100% Detail preview: Show Focus

As part of the government’s drive to reduce carbon emissions and raise awareness of free, clean sources of energy, it has attempted to encourage the uptake of renewable technology through the Low Carbon Buildings Programme. Now in the second phase of the capital grant scheme, a £50m pot is available for the installation of microgeneration technologies by organisations including local housing authorities, housing associations, schools and other public sector building users and charitable bodies.

But while including renewable technology in new-build schemes should be simple, greater gains are to be made by improving the efficiency of, and retrofitting renewables to, existing buildings – and this is one of the key topics that will be discussed at 100% Detail at Earls Court in London later this month.

It is widely recognised that before any renewable technology is considered for a building, its envelope must already be as efficient as possible. Elliot Carter, associate director at PDM Consultants, points out that “the fabric of a building must be improved before you start retrofitting any eco-bling”. Focusing on the less glamorous tasks of making sure a building is efficient using draft proofing, insulation, and double glazing is a priority if the energy created through the use of renewables isn’t to be wasted. Without ensuring the air tightness of a building, fitting microgeneration technologies would be “like pouring water into a leaking bucket”, according to Anthony Heywood, associate director at the BRE.

Conservation areas

Even in conservation areas, it is possible to improve a building’s efficiency without falling foul of planners. In many cases, it is possible to fit double glazing to the rear of the building, even if it cannot be added to the front for aesthetic reasons.

Once the building is efficient, the most effective technology to employ is solar thermal, according to Carter. The technology is currently particularly attractive, with fuel prices driving up heating bills. “Although its success relies on the building having a south-facing roof,” Carter adds. Installers must also be aware of the roof covering and its ability to match the specific solar panel. In the case of solar thermal panels, they are often designed to fit tiled, but not slate, roofs.

Giles Williamson, product manager at Carbon Energy Solutions, a company thriving on the back of increased demand for renewables, believes large-occupancy buildings such as flats can benefit greatly from solar thermal systems. “We’re currently looking at putting a solar hot water system on a six-storey block of flats,” he explains. “If you place a large amount of tiles over an area as large as this, you can go for a communal hot water system.” However, retrofitting into a large heating system will not be without problems. There can be difficulties integrating the system into existing pipework and contractors must make allowances for problems such as legionnaires. No such problems exist in residential applications, Williamson says. “As long as the right cylinder is in use, then all that is required is to put some panels on the roof, wire them up and you’re away – you do need a plumber to do it, though.”

To this end, manufacturers are now designing products that offer a clear distinction between the parts that the roofer installs and the internal parts that the roofer passes through to the plumber or electrician. The National Federation of Roofing Contractors runs courses for contractors in the installation of solar panels.

Careful positioning

Like solar thermal, the correct positioning of photovoltaics for electricity production is paramount. “Sighting issues are crucial with all technologies,” continues Heywood. “Shading has a big effect and installers need to be sure there will be no over-shading for the 20- to 25-year lifetime of the product.” This can pose problems, particularly in city centres, where tall buildings are likely to be constructed, which may block the energy source.

Despite being relatively simple to retrofit, photovoltaic technology will work efficiently only in large buildings, where there is plenty of space for
panels. “To create 1kW of power, you need eight panels, which is approximately 8m2 of space,” explains Williamson. “Most houses don’t have this kind of space. However, you can put them on the side of tall buildings and be confident they will stay there as they’re fairly vandal-proof.”

Carter agrees that fitting photovoltaics on office buildings is a relatively straightforward way of energy creation. “On offices there will be a flat roof and you can get away with putting pretty much anything up there,” he says. “What’s more, if you are replacing the façade of an office building, particularly if it has an expensive exterior like marble, then putting solar panels on the envelope will not add expense. But there’s still the problem of orientation.”

Wind turbines

The same is true of the positioning of wind turbines. Widely derided for their application in urban areas, turbines are best suited to tall buildings where they can receive un-interrupted winds. “Out-of-town retail parks where there are clear spaces can also benefit,” continues Heywood. The top of the building is the best position but, as has been highlighted by their use on houses, noise and vibration must also be considered.

“There is more scope for the use of turbines and photovoltaics on commercial buildings,” says Carter. “We’re going to refurbish and refit an office building in Brixton and we’re looking at the possibility of a wind turbine. Solar thermal isn’t suitable as the building doesn’t require much space heating and has minimal hot water usage. It’s a shame as it’s by far the cheapest.”

At the other end of the scale, ground source heat pumps will be an expensive and messy product to retrofit compared with the plug-and-play nature of solar thermal, photovoltaics and wind turbines. Sites such as schools and hospitals are the most likely to benefit as they are likely to have an expanse of land suitable for its installation. “Heat pumps are the next step forward for new dwellings,” explains Williamson. “In terms of retrofitting it is relatively easy, but only if you have a large area that you are happy to dig up.”

However, Carter believes that a greater hindrance than cost in the uptake of renewables is currently practicalities. “If building owners want to use renewables, they are more put off by sourcing them, getting planning – which can still be a problem – and organising installation. I think an attractive service for a contractor to offer would be a one-stop shop for advice and technical ability. That would be of real benefit to the market.”