Insulating Your Attic

The easiest and most cost effective way to make your home more efficient is to add insulation to your attic. An attic with too little insulation is wasting your energy dollars both winter and summer.
 

You or the contractor you hire should complete a number of preliminary steps before insulating your attic, as follows:

• Inspect the room, ceiling, or attic floor to identify previous or current moisture problems. Check the roof framing, sheathing, finish and the soffit and fascia for signs of moisture (mould, mildew, fungal growth or rot are sure signs of advanced condensation problems). Moisture can come from the outside due to failure of the roof or flashing. Typical problem areas include poor flashing at the hip, valley or the chimney, around bathroom and kitchen vents that penetrate the ceiling, around plumbing stacks and chimney chases and at wiring penetrations and pot lights. Moisture can also come from inside the house, carried into the attic as water vapour by air leakage. Do not install insulation in these areas until any moisture problems have been corrected.
• 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.
   
• Install permanent blocking to prevent loose-fill insulation from clogging soffit vents at the eaves. (This would restrict attic ventilation.)
• Cover wall and drop ceiling cavities to prevent filling these areas with insulation.
• Is the attic accessible? The hatch should be large enough to allow you to bring in materials.
• Check your electrical system. Any wires with frayed or torn insulation will have to be replaced before insulating.
• Check and examine your existing insulation. Replace any damaged insulation.
• Check for wet insulation. Don’t cover it until the source of moisture is removed and the insulation is dry.
• Check the depth of insulation. Make sure the insulation is distributed evenly.
• Check your existing air and vapour barriers. Most houses have a vapour barrier on the warm side of the 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-32 to R-40 is preferable in most instances, but is not always possible. You will also want to determine whether to install fiberglass or cellulose.

If there is six inches of insulation in the attic or roof, it may be hard to justify the cost of installing more according to the principle of diminishing return on investment, in which case you can focus your energy efforts on uninsulated areas first.

Adding insulation to an unheated attic that has no flooring is fairly easy. Simply add batts or loose-fill between the floor joists. Keep insulation away from heat producers like recessed light fixtures or exhaust flues. Also, be sure the insulation does not block attic ventilation. Use plastic or styrofoam air channels to the under-side of the roof to keep the passage clear. When loose fill insulation is installed, its a good idea to clean the soffit vents afterwards to assure they are not blocked.

If the attic has some existing insulation, you can add additional loose fill or apply another layer of unfaced batts at cross angles to the joists. This alignment of the batts helps cover gaps between the first layer of batts.

If the attic is a finished living area, insulate the ceiling and walls. Some of these areas may be readily accessible, but others may be covered with finished interior wall or ceiling materials. Check to see if there is insulation behind them. If there is none, your choices are to blow in loose fill from outside the home or strip off the finished wall and ceiling materials and install batts or blown insulation from the inside.

Ceilings that are also roofs can be big energy losers. For types with attractive beams and exposed roof boards, one solution is cutting panels of rigid insulation and installing them between the beams. Most types of rigid insulation must then be covered with wallboard for fire safety. With ceilings considered too attractive to cover, insulation can be added during a re-roofing project.

While in the attic, see if there is insulation on the attic door or hatch. These areas can be insulated by attaching a fiberglass batt to the upper side, or for entrances with pull down ladders, you may need to buy or build an insulated box to cover it. While it may seem inconsequential, the attic entry door is often a significant percentage of the total attic floor area. It should also be weather-stripped for a tight seal.

Batt insulation is simply pressed into place between the ceiling joists. If you purchased the correct width, it will fit snugly. However, if the joist space is not standard 16 or 24 inches, extra labour will be required to cut and fit batts properly. Loose-fill insulation is an option worth considering in this situation.

The following are some other installation tips:

1. Butt the ends of batts together as snugly as possible.
2. Batts should cover the top plate of the exterior wall but not block the venting. To prevent this space from being blocked, use baffles between each rafter space.
3. Insulate snugly around cross-bracing. You can also cut one batt into a series of wedges and then fit a wedge under each brace.
4. The first layer of batts should be thick enough to completely fill to the top of the joist space. The second layer can then run in the opposite direction, across the joists, blocking any heat flow through and around the joists.
5. Fill any awkward spaces or gaps with pieces of batt or with loose-fill insulation.
    

Loose-fill insulation can be poured by hand or blown in either by the homeowner with rented equipment or by a qualified contractor. The following are some installation tips:

1. Loose-fill insulation can be poured on top of the air and vapour barrier. Level it with a board or garden rake. It’s best to try and maintain an even depth throughout the attic.
2. Pour the insulation to fill all nooks and crannies.
3. At the eaves, take care to keep the insulation from blocking the ventilation or from disappearing into the eaves space. Be sure the insulation extends out far enough to cover the top of the exterior wall.
4. If your loose fill is deeper than the joists, build a crib around the attic hatch so that it can be filled to the edge.
5. Make sure the required RSI value is to standard R32.
6. Don’t forget to insulate around your chimney.
7. Do not cover recessed light fixtures and be careful not to insulate too closely around flue pipes and gas vents.
8. Don’t forget to seal the attic hatch.
    

It is very important to prevent moisture-laden air from inside the house from entering the attic. 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 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.
 

Newfoundland Power offers rebates and financing for attic insulation upgrades in electrically heated homes. Click here for details.

To obtain more information on insulating your attic, click here to view Natural Resource Canada's publication “Keeping The Heat In” online or to order a printed copy.