How cool is our future going to be?

Badwater Basin in California’s Death Valley is the lowest point in the continental United States – a dizzying 86m (282ft) below sea level. It’s a vast, flat, empty space covered almost entirely with crystallised table salt – the remains of a lake that evaporated millennia ago.

If you visit in a comfortably air-conditioned vehicle – as I did recently – the moment you open the door you realise why. This place is hot, hot, hot! In fact, the hottest air temperature ever recorded – 57C (129F) – occurred nearby in July, 1913.

The day I visited it was around 49C (120F). Brilliant sunlight bouncing off scalding white salt flats and bone-dry air didn’t make it any more bearable.

How can people live in a climate like this without near constant air conditioning? How did they ever manage before air conditioning?

Well, plenty did, starting with the local Paiute Indians and continuing, from the 1850s on, with miners seeking gold, silver, borax and talc. Most settlements were short-lived, including a gold-mining town called Rhyolite, north of Badwater.

Founded in 1905, it rapidly acquired concrete streets, water mains, electric lights, telephones, a hospital, an opera house, three railway lines and 50 saloons. But by 1910 the gold had gone and the inhabitants followed.

Today Rhyolite is a popular ghost town, mostly in ruins, but with one exception – an ingenious self build (pictured). It’s a single-storey, L-shaped house built around a generous porch and quite unremarkable, except for one feature – its walls.

When Tom T. Kelly, a local saloon owner, decided to build his own home in 1906 – at the age of 76 – timber was in short supply. But he did have an abundance of used beer bottles.

He was able to construct a timber frame, whose sides he then infilled with 51,000 bottles, most from a company now known as Budweiser.

They were laid side by side, with the bottoms facing outwards, and mortared together with adobe. It took Mr Kelly just five-and-a-half months to complete – not bad for a building that’s still standing.

Now building a glass house in one of the hottest places on earth might not seem the most sensible idea. But Mr Kelly’s bottles were embedded in a construction material commonly used in hot dry climates: earth mixed with water, sand and straw which the hot sun quickly bakes solid.

Apart from being literally dirt-cheap, adobe has another great virtue: it provides mass, which can soak up solar heat during the day and release it slowly at night. Ideal for the wide temperature variations in a desert area.

Adobe walls are traditionally very thick, which Mr Kelly’s weren’t, but they were the depth of sealed air-filled bottles, providing a similar insulating effect to that of double-glazed widows.

No one to my knowledge has tested the U-values of these walls, but the construction method proved popular enough for two other bottle houses to be built locally.

Fossil fuel heating

Why am I telling you this? Well, in the chancellor’s spring statement this March Philip Hammond announced measures to ban fossil fuel heating systems in all new homes from 2025. Not too far off if you’re just beginning your plot search. Three months later Theresa May pledged to make the UK a net zero carbon economy by 2050.

So how should a forward-thinking selfbuilder react? As the Home Builders’ Federation was quick to point out, current alternative heating methods aren’t as attractive, available or efficient as gas, oil or LPG.

The government’s Renewable Heat Incentive currently pays subsidies for seven years on air or ground source heat pumps and wood-fuelled boilers, but these favoured alternatives are all still considerably more expensive to buy than a gas-fired boiler. In addition, heat pumps rely on expensive electricity and produce only low temperature heat.

But there’s another factor here that receives comparatively minor attention. As I write, Britain is steaming into its second heatwave summer in a row. France has just recorded its highest ever temperature.

It’s not quite at a Death Valley level yet, but by 2025 cooling a home is likely to be as important as heating it.

But there’s an answer which works for both now and the future, and it lies with Tom Kelly’s bottle house – at least in part.

Insulation, of course, can retain coolness just as it retains warmth. Sufficient insulation can minimise the need for heating and cooling, however produced, but it requires intelligent design to avoid internal overheating – already a problem with some recent builds.

The answer to that is properly controlled ventilation which, in practice, generally means whole house ventilation with heat recovery. A system of ducts extracts warm, moist air from kitchen and bathrooms and runs it through a heat exchanger – usually in the attic. This warms fresh air distributed through more ducts throughout the living areas. In winter a heating element in the heat exchanger can boost the temperature of incoming air.

The continuous but imperceptible airflow maintains a constant, comfortable temperature throughout the house. It also distributes the heat created by cooking, bathing, electrical appliances and people – to the extent that additional space heating may not be needed for most of the year.

It’s not the whole answer, of course. The orientation of your house is important. South-facing facades need to be shaded, by brise-soleils, awnings, balconies or trees. Triple glazing is recommended and insulated blinds for both winter nights and high summer days. A house built recently on these principles in Camden in London included blinds which close automatically at dusk in winter.

Those principles are best demonstrated by the German Passivhaus approach to building, which guarantees a home’s performance. Don’t expect your average jobbing builder to be too familiar with it. But more and more architects, designers, housing associations – anyone, in fact, who’s not building for maximum and immediate profit – are seeing it, or something very close, as the future.

August 2019