An important factor in meeting carbon reduction targets, and therefore an important aspect of building optimisation, is the source of energy used to heat the building over the course of its operational lifetime. Technology solutions are available that produce fewer harmful emissions than traditional gas heating, but these have not yet been widely adopted. As the Committee on Climate Change make clear in their most recent report, the buildings trade contributes disproportionately to UK carbon dioxide emissions, and power in the buildings sector is the main reason for this.
One alternative to gas that has been around for a while is the ground-source heat pump, a means of extracting heat from the earth and using it to heat a building. Put simply, radiation from the sun heats the earth, and the earth retains a temperature higher than that of the outside air. To extract this near-constant warmth, loops of pipework are laid in trenches outside and work like a fridge in reverse, extracting heat from outside and transferring it inside via a heat exchanger. Usually heat is distributed inside via underfloor heating or, in some cases, low temperature radiators.
Heat pumps use a certain amount of energy to pump fluids around, so it matters where the electricity comes from. If the electricity comes from a renewable energy source, carbon emissions can be entirely negated because heat pumps produce around five times more energy than they require to operate. As the Ground Source Heat Pump Association points out, 400% efficiency in terms of electricity use means that on its own a ground source heat pump will ensure “there will be 70% lower carbon dioxide emissions than for a gas boiler heating system.”
There are obvious benefits to operational expenses as well as reduced carbon emissions (not least because a heat pump requires almost no maintenance and will last for the full lifetime of a building, and because it requires no additional deliveries of fuel during operation). But another important benefit would be future-proofing: a building with a truly sustainable source of energy would be more valuable as a result, and therefore a more attractive prospect for investors as well as developers and owner-operators. As an additional benefit, unlike other power sources a heat pump would be largely concealed outside and underground, making it both aesthetically and ergonomically neat.
It has been pointed out before that ground source heat pumps are costly and often disruptive to install, requiring that a large area of land be dug up. For obvious reasons, they would not be practical in densely urban areas, and even more remote areas could be impractical if, for example, large deposits of salt require the use of expensive stainless steel, or immovable bedrock stands in the way of digging bore-holes. No technology solution will be applicable without adaption to every situation, and each development will require a tailored approach. But ground source heat pumps are a green energy source well worth considering, especially for new builds, and for small-to-medium sized developments off the gas grid.