While previous generations may have been content to live in drafty houses, most people now want comfortable warm houses. A healthy house today is well sealed, well insulated, and properly ventilated.
A well-insulated house is a bit like dressing for the weather. A wool sweater will keep you warm if the wind is not blowing and it is not raining. On a windy, rainy day, wearing a nylon shell over your wool sweater helps keep you reasonably dry and warm. A house is similar. On the outside, underneath the brick or siding, there is an air barrier that does the same thing as the nylon — it keeps the wind from blowing through. Then there is the insulation (like your sweater) and a vapour barrier, which helps keep moisture away from the house structure where it can do damage.
Signs of Insulation Problems
In the winter
In the summer
Insulation Effectiveness
R values and their metric equivalent, RSI values, are a way of labelling the effectiveness of insulating materials. The higher the R value or RSI value, the more resistance the material has to the movement of heat. Insulation products sold in Canada are labelled with R and RSI values. Provincial building codes specify minimum R (or RSI) values for new construction, with different values for different applications. It is important to know what your local building code requires when planning new construction.
Note: The way the insulation is installed plays a large role in its effectiveness. Compressing the insulation, leaving air spaces around the insulation and allowing air movement in the insulation all reduce the actual R value of the insulation.
Table 1 Characteristics of common insulation materials
|
Insulation Material
|
R/in. (RSI/m)
|
Appearance
|
Advantages / Disadvantages
|
|
Batt-Type
|
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| Fibreglass |
3.0 – 3.7
(21 – 26) |
All batts come in plastic-wrapped bales. The products are like fibrous blankets, about 1.2 m (48 in.) long and wide enough to fit snugly between wall studs. | Readily available. |
| Mineral wool |
2.8 – 3.7
(19 – 26) |
Same as fibreglass. | Somewhat better fire resistance and soundproofing qualities than fibreglass. |
| Cotton |
3.0 – 3.7
(21 – 26) |
Not readily available. | |
|
Loose-Fill
All loose-fill insulations typically require a professional installer. |
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| Fibreglass |
3.0 – 3.7
(21 – 26) |
A very light fibrous fill, usually pink or yellow. | Can be affected by air movement in attics. |
| Mineral fibre |
2.8 – 3.7
(19 – 26) |
A very light fibrous fill, usually brown. | |
| Cellulose fibre |
3.0 – 3.7
(21 – 26) |
Fine particles usually grey in colour, denser than glass or mineral fibre. | Provides more resistance to air movement than other loose fill insulations. Can have settlement problems if not installed properly. |
|
Board-Stock
|
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| Type I and II (expanded) polystyrene or EPS | 3.6 – 4.4 (25 – 31) |
White board of small — about 8 mm (0.3 in.) in diameter — foam beads pressed together. | Typically HCs used in production. Must be covered. |
| Type III and IV (extruded) polystyrene or XPS | 4.5 – 5.0 (31 – 35) |
Commonly blue or pink foam board. | Works well in wet conditions, can act as a vapour retarder. HFC usually used in production. Must be covered. |
| Rigid fibreglass | 4.2 – 4.5 (29 – 31) |
A dense mat of fibres, typically less rigid than polystyrene. | Drains water away. Sometimes hard to find. |
| Rigid mineral fibre | 4.2 – 4.5 (29 – 31) |
See "Rigid fibreglass" above. | Drains water away. |
| Polyisocyanurate | 5.6 – 6.7 (39 – 46) |
Foil-faced rigid foam. | HFC usually used in production. |
|
Spray-Applied
All spray-applied insulations fill cavities very well. They must be applied by a specialized contractor. |
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| Wet-spray cellulose | 3.0 – 3.7 (21 – 26) |
Fine particles held in place by a binder. | |
| Open-cell light density polyurethane | 3.6 (25) |
A soft, compressible spray foam that expands into the cavity. | Can act as the air barrier if combined with another material. Must be covered with a vapour barrier. |
| Closed cell medium density polyurethane | 5.5 – 6.0 (38 – 42) |
A rigid spray foam that expands into the cavity and sets up fairly rigid. | Can act as the air barrier and vapour retarder. HFC used in production. Must be covered. |
| Note: All values are approximate and for general comparison only. Some insulations may be irritants or hazardous during installation. Consult manufacturers' recommendations and insulation packaging for proper respiratory, eye and skin protection. | |||
Effective Insulation Systems
Effective insulation systems slow the movement of heat and deal with the movement of moisture at a reasonable cost. To do this, they have the following:
Wall Insulation for New Construction
Typically, this is a wood-frame wall with the potential for insulation in the stud cavity (batts or spray-applied) and on the exterior face of the studs (rigid insulation). See Figure 1. During planning and installation, note the following:
Figure 1 Effective thermal resistance: R 16.7 (RSI 2.94)
Wall Insulation for Existing Construction
The two most common wall types are wood-frame and solid brick. In a wood-frame wall, insulation (loose fill and some foams) is typically blown into the cavities through holes that have been drilled through the drywall or siding. In solid brick, the largest cavity is usually 25 mm (1 in.) wide, which is not enough for any significant increase in R value. The builder must create a cavity. Usually, a new cavity wall is built inside and insulated as a new wall, or board stock and new siding are applied to the exterior. When planning a cavity wall retrofit, remember the following:
Attic Insulation
The attic is often the most cost-effective place to add insulation. Usually, a contractor blows loose fill into and over the top of ceiling joists. For the do-it-yourselfer, batts laid sideways on existing insulation are an easy alternative.
Basement Insulation
Basement walls are unique because they must handle significant moisture flows from both inside and outside the house. The preferred method, from a building science perspective, is to insulate the wall on the outside with rigid insulation suitable for below-grade installations, such as extruded polystyrene or rigid fiberglass.
The advantages are as follows:
The disadvantages are the disturbance of landscaping, the need to cover the insulation above grade, and the relatively high cost.
Interior insulation can be used. This can be done when finishing the basement by using batt insulation in the stud cavities or by installing extruded polystyrene and strapping on the face of the perimeter walls. If the basement won't be finished, you can install rolls of polyethylene-encapsulated fibreglass over the wall. The advantages of interior installation are cost and ease of construction. The disadvantages of interior installations are as follows:
Never apply interior insulation to a basement with moisture problems. Fix the moisture entry problems before insulating (see CMHC's publication A Guide to Fixing Your Damp Basement).
The right insulation system can save you money, reduce the amount of energy you use and make your home more comfortable. Keep in mind that installation costs (including changes to the framing, cladding, and finishes) are usually the most expensive part of an insulation project. The local climate has an impact on the cost-effectiveness of any insulating project.
Check the cost, heat loss and heat gain of all available options. Review all details to ensure that moisture movement is handled correctly. You can then select the right insulating system. When in doubt, consult a professional.
The Final Analysis
If your home is poorly insulated, it usually pays to upgrade the insulation. If you are building a new home, it makes sense to insulate well now, so you don't need to retrofit later.
Need more information and have questions? Contact C4U Inspections today
Serving the Okanagan Since 2005
