Attic ventilation and insulation are important considerations when replacing a roof, and proper ventilation is also usually required by the major shingle manufacturers as part of their long term warranties. Determining the best way to insulate and ventilate your attic space can be complicated. CD Kaller can help determine the right products and install them to provide the best protection for your home.
So what is attic and roof ventilation and insulation and why is it important?
The purpose of ventilating and insulating your attic is to keep its temperature - or the temperature of the space immediately below the roof when the attic is finished - as close to the outdoor temperature as possible both in summer and winter.
Roofs get hot in the summer - 140F or more - and the heat can cause discoloration, cracking and curling of your shingles. One way to help prevent excessive heat on your roof is to use lighter colored shingles (see Cool Roofs). The lighter color reflects sunlight and absorbs much less heat than darker colored materials. Proper ventilation of the attic space can also cool the air under the roof which also helps cool the roof above it. A well insulated and ventilated attic with a cool roof can help reduce your cooling costs in the summer and help prevent damage to your shingles
There are different issues to worry about in the winter and proper insulation and ventilation are probably even more important in colder weather. In the winter the attic or roof space can get warmer that the outdoor temperature due both to heat gain through the roof and through the attic floor. The warmer air in the attic space will hold more moisture than the colder outdoor air and this moisture can cause damage to your roof decking. The warmer air in the attic also allows the roof shingles to stay warmer causing ice and snow on the roof to melt faster. The melted water then hits the cooler gutters and lower part of the roof and turns into ice - and this causes ice dams. An ice dam allows ice to form and back up onto your roof. The ice gets under your shingles and can cause serious damage to your roof. (If you notice an ice dam form contact CD Kaller - we can get rid of the ice and prevent damage to your roof.)
Proper insulation can help heat loss from your home into the attic space and proper ventilation can help remove any warmer air that accumulates. This prevents moisture buildup under the roof and keeps the roof cooler to help prevent melting and the formation of ice dams.
There are several types of insulation that can be used to insulate your attic. They include the familiar yellow or pink fiberglass bats, blown in fiberglass or cellulose, rigid foam and spray foam insulation. These each have their specific applications and are often used together to best insulate your attic.
There are also several different ways to vent your attic or roof including gable vents or windows, ridge and soffit vents, and flat or turbine vents. Sometimes more than one method can work together to best ventilate the space.
Gable Vents - many existing homes already have gabled vents which are essentially small windows at both gabled ends of the home. These allow outside air to circulate through the attic. Disadvantages of gabled vents are that they rely on a breeze blowing through the vents to move the air around and can allow hotter air to accumulate in the part of the attic that is higher than the vent. The effectiveness of gable vents can be improved by adding a fan to one vent to actively create air flow. In some cases it is advised to cover up existing gable vents when adding newer forms of venting to allow the air flow to go in the right direction.
Ridge Vents - are among the more popular forms of ventilation due to their effectiveness and low profile on the roof. This type of vent runs along the roof ridgeline and allows air to escape from the top of the interior space through a combination of convection (hot air rising) on the inside and a venturi effect (wind passing over the vent causing the hot interior air to be sucked out). These are usually used along with soffit or fascia vents to allow air to move along the interior of the roof from bottom to top. The photo here shows an ridge vent being installed. Once installed it is shingled over. The finished roof is shown at the top of the page.
Soffit Vents - are vents placed in the soffits or the space under the eaves of the roof. Soffit vents allow outside air to enter the attic space at its lowest point. These are usually used with other types of vents higher on the roof to allow the air to flow from bottom to the top of the interior space. These vents do not really affect the aesthetics of your home.
Fascia Vents - are similar to soffit vents but are installed behind the fascia on homes without soffits. These allow outside air in through the fascia and are usually used with other types of vents higher on the roof to allow the air to flow from bottom to the top of the interior space.
Flat or Slant Back or Louver Vents - are raised vents that work similar to Ridge Vents in that they are placed high on the roof and allow air to flow from bottom (using soffit or fascia vents) to close to the top of the roof. Several will usually have to be used and place on both sides of the roof to allow adequate ventilation. A disadvantage is that these are raised above the roof and can affect the aesthetics of your home. These are available with electric fans so air is drawn from inside the attic.
Turbine Vents - are larger, usually galvanized steel, turbines that are placed at one or more areas of the roof. The turbine on these vents actively draws air out of the inside space - when the wind blowing. A disadvantage is that these are raised above the roof and can affect the aesthetics of your home.
Roof and Attic ventilation and insulation are essential to saving energy and protecting your roof from serious damage. CD Kaller can help you figure the best way to do this for your home.