Heating Duct Work Wastes up to 30% of Purchased Energy.

old leaky ducts

Hidden beneath your feet and over your head is the heating duct work that can be the largest energy waster in your home. One problem is the simple fact that you cannot see the ducts or the energy they are wasting. You just assume everything is OK, after all, the windows are closed and the front door is shut – the hot water is turned off and the refrigerator has an energy Star sticker. So, just how truly wasteful can the heating duct work really be?

Studies have been conducted in almost every State concerning heating duct work and duct leakage. From California to Florida, from Washington to Arkansas, heating duct work has been placed under the microscope and the duct blaster. The conclusion is certain, too often heating ducts waste more energy than any other single system in a home. Hidden behind ceiling panels and under floor boards, heating duct work is wasting your purchased energy and tacking serious dollars on to your power bill.

Purchased Energy:

heating duct system

Please note that I said “purchased energy”. When a descriptive term like purchased energy is used instead of natural gas or electricity, I think it adds a new dimension to the problem. The energy our heating duct work wastes is energy we have already purchased. It is already on the invoice. It is coming in the mail on the bill from the utility. Sometimes, I think we get a little sleepy and almost believe that we only pay for the power we use.

The furnace operation increases your homes air leakage from 2 to 5 times. Every time the furnace fan ( the air handler ) comes on, it increases the intensity of air leaks. The furnace causes the air pressure to change in the heating ducts and in every room in the house and the change in air pressure facilitates additional air leakage.

With return heating ducts in the attic, when the furnace fan comes on, the holes in the return air duct suck air out of the attic and into the heating system. The supply heating ducts, located under the floor ( in the nasty crawl space ), those holes, when the furnace fan comes on, leak condition air ( purchased energy ) out of the ducts and into the nasty crawl space where it is wasted.

duct blaster test

Duct Testing Strategies:

For the do-it-yourself homeowner, grab some goggles and a pair of coveralls and take the plunge into your attic and into the wonderful world of the under floor space. Turn the furnace fan on and with your bare hand or a smoke source, check the connections and joints of the heating duct work. Some of the worst duct leaks are often close to the furnace in the larger heating ducts referred to as the heating plenum. Pay special attention to the plenum.

Some of the worst air leaks will be found in the round sheet metal ducts that have a connection every 4 feet. They come as flat sheet metal pieces that are curled up and snapped together along their long edge and then connected to another piece every four feet. Anywhere there is a connection, joint or elbow, there is a possible leak.

If your not the adventurous type, you will need the help of an energy auditor that can use a blower door and a duct blaster to get an accurate reading on the size of the holes in the heating duct work. In a home with 1,500 square feet of heated floor space and round sheet metal ducts, it is not unusual to have 500 cubic feet per minute of conditioned air leaking from the ducts.

A basketball contains about 1 cubic  feet of air. In comparison then, 500 cubic feet of air would equal about 500 basketballs full of conditioned air leaking out of the heating ducts every hour. Now that sure sounds energy efficient doesn’t it?

Duct Sealing Strategies:

applying duct mastic

What are we going to do about those 500 basketballs and that 30%? It’s not going to do us any good to just walk around the house and make sure the doors and windows are closed.

Concerning heating duct work, sealing the holes and gaps is one of the most cost effective things we can do to save energy and lower our power bill. Those leaky round metal ducts that leak so much can be sealed for about $600 bucks in a single story, 1500 sq ft home. Depending on how leaky the ducts are and how well you get them sealed up, the return on investment can be just a couple of years.

The connections, joints and elbows can best be sealed using duct mastic. Get a bucket of mastic, slip your hands into some latex gloves and dig in. Takes me back to elementary school and making that special Mothers Day present using finger paint. Duct mastic should be spread over leaky areas nickel thick. It doesn’t have to look neat and clean, after all, your the only one that may ever see it. Just get every connection and get it nickel thick and you will be taking a big bite out of that 30% and your heating duct work won’t be your number one energy waster.

Thanks for stopping by Detect Energy, hope you come back soon, but I won’t leave the light on for you…