In debates about transition and decarbonisation, residential housing stock sits at the heart of a dilemma. It’s a fact that the UK is an old country, with an unusually old housing stock. In England, nearly five million homes (out of a stock of 26.6m) were built before 1919 – around 46% were built before 1964 ¹ . The period 1981 to the present has seen, on average, some of the lowest periods of housebuilding in any time period and certainly much lower than the great housebuilding booms following the two world wars ² . This raises a significant issue in terms of the most efficient means to decarbonise older housing stock so as to make it ready for a climate constrained world. The residential sector is responsible for 17% of emissions, and so it's not immaterial ³ .

We were recently delighted to be able to visit Taylor Wimpey’s prototype ‘house of the future’ site at Sudbury where the company is trialling various technologies in a range of 2, 3, 4 and 5 bedroom dwellings to assess their optimum and cost efficiency as new regulations come through. From 2025 it is expected that all new-build houses will be required to be up to 75% more energy efficient than an equivalent house built under the 2013 regulations as part of the ‘Future Homes Standard’. This ambitious target is concentrating the housebuilding sector, and as we discovered, it amounts to much more than just heat pumps!

In a first for the industry, Taylor Wimpey have built five dwellings (soon to be marketed for sale) that are identical to others in their range, but with significant technological differences. In thinking about Net Zero for new homes, it begins with the ‘skin’ or the building’s fabric. The five houses have triple glazing and A-rated front doors as standard, coupled with thermal lintels which are five times more energy efficient than steel. Four homes were block-built and one timber frame to see how each fabric would perform (block appears to perform better than timber frame).

Internally, four of the five homes were fitted with different technologies to assess performance. These included waste-water heat recovery (where heat for hot water is separated from room heating), mechanical ventilation heat recovery, air source heat pumps (externally positioned), loft-fitted heat pumps, underfloor heating and perhaps most futuristically, infrared panels that heat people and things rather than the ambient air.

The trial allows Taylor Wimpey to understand the benefits, say of fitting heat pumps in the loft rather than elsewhere, or the merits of underfloor heating (simple, low maintenance and low energy), and upstairs using therma-skirt heating that replaces radiators. Battery storage enables energy generated from say solar panels to be stored and used when electricity is more expensive to buy so that surplus energy can be sold into the Grid. Waste-water heat recovery is a technology new to the UK but recovers heat energy via a heat exchanger as water enters the waste gulley and can then be reused to heat mains water. This is also low maintenance and has no moving parts. One of the more complicated technologies Taylor Wimpey is trialling is Mechanical Ventilation Heat Recovery which filters fresh air into a building and recovers warm air from areas of the house through a series of ceiling vents. This passes through a heat exchanger before being expelled. This system, as we saw, entails a complex pipework architecture that adds cost but is viewed as optimally beneficial for people who may have allergies.

In the most advanced trial house – effectively the UK’s first Net Zero dwelling at scale – Taylor Wimpey is trialling infra-red panels, which gently warm people and objects. The panels can be recessed into the ceiling or wall, but thereby remove the need for wet-led systems. Infrared solutions provide a natural, responsive heat and are relatively simple to fit. The company is agnostic as to which technology will emerge as being optimum. They were however clear that heat pumps are not the sole solution and may not necessarily be the best. As part of the trial Taylor Wimpey were clear about cost; fitted technology could not add more than £10,000 build costs to each dwelling. Moreover, in terms of consumer compatibility they would need to be roughly comparable to an equivalent dwelling heated by gas. The results have been surprising; some of the technologies were broadly comparable to gas, being no more than 5-8% more expensive for the consumer. Other technologies were up to 40% more expensive than gas⁴. The Net Zero House, which effectively has a brain commanding optimum use of the various technologies, had a net positive cost for the consumer with so much energy being sold into the Grid that bills would more or less always be in credit. However, this house was not economic to build, may be difficult to sell such is its complexity, and would have material supply chain issues at scale.

What were our conclusions?

Commendably, Taylor Wimpey has no settled view of what the House of the Future will look like. Their pioneering ‘ideas hub’ in Sudbury is testing how a range of potential technologies may work, and which appear attractive from a cost-benefit perspective in meeting the 75% energy efficiency target. The best ideas appear to be the most expensive, but that may alleviate at scale. Some of the technologies appear to require considerable maintenance, whilst others were easy to fit and could be left alone. The most advanced whilst demonstrating enormous consumer benefits would nevertheless be complex to manage and may deter buyers; it was also noticeable that smart cylinders, loft sited heat pumps and battery storage occupied considerable space in already fairly small houses.

This was a fascinating look into the future that will transform the way we build and live. However, it is sobering to bear in mind that with no culture of ‘demolish and build’ in the UK, the new-build sector only represents less than 1% of the total housing stock (England)⁵: The biggest challenge remains what to do about the UK’s ageing, slightly damp and draughty housing stock, whilst interestingly the relentless focus on energy efficiency we saw at Sudbury has no regulatory requirement for cooling, which in the South East could ultimately become as pressing an issue as heating.

Source

1. Age of houses in England 2021 | Statista
2. Ibid.
3. HMG provisional GHG figures 2022 2022 UK greenhouse gas emissions: provisional figures - statistical release (publishing.service.gov.uk)
4. Taylor Wimpey
5. HMG Housing Supply Net Additional Dwellings England 2021-2022 Housing supply: net additional dwellings, England: 2021 to 2022 - GOV.UK (www.gov.uk)