Greenhouse effects

The green house effect: building greener to tackle climate change

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We all know the climate is changing: so must our homes and how we build them.

The UK’s housebuilders will have to consider much more than bricks and mortar if they are to do their bit for climate change. Every new home must now be designed and constructed for maximum energy efficiency. Simplistically, things appear to be on course, but remain work-in-progress. Across the industry, drums are being banged with little dissent about the why, what, and how, albeit with some variations in tune and tempo according to individual agendas. Perhaps not surprisingly, more clarity, less uncertainty and, inevitably, more tangible government support would be welcomed.

The big number is the government target to build 300,000+ new homes annually by the mid-2020s (In 2020, the National House Building Council registered 123,000 homes, and 160,000 in 2019, pre-Covid). In context, a spokesman for the UK Climate Change Committee (CCC) said: “New builds play a critical part in the UK commitment to reach net-zero by 2050 – around 20 per cent of buildings in the UK housing stock in 2050 have not yet been built.” It’s clearly an opportunity with a goal at the end of it.
In terms of progress, it’s reckoned that homes are using 20 per cent less energy now than 20 years ago, alongside growing domestic consumption. Insulation is better, heating and appliances are more efficient. Smart meters are helping consumers to understand energy cost and usage.

In 2019, the Royal Institute of British Architects set up its 2030 Climate Challenge initiative, encouraging architects to design buildings with net-zero lifecycle emissions by 2030. To date, the take-up rate has been small, with a reported 230 of the UK’s 4,000 firms signed up – indicating that architects may be preferring a more independent approach. Whether COP26 will act as a catalyst to swell support, time will tell – the conference will have a full day dedicated to the ‘built environment’.

In January 2021, the government issued its response to the Future Homes Standard (FHS) consultation. Setting out the stall for building regulations changes in England, views had been sought on conservation, power and ventilation. The FHS is to ensure that all homes built from 2025 will produce 75-80 per cent less carbon than those completed under current regulations, with a commitment that new homes will not require any refurbishment to reach zero-carbon as the grid continues to decarbonise, and no new home built under the FHS will rely on fossil fuels. An interim uplift to building regulations will ensure that homes built from 2022 will produce 31 per cent less CO2 than under current standards, ahead of full FHS implementation in 2025.

Why has the wake-up call taken so long? Dr James Campbell, head of the Department of Architecture at the University of Cambridge, says: “Having talked about this for over 50 years, developers and the government finally seem to be demanding that the industry moves in this direction. Climate change has been the driver and there is a genuine political appetite for change. Now, we see clients asking for zero-energy, zero-carbon buildings. Younger architects used to get jobs because they knew about computers; the next generation will get jobs because of the need to understand Passivhaus (see below) and how to use energy software.”

A number of tools and technologies are primed and ready. Giving a steer, the CCC says: “The technology exists to deliver homes which have high levels of thermal efficiency – staying warm in winter, cool in summer, while being moisture-safe and with excellent indoor air quality. By 2025 latest, we recommend that (1) all new builds need to rely on low-carbon heat (e.g. heat pumps/low- carbon heat networks) and be off the gas grid and (2) to have ultra-high energy-efficiency – space heat demand of 15-20kWh/m2/year.”

One of the key elements is airtightness. The situation is improving, but slowly, i.e. homes are becoming less leaky. Data collected by the Building Compliance Testers’ Association (BCTA) backs this up. Barry Cope, scheme director at the BCTA, says: “With homes improving by around 0.1m3/h/m2 @ 50Pa per annum, it will take another 30 years at least for us to achieve levels of airtightness linked to net-zero homes. However, upcoming changes to building regulations look to reduce the maximum air leakage homes are allowed to leak through gaps and cracks. There is no such thing as a home being too airtight, only a home that doesn’t have adequate ventilation to match the performance of the home. A lack of quality control is causing new homeowners to see the effects of under-ventilated properties such as mould and overheating, but these often get pinned on airtightness.”

Green House Building infographic - inline

Image credit: E&T

Passivhaus, arguably the de facto standard for home energy-efficiency, is growing in significance. Local authority developers such as Exeter City Living (ECL) are building more Passivhaus housing – airtight performance means both energy efficiency and air quality is up to 90 per cent better using heat-recovering ventilation and filtration systems.

