When it comes to heat pumps, there are three main options available, giving a wide range of suitability for different installations.

Ground Source Heat Pump GSHPs take advantage of the fact that the top 15m of the Earth's crust maintains a year-round temperature of approximately 12oC. Heat is taken via pipes buried in the ground. The pipe is usually a closed circuit filled with anti-freeze that absorbs heat from the ground. This heat is then concentrated and available for domestic hot water and underfloor heating.

Installation of a GSHP requires space for the pipes to be laid in horizontal trenches in the ground - approximately 2.5 times the internal floor area of the property. If there is insufficient land, vertical boreholes can be drilled, dependent on ground and geological conditions. The heat pump itself needs to be housed inside, typically in a plant or utility room, along with the other system units.

Air Source Heat Pump ASHPs work in a similar way, except they extract available warmth from passing air rather than from the ground. Air source may be the solution to projects where the use of a GSHP has been considered, but it is not possible to drill in a ground probe or install a surface ground loop on the property.

They are the easiest heat pumps to fit, either in a retro-fit or new build situation, since they require no groundwork or building work to install. The only space required is beside an outside wall, making them ideal for well-insulated houses and apartments. The other system units will need to be housed inside the property.

Exhaust Air Heat Pump

EAHPs extract air via ductwork connected to the warm areas of a building such as bathrooms, kitchens and utility rooms. Heat is removed from the air and transferred into the heat pump's refrigerant circuit before being discharged to the outside. The vapour compression cycle of the heat pump then raises the temperature of the refrigerant and transfers the heat into a water based system that can either warm the domestic hot water or heat the building. Units operate at low noise levels and can be positioned in a kitchen or utility area of the property.

Project Suitability

EAHPs are suitable for use in properties between 45 and 160m. Air source can also meet the needs of these types of property, along with detached houses or varying sizes and barn conversions. Ground source can be used in most types of house and barn conversions.