Insulation – Part 2
Proper insulation is probably the most important factor in staying warm at an affordable cost. There are four basic types of insulation used in construction today: fibreglass, cellulose, rigid foam sheets, and spray foams. Each of these can provide a cost-effective solution towards insulating your home and insulating your wallet from energy costs that are only going to rise.
Before deciding on which insulation to use, there are several factors to take into account:
- Resistance to high temperature
- Resistance to moisture flow (will it function as a vapour barrier?)
- Resistance to air flow (will it function as an air barrier?)
- Does it need a fire-rated cover?
- How easy is it to install? Can you do it yourself, or will you need to pay a contractor?
- How effective is it for the space available?
- Final cost of the installation, and the heat saving
Cost is a major factor to consider. In terms of dollars per RSI value, fibreglass and cellulose are probably the most economical. These materials are ideal where physical space is not an issue, such as an attic. Both fibreglass and similar products such as mineral wool, and blown cellulose, need a vapour barrier and sometimes an air barrier to be fully effective, which does add to the overall cost. Today we will concentrate on fibreglass insulation.
125 square feet of pink fibreglass insulation batting, 3½” thick, costs about $50, and has an insulating value of R12 (RSI 2.1); 50 square feet of this insulation, 5½” thick, also costs about $50, and is rated at R22 (RSI 3.9); 56 square feet of R35 (RSI 6.2) costs about $65.
Suppose you have a 1000 square foot attic to insulate, and you’re looking for an RSI value of 9, which is soon to be the minimum requirement for an electrically heated house in Ontario. RSI 9 equals R 51. Four layers of R12 batts would give a value of R48, which is fairly close. You’d need 32 bundles, at $50 each, or $1600, plus whatever you’d need to make an effective vapour barrier from the rooms below. If you want even more protection and savings, adding a fifth layer of batting would cost you another $400, but your winter heat loss through the roof would be practically nothing.
Using two layers of the thicker R 22 batts to give R44 protection (RSI 7.75) would also cost about $2000. If you decide to go with a layer of the R35 (18 bundles, $1170) and a layer of R12 (8 bundles, $400), you can get a total of R47 for about $1570. So as you can see, it pays to plan the project carefully and explore various scenarios.
The good news, however, is that if you have to watch the budget, you don’t have to do everything at once, especially if this is a do-it-yourself project. In addition, as you almost certainly have some insulation in the attic, you can put the new insulation on top of it. However it should be in fairly good condition, and the vapour barrier must be intact.
There are some things to beware of, however.
- Always step on the joists, never on the space in between – if you do, you’ll probably find yourself in the room below.
- Check the condition of any electric wires – for example, squirrels might have gnawed on them, or there might be recessed lighting which must not be in contact with insulation. If you have any doubts, get a qualified electrician.
- Only one insulation can be used around any hot surface, especially a chimney. This is mineral fibre, such as Roxul, which is non-flammable and fire-resistant. Fibreglass in non-flammable, but is NOT fire-resistant.
- Do not cover any attic vent with insulation. These are here for a reason, to prevent the build-up of humidity in the attic. Too much humidity and you can lose some of the value of the insulation and get mould.
- If you have vermiculite insulation, be very careful. One particular brand sold in Canada for several years, Zonolite, contains asbestos. This was available in Canada until the late 1990s – at one time, the Federal Government would subsidise the cost to homeowners.
- If you suspect vermiculite, you should have it analysed to see if it contains asbestos. If it does, for your own safety and that of your family, you should consider getting it removed by a qualified professional.
All of this may sound like a lot of time, effort and money, but don’t forget this is an investment that will pay for itself over and over as energy prices go up. There is only so much oil in the world, and the price is not going to drop. Every major recession in the last 60 years has been caused by rising oil prices. Only conservation and more efficient use of this resource can save us in the future.
By the way, if you want to get your attic insulated to Passive House standards, you should consider R65 or better (RSI 11.5).
Next week, we’ll talk about insulating the basement.
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