Ensuring your attic insulation is performing as required is always a great way to save money and make your home more comfortable. You can even prevent premature failure of shingles, sheathing and other roof components. If you are contemplating checking or adding to your insulation in your attic read these tips before committing to a product or contractor.
Thickness isn’t the only way to determine the effectiveness of insulation.
Materials that are good for insulating purposes are poor at conducting heat. To provide a standard of comparison for insulation materials, “R-value” is used to measure resistance to heat transfer. The higher the R-value per inch of insulation, the more effective the material in resisting the escape of heat.
For new housing, the 1995 Ontario Building Code requires:
R32 for Ceilings
R12 for Walls
R8 and R12 for solid masonry/ concrete/frame basement walls
R20 for cathedral ceilings
R26 for floors over unheated garages/crawlspaces/overhangs
When you buy home insulation, it’s a good idea to look for the manufacturer’s instructions on the insulation packaging to make sure it meets the standards set by the Canadian General Standards Board (CGSB). In 2007 the new building code takes effect and includes many upgrades to requirements for insulation and other “green” improvements.
Types of Insulation
Insulation has come a long way since the days when newspaper, sawdust or
woodshavings were used. The following are common examples of modern nsulation.
Loose-fill insulation: These include glass fibre, cellulose fibre, mineral fibre and vermiculite. Some of these, such as glass and mineral fibre, may be blown as well as poured. The R-value per inch varies from 2.1 to 3.6 depending on the type and insulation method.
Batt or blanket insulation: This is normally made from glass or mineral fibre. Batts come in different widths and thicknesses. The R-value per inch varies from 2.9 to 3.3 according to the type. The total R-value of the batt depends on the thickness.
Rigid board insulation: Included in this type of synthetic insulation are
extruded polystyrene, expanded polystyrene, phenolic foam board and polyurethane slabs. Though the R-value of these products is rated at 3.9 to 6.0 per inch, great care must be taken to ensure they are properly installed or they could create a severe fire hazard. Rigid board and foamed insulation will burn, and should never be left exposed. They must be covered with an interior wall or ceiling finish acceptable to the Ontario Building Code, such as gypsum board, gypsum lath, fibreboard, plywood, particleboard or wall tile.
Foamed insulation: Polyurethane foam is a relatively new product and must be installed in walls by factory-trained installers. Complex equipment and mixes are used, and improper installation could cause damage to your house. The R-value of polyurethane foam is about 6.0 per inch. This material hardens almost immediately, can catch fire and should be completely covered in the manner described in the Ontario Building Code. Polyurethane foam is now available pre-mixed in pressurized containers. These are either hand-held spray cans for smaller jobs such as sealing of drafts around window frames, or large “floor” canisters for heavier use.
When choosing the type of insulation you need, think about resistance to water, bacteria and household pests, the cost, ease of application and perhaps rigidity/flexibility. Check with at least three different contractors or building supply companies to find out what is best for your application. Your local Canada Mortgage and Housing Corporation office can tell you which material has been approved by the CCMC, or your local building center.
Vapor Barriers and Ventilation
Under winter conditions, the warm moist air inside heated spaces passes into the cold outer areas of the building and condenses in roofs and walls. To control the movement of moisture into other areas, vapor barriers should always be installed on the warm side of the ceiling or wall. Good ventilation in attics and roof spaces helps keep the insulation dry and retains its effectiveness, prevents mould growth, corrosion and wood rot and reduces paint peeling problems.Even houses that have a properly installed vapor barrier allow some leakage into
the walls and attic. In all cases, moisture must be allowed to escape to avoid problems. Outside walls generally allow vapor to escape freely as they are not airtight–but attics require ventilation. If you see frost on the undersife of your sheathing in the winter you know you have a moisture problem in your attic which needs immediate attention. Common causes are; bathroom exhaust fans that vent directly into attic or a duct that has become disconnected; or your stove exhaust maybe improperly vented into your attic. If this is not within your comfort level of “Do It Yourself” projects, call in an expert and save yourself the agony of a more expensive repair in the future.
There should be one square foot of unobstructed ventilation opening for each 300 square feet of ceiling. These openings should be located to establish good cross ventilation with one-half the required vents to be in the soffit and the other half on the roof near the ridge or high in the gable ends. Don’t forget that every home needs a good supply of fresh air. Just as we need air to breathe, fuel-burning appliances need air to operate safely. A special duct to supply outside air may be needed. 25% of ventilation is required from soffits and 25% from top of attic, the remaining 50% can come from any location. Built up wood soffit vents are the correct method of venting soffits although building inspectors will allow use of Mor-vents or Sur-vents, a foam product designed for soffit venting.
Doing it yourself?
If you’re going to work in the attic, follow these safety guidelines;
Provide lots of light, take up trouble light and extension cord and hang it from a central location. Don’t walk on the ceiling–you will fall through. If not used to walking on rafters and trusses lay boards on joists to form a walkway. Always wear a hardhat for protection from protruding roof nails and bumps. Wear coveralls, gloves and a breathing mask if you are working with glass or mineral fibre. Animal and roden feces is dangerous to your health. If you suspect you have mould or feces in your attic, don’t enter and call in the experts. Always wear breathing mask and use goggles to prevent eye irritation.
Watch for electrical wiring. Do not disturb.
Keep insulation at least three inches away from electrical equipment
and chimneys. Use only CCMC approved material and don’t block the ventilation from the eaves.
If there is no vapor barrier, consider installing one, taking care that it’s placed on the warm side of the wall or ceiling you’re insulating. Vapor barriers should never be placed on the cold side of insulation.
Whether or not there is a vapor barrier, major air leakage into the attic from the rooms below should be sealed off before adding insulation. Common air leakage areas are around attic hatches, chimneys and plumbing stacks and up through interior walls.
Have a look
When the contractor tells you the work is completed, have a look for yourself. If you contracted for eight inches of insulation in your attic, take a ruler and measure.
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