Heating & Cooling

Ducted Air Source Heat Pumps (DASHPs) are potentially easy to retrofit into a home that already has a forced hot air furnace because they use the existing ductwork. The heat pump unit sits outside of the building similar a to a whole house air conditioner. This is where the heat or cool is generated using a refrigeration cycle. Heated or cooled fluid flows through flexible pipes from the outdoor unit to the indoor air handler that is tied to the home’s ductwork, similar to an oil or gas-fired furnace but a heat pump is able to do cooling as well as heating. As with any central heating system, room temperature is monitored and controlled using a standard wall thermostat or multiple thermostats in a multiple zone system.

For homes without ductwork: Insulated ducts can be installed in basement or attic areas to carry conditioned air to where it is needed. (Also investigate ductless mini-split ASHPs below.)

Heat pumps are all electric and burn no fossil fuels to operate. They are highly efficient at using electricity for heat and in summer they are efficient air conditioners for cooling. The latest models can provide heat efficiently in outdoor temperatures as low as 5 degrees F.

Ductless mini-splits that are Air Source Heat Pumps (ASHPs) that are fairly easy to retrofit into a home and can be used as central heating or as Area Heating (See below). The heat pump unit sits outside of the building similar to a whole house air conditioner. This is where the heat or cool is generated using a refrigeration cycle.. Heated or cooled fluid flows through flexible pipes from the outdoor unit to the indoor head unit. Room temperature is monitored and controlled using a remote control-style thermostat.

Indoor head units come in a number of styles with different options. Some outdoor units can be set up with multiple heads to serve different rooms or zones, each with a separate thermostat. Multiple min-splits can be installed to heat an entire home or building.

Heat pumps are all electric and burn no fossil fuels to operate.

Mini-Split Heat Pumps are an economical way to heat/cool areas or whole homes. They are highly efficient at using electricity for heat and in summer they are efficient air conditioners for cooling. The latest models can provide heat efficiently in outdoor temperatures as low as 5 degrees F.

Heat pumps have a COP of between 2 and 3 which means they provide 2 to 3 times more heat than a standard electric resistance heater.

Ground Source Heat Pumps (GSHPs) are the most efficient kind of heat pump because they use the fairly constant (but mild) temperature of the earth as a heat source—typically 40-50 F, One common approach is to drill a well a few hundred feed below a building where the water column becomes a heat sink in summer and heat source in winter. In other designs, a large area of land is excavated 4’ to 10’ deep, long water pipes are looped inside of it and then the pit is filled in again with earth. This also becomes the source of heat or cool in winter or summer.

The heat pump unit sits inside of the building. It generates heat or cool through a refrigeration cycle that utilizes the steady temperature of water stored in the ground. For heat, this closed loop of water flows through the heat pump which extracts heat from it which it sends to the home by way of a radiant floor or air handler tied to the home’s ductwork. Since a heat pump is able to do cooling as well as heating, ducted forced air is most typical. As with any central heating system, room temperature is monitored and controlled using a standard wall thermostat or multiple thermostats in a multiple zone system.

Heat output from a GSHP is of medium (not high) temperature, so when designing a building that will use a GSHP, medium to low temperature heat distribution methods are necessary. Existing oil or gas-fired forced hot water heat distribution baseboard registers usually will not be workable with GSHPs.

GSHPs are more costly and difficult to install, especially in retrofit situations. Some contractors are focused on the installation of GSHP systems but mechanical engineers are often hired to supervise system design, product selection, installation, and integration with heat/cool distribution.

Heat pumps are all electric and burn no fossil fuels to operate. They are highly efficient at using electricity for heat and in summer they are efficient air conditioners for cooling. The latest models can provide heat efficiently in outdoor temperatures as low as 5 degrees F.

Wood pellet boilers and furnaces are potentially easy to retrofit into a home that already has an oil or gas-fired boiler or forced air furnace. This is because they have high temperature heat output that is very similar to the fossil fuel-fired units that have been installed for the past 100 years. Therefore they can directly replace existing boilers or furnaces.

The biggest difference is the fuel: Wood pellets take up more space than similar quantities of oil or propane and they generate some ash which needs to be dealt with every few weeks by the owner.

But wood pellet systems have similarities to oil and propane: Pellets are delivered as needed in bulk, from a truck, through a hose. Wood pellet boilers and furnaces run automatically without the need to load fuel. As with any central heating system, room temperature is monitored and controlled using a standard wall thermostat or multiple thermostats in a multiple zone system.

Note: The sustainability of burning either wood or wood pellets depends on factors such as the efficiency of the stove, the sourcing of the wood or pellets, responsible forestry practices, and the impact on local air quality. When using wood burners, it's crucial to choose newer, more efficient models and to burn well-seasoned wood to minimize emissions. For wood pellet stoves, using high-quality pellets and considering the overall energy lifecycle are important factors in maximizing sustainability. The efficiency of the burners are also an important consideration in reducing the amount of carbon dioxide emitted.