insulation and ventilation

Keeping a potential
hot spot cool

If you're finishing your attic, you’ll need to take insulation and ventilation very seriously in order to be comfortable in your new space. Most locales have stringent codes regulating how much venting and insulation a room must have. An improperly insulated and ventilated renovated attic room can also become unbearably hot and stuffy in the warmer months. And in winter, your much-desired heat will rise to the ceiling and out through the roof, rather than keeping your house warm, so you’ll essentially be sending your energy dollars out along with it.

Unused attic space often uses a passive (or static) ventilation system. This entails an intake vent at the eaves to draw in fresh air, and an exhaust vent under a gable or the ridge beam to let out warm air. Make sure your attic includes these vents, and be careful not to remove or block them during your renovation.

You can take ventilation one step further by making it active, or powered. An attic exhaust fan pulls in air and expels it through a vent. You can connect your fan to a switch or use a thermostatic fan, which is hooked up to a thermostat that will automatically turn the fan on when the temperature reaches a certain level.

Ventilation works hand in hand with insulation. Unfinished attics already contain insulation in the floor. If you are finishing your attic, you’ll want to put in ceiling insulation that has a vapor barrier, a layer of watertight material that prevents moisture from your home's interior from penetrating the roof, where it can condense and damage not only the insulation but your house's structure. The vapor barrier should always be placed facing your living space.

Insulation is graded by R-values. The higher the R-value, the better the insulation. Depending on where you live, your R-value could be anywhere from 30 to 40.

Ask the Experts

The floor of my attic already includes insulation. Should I just leave it in?

Probably not. The insulation most likely includes a vapor barrier, which is used to separate heated living space from unheated rooms or the outside. If you plan on heating your attic, you'll need to replace this with insulation that does not have a barrier. If there is no barrier in the existing insulation, you can leave the insulation in, or add new insulation on top of it. Insulating the floor can help keep your attic and the lower levels more comfortable, as well as provide extra soundproofing.

You're lucky to catch this problem now, before it gets even worse. Even small attic crawl spaces perform the important function of venting hot air away from the roof and thus keeping the roof cool. If you live in an area that has cold winters, a roof that’s too warm will cause ice and snow to melt, trickle down your roof and refreeze to form ice dams at the eaves. Water collects behind the ice dams, where it eventually seeps into and damages both your insulation and your house's structure. Proper insulation and ventilation will prevent ice dams from forming again.

Can I put in insulation and ventilation myself?

While laying in insulation and installing vents is a fairly easy do-it-yourself project, it helps to have expert advice from an HVAC specialist or contractor. Where and how to insulate and ventilate can vary depending on the climate for your region and even your roof pitch. If you do install fiberglass insulation yourself, be sure to wear long sleeves and pants and a face mask to prevent irritation from any stray fibers. Although most newer types of insulation are encased in a sleeve that contains the fibers, it's always better to play it safe.