the vapor barrier. Standard insulation rolls and batts have a vapor barrier on one side. The Vapor barrier should face the heated living space. With loose fill, put down six-mil polyethylene before installing the insulation, unless the spaces are so irregular or inaccessible that such a vapor barrier placement is impossible.
Be sure to place insulation our far enough to cover the top of the outer wall. At the same time, be sure you don’t block the vents under the eaves, if there are any. That may mean putting a piece of scrap wood or cardboard at each end of each run with the loose fill to avoid plugging necessary ventilation.
In all likelihood you’ll be running into light fixtures and a maze of wires up there. Unless the fixture is labeled “IC,” be sure that it isn’t accidentally covered during installation. Put baffles around the light fixtures and check for a minimum three-inch clearance. Insulation should never be in contact with bare wires. BARE WIRES! Call the electrician!
The loose fill is fire-resistant and can be in contact with the boxes that hold electrical connections. With batts and blankets, be sure that any paper coverings are peeled back or cut off to at least three inches away from any electrical junctions or fixtures.
Let’s say now that you have an unfinished attic, but the floor is already in place. If you’re not going to use the attic, and there’s no reason at all to heat it, now or in the future, your best bet will be to put insulation between the ceiling and attic floor. If you want to do it yourself, you will need to take up the floor and put insulation between the exposed floor joists. Then you can put the floor back down again so the attic can be used as unheated storage space. The contractor will need to remove several boards, but will then be able to blow the insulation the length of the joists.
Alternatively, let’s suppose the attic space is going to be used as a sewing room, play room workshop or other purpose that requires heating. Then you’ll want to insulate the roof.
Chances are your roof beams are on 24-inch center, so there will be standard batts in the six-inch fiberglass or rock wool insulation that will fit for insulating the roof. If yours is an older house you may not have those standard spacings, in which case you’ll have to cut batts to fit, or buy sheets of polystyrene foam board and cut to fit. If you use the polystyrene foam board, the way to buy is the “R” numbers. In general, these panels have high insulation value for their thickness. Again, try to insulate to R-30 or more if possible.
Caution. These foam panels release deadly fumes if there is a fire in your home. They should be covered with Sheetrock to minimize that danger and meet most fire codes. More insulation information will be presented in the next few days.
Taken in part from 547 Tips for $aving Energy in Your Home by Roger Albright