Adequate attic ventillation
user-1093260
| Posted in Mechanicals on
The home I am building has a hip style roof system with a 10/12 pitch. There is a lot of unused space up there but a limited amount of ridge vent and the soffits are vented most of the perimiter. My builder is concerned about the amount of heat and its effect on the roof shingles. Should I add a roof vent and if so what type would work best. Thanks for the help. Dana
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Replies
Attic ventilation has only a very modest affect on shingle temperature, ESPECIALLY on high pitch roofs that get very good convection-cooling on the exterior. The color (or more accurately, the solar reflective index or "SRI") makes a much larger difference. High SRI shingles come in a variety of colors now, but in colder climates add more to the heating energy use than the cooling energy use they offset. See:
http://coolcolors.lbl.gov/
http://coolcolors.lbl.gov/assets/docs/fact-sheets/Cool-roof-Q%2BA.pdf
Whether you need to add a roof vent for OTHER reasons depends on your location/climate- find yourself on the climate zone map or give us a ZIP code/city to work from.
Sorry, I forgot to mention I am in zone 6.
Dana,
Unless you have a building inspector who has raised objections, you have nothing to worry about. However, if you really want to have more ventilation near the peak of your roof, you can install a few ugly mushroom vents in your roof.
If you have problems that some people blame on insufficient attic ventilation -- for example, ice damming -- there are remedies which are far more effective than attic ventilation (namely air sealing the ceiling plane of your house and adding more insulation on your attic floor). For more information on solving ice dam problems, see Prevent Ice Dams With Air Sealing and Insulation.