Page 45 - Green Builder Homeowner's Handbook 2016

Exteriors / Roofing / Structure / Insulation / IAQ / Windows / Heating / Lighting / Appliances / Faucets & Fixtures / Finishes / Cabinets & Tops / Alternative Energy

Mini-Split Heat Pumps Air-Source Heat Pump

Virtues Flue Warm
gases air to
¦¦ Can provide Burner house
heating Cold air Circulating
and cooling return fan

¦¦ No need for a
chimney or
exhaust flue

¦¦ More fuel efficient
than a fossil fuel
furnace or boiler

Caveats

¦¦ Not practical in
very cold climates

¦¦ Does not get air as
hot as a furnace

CREDIT: MITSUBISHI HIGH-EFFICIENCY BOILER
Hot Water Wiz
DUCTLESS MINI-SPLIT HEAT PUMPS, or MSHPs, are
a good heating and cooling option for homes without A boiler burns oil, natural gas or propane to heat water. That heated
duct systems. Mini-splits can supplement an existing water is then pumped through a system of pipes to radiators,
wood stove or condition a new addition, and they are baseboard heaters or a radiant floor.
also ideal for super-efficient new homes. Mini-splits have two
main components: an outdoor compressor/condenser and an A good boiler will offer efficiencies of 90 to 95 percent and will
indoor air-handling unit. A conduit, which houses the power include many of the same technologies as a high-efficiency furnace.
cable, refrigerant tubing, suction tubing and a condensate These include a modulating burner that matches the heat output
drain, links the outdoor and indoor units. MSHPs are quiet, to whatever the thermostat is calling for at the moment, advanced
efficient and flexible, and because there are no ducts, they are heat exchangers to extract more heat from the same amount of fuel,
easy to install. Here are a few points to consider if you are in and the ability to recover heat from the exhaust gas by condensing
the market for a mini-split: it. The resulting exhaust is cool enough to be vented out of a plastic
¦¦ Choose the Right Mode. MSHPs work best when pipe. In the best cases, this condensing process can squeeze 10 to 12
allowed to modulate. Using them in “on/off” mode not only percent more usable energy out of the fuel.
compromises their efficiency, but will likely result in wide tem-
perature swings and discomfort. AIR-SOURCE HEAT PUMP
¦¦ Know Yourself. Because MSHPs don’t rely on ducting Reverse Motion
to distribute air, be aware that your habits may affect tempera-
tures in different rooms. For example, if you tend to leave your A heat pump is basically an air conditioner that works in reverse to
bedroom door closed all the time, it may be warmer or cooler provide heat. The heat pump captures and concentrates heat from
than the rest of the house. one area, then releases it to another.
¦¦ Build Efficiently. The number of MSHPs required to
heat your home depends on its square footage, but also on your In heating mode, the heat pump takes heat from the outdoor air
home’s layout. A small, very efficient two-story house might and delivers it to the home’s distribution system. In cooling mode,
be served by just one MSHP, but be aware that there may be it reverses direction to work like an air conditioner, extracting heat
temperature differences between the two floors, even if you from inside the house and blowing it outside. In cooling mode, this
use distribution fans. waste heat can also be used for water heating. The most common
¦¦ Bigger May Be Better. Oversizing MSHPs—choosing type is the split system, which uses separate indoor and outdoor
units rated for a larger house—is okay. Oversizing can even units, but you can also get packaged systems that place everything
be beneficial, since MSHPs modulate their capacity and reach in a self-contained outdoor unit. While air-source heat pumps can
their highest efficiency when running at the lower end of their offer efficiencies of 200 to 300 percent, they’re most efficient in the
capacity range. southern part of the country. A backup electric or gas heater may
be needed when the outside air drops below a certain temperature.
www.greenbuildermedia.com Although different versions are made for forced-air and hydronic
distribution, the forced-air type is the most common. Heat pumps
don’t get air as hot as a furnace or boiler, so may require more
airflow to maintain the same temperature.

The Homeowner’s Handbook 2016 GREEN BUILDER 43