“Our work has helped reduce the cost premium of building to Passivhaus standard to less than 5 per cent,” says ECL managing director Emma Osmundsen. She makes the point that Passivhaus should not limit design creativity, but be an objective from the outset. “Building to Passivhaus standard can add some challenges, but our experience and understanding continues to grow with every development,” Osmundsen continues. “Essentially, we adopt a ‘fabric first’ approach to maximise component and material performance. One particular material is Porotherm blocks for their thermal performance, and when used with wet plaster, improved airtightness is achieved more simply than with other methods.” Triple glazing is also a key factor to achieving the necessary thermal performance, along with careful detailing to avoid cold bridging. The increased air tightness requires a mechanical ventilation system with heat recovery (MVHR), which improves air quality and reduces heat loss.

According to the CCC, there is a real need to focus on reducing the whole-life carbon impact of new homes, including embodied (material production) and sequestered (stored) carbon. Using wood in construction to displace high-carbon materials such as cement and steel is one of the most effective ways to use limited biomass resources to mitigate climate change. Every 1kg of timber removes 1.8kg CO2 from the atmosphere. “Increasing [the number of] new homes built in the UK using timber frame construction systems to 270,000 annually could triple the amount of carbon stored in UK homes to three million tonnes a year,” says a CCC spokesperson. Factor in insulation alternatives such as hemp lime, hemp fibre and sheep’s wool and more beneficial savings will result.

Housebuilder Barratt Developments acquired Oregon Timber Frame in 2019 in pursuitof its objective to extend the company’s use of modern methods of construction (MMC). Oliver Novakovic, group technical and innovation director, says: “We set a target of delivering 25 per cent of homes using MMC by 2025, particularly featuring timber frame. In acquiring Oregon, the business is responding to the opportunities that timber materials can provide for both productivity and environmental performance.”

Returning to some of the ‘new’, or not so new ascendant technologies, more and more solar panels are being installed on properties up and down the land. “I see solar photovoltaic (PV) moving from often token amounts to satisfy planning requirements,” says Stephen Barratt, managing director of energy specialists Solar Sense. “Modern thinking is to have roof power from earliest to latest – covering east and west roofs achieves that. The cost of PV panels has reduced from £3 per watt to 20p per watt in ten years, so cheaper than other sources and with batteries coming down in price to give night power as well.”

To make a real difference, solar technology needs to be rolled out far more widely across the UK – a big ask, especially as most PV panels are made in China, so rising demand could put pressure on supplies.

Alongside the need to save energy, the growing popularity of electric cars is surely a compelling event driving up demand for home-​grown electricity. Most chargers are now smart and can be switched to use free surplus PV power. Paul Lawler, head of communications at Bellway Homes, explains that the company’s policy now is to install an untethered 32A 7.4kW ‘smart’ Ethernet or Wi-Fi and metered electric vehicle charge point (EVCP) on all developments where charging is required.

Is there a need to see a robust national strategy for new builds to have EVCPs as standard – more rule than exception? Perhaps all in good time. Taking a broader view on electricity supply, another housebuilder, Wates Group, is exploring grid management technology. “This will allow energy to be imported and exported to the grid at optimum times,” explains principal design manager Stuart Jones. This will not only reduce people’s energy bills and carbon use, but at the same time smooth peaks and troughs in the grid demand and generation profile, he elaborates.

Are heat pumps the only answer? “Heat pumps are progressing and proving highly reliable without the servicing and risks of gas while saving carbon,” Solar Sense’s Barratt explains. “Switching all gas boilers to heat pumps is a tall order; in towns, flats and smaller houses should probably go to stand-alone electric heaters as home insulation improves. Larger and rural homes, together with anyone with oil-fired boilers, should opt for heat pumps.”

Despite the challenges and uncertainties, the boundaries of what can be done are being stretched to meet climate change demands. Some of the leading builders are creating new opportunities and engaging with the tools at their disposal – there’s a lot of learning and knowledge to acquire.

