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Your Central HVAC System Sucks

If you have central air conditioning in your home, with ducts routing air from the condenser to the rooms, your system sucks. Don’t just take my word for it, ask Austin home performance expert Kristof Irwin.

Kristof and I were discussing his choice to use ductless mini-split systems in a net zero remodel he performed in South Austin, and he took me back to HVAC boot camp to explain the fundamental issue that ducted HVAC systems suffer from: ducts leak.

All ducts leak as anyone who has experienced an ECAD Audit in Austin can attest. The ECAD form even explains that average duct leakage is 27% in Austin. Even new construction experiences cold air loss in summer though current code in Austin requires less than 10%. So the largest component of the average Texan utility bill is their HVAC system. And over a quarter of the cold air they produce in the typical ducted system is blown into the attic. Isn’t that crazy? A quarter of your frosty cold air is just wasted.

That’s not the only issue though. Think about the three systems – house, HVAC system, and outside, shown in the sketch below.

HVAC Sucks

If your ducts leak 10% the replacement air has to come from somewhere

The HVAC fan pulls air from your home through return air ducts. The air is blown across the condenser, loses heat and humidity and then blows back into your living space, minus whatever leaks from the ducts. So the system is effectively depressurizing your home. The low pressure in your home then attracts the heat and humidity outside your home, and sucks it into your home through any leaks between the inside and outside.

So the by-product leaky (which means all) ducts, is that the very air you are trying to keep out of your home (hot, humid) is sucked in. What’s the solution? Check back to see How to Make Your Home Suck Less



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Garreth Wilcock is an Austin EcoBroker®

Specializing in: New Green Homes in Austin.

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