Cold comfort

// the building envelope

Technical Editor of HA Magazine, Bruce Meechan, continues his series of columns on heat pump technology.

After an unusually mild autumn and run-up to Christmas, the British climate reminded us just what winter should feel like, with prolonged low temperatures and generally miserable weather from the New Year onwards. Then more recently, of course, the papers had a field day with pictures of blizzard conditions the length of the country when an Arctic blast arrived on exactly the same day in late April as back in 1982.

Almost a month after Easter and the start of British Summertime, the hills were white from the North-east down to Dartmoor in Devon, while business owners in the Cairngorms were rubbing their hands at the prospect of a significantly extended skiing season this year. 

However, with average temperatures for April in the low 40s, there is no doubt that most of those who were already considered ‘fuel poor’ will have been forced to spend out even more than they will have budgeted on heating their homes. And, once figures are available, boiler manufacturers will be reporting higher than expected sales as worn out units gave up the struggle.

The challenge for air source heat pumps is potentially greater, as in these conditions their “fuel” comes pre-chilled and they are having to work far harder. In fact manufacturers and installers of models that have not been developed specifically to suit the UK’s temperate maritime climate are likely to have been dealing with numerous call–outs.

The electricity consumption for all air source heat pumps inevitably rises as ambient temperatures drop, but specifiers can mitigate against this by choosing those with the best seasonally adjusted coefficients of performance. Certainly, studies by the Energy Saving Trust and BSRIA indicate that manufacturers’ investment in research and development not only improves reliability, but greatly reduces the incidence of defrost cycles for the heat pumps during frosty weather.

The previous winter saw a spike in statistics for our disturbing and persistently high excess winter deaths – due in part to problems with mutations of the flu virus. We know, however, that offering the frail and elderly affordable warmth and a good indoor environment, greatly improves their health. And high efficiency heat pumps can play a crucial part in achieving that.

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