At Future Ready Homes we love our heat pumps. 

Installing a heat pump is the fastest and easiest way to dramatically reduce your carbon footprint, because it doesn’t burn oil or gas. It’s fantastic technology capable of delivering amazing results – seemingly defying the laws of physics by producing efficiencies of 400% or even 500%. 

Yet a huge amount of resistance to heat pumps remains. ‘A heat pump wouldn’t work in my home’ is a refrain we hear all too often.

So we went to meet Nick and Margaret, owners of a 400 year old stone farmhouse in Clunbury. Their heat pump was installed by local heating engineer Josh Stead. It’s heating their previously cold and draughty home evenly and easily, at 500% efficiency – meaning for every one unit of electricity used to power it, it kicks out five units of heat. For comparison a new condensing gas boiler will deliver 94% efficiency at most.

Works to the ‘fabric’ of the house 

Nick and Margaret fell in love with the farmhouse despite knowing it needed lots of work to restore it. 

‘We had been put off previous houses we might have bought by the surveyors’ Margaret says. ‘So this time, because of the beautiful surroundings and location, we just thought despite the obvious structural issues with the house – we know it needs lots of work and we’ll find out the scary details in due course, we just want to go for it.’

The original heating system was an oil boiler. Despite being a relatively modern condensing boiler, it cost £2,000 a year in oil and even then, didn’t get the house warm. It was unevenly heated and some of the rooms were really cold. ‘Moving around the house you would go from a room which was reasonably warm to a cold temperature somewhere else. There was no heating in either bathroom, and none in the kitchen. I nearly froze that first winter’ says Margaret.

The house needed a total overhaul including some structural work, so Nick and Margaret took the opportunity to do some energy retrofit works to the building fabric at the same time.

‘We didn’t do anything fancy, except for the rather clever windows. The old single glazing was leaking heat but we were stuck with it because the house is listed, so we employed an architect friend to design some high-performance secondary glazing.’ The secondary windows used dual-pane technology, giving an overall thermal performance equivalent to triple glazing with a U-value of around one. 

‘We wanted to make the house less draughty and better at holding onto heat, so we improved the air tightness as well as the insulation. To avoid any moisture problems which might rot the old timbers, we were careful about using natural ‘breathable’ insulation materials, things like sheep’s wool and hemp plaster. We used traditional oakum for filling gaps in the timbers.’

While rebuilding some of the old stone walls, they were also rendered with Diathonite. Diathonite is a natural cork and lime insulating layer which is ‘vapour open’ so it allows the walls to breathe. Nick explains ‘Much of the insulation was applied externally to help keep the walls warm and dry’. Simple and effective. 

The solid floors were left uninsulated.

None of these improvements to the fabric of the house actually make the heat pump run more efficiently. What they do is reduce the rate of heat loss from the building, in other words make it better at holding onto the heat that the heat pump is generating. The numbers are impressive, heat loss was reduced from 14kW to 8kW at -4 degrees C. 

Installing the heat pump

‘We were really keen to replace the old oil boiler with an air-source heat pump’ says Nick.  

Enter Josh the heating engineer. ‘Heat pumps are fantastic pieces of kit. I used to fit oil boilers, living out in the sticks as I do, but I don’t bother anymore, I only fit heat pumps,’ says Josh. 

‘Fitting a heat pump isn’t rocket science. Any heating engineer should really be able to get a SCOP of 4 out of one, it’s just about doing your heat loss calculations accurately and taking care over how you design the system.’

The ‘SCOP’ or seasonal coefficient of performance is a measure of how efficient the heat pump is, using data for 12 months to even out seasonal fluctuations in weather and temperature. At a SCOP of 4 it is generating 4 units of heat for every 1 unit of electricity it consumes.

Nick says proudly ‘I’ve done the maths and this year’s result is 4.98 – we think that’s close enough to call it a nice round 5!’

‘The secret to the high efficiency of the heating system is to run it at a low flow temperature of 40°C. This means we needed new, larger radiators, and plenty of them. Where we couldn’t fit a large radiator due to lack of space constraints, like in the kitchen, we’ve got fan assisted radiators instead. The system runs at about half the former cost per kWh. Thanks to the reduced heat loss, we’re now heating twice as many rooms for nearly a quarter of the overall running cost. Thanks also to Octopus who have some clever heat pump tariffs, which give us cheap electricity at certain times of day and night but a higher penalty rate in the evening, in total we’re spending around £1100 a year now for heating and hot water.’

‘The house is a joy to live in now. It’s full of character, and evenly heated to a lovely warm 21-22°, even on the coldest winter days’, says Margaret.

Would a heat pump work for your home? Nick and Margaret’s experience suggests that it would, and it could save you money on your energy bills too.

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You can visit a heat pump local to you, including Nick and Margaret’s, through https://www.visitaheatpump.com/  

Josh Stead can be found on FaceBook or email info@jtsteadheating.co.uk or for more local installers that come with recommendations visit www.futurereadyhomes-directory.org.uk

For expert impartial retrofit advice from local charity Marches Energy Agency email tony.baker@mea.org.uk or visit www.futurereadyhomes.org.uk