Pressure Balancing Systems

a simple answer to a moldy HVAC problem

Product receives Honorable Mention in the 2004 AHR Expo Innovation Award Competition

R.A.P.'s (Return Air Pathway) are passive pressure balancing systems for use with ventilation or forced air heating or cooling systems where it is often impossible to provide both supply and return ducts to every room.

Closing the bedroom door can cause mold growth!

When a building is conditioned by a forced air system, the air flows from and back to the air handler.  By design, the flow should be balanced as it moved through the system.  It is common practice to put a supply outlet in each room and use centralized returns, assuming that the rooms themselves will serve as the return ducts.  In this situation, room doors can become dampers, blocking the return flow. 

Pressure imbalances are developed in the building when air from the supply register of a forced air system is obstructed from reaching the return register.  The pressure differences seek to balance themselves by leaking through available cracks and holes.  The out-of-balance condition will reduce the efficiency of the system, reduce the comfort in the space, and worse, cause moisture to condense in the wall system, enhancing the growth of mold and mildew and will eventually cause breakdown of building materials.

Ideally, there should be a return in every room, bypassing the role of the rooms as return ducts.  If that is not possible, undercutting the doors provides some relief, but this is usually insufficient. Adding R.A.P.'s will reduce cold and hot spots, allow the system to work more efficiently, and balance the pressure in the building to reduce the chance of inadvertent leakage.

For further information please see The Problem of Pressure (pdf). Tamarack prepared this article for the benefit of the South Florida Builders Association in August 2002.

The R.A.P. systems provide the superior balancing characteristics of a simple through-the-wall penetration, while reducing the problems of light and noise transmission.  The baffle in the R.A.P. smoothes the flow of air, straightening the turbulent paths. But because light and sound travel best in a straight line, only the most direct light and sound sources move easily through the pathways and privacy is greatly enhanced.

The R.A.P. is designed for installation into new construction.

(Picture Coming Soon!) The R.A.P.R is designed for retrofit applications

Specifications at a glance

√All models include a sheet rock flange.

√The depth between the flanges is 3.5"

√The overall depth is 4.625"

√Each unit comes with a pair of white grilles

Sizes

The R.A.P. is available for both new construction (single sleeve) or for retrofit applications (fitted sleeve) in the following sizes.  If ordering for retrofit applications, insert "R" before the size (ie:RAPR12.4) when you place your order. RAP's are sold in cases of 5 of a single size.

To determine what size R.A.P. is best for your application:

1. Determine the amount of air being delivered to the room through the HVAC supply vent.

2. Select the combination R.A.P. and door gap that will match the flow of air delivered.

Example: 177 cfm is being delivered. There is a 1" gap under a 30" wide door (50 cfm). The R.A.P. you would need would be 12.12 (127 cfm). 50+127 cfm = 177 cfm

For more information, a product brochure, or technical and pricing assistance, please contact us at 800-222-5932 or E-mail us at: sales@tamtech.com