How a pond can keep your home cool
Kevin McCloud on making the most of nature's air conditioning systems
There was a medieval time when meteorologists blamed meteors for the changes in the weather. Comets were responsible for the crops failing and the populous starving. Now it is all our fault and climatologists point to the climate as the driver of big change in our weather systems. Our winters are becoming milder and wetter, and our summers warmer.
Weather is of not necessarily an indication of longer-term climate change. Weather patterns fluctuate in any case. But the past few years have brought a flavour of what is to come. Heat waves, dry landscape and temperatures approaching 40°C. It is as though what they said would come true is becoming a reality, but much quicker than anyone thought.
Climate change is happening
Climate change is happening, we’ve all come to understand that. But in our lifetime? We all thought we had a few more decades to turn our boilers up in winter and ramp up the air con in summer.
And air conditioning is a big contributor to greenhouse gases. Although modern machines use refrigerants which are much less damaging to the atmosphere, older units – the vast majority on the planet – do not. They are slowly leaking their gases, which are hundreds of times more contributive to global warming than CO2.
Meanwhile developing countries are turning to air con as a technology for their burgeoning middle classes. According to the International Energy Agency, cooling buildings accounts for 16% of all electrical use in buildings and the market for air con globally has risen 4% every year since 2000. To give you a sense of scale, the number of people on the planet equals seven billion and the number of air conditioning units is two billion.
So will one more make a difference? If you have air con installed this summer will it alter the course of our climate’s destruction? The answer is, of course, yes, because you are a contributor to the bigger number – as we all are. It’ll also dent your bank account. On a positive note, there are some good alternatives.
But looking at the offering from property developers you wouldn’t think so. The average new home has no solar shading, almost no thermal mass, poor cross-ventilation, no stack ventilation and no evaporative cooling. And yet all these technologies can be yours.
You don’t need to be building a new home either. You can exploit the magic of these scientific principles in your own house or flat. Solar shading? Fit external shutters or a deck and canvas awning or a posh brise-soleil to form a canopy over your windows. Or just plant a deciduous tree to shade your home and cool it using the tree’s own mantle of cool humidified air. Trees are nature’s air conditioners.
Thermal mass is very hard to retrofit into a home but it’s not the be-all and end-all. Ventilation is more important. You could fit a light-well over your stairs with an opening skylight above for stack ventilation. It would mean remodelling the roof a little but it would give you a ‘chimney’ through which warm air in the building can rise and then ‘purge’ itself out. The delight of this principle is that just as warm air rises up and out, so it will draw in cool air from open windows and doors at ground level.
This brings me to windows, which should be securely left – but strategically — open in hot weather. If you can work out where a breeze is coming from on any day you can maximise its cooling effect by opening windows on the side it’s coming from and on the opposite side of the house too, to provide cross-ventilation.