Eco-home scores high with low temperature heat pump installation

High Trees, Normanton, Nottinghamshire

Mark Lewis’s newly self-built two-bedroom cottage for his retired parents has a low temperature heat pump at the centre of an eco-friendly lifestyle design for maximum comfort, economy and efficiency.

What is the background to this initative?

It was designed with an older couple in mind. This eco-home is designed for low energy costs and no worries about heating. It’s built from structural insulated panels (SIPs), clad externally with brick slips, and it is all on one level, apart from a 30 sq.m mezzanine above the kitchen.

What else adds to the green credentials of the project?

A 6-Class Daikin Altherma low temperature R-split air to water heat pump and 3.0 kW solar panels that can enhance the heat pump’s overall efficiency. If the heat pump is on and the solar panels are producing electricity, energy from the panels will be used before anything is taken from the Grid.

We received a £5,000 grant as a self-build eligible property. A new developer can’t access the scheme, but you can for a self-build – or for a retrofit if you are taking oil/gas/direct electric heating out.

Mark Lewis, managing director of Cambridge-based Airway Group

How is the heat distributed indoors?

The heat pump serves 11 underfloor heating zones downstairs, which are always open. A Daikin Madoka controller allows small adjustments of the indoor temperature, when needed. The mezzanine has no heating, but is warmed by convection currents from downstairs.

What about domestic hot water?

The heat pump also serves a 230-litre Daikin domestic hot water cylinder. This has an integrated Hydrobox, containing a pump and other hydraulic components needed for the heating and hot water systems. The cylinder shares a small storeroom with the manifolds for the underfloor heating system.

How effective is the heating system?

With the flow temperature below 30oC the floor gets only to about 26 or 27oC – but the indoor air temperature is still a comfortable 23 or 24oC. Rapid heating could be a problem – but when it’s on all the time it runs beautifully. It’s a perfect case for commissioning, then just leaving it alone.

And in technical terms, how’s it doing?

Last time I checked, the seasonal coefficient of performance was 4.7. It’s running in weather compensation mode as well, so it’s going to produce some really high performances.