Heat Islands Becoming Heat Continents
As we all roast this summer, we are in the midst of a vicious circle of our own making that is just making things worse. It gets hot and sunny and we build black roofs and parking lots. It gets hot under and around them (the heat island effect) and we fire up the AC units to compensate, making more heat, using more energy, generating more smog. Soon the entire city is roasting under a brown bowl of rotten air. The little water that rains could be retained in the soil and on the roofs but it is routed to the sewers, carrying coliform with it and closing the beaches just when we need them most. The Star points out that the effect is not insignificant-" The phenomenon is abrupt and dramatic. When temperatures are plotted on charts, they climb what appears to be a steep hill at the edge of suburbs. They plateau over those vast expanses of shopping malls and cul de sacs. Then, over the inner city, they scramble up to the peak. Large parks, or neighbourhoods with plenty of old trees, sometimes soften the pattern.The difference between countryside and core can be as much as six degrees — enough to turn a region-wide pleasant day into an urban scorcher, or a widespread scorcher into an inner-city killer."
It didn't have to be this way. The parking lots could be porous pavers of green, retaining water and rejecting heat. The roofs could be green, holding moisture and insulating the spaces below. We could plant trees everywhere. We could ban paving front yards. We could put demand metering on all air conditioned buildings so that people would insist on alternative methods of cooling our cities. We could begin to see that cooling is not an operating cost issue but a capital cost one- put the money up front to do it right. ::The Star
There is a heat emergency on right now in Toronto; where I sit, an 80 year old maple is shading our old house. Being on a narrow urban lot, our south flank is shadowed by our neighbour. Having the street oriented on a north/south axis, we get morning sun and afternoon sun but none in the mid-day. Big windows front and back let the wind blow through. Eight inches of solid brick gives us the thermal mass to keep out the heat during the day and retain it all night. One hundred years ago they knew how to design a neighbourhood; it is time to learn from it.