Of all the reasons to ventilate an attic the most important is to preserve the structural integrity of the roof. At all times during the year, heat and moisture accumulate in every attic. When left uncontrolled, excess heat and moisture can result in significant damage to the roof and structure, reducing normal life expectancy. Proper ventilation validates most shingle manufacturers’ warranty and protects the investment in your home.
First, it's key to know that the Sonoma County attic venting codes are primarily designed for moisture removal, not superheated air in a hot climate.
When warm air from the house gets into the attic, it can cause condensation, or at least drastically increase the humidity in the attic. Moisture is the number one enemy of buildings
Cool evening air from the marine layer in the Santa Rosa area can create condensation that collects on insulation and wood during the summer. In the winter, naturally wet conditions mixed with moisture escaping from the home’s living space can condense in the attic on wood and insulation which can lead to damaging rot and costly repairs. A properly ventilated attic helps remove harmful moisture.
A poorly ventilated attic can also generate and trap much more heat. As the sun beats down on your roof, the shingles heat up, reaching temperatures up to 150°F. This heat is transferred through the shingles, to the roof deck, to the rafters and framing, and to anything else inside the attic. All of these materials will absorb and radiate the heat to the living space below which can lead to discomfort and increased usage of air-conditioners.
There are essentially three types of attic ventilation techniques commonly used by professional roofing contractors. The two passive types are dormer vents and continuous ridge vent.
Dormer vents are the age old standard because they work very well. They are low profile, galvanized steel construction and vent common attic spaces very efficiently.
Continuous ridge vent is more effective in venting sloped or vaulted ceiling areas.
The third type is forced air (thermostat controlled) attic fans. These move and evacuate large volumes of air for maximum venting. They usually require separate wiring in the attic.
No matter what type works best for you, attic ventilation is essential in protecting your home and making it more comfortable while lowering energy costs. Be sure to ask your roofing contractor what makes sense in your situation.