When most people hear the word residential, they think detached tract or custom home. Others are used to renting space in a multi-occupant building and might see condominium ownership in their future plans. But whatever your residential housing style (custom home on acreage or condo in a high-rise) geothermal heat pumps (GHPs) can bring green heating and cooling to your living space.
GHPs can deliver your heating and cooling by radiant means in floors or wall/ceiling plates, or you can stick with ducted air, which provides opportunities to filter and replenish your interior air without opening windows (security?) and to control your humidity, year round. The benefits of GHPs can be delivered in many forms, and they cause even less architectural and use planning compromises because the underground loop doing most of the work takes the place of an outdoor fan coil unit as in regular air conditioner condensers.
If you’re planning a new home but the plans are not yet drawn, you can opt for an even more thermally resistant building envelope in advance. This is always the first low-hanging fruit of the energy efficiency equation. The lower your heat loss and heat gain, the smaller your GHP unit can be. That reduces the size and cost of your equipment, and the size and expense of the underground heat exchanger that’s necessary. Like those Fram oil filter commercials of yesteryear—you can spend something now (on envelope enhancements) or you can pay a lot more later (in larger and more expensive HVAC equipment, and greater yearly operating expense).
The retrofit of GHP equipment into your existing building is a greater challenge than designing it into one that isn’t yet built. That’s the story of all retrofits, unfortunately, but this one will make you happier every day you live with the result. Ground loops are sometimes challenging, but you’d be surprised how clever your installer can be when vertical or horizontal drilling is called for. It creates only temporary and minimal surface disturbance and this is easy to take when you consider the stakes. You’re installing something that will provide you renewable heating with greater lifetime capacity than the oil in an ocean-going tanker!
Some cautions and reminders for retrofits are in order. If you plan on retrofitting a GHP system to replace a radiant in-floor piped delivery system you’ll have no major changes to face. A water-to-water GHP unit will make whatever target temperature you require. If you’re planning on replacing a ducted fossil-fueled furnace with air conditioning, things are likely to be different. Your installer will explain that the delivery temperatures and air velocities for fossil furnaces and heat pumps differ. So, to preserve comfort and maintain efficiency, new (larger) ducting may be required.
This is part of the infrastructural design that will fold larger volumes of air into living spaces at lower velocity. You’re comfortable without drafts or wiggling curtains, and are often unaware your HVAC equipment is operating. As with any home improvement project that does some renovating, it is a good idea to toughen-up your thermal envelope where possible with added insulation, caulking & weatherstripping, or changing out old windows for new ones.
Right: Flex duct being secured with (sticky) aluminum tape to a hard duct wye for distribution. The R-8 reflective duct insulation will cover the connection and be taped in turn for a complete insulative coating.