With underfloor heating, warmth passes into the room from the floor and it is therefore important to reduce building heat loss, including downward heat losses into the ground or the floor below. Recent changes to Part L of the Building Regulations have focused attention on the importance of insulation levels within domestic dwellings and in a new building that meets the regulations, there will always be an adequate level of floor insulation, and in these circumstances pumps can provide 4 to 5 kilowatts of free energy for every 1 kilowatt of electricity used to power them.
Usually, the aim should be to insulate the building so that less than 50 watts of heating are required per square meter of floor space. This will then ensure that the UFH water temperatures can be kept to a minimum and the heat pump can operate at a higher Coefficient of Performance (COP) -typically 4 – 5 for a ground source unit. In general it is more cost effective to increase insulation levels than it is to install a larger pump and buildings that exceed the requirements of Part L of the Building Regulations are most suitable.
In theory, there is nothing to prevent a heat pump from working in a building with a higher heat loss, such as a property that requires up to 80 watts per square meter. However, higher heat loss requires higher heating water temperatures from the heat pump – typically 55°C rather than 35 – 45°C, meaning the heat pump’s COP may suffer although the heat pump may still be sufficient to heat the property.