Can AirScape WHFs be installed vertically?

Yes. All our AirScape models can be mounted vertically. A few things to keep in mind:

  • For ducted models, it is important for noise control to have the duct work bend 90 degrees, the orientation doesn't matter.
  • Make sure the actuators and electrical box (where the wire runs out to the fan on ducted models) are accessible.
  • recommend using longer mounting screws and/or bracing it underneath with a 2x4 across the bottom of the intake unit.

You can always talk to one of our our experts about your specific install situation.

How many windows need to be open?

Typically, three to four windows partially open is good on medium to high speed; you can do less on low. Open windows in various rooms to ensure whole house circulation; or focus low-speed circulation at night into the sleeping areas.

We don't have an attic, can we use a whole house fan?

A DVS is designed for homes with no attics. These units mount on an external wall and then are boxed in with framing and sheetrock to “hide” the body of the fan. Some creativity will be necessary to find the right spot and make the box appear as inconspicuous as possible. It is necessary to have an access built to access the electronics of the unit.

A smaller option (less airflow and smaller dimensions) would be to use a 1.7 and mount it on an external wall on the outside of the house. A roof and side would be built around it, with vents on both sides allowing the fans to exhaust. These vents should be stationary stormproof louvers built about 12” form the fans to reduce turbulence caused by the louvers and protect the fans form possible weather intrusions. The total size box this would create would be about 30” high, 14” deep and 48” wide.

We have a sealed/airtight/conditioned attic, can we use a whole house fan?

Conditioned attics definitely add a challenge. It can be done but requires a more involved installation. Talk with one of our experts.

Summers in my area are hot and humid. Can I still use an AirScape to save energy?

An AirScape can't create cool air, it relies on cool outdoor air. So if summer nights are hot and humid, natural cooling won't help much. However, it can often reduce your dependence on A/C during the shoulder seasons, and whenever it is dryer and the nighttime temperatures do drop. Our rule of thumb is whenever the night air goes below 80F with humidity is less than 50%, natural ventilation cooling can be effective for you.

I have heard people recommend different amounts of airflow than your website does for our house size. Why is that?

OK, this gets a bit involved, but definitely worth understanding.

Traditional whole house fans were popular in the 1950s, before A/C was common, mostly in the South and Midwest. In order to achieve cooling in these hot, humid climates (imagine a night that stays hot and sticky all night long) the air must move fast enough to create evaporative cooling on the skin (like a fan blowing right on you on a hot day). You need to FEEL the air moving over you.

Many recommendations are based on these old-fashioned uses of whole house fans. Even PG&E in California has recommendations matching these old numbers, which are totally unnecessary in California climates.

AirScape fans work differently, so our numbers are not based on creating evaporative cooling when there is no source of cool air outside. Our numbers are based on bringing in cool night air and moving it through the house faster than the stored heat radiates out of the walls, floors and furniture. This is the core concept of the modern whole house fan.

According to physics, the more mass something has, the more heat it can hold. So your walls hold a lot more heat than the relatively light air in the house. As long as the air moves through faster than the heat radiates out of the structure into the air, the house will cool off (assuming the air outside is cooler than the air inside). This is why running the fan on a low speed throughout the night is recommended—to ensure that all the heat has been drained from the structure. It takes all day to heat up, and it takes just as long to cool down.

When in doubt, more airflow is a safer bet than not enough. No one ever regrets too much airflow, but they do regret not enough airflow.

Some fan companies give their noise level in Sones, you use dBA... what's the difference?

Sone ratings are subjective measurements that are difficult to measure in a lab setting. We rate our fans by dBA - which is more readily quantifiable and consistent and can be done in a lab setting. dBA is the closest measurement to what the human ear actually hears that can still be scientifically measured.

Why can't the fans be automatic?

Safety – they require an inlet be open to allow airflow and keep air from being drawn through your chimney, gas lines, etc that could be dangerous. Someone needs to open the windows when they turn the fan on.

Temperature - Interior and exterior temperatures need to be considered, as well as humidity. It might be 70 outside but muggy, and that might not be air you want to have automatically cycling through you house. There also needs to be a fail safe to make sure no A/C or furnace runs at the same time as the whole house fan, to avoid losing all your heat or cool into the attic.