Insulation & Weatherization
- What does the term "R-value" mean?
- How much insulation should I have in my attic?
- If I install more insulation in my attic, what type should I use?
- How much insulation should I have under my floor?
- My home is built on a slab – is there a way to insulate my floors?
- Is it better to insulate the attic floor, the roof, or both?
- Is it a good idea to add additional insulation to my walls, and how is this done?
- Can I compress 15cm (6 inch) R-19 batts to fit into a 2"x 4" cavity, and will it be more effective than 9cm (3 1/2 inch) batts?
- I've always heard that "heat rises". Why do I need to insulate my floors?
- If the walls and ceiling of my home are well insulated, do I really need to insulate my basement? What is a "vapour barrier" and how important is it?
- I've heard that you can make a home "too tight" – should I be concerned about this?
- Is it better to caulk my windows and doors on the inside or the outside?
- How much ventilation should I have in my attic?
- How much ventilation should I have in my crawlspace, and should the vents be closed in the winter?
- What is the best way to ventilate a cathedral ceiling?
- Can I insulate over recessed lighting fixtures (pot lights)?
- What is a "thermopane" window, and how does it work?
- My home has single-paned windows – would it be better to replace them with double-paned windows or to add storm windows?
- Why does moisture form on the inside of my windows in winter, and how can I minimize the amount of moisture?
- What are "Low-E" windows?
- I'm considering having vinyl siding installed on my home. Will this reduce my heating and cooling costs?
Q. What does the term "R-value" mean?
A. R-value is a measure of how well a material resists the passage of heat. The higher the R-value, the more effective insulation is in keeping the home warm in winter and cool in summer. Insulation should always be judged by R-value rather than inches, as different insulation materials have different R-values per inch of thickness.
Q. How much insulation should I have in my attic?
A. Attics should be insulated to R-40 (R-44 in colder parts of B.C.) whenever possible.
Q. If I install more insulation in my attic, what type should I use?
A. Either loose fill (typically fibreglass or cellulose) or batt insulation (usually fibreglass) will work well. Most homeowners find it easiest to use batt insulation, while many contractors find loose fill easier and less expensive to install. If possible, install the new batt insulation perpendicular to the attic floor joists to reduce heat loss through the joists. Loose fibreglass or cellulose can also be used, by pouring it and levelling it with a board or other implement. In either case, make sure that existing attic vents are working properly and that they are not blocked by insulation, dirt or other material.
Q. How much insulation should I have under my floor?
A. Floors over unheated crawlspaces or basements should be insulated to R-28, while floors over open air (such as overhangs) should be insulated to R-40 if possible. If your home has a basement containing your heating system or other sources of heat, you should insulate the basement walls to R-12, rather than insulating the floor above.
Q. My home is built on a slab – is there a way to insulate my floors?
A. In slab construction, much of the heat lost through the floor leaves through the edge of the slab. To stem this loss insulation can be added to the foundation wall and slab edge. Additionally, a 500 mm vertical or near horizontal layer of insulation (R10 or R12) can be installed in the soil.
New homes with radiant heating in the floor must also have insulation under the slab.
Q. Is it better to insulate the attic floor, the roof, or both?
A. Unless you are finishing the attic for living space, you should insulate the attic floor to contain the heat within the living space.
Q. Is it a good idea to add additional insulation to my walls, and how is this done?
A. If your walls currently have no insulation, insulation can be blown into the cavities through holes drilled through the exterior of the home. This should only be done by a reputable, qualified contractor. If there is already some insulation in the walls, you should not attempt to add any more.
Q. Can I compress 15cm (6 inch) R-20 batts to fit into a 2"x 4" cavity, and will it be more effective than 9cm (3 1/2 inch) batts?
A. While insulation batts are easily compressed, the R-value will be significantly reduced – it is best to use the correct thickness and not compress the insulation. You should also avoid storing heavy materials on top of attic insulation for the same reason.
Q. I've always heard that "heat rises". Why do I need to insulate my floors?
A. Actually, heat moves from warm to cold. If your home is built over a crawlspace or unheated basement, you can lose a lot of heat downward through the floors. Insulation will help reduce that loss and also make your floors feel warmer in the winter.
Q. If the walls and ceiling of my home are well insulated, do I really need to insulate my basement?
A. Because basements are within the house's envelope, the walls should be insulated.
Q. What is a "vapour barrier" and how important is it?
A. A vapour barrier, also known as a vapour retarder, is a material that resists the passage of water vapour. A properly installed vapour barrier (facing the warm-in-winter side) can minimize the chance of water vapour condensing inside your wall insulation, which not only reduces the insulation's effectiveness but can also cause damage to your home.
