Can an old, poorly insulated building be retrofitted with a heat pump?
A question that I hear being asked all the time is whether an air source heat pump can properly heat an old building that predates modern building standards.
The accepted wisdom is that an old building such as this will be far too draughty and poorly insulated for a heat pump to be capable of providing sufficient heat to maintain a comfortable interior temperature.
However, this case study is living proof that old buildings can indeed be retrofitted successfully with heat pump technology. Not only that, but the cost savings and carbon emissions savings can be quite significant, particularly when the government incentive schemes are factored in to the calculations.
This was an exceptionally interesting job, which entailed the design and installation of an air source heat pump system to replace an existing oil fired boiler and ducted air heating system in an old church.
In partnership with Low Carbon Exchange and MBL Consultants the company commissioned have provided a cost effective and viable heating solution whilst also maintaining the historic integrity of the building.
Using the latest Clivet WBAN 105kW Air source heat pump with twin compressors and built in inverter driven smart pumps the system is capable of delivering 60˚C effortlessly to the emitter circuits.
The combination of Jaga fan assisted radiators and a Uponor wet under floor system maintains a balanced and comfortable environment with a fully programmable and weather compensated control system.
The Church was also in the process of claiming the Non Domestic RHI tariff which provided a revenue for the following 20 years.
How does an air source heat pump work?
An air source heat pump collects heat from outside a building using a refrigerant fluid, which is a type of gas that has thermodynamic properties that allow for the efficient operation of the refrigerant cycle. It then moves the heat inside, transporting it in the refrigerant, at which point it makes that heat available for heating the building.
The refrigerant cycle is a scientific process that uses a series of steps, including compression and condensation to effectively make use of electrical energy to move heat energy around the system. In the case of heat pumps, the movement of heat is from the outside of a building to the inside.
The means of transmitting heat into the building in this case is underfloor heating. Underfloor heating is particularly suited to use with heat pump systems because heat pumps operate more efficiently at lower temperatures.
Underfloor heating can operate at these lower temperatures thanks to the large surface area that is available for the transfer of heat from the water in the underfloor heating pipes, through the screed and into the internal space of the building.
Think of it like this. To heat a building, you can either have a very hot heat source with a small surface area for heat transfer, such as a fireplace, or you can have a lower temperature heat source that transmits a smaller amount of heat per metre squared of surface area. The trick is that the small amount of heat per square metre soon adds up across the entire surface are of the floor, thereby heating the building effectively.
This case study shows very well that an air source heat pump is perfectly capable of heating an old, poorly insulated building.
Steps were taken to improve the insulation and heat demand of the church, but these were not prohibitive.
Making use of underfloor heating is a very good way to ensure the heat pump system operates efficiently, thanks to the low temperature of such heat delivery systems.
Combined with the government incentives, this scheme makes for good value for money over the long term.