1920s house in westchester ny (geothermal?)
i own a house built in the 1920s and still using what i think is the same oil-powered furnace for at least the last 60 years. time for an upgrade. everything i am reading suggests that geothermal in a house without ductwork or any modern systems is the way to go due to the various rebates available that would offset the cost of the full install. we also plan on removing the siding, insulating, and replacing windows. a few questions:
- in the northeast, i believe a backup system is typically needed in case underground temperatures get too low for the heat pump to operate. is this right? is the typical backup system a boiler (hydroair)? are the "backup" systems typically big enough to heat the whole house?
- in terms of general comfort, what temperature range can you keep a house that has a geothermal heating system? for example, if (i mean when) my wife gets cold, can i increase the temp by 2-3 degrees easily? i know that geothermal systems are slow to respond but will the backup system kick in to do it immediately?
any other advice?
We're in Massachusetts and have installed geo systems for many years. We have no problems needing aux heat due to anything but system capacity. That is, we design to +5°F and size the equipment to that design temperature. Just like any other heat pump or fossil fuel system, when you reach design temperature, every degree of drop below that results in a decrease in the indoor temperature, unless the equipment selected has some factor of over sizing on a design day due to equipment selections. That said, we always install electric resistance heaters as aux heat should something untoward happen, such as a pump going down in the middle of a cold snap. They at least have heat, albeit expensive heat.
Our earth coupling method of choice in our area is a standing column well. This is a little more costly for the initial installation but the results are greater economy than a closed loop system. Proper system design by a IGSHPA certified person should be able to answer any forseen drawbacks you might encounter. It is possible to design for the coldest weather and absent any auxiliary heat, you'd be no worse off than any fossil fuel system.
As to indoor temperatures, we achieve the same temps indoors as any fossil fuel system. Our concept is to combine a split HP unit with a high efficiency, variable speed air handler. This allows us to do system zones beyond those zone achieved with multiple pieces of equipment and still maintain very quiet systems. Since you're gutting the house, I think it's a very cost effective and certainly environmentally sound system to install in your home. Properly designed and installed you should be just a comfortable physically as any properly designed and installed fossil fuel system. You can also take advantage of desuperheaters to heat and/or boost your domestic water needs and if you want radiant heat, you can choose to use water-to-water heat pump(s) and used chilled water for cooling. The options are many but you'll want to deal with a very knowledgeable and experienced contractor. You might also consider solar electric as the next logical step that will help reduce the operating costs of the geo system and move you closer to a zero cost for heating and cooling.
BTB, the tax CREDIT for both geo and solar remains at 30% of the total cost of the job (ducts, equipment, wiring, earth coupling, landscaping, etc.) and you can spread the credits over the next few years with the last year being 2016.
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I do a lot of Geothermal installations in Oregon but everything skippedover said is correct, you can design for whatever load you need, you can size your well/loop to your system. As far as how easily it warms up the house it all depends on how your system is sized vs your heat load vs the outdoor temperature. A lot of geothermal systems we do have electric strip heat as a backup but you could use propane depending on your fuel rates. What I like about propane(if no gas is available) is that if you lose power often you can put in a smaller generator to run your furnace than you would need for your full geothermal system however geothermal with propane backup is usually not as efficient as a fully geo dedicated system.