Attic or Ceiling Insulation
An attic with too little insulation is wasting your energy dollars both winter and summer. Insulation is designed to resist heat flow in either direction and should be installed between conditioned and unconditioned areas of a home. The most common forms of insulation include fiberglass batts and cellulose or fiberglass loose fill.
Insulating with loose-fill fiberglass and cellulose or fiberglass batt insulation is relatively inexpensive, and usually pays for itself in two to eight years, depending on the situation. Fiberglass batts can be easily installed by the average homeowner. Cellulose or loose fiberglass is typically installed using an insulation blowing machine. For small areas or "topping off" existing insulation, either material can be poured and spread out by hand. For larger areas, consider using an insulation contractor or check into the possibility of renting an insulation blower.
Insulation levels are referred to by R-value. The R-value of a given insulation material is an indication of how well it resists the transfer of heat. The higher the R-value, the more it will reduce heat loss or gain.
The first step in determining the need for more insulation is to measure the existing insulation. Keep in mind that adding more insulation has diminishing returns. For example, the first R-12 of ceiling insulation pays for itself very quickly, whereas the next R-12 added will have a longer payback.
Attic Insulation
The amount of insulation you can install in your attic is determined by the size of the joists and whether or not your attic has a floor. A settled density of R-40 is preferable in most instances, but is not always possible. You will also want to determine whether to install fiberglass or cellulose.
Preliminary Steps
You or the contractor you hire should complete a number of preliminary steps before insulating your attic, as follows:
- Identify all recessed lighting fixtures, vents, chimneys, and other heat-producing devices in all areas where insulation is to be installed. Recessed light fixtures (potlights), unless CSA approved for covering with insulation, can only be insulated if they are protected by a large enough box to keep them from overheating. A wood or drywall box either 35cm wide x 1.2m long x 30cm high (14" wide x 48" long x 12" high) , or 53cm wide x 74cm long x 30cm high (21" wide x 29" long x 12" high) placed over a pot light will, as a rule, keep it from getting so hot that it creates a fire hazard. Caulk all joints and seams in the box and caulk the bottom of the box to the ceiling. Also, caulk where all electrical wires penetrate the box. (The idea is to create a perfectly airtight separation between the ceiling and the attic.) The sides and top of the box can then be insulated.
- Inspect the room, ceiling, or attic floor to identify previous or current moisture problems. Signs include paint peeling, warpage, stain, fungus growth, rotting, or other structural damage. Do not install insulation in these areas until any moisture problems have been corrected.
- Inspect the ceilings to ensure they will carry the weight of the insulation. (In most cases this is not a concern, as both fiberglass and cellulose weigh very little.)
- Install permanent blocking to prevent loose-fill insulation from clogging soffit vents at the eaves. (This would restrict attic ventilation.)
- Seal all air leaks into the attic from from the house, particularly around plumbing stacks and attic hatches.
- Cover wall and drop ceiling cavities to prevent filling these areas with insulation.
- If knob and tube wiring is present, a licensed electrician should certify that insulation can be safely installed.
Once the above steps have been completed, insulate all attic areas to the maximum settled density possible, usually R-40. A floored attic may limit the amount of insulation that can be installed. To maximize your energy savings, insulate all attic entryways such as hatchway openings, kneewall access doors, and walk-up stairways.
Attic Ventilation
Conventional wisdom is that attics should be ventilated to the outside to keep them cooler in summer and drier in winter. The truth is that ventilation in accordance with current building code rules will do little to keep an attic cool in summer, and will control moisture in attics only if there is a continuous and effective air barrier between the attic and heated space below. An attic can be ventilated to "Code" or above, and there can still be moisture problems. It is very important to prevent moisture-laden air from the house from entering the attic. (See "Seal all air leaks..." above.) Wind turbine exhausters are not recommended as a solution to moisture problems in an attic as they will increase the pressure differential between attic and house, and if there are any air leaks from house to attic, may actually increase the moisture level in the attic in winter, and also increase heat loss. It is wise, however, to install attic vents to current building code requirements.
Differences in home construction and design are a major factor in choosing the right type or combination of vents. Vent location, style, and size are all factors to consider when insulating your attic.
A qualified contractor will know the formula by which to determine how much ventilation you will require. Important factors in the formula include the existence of vapour retarders, location of existing ventilation in relation to the eaves, and square footage of the attic.
The contractor should be able to tell you the type, number, and location of all vents to be installed. Choices will include roof vents, gable-end louvres, rectangular louvres, soffit vents, ridge vents, and turbine vents. All necessary precautions should be taken to ensure a watertight installation..
