Power Ventilator

[lindl2]

Question on the correct venting of a roof with a power ventilator. I inspected a home this weekend that has a hip roof style. The only ventilation the roof has is a power ventilator. No soffit, ridge, gable or roof vent system. Should there be some type of free air venting through the attic. The home is over 100 years old so its not very tight, plus my feeling is its pulling all the AC/heat out through the ventilator. The roof isn't in that bad shape?

[SonOfSwamp]

Power vent is a money/energy loser. Costs more to run it than it's meant to save.

It's like trying to get energy from a water wheel by (electrically) pumping water to the wheel.

WJ

[fqp25]

There should be soffit venting.

More about Power Venting, from Air Vent

Check the 6th Bullet point under Design Considerations.

Frank

[msteger]

Originally posted by lindl2

Question on the correct venting of a roof with a power ventilator. I inspected a home this weekend that has a hip roof style. The only ventilation the roof has is a power ventilator. No soffit, ridge, gable or roof vent system. Should there be some type of free air venting through the attic. The home is over 100 years old so its not very tight, plus my feeling is its pulling all the AC/heat out through the ventilator. The roof isn't in that bad shape?

Depending upon the type of shingle installed, the power ventilator may have voided the shingle warranty. I recommend against them and recommend instead using ridge and soffit venting. Power ventilators and other types (other than ridge/soffit) can allow for hot spots and can prevent a uniform airflow up under the roof.

[Jim Baird]

The building science guys don't like them on retrofits because they can pull the conditioned air up into the attic and waste it if you don't have the balance provided by soffit venting. Hips are very popular now, and I think a lot of builders forget about the vent factor.