SOME MORE HOT AIR

Another article from regular contributor Ewan Kennedy as he explains his experience with alternative heating systems.

Some more hot air

A feature of our present coalition government is their ability to take an idea that is basic common sense and apply a form of creative madness to it. The proposed ban on selling a tenement flat with a boiler in it propels this into the stratosphere.

Twenty five years ago, one of Glasgow’s restaurant entrepreneurs purchased my old office, triggering my early retirement, as city centre replacements were impossible to find, but also providing us with enough cash to knock down a relatively new, but shockingly built, kit house and build a new one on the same site. This required us to investigate heating systems in some detail. Around that time, thanks to having some good friends in Luebeck and also in Stockholm, I had had some interesting visits, staying in private houses, during which I learned quite a bit about how people keep warm in the cold North European winters.

The parents of my friends in Luebeck lived in a retirement complex, comprising a crescent of houses sharing a common heating system powered in their case by a biofuel boiler, but that could easily have been a ground source system.

In Sweden I learned that ground source systems had been in use for many decades. There was a story, which I didn’t try to verify, that when the metro system in Stockholm was extended, the local authority had to compensate people whose deep bore systems were destroyed by the tunnelling. 

I also learned at first hand a bit about the north European stoves, kakenlungnar in Swedish, Kachelofen in German. They are the total opposite of the trendy English woodburners that people install, that burn their way through a forest in no time, sending most of the heat up the lum. These have extremely small fireboxes, surrounded by thousands of firebricks with air passages among them. Like big storage heaters, they take a couple of hours to heat up and stay hot with minimal restocking. I mention them simply to show that burning solid fuel isn’t always evil. 

There follow some brief observations on what is possible and a note of our experience to date.

There are two main types of green heating system, air source and ground source. We opted for a ground source system, so I have no direct experience of air source. Both work by simply extracting heat already present in the natural environment via an electric pump. The technology is virtually identical to what is used in refrigerators, so Scotland  already has plenty of central heating engineers, even if some of them don’t know that yet.

For obvious reasons, air source systems are the easier and cheaper system to install; they require just a hole in the outside wall, with the device attached. I believe that they are the less efficient and that they have to work hard in cold weather. I’ve also heard that in extremely damp conditions ice can form on the outside, as the temperature of the air being emitted is below zero. The device then uses expensive electricity to keep itself operating. In some parts of the world they are useful to keep the house cool in summer.

A ground source system takes advantage of something we all learned at primary school, that the centre of the earth is very hot. The systems work by circulating water laced with antifreeze through the ground and passing the warm(ish) water through a heat exchanger. 

Some systems use a series of pipes sunk in trenches a few metres deep, but this requires a considerable area of ground, which becomes out of bounds for anything that might involve deep digging later. They are ideal, for example, for a community hall with a large carpark outside, but hopeless for a normal house with a small garden.

We opted for a system that involves two deep boreholes, 95 metres deep. Counterintuitively, this is probably cheaper than the shallow trench system, as there’s a lot of work involved in digging. Specialist contractors arrived and set up something reminiscent of early Texan oil rigs. We soon saw why they wore full oilskins in sunny weather; when they struck water there was a jet thirty feet in the air. They were happy when the drill hit rock, which, they told us, was also easier to drill through.

The heat is passed into a massive tank, supplying water hot enough for all normal purposes and also underfloor heating. It has proved very satisfactory to date, and the cost of heating and providing hot water is less than at our old Glasgow flat.

The main disadvantage would be that the equipment is massive and noisy, so it requires its own, sound proofed room. You couldn’t put it in a normal house without significant loss of useable space.

It’s also really only suitable for a new-build property, if underfloor heating is to be involved. Retro-fitting in an existing house will always be difficult.

And it’s a lot dearer than air source. Ours cost about £20,000 and we got a grant of £4,000 towards that. Costs would be higher now, but there are more companies around.

In summary, I’d say that a system should be mandatory for all new builds and especially for social housing, where it can be communal. Since our house went up, we’ve seen our local housing association build affordable homes in the village, in part of an area near a river with a flood plain. Had anyone in officialdom thought about it, there was a wonderful opportunity to use the flood plain to install a cluster of bore holes linked to a communal ground source system. Instead, the houses have full electrical systems. Needless to say, there are no chimneys and in the power cuts, which often occur when trees come down, people simply freeze.

MY COMMENTS

My thanks to Ewan to sharing his personal experience. Apart from the fact that most heat pump systems cost at least four times the cost of a replacement gas boiler, most suppliers mention that for them to be effective considerable improvements in insulation are also required. This can easily put another 10k plus onto the bill.

I am, as always

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