AirScape Engineer's Blog

You may consider a raised frame for your 1.0 or 1.7 WHF for additional sound reduction. The raised frame increases the distance between the fan and living space. Like our ducted models, making the fan slightly more remote from the living space will decrease the overall sound level. The height of the frame will depend on the total vertical clearance of your attic. The construction is very simple and will add a few additional steps to your installation.

STEP 2:  Caulk all of the frame gaps and joints. Place the provided foam rubber gasket on top of the raised frame.

STEP 3: Secure the unit to the framing (1.7 WHF shown). From the living space caulk all gaps between the unit and the framing.

STEP 4: It’s not a bad idea to add some insulation around the raised frame. You can now follow the remaining steps in the installation and operation manual to finish your install.

PART 1 / PART 2

Your AirScape is already the quietest whole house fan on the market, but there are a few install techniques to make it even quieter. We’ve decided to dedicate a few blog entries to some techniques that will help with sound reduction.

We’ll start with a simple installation step that works with all AirScape models. You can easily line the inside of the framed opening (between the unit and grille) with duct board. Duct board is a resin bonded fiberglass board that has acoustic and insulative properties. The fibrous mat surface of the duct board helps absorb sound and allows for the smooth passage of air. The fiberglass body of this material usually has an insulation value of R-4. The duct board can easily be installed in new or existing installations using either adhesive or screws and flat washers. In fact, we love this material so much we lined one wall of our new office with it (our lead engineer’s rants on energy efficiency, life, and politics are a little more muffled now).

Duct board resources:

http://www.specjm.com/products/ductboard/enviroaire.asp

http://www.owenscorningcommercial.com/data/products/product.aspx?id=271

http://www.certainteed.com/products/insulation/hvac-mechanical/317382

PART 1 / PART 2

We often get asked if AirScape whole house fans can be installed in attics with loose fill insulation. The answer is yes, with one additional install step. The idea is to stop the insulation from being displaced by the air movement generated by the AirScape. We now offer a breathable synthetic fabric that can be placed on top of the insulation to stop any displacement. The installation is as simple as laying the material down in the attic where the fan discharges and tacking or weighting it down. The final step would be to turn the AirScape on and adjust the fabric material as needed.

The Loose Fill Insulation Cover (LFIC) is available in 9′x10′ sheets and can be found on any of the product pages on the website.

Often a WHF will not easily install in the traditional horizontal position. In some instances trusses or other obstructions will interfere with a normal installation. More often there is not enough clearance between the attic floor and the roof. One solution is to create a plenum box which the WHF will attach to. The plenum box can easily be constructed out of plywood and 2×4′s.  The red line in the photos represents the plenum box constructed for an AirScape 4.4e installation. The flexible ductwork and fan can then be mounted straight off of the damper box (the ductwork may have to angle slightly upward so that the fan does not touch the attic floor). A 90 degree bend in the ductwork is not necessary for sound attenuation in this application.

Installation Notes:

- Line the inside of the box with a layer of sheetrock to maintain any required fire ratings

- Use a sound attenuating duct liner for maximum sound reduction

- Seal all framing joints with latex caulk to make the box air tight

- Insulate the outside of the box to minimize heat loss

- Support any sags in the ductwork with additional chain

We get a lot of questions about the ‘R value’ of our damper doors, so we felt that it’s worth going over the basics.

The so called ‘R value’ is denominated in  the units of (square-feet x degree x hour/ BTU). Sounds complicated, but all you really need to know is:

Heat Flow  Q (in BTU per hour) = Area x (temperature differential) / R-value

[For you techies, this formula is valid for steady state, and assumes an infinite plane area.]

Let’s do the math for our whole house fan dampers.  We’ll assume VERY cold conditions in the attic (0° F) and 70° F inside.

Bottom line:  There is not much heat loss through a well insulated whole house fan damper door.  The question that you SHOULD be asking is: “How well sealed is the whole house fan damper door?”

Most residential windows will have R values of 1 to 3. Another question that we get all the time is : “What is a BTU ?”

BTU stands for British Thermal Unit.

1 BTU is approximately the energy released by burning 1 paper match.

100,000 BTU’s make up one therm – that’s how you purchase natural gas, and right now that costs about $1.50

A gallon of gas has about 114,000 BTU.