Geothermal HVAC in a home – can it be done in Austin? This was the question I was posed on the phone last week, and the first thing that sprung to mind was the net zero capable community of SOL Austin which features geothermal HVAC options. I checked the MLS home sales in the City of Austin in 2010, and just 3 of 9694 sales were labeled as having geothermal HVAC – all of them above $325,000.
The next thing that suggested itself was calling in the expertise of Kristof Irwin of Blue Heron Builders – he specializes in remodels and construction of net zero capable homes in Austin. His answer was surprisingly simple – yes!
He said he could build a 1500sqft home with geo-thermal HVAC for under $300,000 – possibly $275,000. The system is around twice the cost of a regular HVAC, he explained. The ground is used as a heat sink for the refrigerant used to cool the home, so rather than having an external unit using a motor to compress refrigerant from a gas to a liquid, you use a hole in the ground. The refrigerant is pumped into the heat sink where it cools down sufficiently to begin the heat exchange cycle with your home once more. The energy required to pump is less than the energy required to compress a gas, so the net result is lower energy bills.
Kristof then went on to explain that he wouldn’t necessarily choose a geo-thermal HVAC to attain the goal of a net zero capable home – one which through provision of on-site electricity production could produce the same amount of energy as it consumed over a year. (In short, a high performance home without the pesky burden of energy bills) He said that he would also look at ductless mini split heat pumps which eliminate the challenge of duct leakage in a home and allow a more fine grained control of the zoning. You only condition the rooms you are in, so save on conditioning the whole house.
He also pointed out that the ductless mini split systems can also improve the humidity control in a house, which is crucial as building envelopes become tighter. I’ll talk more about the perils of humidity in a new green home in an upcoming post.
Garreth Wilcock is an Austin EcoBroker®
Specializing in: New Green Homes in Austin.