Bellway Homes is constructing ‘exemplar’ plots to assess the impact of low-carbon/electrical space and water heating on customers’ energy bills. Designed around government information released so far, the aim is to assess fabric and heating options alongside technology such as solar PV with battery storage, waste-water heat recovery and mechanical ventilation with heat recovery.
Wates has worked with Cardiff Council for the installation of heat pumps, solar PV panels, batteries and EV charging points for 1,700 new homes as part of the Cardiff Living Project.​ “The homes will be to a fabric standard 17 per cent better than current building regulations, using MMC,” Jones explains, “including sites being built to Passivhaus standards to reduce homes’ energy output and carbon footprint.”

Barratt Developments says that all its new homes will be ‘zero-carbon-ready’ from 2030, but to get there the company understands the need to innovate, test new technology and develop new talent. “We’re starting work on a prototype zero-carbon, wildlife-friendly home that will surpass the 2025 FHS and can be built at pace and scale. We’ll trial innovative construction, as well as a range of smart and sustainable technologies. Some may not succeed, but all will move us forward,” says Novakovic.

There are considerations that might collectively make the business of building more energy-efficient homes more commercially attractive. Economies of scale should see costs of technology and innovations fall. In parallel, construction costs may rise as building regulations become more demanding. Inevitably, some burden of cost will fall upon home buyers, who will also need to be convinced of the benefits and understand how to use the new technology. Therefore, there may be mortgage offer considerations. Wates is currently working with Sero Energy and Monmouthshire Building Society to pilot a green mortgage product that will factor reduced energy costs into the affordability calculation for a property.

A design and potential cost factor that has arisen since the pandemic is the increase in home working. Unless there’s a big swing back to the office, more and more of us want workspace in our homes – not just somewhere for a desk, but with the right light and ventilation provisions.

However, building 300,000-plus homes a year will need a sizeable, experienced, and increasingly qualified workforce. In a Construction Industry Training Board survey, 78 per cent of respondents said there was a skills gap for decarbonisation in their occupation or profession. CITB concluded that a rapid increase in skills is needed, with large-scale re-skilling and key issues addressed, including build quality, sector reputation and training readiness.

Building energy-efficient homes may be today’s headline grabber. But ultimately, the key is to ensure that all efficiencies and savings deliver on the promise.

Long-life buildings

Choose refurbishment over demolition

It is still relatively common for industrial and commercial developments to start with demolition – not a good thing when dealing with climate change.

There are two main issues – the first is the construction of short-lived buildings. Current legislation works on life-cycle analyses that assume a building lasts 60 years. So, developers build buildings that will only last 60 years. “We need to think more long-​term,” says Dr James Campbell from the Department of Architecture at Cambridge University. “Our students are already designing projects where the carcass will last for centuries and the interior can be refitted.”

Second, under the current tax regime new-build is VAT-free (or lower rate), but conversions are charged at the full rate – so it is often cheaper to demolish and rebuild. “We need a tax regime that encourages good practices, not incentivises bad ones.Upgrading most existing buildings to meet modern standards of insulation and air-tightness is difficult, but far from insurmountable,” says Campbell.

What the experts say

Existing housing: ‘The elephant in the room’

“One of the biggest challenges is our existing stock. At least 19 million homes in the UK need to be retrofitted to become low carbon. To achieve the government’s net-zero targets by 2050, three homes every minute will need to be retrofitted with energy-efficient improvements. We are delivering a zero-​carbon retrofitting service for social housing landlords to include a feasibility service, installing pilot properties, large-scale installations and monitoring.” Stuart Jones, principal design manager, Wates Group

“Zero-carbon homes are an essential part of the puzzle, but will not in themselves deliver the UK’s climate goals. We must improve the footprint of the existing housing stock. This must involve collaboration and bold long-term government decisions. As a nation we must not shy away from raising awareness among homeowners.” Bukky Bird, Barratt Developments

“Improving existing builds will significantly reduce the strain on energy suppliers – homes can be kept warmer for longer using less electricity and gas. Existing homes need to be assessed for air leakage, insulation and ventilation, but must be improved together. Tests can even tell which rooms to target to gain massive performance. Large-scale roll-out of heat pumps will build supply chains to enable deployment of retrofits.” Barry Cope, Building Compliance Testers’ Association

“The owner-occupied sector is the biggest, yet worst-performing tenure group. The RICS is investing significant resources and expertise to address the challenges facing the private sector, working in collaboration with government and property stakeholders to create long-term solutions.” Matthew Collins, RICS

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