So you’ve been hearing about heat pumps: your friends have one and they no longer have a big fuel bill; how they use the earth’s temperature to heat and cool your home . . . . But you still have your doubts. Will they work where you live? Can you just replace your gas furnace with a heat pump? How much of an investment or construction project can you expect? Of course, it’s all relative! (Everything is relative, right?)
But just to take on a few misconceptions, let’s talk about the viability of a heat pump in an area that has a mild but definite winter— say, coastal Georgia. The first thing to remember about a heat pump is that it borrows warmth from the earth, which tends to stay around the average temperature of the region, year-round. So if the average low in Savannah is 56 degrees, that is roughly the ground temperature below the surface, year-round. Since heat pumps work in places with an average low down to 25 degrees, this would be a viable option in places like Savannah. [Commercial break: Here’s a blog post we did on heat pumps last year: http://www.acdoctor.com/blog/heat-pump-hvac-option-home/)
Just to be clear: We’re talking about a ground-source heat pump. It works like an air conditioner. It draws cooler air across a coil called the evaporator that contains very cold refrigerant (a liquid that boils at a super-low temperature). When the refrigerant (also called coolant) boils, it turns to a vapor. The vapor is sucked into a compressor where it turns into a high-pressure, super-hot vapor that’s then forced through a coil (called the condenser) that’s part of the indoor unit of the heat pump. As cool air passes over the coil, the vapor cools and returns to liquid form, releasing heat that is then blown through a duct system to heat the home. The liquid refrigerant cools down by releasing its heat into the home. Then it’s pumped back outside. On the way, it passes through an expansion valve, lowering the refrigerant’s pressure and temperature once more so it can boil more easily. In this cooling mode, the heat pump works in reverse, extracting heat from indoors and sending it outside.
Sounds complicated? Well, it is, a bit. But HVAC experts have a good handle on the technology, and it’s getting better all the time (as the old song says). So to answer our own questions . . . Yes, heat pumps are now made to work in climate zones that have a real, definable winter— such as Vermont. As well, heat pumps are now available in ductless mini-splits, so we can do without ducts. This is great news for anyone who has an aging system with leaky ducts, or someone who’s recently added a room or renovated a garage or basement area that was previously unconditioned . . . or anyone who simply wants to save on the cost and hassle of ductwork— which, by the way, loses a substantial amount of heat or cooled air as it transports the air to its destination in your dining room.
Now here’s the bad news: A heat pump can run up to 25% more than a conventional furnace in upfront costs (purchase and installation) and, it’s reported, they ‘growl’— that is, make a discernible noise during operation. So if you like a super-quiet environment, that could be a negative factor. Ductless mini-splits are great for small spaces, but don’t work for a large, poorly insulated older home.
However– good news time!– a heat pump would save you money year after year on fuel. The cost of operating them will show up on your electric bill, and it’s generally quite light. And of course, for greens, it’s an environmental no-brainer. A heat pump doesn’t use fossil fuels and is much easier on the environment. For more information about using a ductless heat pump in a cold climate, read this: http://www2.buildinggreen.com/blogs/7-tips-get-more-mini-split-heat-pumps-colder-climates. (The comments are useful, too.)
And if you’re ready to start window-shopping, start here, in our comparison of brands: http://www.acdoctor.com/Heat-Pumps-p-1-c-63.html