The Duchy owns lots of property in the UK. Many of the houses across the various estates are pre-1900. There are about 6 million pre-1900 homes across the UK and the country will not meet it’s net zero target in 2050 unless these homes are retrofitted. But doing that work and retaining the external appearance of these homes (many of them listed) and preventing condensation and mould is challenging.
The Duke aims to have his whole property portfolio net zero by 2030.
A semi in an estate in Aldford, Cheshire was chosen as a test case. It is a listed building in a conservation area.
Annual energy use has been halved. Energy used to heat the home has been cut by 94%. Whole-life emissions (now to anticipated demolition and disposal of rubble) are down an estimated 83%. Nobody is mentioning cost, but the pilot was done with the Duchy paying and the contractors were given a lot of leeway.
What follows are points gleaned from the report in the Times in no particular order:
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The contractors started with an airtightness test and thermal imaging to pinpoint heat leaks. The house did well on the airtightness test (windows are not the originals). It was 25% better than expected on thermal efficiency for the walls.
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It takes a lot more energy to build a house than to run it
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Contractors used natural, local materials. EG woodfibre board, lime plaster instead of gypsum. Where timber was needed this was sourced from trees grown on the estate. Wherever possible bricks and slates were reclaimed from other estate properties.
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Heatpump for heating and hot water
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The emissions calculation includes “cost” of transporting materials to the site
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Wood heater with direct supply of external air, burning logs from the estate
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A system that uses warmth from waste shower water to preheat cold water that will be used in the shower.
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Airtightness is measured by number of times air is changed in an hour. The average for a new home is 8 times per hour.
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This home started at 6.3 (very good fits for the windows) and is now 4.2 with an invisible membrane sealing the house. Because the house is in a conservation area this was done internally (it is more simple when done externally)
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Under 5 changes an hour you need an MVHR system to reduce condensation and mould.
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No PV because the house is in a conservation area. The Duchy is considering a central PV farm to provide power to all properties in the estate.
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But it does have an EV charging point.
Clearly the Duke has some advantages here over a person who owns a single property.
Houses in the UK now need an Energy Performance Certificate (EPC) at time of construction, renovation or transfer. This grades the house from G (poor) to A (excellent). There is no mandatory rating, but the people laying out the money must know what they are getting. This house moved from E to C. There are debates about the current EPC scoring system and it’s fitness for historic buildings. Especially when it comes to factoring in the MVHR which is regarded as pure load, when it fact it is there because the house has improved other aspects of it’s efficiency. Under the proposed new scoring scheme the house will get a B.
The project did not aim for an outright high score, but for a more attainable and realistic retrofit that could be used across the Duke’s holdings.
Visually the house still appears as a piece with those around it.