Tech Support

Sound Reduction part 4 – Ducted Models

The final step on our journey of sound reduction brings us to ducted AirScape models. As you already know the ducted design of the 2.5 WHF, 2.5e WHF, 4.4e WHF, 4.5 WHF, and the Kohilo 2.8 allow for maximum airflow with a minimum of noise. Improper installation of these models can increase their sound levels. We touched on this subject earlier in the blog “4.5 Installation – Maximize Airflow, Minimize Noise.” There are a few things you need to consider when installing a ducted model.

90 DEGREE BEND –  The 90 degree bend should be as smooth as possible to maintain the 20″ diameter of the ductwork. Kinking the ductwork will increase the sound level and reduce airflow because the air does not have a smooth path to the fan.

EXTENSION –  It is important to extend the ductwork as far as possible away from the damper box. This needs to be done without distorting the 90 degree bend in the ductwork. Extending the ductwork fully moves the sound source (the fan) to the farthest point from the living space.

D-RINGS –  The 2.5, 2.5e, and 4.4e fans have D-rings which are used to hang the fan from the attic rafters. Only 4 of the 8 D-rings are used in the installation. The unused D-rings should be taped down to avoid excess rattling.

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Sound Reduction part 3 – Raised Frame w/ Ductboard

The next logical step for sound reduction is to combine the raised frame concept and add the duct board mentioned in part 1. In the following steps we’ll show you how to do this type of install.

STEP 1:  First we created two frames with inside dimensions of 14.5″x22.5″ using 2×4’s.

STEP 2:  Next we made a box using the two frames from step 1 and 3/8″ plywood. For this example we made our raised frame 17″ tall using (2) 25.5″ x 17″ and (2) 18.25″x17″ pieces of plywood. The vertical clearance of your attic will determine how tall of a box you can create. The picture shown is with one side removed.

STEP 3:  Position the box over the framed opening and secure. Caulk all of the seams and gaps of the newly constructed raised frame. Attach the provided gasket to the upper frame of the box. Line the box between the 2×4 frames with duct board. In this example we used (2) 24″x10.75″ and (2) 16″x10.75″ sections of duct board. We decided to go with a friction fit, but adhesive or screws with flat washers would work as well.

STEP 4:  Position the unit on top of the raised frame (1.7 shown). Secure using the provided screws. From the living space caulk all the gaps between the unit and the framing. You can now follow the remaining steps in the installation and operation manual to finish your install.

PART 1 / PART 2 / PART 3

Sound Reduction part 2 – Raised Frame

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 1: We made a raised frame using some scrap 2×4’s. The inside dimension is 14.5”x22.5” matching the framed opening. Secure the raised frame to the attic floor.

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.

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Sound Reduction part 1 – Duct Board

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

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Installation for attics with loose fill insulation

Loose Fill Insulation

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.

4.4e/4.5 Install: Low Attic Clearance

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