All Green Heating, Ventilation, and Air-Conditioning equipment should, first of all, be checked for energy efficiency. While the heating and cooling equipment in a home provides a comfortable living environment, it is a major energy consumer. For this reason, in “greened up” homes the heating unit – furnace or boiler – is replaced with a green heating unit with the Energy Star label. For instance, a conventional heating unit with an operating efficiency of 60 to 65 percent is often replaced with a condensing boiler or furnace with a 90 percent operating efficiency.
The increase in efficiency is due to a redesign of the heat exchanger, which extracts the heat from the exhaust gases that normally escape up the chimney. During the process, the temperature of the exhaust gases drops to a point when the water vapor condenses, producing additional heat. The temperature of the flue gases with a conventional furnace is about 45-550 degrees F, while with the high-efficiency units it is about 120-130 degrees F.
Green Heating, Ventilation, and Air-Conditioning – Types of HVAC Systems
A geothermal heating and cooling system is one of the most commonly used types of HVAC system, found rather in new construction than in existing homes. Basically, this system is a modified heat pump system, often referred to as a ground source heat pump. As opposed to an air source heat pump where the compressor/condenser is located on the outside of the house, the geothermal heat pump is usually located in the basement or utility room.
The geothermal heat pump is packaged in a single cabinet that includes the compressor and refrigerant heat exchanger, as well as various other controls. During the winter months the heat source is the earth, and during the summer the system uses the heat sink.
The system circulates a water or antifreeze solution through a loop of high-density polyethylene pipe buried in the ground. Two types of loops are used with this green heating system: open and closed loops.
The open loop system is simpler, however it is less common. It circulates a constant source of ground water through the heat pump’s heat exchanger, discharging it back to the same aquifer. The supply and return lines, however, must be placed far enough apart so as to ensure thermal recharge of the source.
In a closed loop system, the polyethylene pine can be laid out either vertically, in holes 75 to 500 feet deep, or horizontally, in trenches dug below the trench line. How it is laid out will depend on the ground conditions and available space. If there is a pond or stream that is deep enough and with enough flow, closed loop coils can be placed on the bottom of the pond/stream.
The water/antifreeze solution circulating through the heat exchanger in the heat pump cabinet will either add or extract heat, depending on which cycle the system is operating under.