After running initial SAP calculations on the proposed fabric specification, we could see he was passing the SAP on fabric alone, so we started looking at potential heating systems. The client was aware that oil is the most carbon intensive fuel source, so wouldn’t perform well in SAP, but could potentially be offset with the use of PV. He’d heard mixed reviews on air source heating and didn’t want to dig bore holes or trenches for a ground source system. Finally, he didn’t want to rely solely on solar PV and direct electric heating. He asked us to compare Air Source Heating with a log burner against Oil and Solar PV.

We used a heat loss coefficient calculation to size a heat pump, then looked at average costs involved with supply and installation of the sized heat pump he’d need. We then looked at average costs of supply and installation of a log burner to help improve thermal comfort through the winter months. We then input this into the SAP software and produced a Design Stage SAP Calculation. We then did the same with an oil boiler and an array of PV, again producing a Design Stage SAP Report. We listed our findings in another report and weighed up the costs involved with the performance.

In this instance, the air source heating and log burner had a marginally more expensive initial cost. However, it would cost considerably less per year to heat the building, so would be a much better option. In addition, the size of the PV array needed to produce the same SAP rating would mean some changes would be needed to the roof design. The client decided to go with the air source heating option.