Can I fit a heat pump? What do I need to know?

At the start of 2022 we finally got rid of the gas supply to our home, and retrofitted an air source heat pump. With the high proportion of renewables in grid electricity now, this has led to an absolutely huge cut in our household carbon emissions, and we are delighted with how it has performed so far.

picture of a heat pump
Our Mitsubishi Ecodan

While we were planning this, I wanted to know more about what the process entailed and what we would need to think about – so I decided to write an article about it. I learned so much that I ended up writing a two-parter.

Among the things I discovered were that:

Heat pumps can work perfectly well in a old building with only a moderate amount of insulation – but the higher the heat loss from the fabric, the bigger the pump will need to be, and perhaps more crucially, the bigger the area of radiators you will need. If the fabric is really inefficient, you would need so much radiator you’d need to use the floor – ie dig it up, and install underfloor heating. At this point, you might opt to improve the insulation and airtightness levels of the fabric instead, and reap the benefits of increased comfort and lower fuel costs.

Air source heat pumps can be used in small terraced properties without causing undue noise nuisance, so long as they are sited carefully. Note that if the weather is nice enough to be sitting outside, the heat pump won’t be running much anyway.

Heat pump technology itself is reasonably straightforward – what can be harder is finding a good installer who really understands the relationship between pump, heating system, building fabric/heat loss, and your needs as a household. But a large number of very satisified customers proves that when done well, a heat pump is an excellent way to heat an old house, as well as being the obvious choice in a new one.

The articles I wrote (for SIGA) are here – Retrofitting a heat pump Part 1 – It might be easier than you think and Part 2 – The practical detailsĀ 

I also want to link this article by Jeff Colley in Passive House Plus magazine, about the wonderful Tipperary Energy Agency Superhomes programme in Ireland. I learned a great deal from what TIA achieved, and I mention some of this in my articles. But Jeff’s write-up gives more detail about the programme, and the results they achieved from combining whole-house fabric retrofit, good ventilation, and the installation of air-source heat pumps. Jeff’s article on the Superhomes programme is here.

Lastly, no post on heat pumps is complete without adding a link to John Cantor’s incredibly informative website (and the assocated book, ‘Heat Pumps for the Home’. John has been patiently informing the world about heat pumps for decades, and he is one of the most knowledgeable people on the subject anywhere.