Low-Carbon Struggles

  • Date: 12/03/20
  • A correspondent

Green heating systems can be a nightmare

This article was sent by a correspondent who wishes to remain anonymous.

We built a new house seven years ago, after spending two years researching the best, most modern way to construct it, with a view to managing the increase in energy prices. After consulting several architects and heating consultants, we decided on a thermal mass house construction, I won’t go into too much detail, but essentially it means building a house using a solid interior structure and then heavily insulating the exterior walls floor, roof and using thermal-insulated aluminium window frames and triple glazing.

However, the main concern was the type of heating system. We consulted four heating consultants to try and establish the best system to install and this is when the fun started. Again, I will not go into too much detail of the options, but we were astonished at what we were told.

Solar

Installation would be quite expensive and the system would not be particularly efficient. Although we had a south-facing house, the roof area facing south was not large due to an earlier planning restriction on the roof height. The consultants explained that solar would not give adequate heat anyway, and we would need to supplement it with either gas, oil or a heatpump.

Air source heat pump

When pressed, two of the consultants admitted that air-source heat pumps had issues: the cost of supply and installation, the space requirement, and there can also be noise issues. But the bombshell came when they stated that air-source heat pumps lose efficiency at around 2–3°C. Below freezing, the air-intake vanes need heating with an electric element; otherwise they seize up and can’t be used. We were shown a graph, demonstrating that the drop off in heat recoverable at low temperatures was dramatic, and we pointed out the obvious concern that cold weather was when we need the heat. It was explained that we would then require a supplementary heating source, such as electricity, gas or oil.

Ground-source heat pump

A ground-source heat pump and the associated equipment carries a capital cost of tens of thousands of pounds. It also requires a large area of garden, to be excavated to around 2 meters depth, for the underground pipes. Alternatively, it is possible to bore a hole deep into the ground instead, but precisely what depth is unknown and depends on the strata below the house. There would be no guarantee of the energy output gained by this method, so we would have no idea if the spending would deliver adequate heat and hot water.

The costs varied depending on the supplier, but as a ballpark figure the solar came in at around £9,000, the air source pump/exchanger around £8–10,000, the ground source heating in its flatbed variant at around £16,000, rising to £23–30,000 for a borehole variant, depending on the depth and the size of heat exchanger required. It should also be noted, that the heat pumps would require a high input of electricity to work the pumps and heat exchangers.

In the end, the two candid energy consultants admitted that the mains gas that was already available in the village would be the most cost-efficient approach, even with our high-efficiency thermal-mass house construction. In their opinion, the other forms of heating were more suitable for areas off the gas grid. Unsurprisingly then, we opted for gas.

We are glad we researched these questions so carefully. I have recently read several articles about newly constructed houses whose owners have installed green energy systems and have then had to cope with energy bills running to thousands of pounds per annum, even for modest dwellings. Even Kevin McCloud of Grand Designs fame was involved in one of these projects.[i]

To end, even with our expensive build we have seen our energy bills increase by almost 55% in the seven years since we moved in. This is despite us never having used the upstairs heating and the underfloor heating of the ground floor operating only as and when required to maintain the ambient temperature in the living areas. The electricity element has been the main driver.

Who do they think is going to buy the new green ecohouses? Are developers going to be honest with prospective owners about the energy costs they are going to be taking on? Electrical heating on cold days in winter will not come cheap. It won’t take long for the true cost or heating these properties to become public knowledge. The building industry should simply refuse to go along with this madness.


[i] https://www.swindonadvertiser.co.uk/news/9778336.residents-raise-list-of-problems-with-grand-design-mans-housing/

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