Adding insulation to an attic is one of the best ways to improve the energy efficiency of a home.
What is R-value?
R-value is the resistance to heat flow that insulation has. In other words, it measures the amount of heat that is allowed to pass through the insulation. The higher the R-value, the better the insulation will be able to keep heat where it belongs.
Types of Attic Insulation
· Batt or roll insulation: fiberglass insulation made into long blankets. It can be purchased with or without a vapor barrier attached.
· Loose-fill insulation: made of fiberglass, rock wool, or cellulose. This type is blown in by machine.
· Radiant barrier: reflective material that may be backed by paper or plastic. It works by reflecting the sun’s energy away from the interior of the house. Radiant barriers are most effective in hot climates.
Before You Begin
Seal off any areas that might be leaking air into the house with caulk. Check any duct work for areas that need to be resealed. It is also advisable to have an electrician check the attic for any loose or bare wires, as these are fire hazards.
You can use this tool to determine the most economic level of insulation for your climate and situation.
When working in an attic it is important to walk only on the joists and not on the drywall in between. The drywall cannot support your weight and it is likely you will fall through. It may be helpful to place plywood boards around the attic for you to walk on, removing them as you work.
Be sure to begin your work at the perimeters of the attic and work your way towards the attic door. Compressing insulation lowers its R-value, so it is important to not walk on it once you have installed it.
Wear a dust mask and long sleeves, long pants, and gloves.
Batt insulation is the easiest to install. If the attic is not already insulated, simply roll out the insulation between the joists, cutting it with a serrated knife where necessary. If you are using faced insulation, be sure the vapor barrier is facing the correct direction (towards the interior in cooler climates, towards the exterior in warmer climates).
If there is already insulation in your attic, unroll the new insulation in a perpendicular direction to the existing insulation. This will minimize the compression of the existing insulation and will lessen the heat transfer occurring in the joists themselves. Be sure to either buy unfaced insulation or remove the vapor barrier from the roll before installing it over existing insulation.
Radiant barriers are used in combination with other insulation. They reduce the amount of radiant energy that is passed into the attic, thereby reducing the amount that must be absorbed by the other insulation. Radiant barriers are most often installed to the framing of the roof, either the rafters or the trusses, with the reflective side facing the open space of the attic. It should not be installed on the floor, as it will not work if it becomes covered with dust.
It is recommended that a professional install loose insulation as it must not cover vents or any equipment that produces heat. Special equipment is also necessary to blow the material into the attic. A professional will have a better idea of how much to add to account for the settling that will occur after installation.