If your house could talk, would it be saying "let me breath"? That just might be what it would say if there were an inadequate amount of ventilation in your attic.  Proper ventilation in your attic is needed to reduce the effects of heat and humidity. These two elements can be costly to the structure and energy efficiency of your home.

Heat: In the summer an improperly vented attic can reach temperatures of up to 150 F. These kinds of temperatures can reduce the life expectancy of your roofing materials. It will also make the interior temperatures of the home less comfortable and increase the cost of home cooling.

Humidity: Most of the humidity comes from within the home. Every time you shower, dry clothes, cook, run water or even breath you are releasing moisture into the air that can find its way up into your attic. During the colder months this moisture will condensate and seep into the rafters and roof sheathing. Once in the wood it can create mildew and decay in the wood. Delamination can occur in plywood sheathing. Roof shingles are affected as well.

Before you decide you need added ventilation, make sure you are getting the most from the ventilation you have. Don’t cover any of your vents in the winter time thinking you are saving on your heating bill. If the floor of your attic is insulated with six to nine inches of insulation this is considered adequate by Toady's standards. Covering these vents will only hold in moisture that will create the problems mentioned above, and the resulting dampness in your insulation will also lessen its effectiveness. If you have soffit vents (vents in your overhangs) make sure that your insulation has not blocked them. Often when insulation is added to older homes by a non-professional or homeowner, these vents tend to be overlooked during installation. Other common areas that lessen the value of the ventilation you may already have are found in older cape style houses. In most capes there is a small overhead attic space and a side crawl space behind the knee walls in the second floor bed rooms. Air flow is needed from the crawl space area to the upper attic area and out through vents. All to often a well intentioned home owner will insulate between the rafters from the crawl space into the attic blocking the air flow. The proper way to insulate this area is to insulate the crawl space floor and the back of the knee walls. The only part of the rafters that should be insulated is behind the vaulted part of the interior ceiling that follows the roof line. This is the crucial area. you may need a spacer installed between the insulation and the sheathing to maintain the air flow into the upper attic. This holds true for all vaulted ceilings. Air flow from soffit vents through a spacer behind the insulation and out a ridge vent is the typical method for ventilating a vaulted ceilings. A combination of soffit and ridge vents work like a natural chimney and can be used for open attic spaces as well.

TYPICAL CROSS SECTION FOR VENTING OF CAPE ATTICS

The information contained on this page is not exhaustive and is meant to be only an overview.  For complete documentation on this subject please contact local or State heath officials.