The importance of venting your attic cannot be overlooked. In cold climates, improper venting can lead to moisture buildup which causes mold growth, wood rot in extreme cases, or even ice in the attic insulation. In hot, dry climates, stagnant air can dry out your tresses, increase your energy costs for air conditioning and make your house uncomfortable.
If your home is like most that we inspect, it is severely under vented. You can add more soffit and exhaust vents, but at what cost? Power venting may be a more cost effective and efficient method of achieving your goal. However, venting is just part of the problem. A well ventilated attic will reduce the convective load. The largest component of heat gain or heat loss in any home is infrared heat. Control this and you can really save!
We have found in our full scale testing of homes with a radiant barrier installed that passive ventilation is not sufficient to remove the millions of BTU's changing direction from the reflective surface and that power venting is required.
Solar Fans: Sounds like a great idea right? The Sun comes up, creates free energy, spins a fan to remove the hot air from the attic. In theory, this makes sense. The reality however is much different.
Question: "At what point during the day will the solar fan put out the most amount of power?" (assuming a Southern exposure for the PV panel).
Answer: Solar noon.
Question: "When does the attic require the most amount of venting?"
Answer: Between 1:30pm and 7pm. When the attic requires the most amount of venting the solar fan is putting out the least amount of power.
We import a vibration free, powerful, reliable powered attic fan manufactured in Germany. This attic fan is unlike any other available: quiet, powerful and very efficient. We include an adjustable thermostat and an optional mounting box with this system.
This fan features an external rotor to which the fan blades are welded. This unique design reduces blade flex and vibration and eliminates one of the shaft bearings. The bearings are sealed and never need attention. Install it, set the thermostat and forget about it. The 14" fan consumes 245 watts. At a national average of .10/kWh running for eight hours a day that's less than $6 per month. There are sites on the 'net that say the power consumption of an attic fan does not offset the cost of running it. The goal is keeping your A/C off as much as possible, which consumes 1600 watts per ton. Logic would dictate running a fan for $6/month would be preferable to longer run times on your A/C unit from the stagnate, overheated attic air and the load on your ceiling.
The installation seen above was installed by an engineer. This will have virtually no effect on exhausting air from the attic at the opposite end since most of the air will be entering around the fans. As you can see he also installed fiberglass up against the roof decking which will only serve to store tremendous amounts of heat all day, cook his roofing system then allow it to dissipate long after the sun goes down. The people who bought this home had $475/mo energy bills for a 1700 sq foot home.
Here is a roof mounted German fan mounted where a Home Depot fan used to be. For increased performance, the dome shaped Home Depot attic fan cover on the roof can be replaced with the correctly sized Aura Vent. Two 10" fans mounted side by side. Choose this option when a larger gable vent is not available.
Gable mounted solar attic fan doing nothing but wasting time and money. With the opening next to the fan there will very little air actually been removed from the attic space. The opening next to the fan needs to be blocked off.