Duct System Leakage

The Problem:

Ducts are used to supply conditioned air to different parts of a building.  Duct systems are generally made from sheet metal, duct board, or flexible duct tubing.  There are many connections, joints, and seams in a duct system, all of which are possible sources of leaks.  These leaks not only waste energy, which result in increased utility bills, but they also degrade air quality, which introduces contaminants and irritants into the system.  Insulation does not stop air leakage, but rather acts more like an air filter.  The picture on the right is an example of how insulation shows traces of air leakage.

Dirty lines on the inside of this duct wrap insulation show where the leaks were.

Testing:

Minneapolis Duct Blaster

A diagnostic tool which pressurizes a duct system is used to test its leakiness.  Perhaps the most widely used is the "Minneapolis Duct Blaster" made by The Energy Conservatory.  In this test a fan blows air into the ducts and pressure differentials are used to determine the rate of air leakage.  It is common to see leakage rates of 250-400 CFM in older duct systems.  This amount of leakage can result in a 30% or more reduction in operating efficiency, wasting hundreds of dollars every year.

Solutions

Every connection and seam is a possible source of leakage, and must be properly sealed.  Factory made boots and elbows have seams which leak air.  Even the longitudinal seams on metal ducts should be sealed.  Despite its name, duct tape is NOT suitable for sealing ductwork.  Duct Mastic is the best sealant to use.

Before Sealing	After Sealing with mastic and reinforcing mesh. Leakage reduction of about 8 cfm

Get your Ducts Tested

If you live in the Dallas/Fort Worth area, please call us at 972.283.0163 to schedule a diagnostic test on your ducts.  We use the "Minneapolis Duct Blaster" to measure the leakage rates of your system.  The cost for this diagnostic service is $150.  If you have multiple AC systems, add $50 for each additional system.

Duct Sealing

It is impossible to seal a system 100%, but we aim to reduce your leakage as much as reasonably possible.  Often we can reduce leakage to 10% or less.  The cost of this service is $1.75 per CFM reduction in leakage.  After our work is complete, we retest your system and you only pay for the amount of air we saved.  In many cases, your energy savings are enough to pay for this service the first year.

Duct Sealing Service is only available November through April.

See also

Whole House Energy Audit

Discounts - Save $50 When you combine our Energy Audit and Duct Testing services.