I was recently invited back to Widdop Gate Cottage to look at the refurbishment from a former Scouts Hostel into a residential dwelling. It was just over a year ago when I was asked to put forward suggestions for a sustainable and affordable heating system. There were some early feasibility discussions on installing a biomass heating system to provide heating to the Widdop Gate Cottage and Widdop Gate Barn, which is a holiday let, next door. This was quickly ruled out on cost grounds, which was a shame, as the holiday let is heated by oil.
All of these factors lended themselves to installing an Air Source Heat Pump (ASHP), as the primary heating and domestic hot water (DHW) system. Also included as part of the heating were two wood burning stoves. These would provide supplementary heating in the coldest parts of the year, should it be required, also as a fallback, should the ASHP go faulty.
As the former Scouts Hostel was being gutted, it was possible to specify higher levels of insulation and draught proofing, double glazed windows, and to install a zoned under floor heating system on the ground level, with oversized radiators upstairs.
The ASHP chosen was the 14 kW Mitsubishi Zubadan which is larger than required. The unit only consumes the amount of power being demanded, e.g. if there is a call for 8kW of heating, the unit modulates down to 8kW. ASHP also do not require a thermal store which makes installation more economical.
The main thing to come out of the review so far is not to set both heating and DHW to “manual” as this can confuse the controls.
The new tenants have only been in residence for a few weeks, so are still tuning their occupancy to heating requirements. A heat meter has recently been fitted to accuractely meter the heat produced. In retrospect it would have been useful to also fit a simple kWh meter to the electricity supply of the ASHP. This would have allowed more accurate monitoring of the coefficient of performance (COP), and the running costs of the ASHP.