Home Ventilation

Contrary to popular belief, to ensure your home's optimum performance and health, it is best for your attic space to always be the same temperature as the ambient, outside air-no hotter and no colder. Ventilation is the primary source for maintaining this congruency between the attic and outside environment. During the summer months, ventilation cycles air through the attic to keep it from heating up on hot summer days. In some areas of the country it is not uncommon for unventilated attics to reach 130-140 degrees! Allowing your attic to reach these temperatures severely increases the load on your air conditioning, and inevitably significantly increases your cooling costs.

When we live in our homes and cook, clean, and do laundry, we end up creating a lot of moisture in the air. In the fall through spring, ventilation prevents this moisture from rising all the way through the attic and condensing on the underside of the roof deck. We all know that heat rises, so heat generated from heating your home will eventually find its way into your attic space. If ventilation is not present, the warm moist air will rise and eventually reach the underside of the cool roof deck and condense. This moisture over time can rot roof decking, ruin insulation, and foster mold. With ventilation, this air is siphoned out of the attic before it ever has a chance to reach the underside of the roofing surface and condense.

Intake vents to pull air into the attic will always be found at the bottom of the roof, usually under the eaves. Where there are adequate overhangs to include venting, this is the perfect solution for your intake needs. The following Amazon module shows some of the products that would serve this purpose. For each of these products, take note of their dimensions and how they will count against your needed requirement.

In some cases there is not an adequate overhang under the eave to include additional vents. In these cases it is necessary to use vents that are located on the edge of the eave. Please click the following links for examples:

Air Vent: Vented Drip Edge

Air Vent: The Edge Vent

BendTek, Inc: Vented Drip Edge

There are also a variety options for exhaust vents on your home and much depends on your aesthetic preferences. For many years the standard in roofing was vents located at the top of the roof plane like you see in the picture to the right. These vents are cost effective, durable, and can sufficiently exhaust air from your attic. However, in the last ten years, ridge vents have become the popular choice with homeowners. They are more efficient than traditional vents and they are thought by many to be more aesthetically pleasing. They are more susceptible to wind damage than traditional vents, however. In most cases it comes down to the preference of the homeowner about which solution to choose. The following Amazon modules show some of the popular options available today.

Some circumstances require special consideration when evaluating your ventilation. A few are explained below:

Cathedral Ceilings - Some homes are designed without any attic space, so in some areas of the home, the underside of the roof deck also serves as the ceiling. With this limited space between the roof and living space, it is very hard to create adequate ventilation. Some homeowners try to insulate this entire area as much as possible and hope for the best, but in many cases efficiency is still compromised and condensation occurs. With new homes it is always ideal to create at least a couple of inches of airspace for ventilation. For existing homes you can build what is called a "cold roof" over the area. A cold roof is a system where, to create some air space, you can lay battens down on the existing decking, nail new decking to the battens, and install new roofing materials on top. The airspace created by the two layers of decking can then be vented to increase efficiency and prevent condensation. This is a more costly solution, but in the long run will pay for itself in lower cooling costs and a healthier home.

Structural Insulated Panels - Structural Insulated Panels can pose interesting challenges when venting and preventing condensation. Due to the jointing of the panels, moisture can sometimes make it way in and wreak havoc to the panels. I always recommend following manufacturing specifications on how to seal between the joints, as well as how to treat the back surface of the panel. If you follow these specifications your installation should be successful.

Sealed Attic - It is becoming more and more popular in new homes to do away with ventilation and instead seal the entire attic with spray foam insulation. This is a costly solution but is effective from an efficiency and condensation standpoint. It is very difficult to achieve a sealed attic in retrofit situations, however. Reaching every square foot of the attic to get a complete seal makes it very difficult and costly. For these reasons, I usually suggest traditional ventilation methods for existing homes.