Natural Attic Ventilation
You might wonder why we’d put insulation to stay warm and then let cold air into the attic through vents, but it’s actually a smart way to make your home strong and energy-efficient. Here’s why: during winter, letting fresh outdoor air into the attic keeps it cool, which prevents the formation of ice dams (when snow melts on a warm attic and then freezes at the gutters, causing roof damage). Proper insulation and sealing also keep attics cool in winter by blocking heat and moist air from below. In the summer, a well-ventilated attic lets hot air escape, protecting the roof and getting rid of moisture. The insulation stops heat from coming into your house.
The most common mistake homeowners make when adding insulation is blocking the air at the edges of the roof. NEVER COVER THE ATTIC SOFFIT VENTS WITH INSULATION — use vents along the rafters and under the eaves to keep the air flowing.
Attic Fan Ventilation
Attic fans cool hot attics by drawing in outside air through vents and pushing out hot air. But if your attic lacks proper sealing and has blocked vents, these fans can pull cool indoor air into the attic, making your AC work harder and increasing your electricity bill. To prevent this, follow our sealing and insulation tips, and ensure your attic has natural ventilation with passive vents.
How to DIY
When adding more insulation, it’s easiest to use fiberglass rolls for a DIY project. If you already have insulation between the rafters, put a second layer on top, but make sure it’s unfaced, without a vapor retarder. This covers the tops of the joists and reduces heat loss or gain.
Start from the edges and work towards the attic opening. Never put insulation over recessed light fixtures or soffit vents. Keep insulation at least 3 inches away from “can” lights, unless they’re IC (Insulated Ceiling) rated. If you’re using loose fill insulation, use sheet metal to create barriers around the openings. For fiberglass, you can use wire mesh for this purpose.
How to Install Rafter Vents
To make sure your attic floor is fully covered with insulation near the edges, you need to use something called rafter vents (also known as insulation baffles). This, along with sealing any air leaks, helps your insulation work better. Rafter vents make sure that the vents under the roof’s overhang (soffit vents) stay open and allow outside air to flow into the attic and out through vents near the roof’s peak or on the sides.
To put in rafter vents, staple them right onto the underside of your roof. They come in different sizes to fit the space between the rafters where your attic ceiling meets the floor. Once they’re in place, you can add your insulation all the way to the edge of the attic floor. But if you’re using blown insulation, you might need to add something like a piece of rigid foam board at the outer edge to stop the insulation from going into the soffit.
PLACE RAFTER VENTS
Put rafter vents between the beams where the ceiling and floor meet.
Insulate around the rafter vent and extend it to the attic floor’s edge.
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