Everybody knows the importance of a good roof, but how many homeowners ever give their attic a thought?
What's an attic for, apart from storing stuff? (Which you shouldn't do, by the way.) While the roof keeps the rain and melting snow outside, the attic with proper insulation and a vapour barrier keeps both warm and cool air inside. Did you know that as much as a third of what you spend on heating and cooling could be escaping through your roof?
In the winter, your furnace works to heat your home. But without good insulation in your attic, that warmth is wasted. In the summer, the sun beats down on your roof, causing excess heat to build up in the attic. And if you have poor insulation, the heat from hot ceilings next to your extremely hot attic will force your air conditioner to work overtime. This can put stress on your cooling system and cost you a fortune.
Insulation in the attic is very important -- it slows down the heat loss from your living space. There are a variety of insulation materials, each with an "R" value, which is the standard of effectiveness. "R" stands for resistance to heat flow; the higher the R-value, the greater the resistance.
People often ask me how much insulation they need in their attic. Well, it's almost impossible to have too much. But most attics across the country should have a minimum of 12 inches of loose fill or fibreglass batt insulation. It's pretty easy to check if you've got enough -- just get a ladder and a flashlight and peek through your attic access.
If there isn't enough, it's not a big deal to add more. If your attic already has insulation that rises to the top of the joists, additional blankets or batts can be added perpendicular to the joists, or additional insulation can be blown in as required.
Blowing cellulose insulation into an attic requires a qualified contractor with the proper equipment, but the job can usually be done in a couple of hours. And the cost will be recouped in a few years through energy savings.
When you add insulation to your attic, make sure you don't let it touch any part of the roof, or block any vents in your soffit that let air circulate. You must make sure that lots of air flows through your attic -- but that air can't come from the living space below. It's got to come from outside.
When I tell people to make sure there's a thermal break and no airflow between the living area and the attic, but that they also need to ensure the attic is well ventilated, they often get confused. Why would you want your attic to be well insulated and then ventilate it -- doesn't that defeat the purpose of insulating in the first place? But insulation and ventilation are two different things.
It's not actually the attic that's insulated -- it's your living space, which should be sealed and insulated at the attic floor. The attic is outside this envelope, so don't avoid ventilating your attic because you're afraid of letting cold air into the house.
Having a vapour barrier between the warm living space and the cold attic is very important. Without it, warm moist air produced in the home will rise into the attic. Why does that matter? On any given day, up to 50 pounds of moisture from washers, dryers, baths and showers -- even your own breath -- can travel up through your ceiling and into the attic. If this moisture isn't vented, it can condense on the underside of the roof sheathing and rot it, and that could lead to mould and mildew.
In the winter, warm moist air will condense in the cooler attic, which, without venting, can soak your insulation, making it useless. Good airflow also helps with ice dams, which form when warm air in the attic melts snow on the roof from the underside and creates runoff that refreezes on the colder eave, eventually building up to a dam.
Check your vapour barrier for air leaks and seal them. These are often found around the attic hatch, plumbing stacks, ducts and ceiling light fixtures that enter the attic. A good clue for these air leaks is dirty insulation in certain areas -- that shows you have air movement.
Good vents can move hundreds of cubic feet of hot air out of your attic every minute, so make sure you have enough venting.
There are many different types of vents on the market for roofs and soffits. Check with your roofing professional or your contractor to select the best ones for your roof style.
Another important point to remember: If there are asphalt shingles on your roof, the attic must be ventilated properly to comply with the terms of the manufacturer's warranty.
Through a combination of proper insulation, air sealing and ventilation, you can help prolong the life of your roof, and save money on energy.
Mike Holmes is the host of Holmes on Homes on HGTV. E-mail Mike
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