Geothermal rebates in New York
user-6828125
| Posted in Mechanicals on
HVAC Question: With the $6,000 rebate we New Yorkers get on geothermal install, does it now make sense to go geothermal vs i.e. Daikin vrv system. This is for an average 3,500 sq ft house thats 20 years old using baseboard heat. Thank you!!
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First of all, I hope that you can update your user profile so that your name is displayed instead of "User-6828125." Here is a link to an article that explains the steps: How the GBA Site Displays Readers’ Names.
Second, the economics of a "geothermal" system (more accurately called a ground-source heat pump) are very dependent on site conditions and the bids provided by local contractors. If you are interested in a ground-source heat pump, get some bids to see if the cost is close to the Daikin system that you are also considering.
For more information on this issue, see Are Affordable Ground-Source Heat Pumps On the Horizon?
Thank you!! The article was perfect.
Randi
No matter what you eventually go with for mechanical systems, start with a careful room by room Manual-J load calculation, performed by a qualified third party such as a certified professional engineer or RESNET rater, and specifically NOT an HVAC contractor (who will 19 out of 20 times have grievous errors of omission/commission.) That's twice as important when going with something as expensive per ton as ground source heat pumps and many-zoned VRV systems.
If you have a heating history on the place, you can sanity-check the Manual-J using the amount of power used during the coldest months of heating season against heating degree-day data from a nearby weather station. This is something that is fairly quick & easy to do, and if done correctly is at least as accurate as a Manual-J for determining the whole-house heat load (and ultimately the size of the heat pump needed to support that load), but won't tell you a thing about the room-by-room loads. The room by room loads will still be necessary for designing the system, but at least you'll have an upper bound staked out for what the total should be. That way you'll be able to avoid ending up with a 5-6 ton heat pump "solution" for 2.5-3 tons of actual load. (Yes, oversizing when simply handing it over to the contractors is often that large- and expensive!)
Details on how to run load numbers from the wintertime power use can be found here:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/out-old-new
An example of a ridiculously oversized GSHP system was installed in an award-winning house in CT recently:
https://www.ctzeroenergychallenge.com/participant_overview.php?ID=Moser
https://www.ctzeroenergychallenge.com/participant_specs.php?ID=Moser
Working backward from the annual energy use numbers for the base case code-built home, the design heat load of even the base case would come in under 2 tons. The as-built house is somewhat better than code, and has a likely load of about 1.5 tons, yet they installed a whopping FOUR TONS of GSHP in that house, as well as a solar array almost as ludicrously oversized for their annual power use!
Had they spent even half the GSHP budget on a higher performance building envelope they could have cut the size of the PV in half and heated & cooled the house with 2-3 mini-splits.