This week I would like to talk about a very specific aspect of your homes ventilation system (the V in HVAC), Ductwork. So often we overlook this very simple but very integral piece of a home’s HVAC system. Frequently the issues with duct system are neglected in favor of getting a bigger system in to solve cooling or heating problems. This has several consequences.
The Dept. of Energy estimates that the AVERAGE home loses 25% - 40% (Energy Star puts it at 20%) of its heating/cooling capacity through the ducts. The AVERAGE home… I have seen houses where the ducts aren’t properly connected (and have even found a case where they weren’t connected at all) and can get 90%-100% loss!! On average about 50% of your bill is on cooling and heating, if you can cut back that leakage by 10% - 25% you could be saving around 5% on your energy bills (just keep in mind that getting under 10% leakage on a basic retrofit is pretty good).
With tighter and tighter homes being built (sealing up leaks from building envelope), many homes can have “right-sized systems” which can bring the leaky duct issue right to the forefront. With fewer holes to the outside less capacity is needed from the heating and cooling units. That means we can install a smaller system and a smaller system will run longer than an oversized a/c or heating unit (though counter intuitive, a smaller system that runs longer is more efficient and more comfortable, but that’s a whole ‘nother article). But if the smaller system is running longer, it will blow more overall air which means even more heating/cooling capacity lost.
If you are thinking about upgrading your a/c or heating system make sure your contractor takes a look at your duct system. This should at the very minimum include a visual inspection. However, a visual inspection will NOT show you all of the leaky areas, just the obvious ones. A better solution is to have them do a Duct Blaster test. This will give you a quantifiable number in cfm (cubic feet per minute) as to how much you are leaking. Add to that a little work with a smoke pencil, and you are going to have a great ideal of what needs to be done.
This link is to Energy Star’s guide to hiring a duct contractor.
This one is link to an Energy Star duct sealing brochure. It has more info and a couple of good illustrations of where leaks can happen and what can be done to fix them.
If you have any questions about Energy Retrofits feel free to post them in the comments section or contact me with the information below:
Kerry Hutchison
Project Manger
TexEnergy Solutions
817.538.1202
kerry @ texenergy.org
TexEnergyAudits.org
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