The multi-million makeover menu

Looking beyond the lowest-hanging fruit,
Matt Ross weighs up solid wall insulation and boiler benefits – and gets excited about fuel cell CHP.

The mixed heritage of our housing stock – those millions of Victorian terraces, the inter-war suburbs and post-war estates – is here to stay. So there’s no way round the fact that, to make our housing stock more sustainable, we must refurbish our existing homes. And there’s not much argument about where to start. The first priority is to improve standards of insulation.

“Fuel cell CHP plus cavity and loft insulation could halve a three-bed semi’s CO2”

Recent government figures indicate that there are over ten million existing homes with cavity walls that could easily be filled with insulating foam. This straightforward retro-fitting operation can cut annual carbon dioxide emissions in a typical three-bed semi by 600kg or more – taking a hefty 10% off the average UK home’s emissions.

Then there’s loft insulation – hand in glove, as it were, with the filling of cavity walls. A report by BRE (formerly the Building Research Establishment) for Defra reveals that more than 17 million homes have less than 150mm of loft insulation. Getting that brought up to scratch costs a few hundred pounds at most, and can save some 300kg of CO2 emissions annually.

Other relatively simple retro-fitting includes draught proofing and the proper lagging of older hot water tanks.After that, though, making further progress on the insulation front becomes much more complicated. Upgrading to modern, double-glazed windows would certainly cut emissions and energy costs, but does not come nearly so cheap. The BRE report also finds that about ten million homes lack underfloor insulation, although here again it would take a long time to recoup the cost – unless the floor was being relaid in any case.
 
Then there’s solid wall insulation. There are 4.6 million older British homes without cavity walls, and retro-fitting solid insulation could make a massive impact on their emissions, potentially saving two tonnes or more of CO2 per house per year. It would come with a price tag, however, of more than £3,000. In terms of cost effectiveness, says John Henderson, the BRE report’s author, this puts it “on the outer bounds of what one would consider to be worthwhile”.

And there are other drawbacks. Sheffield City Council architect Jim Breakey, who runs a pilot sustainable refurbishment scheme for housing market renewal pathfinder Transform South Yorkshire, has rejected the idea of fitting solid wall insulation to the front of his demonstration home. “It would stick 75mm over the pavement – a public highway – and we’d have to extend the roof to cover it,” he explains.

There is no national planning guidance on solid insulation, notes eco-homes assessor and chartered planner John Kettlewell, who fears that householders could find themselves in “complicated arguments” with their council. “It would be nice if the government took the opportunity of creating a new regime for all this, because we need to encourage people to insulate the existing stock,” he adds. Mitesh Dhanak of the Eaga Partnership, which runs government insulation schemes, argues that “at some point, we have to persuade people to fit solid insulation. It’s a big chunk of the housing stock.” But, as yet, the technology is too intrusive, too untested and too expensive to attract most homeowners.

Solid wall insulation also has few fans among the guardians of our historic built environment. But there are other ways of making protected buildings more sustainable. Ben Stubbs, whose sustainability team at Constructing Excellence developed the Heritage and Lottery Fund’s recently-published ‘Planning Greener Heritage Project” guidance, points to the huge efficiencies that can be gained via roof insulation and tackling chronic draughtiness – whereas some historic buildings (if not Victorian terraces) have plenty of thermal mass in their thick walls already. Stubbs cites the long derelict late 17th century Valentine’s Mansions at Gant’s Hill in Redbridge as a prime example of sustainable restoration, featuring a biomass boiler, high spec roof insulation and low energy lighting – plus real community involvement and a focus on biodiversity in the surrounding park. Another success story is a listed Georgian tenement in Edinburgh where the marriage of the building conservation agenda with contemporary energy saving technologies (secondary glazing, loft insulation and new boilers) is now saving around one tonne of CO2 per home.

The microgen route

Paradoxically, perhaps, renewable power generation technologies may prove more popular. “Renewables aren’t anything like as cost-effective as insulation,” says Henderson. “But people tend to put them in for other reasons, even though on paper it looks like a crazy thing to do.” A quick set of calculations (using figures from government research for the new Carbon Emissions Reduction Target scheme) shows that, in terms of CO2 saved per pound, heat pumps are more than three times more expensive than cavity wall insulation, while mini-wind turbines are six times pricier and photovoltaic cells cost 14 times as much.

Prices may tumble as demand grows, particularly with the 2016 deadline for new homes to achieve zero-carbon ratings. Then the more reliable technologies – such as heat pumps, which can save three to four tonnes of CO2 emissions a year but currently cost the best part of £10,000 – could look economic. But the danger, says Henderson, is “that we get close and everybody says: ‘Uh oh, this is going to be really expensive,’ and they dumb down the regulations.”

Renewables aside, there are still 16 million old style boilers in UK homes. Replacing them all with condensing models, which trap exhaust heat, could save over 350kg of CO2 per unit annually. Or, looking just a little further ahead, there’s the prospect of widespread take-up of domestic-scale combined heat and power (CHP) systems, which generate electricity while heating the home.
 
One significant problem to date has been that gas CHP systems generate about seven times more heat than power – a particularly inappropriate ratio for the well-insulated homes which prospective ‘early adopters’ tend to live in. There’s a real prospect, however, of fuel cell technology changing that equation. And mass-market commercialisation of a fuel cell-powered CHP, developed by specialist firm Ceres Power, came a big step closer in January this year when British Gas signed an agreement with Ceres securing exclusive distribution rights.

“With fuel cell devices, the ratio of heat to power produced is more like 1:1,” says Ceres’ commercial director Bob Flint. “For a typical British Gas customer, we’d expect to see savings of up to 670kg of carbon [i.e. almost 2.5 tonnes of CO2], and about 25% of their total energy costs.” While the system – which is expected to cost £1–2,000 more than a condensing boiler – will initially run on hydrogen extracted from natural gas, it could also run on carbon-neutral fuels such as waste methane or biofuels. Indeed, given that boilers have their own natural replacement cycle, this may be the best way forward. “There are 1.5 million boilers sold in the UK each year,” says Flint, “and this unit is designed to plug into the same space.”
 
In a poorly insulated three-bed semi whose boiler needs replacing, fitting a fuel cell CHP alongside cavity and loft insulation could cut carbon emissions by more than half, without inflating the refurb bill by more than £2,000. Over a decade or so, that kind of refurbishment looks realistic on a national scale – particularly because householders would recoup their investment over a few years in lower fuel bills.
 
Window buying made transparentShould your refurb run to replacing all the windows? The price tag can make it hard to count that as ‘low hanging fruit’.

As for its effectiveness, in the past, the notorious blandishments of dodgy double-glazing salesmen ‘helped’ muddy the waters. Replacement windows became a subject where lack of clear guidance was a real barrier to effective action. Not any more. The nicely named British Fenestration Society has now introduced a standardised ratings system. Choosing the best carbon-cutting windows should be no harder than picking an energy-efficient kitchen appliance – you just look for the A-G energy rating label, or search the options at www.bfrc.org
Matt Ross is features editor of ‘Regeneration and Renewal’.

27 June 2008

Matt Ross

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