Q. I've heard that you can make a home "too tight" – should I be concerned about this?
A. No house can be too tight, but it certainly can be under-ventilated. Leakiness is not ventilation. A lack of controlled ventilation can lead to a build-up of moisture, odours, bacteria, fungi and combustion gases such as carbon monoxide, carbon dioxide and other pollutants.
Ventilation prevents excessive build-up of these and other indoor contaminants that can affect your health and comfort and damage buildings. For more information, see our h.e.l.p sheet, Good ventilation is important [PDF, 104 Kb].
Q. Is it better to caulk my windows and doors on the inside or the outside?
A. Any large gaps on the outside should be weatherproofed to keep rain out, but the inside is generally the best place to caulk to keep the heated air inside, along with any water vapor that could condense in a cold wall cavity.
Q. How much ventilation should I have in my attic?
A. In most cases, you should have 0.1 square metre (one square foot) of net free vent area for each 14 square metres (150 square feet) of attic floor area. Net free area is the actual area that air can flow through. With screens and louvres, you can assume that is roughly half the gross area.
Q. How much ventilation should I have in my crawlspace, and should the vents be closed in the winter?
A. If the crawlspace has a dirt or gravel floor, the first thing you should do is cover it with a waterproof membrane (e.g. 6 or 10 mil polyethylene). The BC Building Code requires that an unheated crawlspace have vents totaling 0.1 sqaure metre (1 square foot) of free vent area for every 46 square metres (500 sq.ft.) of crawlspace floor area. An unheated crawlspace is deemed to be one with no heating ductwork (supply or return) in it. The floor over an unheated crawlspace should be insulated (preferably with R40 or more).
Q. What is the best way to ventilate a cathedral ceiling?
A. Cathedral ceilings should have continuous soffit vents and a ridge vent to allow air circulation between the insulation and the underside of the roof. Insulation should be installed with at least 2.5cm (1 inch) of clearance from the underside of the roof. There are plastic baffles available that can be used to maintain this air space. A continuous vapour retarder is also required to minimize migration of water vapour into the insulation.
Q. Can I insulate over recessed lighting fixtures (pot lights)?
A. Only if the fixtures are designed to be covered with insulation. Otherwise you should maintain 7.5cm (3 inches) of clearance around the fixtures and leave the top of the fixture uncovered to avoid potentially hazardous heat buildup within the fixture. The only acceptable way to insulate the older pot lights is to build a sealed box over them and then cover the sides and top of the box with insulation. Minimum box dimensions shall be either 35cm wide x 1.2m long x 30cm high (14" W x 48" L x 12" H), or 53cm wide x 74cm ling x 30cm high (21" W x 29" L x 12" H).
Q. What is a "thermopane" window, and how does it work?
A. A "thermopane" or double-paned window has two panes of glass, separated by a trapped air space. The trapped air acts as an insulator, reducing heat loss through the glass.
Q. My home has single-paned windows – would it be better to replace them with double-paned windows or to add storm windows?
A. Both double-paned or thermal windows and storm windows work by creating an insulating air space between the panes of glass. If your existing windows are in good shape, storm windows will usually be more cost-effective. If your existing windows are damaged or if you are replacing them for aesthetic reasons, you should install Energy Star qualified windows. Look for the ENERGY STAR® logo or visit the NRCan website to find qualifying windows in your area.
Q. Why does moisture form on the inside of my windows in winter, and how can I minimize the amount of moisture?
A. Condensation will occur whenever warm air hits a cold surface because warm air can hold more water vapour than cold air. If you have single-paned windows, adding storm windows will keep the inner pane of glass warmer and reduce the amount of condensation. Monitoring your indoor humidity and keeping it in the range of 40 - 50% (even less in very cold weather) will also help. For more information, read our h.e.l.p. sheet, Reduce condensation in your home [PDF, 79 Kb].
A. "Low-E" windows incorporate a microscopically thin layer of a metal oxide which reduces the amount of heat transferred through the glass without reducing the amount of light.
Q. I'm considering having vinyl siding installed on my home. Will this reduce my heating and cooling costs?
A. Vinyl siding is typically installed over a thin layer of foam insulation material. Although this material has some insulating value, it is minimal. You should be skeptical of any claims of substantial energy savings. The main benefits of vinyl siding are enhanced appearance, reduced maintenance and potentially increased resale value.
