We want to add exhaust ventilation to our attic (hip-style composition roof). Which type is most effective, passive or power?

  • Exhaust is produced by combustion of fuel, an engine or a gas fire hot water heater produces exhaust. Perhaps you mean ventilation. More details about your house, where you live, expectations etc will help to answer your question. – Alaska Man Apr 6 '19 at 17:39
  • I meant attic exhaust ventilation. We live in Willamette Valley part of Oregon, in a 1948 bungalow house. We want to exhaust out hot air from the attic. – RET Apr 6 '19 at 17:45
  • Keep in mind that in a snowy area, your attic venting is critical to keep the roof surface at outside air temperatures and thus keep the snow on the roof from melting/refreezing, thus forming the infamous ice dam. – ThreePhaseEel Apr 7 '19 at 2:16

Around here (California) all of the roofing contractors are installing solar powered attic vents, the ones where the solar panel is part of the fan assembly. No wiring and yes, they only work on sunny days, but that's the only time you really need them!

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  • That's so cool I haven't seen any here in Toronto yet. I'm sure we'll get them soon. – Joe Fala Apr 7 '19 at 0:44

Passive is best if it's practical to install. It usually requires a lot of work. A mechanical ventilation system is expensive and may require repairs and maintenance. A good compromise is one of those wind powered turbines

Turbine ventilator

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Southwest Solutions Group

Use the manufacturers guidelines to size how many at what size you need.

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  • It seems like adding an electric-powered vent might be unnecessary if we have plenty of passive vents in the roof ~ like they might compete somehow. Is that correct? – RET Apr 6 '19 at 20:59

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