Mass renovation project halves energy use of existing homes

CC BY 2.0 Energiesprong International

What if we declared climate change a crisis and put some serious resources to this type of initiative?

We’ve seen plenty of projects putting solar on affordable or social housing. But every good TreeHugger knows that, before looking at renewable generation, we should first figure out how to reduce overall demand so there’s less renewable energy that needs to be generated.

Lloyd has highlighted the work of Dutch initiative Enegiesprong in the past, identifying it as one of just five solutions that could collectively roll back carbon emissions. So it was good to see that this effort – which involves pre-fabricated insulated cladding, rooftop solar, smart water heaters and other relatively off-the-shelf solutions to retrofit existing houses – is now making inroads in the UK too.

As Business Green reports, some 150 social housing homes in Nottingham, England, are becoming some of the first to receive funding (from the European Union, Brexiteers should note!), and initial pilot homes are showing a rather impressive 50% drop in overall energy bills.It should be noted, of course, that costs are relatively high – £85,000 per property, in fact – which means the savings of £60 or so a month are going to take many, many decades to recoup if we look at energy bills alone. It’s worth noting, however, that Energiesprong also claims significant reductions in home maintenance costs, improvements in overall health and comfort, as well as the fact that the home looks significantly nicer from the outside too. Add to that the fact that mass adoption of this approach would accelerate Britain’s already falling need for energy generation, and one can imagine that there are significant societal savings too. Oh, and then there’s this thing called climate change…

Given some of the other projects our elected leaders are willing to squabble over cash for, I’d personally argue that this is money well spent. And the more such projects are undertaken, the lower the costs will become. Here’s hoping we see many, many more.

Net Zero Energy housing from Energiesprong on Vimeo

Reduce demand in existing buildings!

One can never lose sight of the fact that there are millions upon millions of buildings that are existing and are not energy efficient, and that have to be renovated or replaced. Another speaker at the Drawdown session, Larry Brydon, reminded me of EnergieSprong, a European concept upgrading buildings that is slowly coming to North America. It’s an industrial scale prefabrication of cladding that wraps existing buildings with foam, cladding, windows and doors to take it to Net Zero energy in a day or two.

It works well for repetitive designs like rows of townhouses or apartment buildings where there is less exposed area per unit, but retrofitting single-family houses will be another story.

exterior of houses
© Rick McCullagh

These townhouses shown in Passivehouse+ might well be, both efficient and almost carbon free.

Making old Victorian houses energy efficient is hard, and is often done with a lot of spray-in plastic foam. Even in my own Edwardian house renovation I used a little foam in tight spaces. Doing a renovation of a townhouse to the Passivhaus Enerphit standard (a Passivhaus standard for renovation) is really hard.

rear of renovation© Rick McCullagh/ The new rear elevation

That is why this retrofit of two Victorian townhouses in Manchester is so exciting. John Cradden writes in Passivehouseplus magazine about how it not only hits the tough Passivhaus Enerphit standard, but is foam free.Renovations are often done by bringing in the spray guns and sealing it all tight with six inches of urethane foam. I once attended a lecture by a so-called energy expert and author who proudly described how he lined his 200-year-old stone house with foam and we all rolled our eyes, the architect next to me saying, “He just destroyed that house.” Moisture has to move through old walls, and often has to be driven out by a little interior heat. If there is a strong freeze-thaw cycle, a wall can disintegrate.

framing© Rick McCullagh/ I see a little bit of foam there!

For a start, the building fabric contains practically no petrochemicals, all the materials and construction details are fully breathable, the dwellings still sit on their original footprints, and almost all 200 tonnes of brick in the property as well as all the original joists and rafters are still in place. “It’s keeping the embodied energy, the embodied carbon that was put in there when it was originally built… keeping that on site,” says its developer, Kit Knowles.

This is really a very smart renovation, with so much concern about moisture management. Cradden writes:

Describing construction’s fight against moisture ingress as the “blackest of black arts”, Knowles was keen to ensure that all the walls and construction details were genuinely breathable and diffusible. While a common approach in construction is to have a gradient of breathability across a wall, Knowles say this often results in an interior layer that restricts the movement of moisture. His philosophy instead was to make every layer in the walls, roof and floor highly breathable all the way across, to support drying both inside and out, should any moisture get in….“It’s impossible to stop water getting in. You can’t rely on your layers being absolutely perfect. It’s about making sure that any moisture that does get in there can readily dry out.”

There are eight million pre-1930 houses that need to be retrofitted in the UK and untold millions more around the world. They can’t all be enerPHit, but the lessons from this house apply universally: Embodied carbon matters. Moisture movement matters. You can’t just foam the crap out of everything and say it reduces carbon because it doesn’t.

passivehouse plus coverPassivehouse+/Screen capture

Read more in Passivehouseplus, one of my favourite magazines.