Do you know your Duct Leakage Rate?

It has been cold and rainy in the Bay Area lately and that means your furnace has probably been running overtime. So whatever inefficiencies in your heating system are amplified from the extended run time. Though the furnace efficiency or AFUE ratings gives you an indication of the unit performance, most homeowners don’t realize that the average duct system is an even bigger source of loss for heating and air conditioning system.

California Energy Commission (CEC) – a California State Government agency commissioned a study a few years ago and found that the average duct leakage rate on existing homes in California is at a staggering 30% (copy of the letter can be found on our website www.sandium.com). This leakage takes the warm air generated by the furnace and dumps it directly into your crawl space or attic. As a result of the study and a need to conserve energy, the State of California makes it a requirement for all inland regions of California that ducts be sealed as part of any furnace or AC replacement work. It is not a requirement in the San Francisco Bay Area yet and that’s why most contractors don’t do it or mention it to the customer. But if you are concerned about your utility costs and the environment, it is definitely an area to look.

To find out the duct leakage rate, a contractor equipped with duct testing equipment can perform a pressure test at your house. The set up and test take about 1-2 hours. Sandium is currently running a web coupon special for the test at $149. Based on the result of the test we can then determine whether or what action should be taken on the ducts. For residential customers PG&E has rebate of $350 to $600 for duct sealing if the leakage rate is brought below 15% but they require ducts to be tested by a certified contractor before and after.
We have done many tests in the south bay area and what we have found is that houses in Los Altos, Los Gatos and Saratoga area sometimes have a higher leakage rates than others. That is mainly because those houses were generally built 50+ years ago and have underfloor metal ducts that in many situations are rusted out. In those types of cases we recommend replacing the ducts. And for new ducts installation we can usually keep the leakage rate below 6%.