At Ecobuild yesterday I had a long talk with a consultant who has carried out a detailed carbon footprint analysis of the relevant merits of liquid propane gas and oil for people who live off the gas grid (LPG won). Although this was done for a manufacturer, it was carried out by an independent consultant and peer reviewed. And he had no industry axe to grind. His next piece of work was on the impact of the production of blue jeans, and was just as fascinating if less relevant.
It was refreshing to talk to somebody who dealt in the world of hard facts although it did strike me that working out the carbon impact of fuels is much simpler than it is for most building materials. After all most of the CO2 emissions come from burning the fuel. But there are other organisations taking carbon footprints and life cycle analyses seriously, and although in buildings one always has to weigh one impact against another, it is valuable at least to have the facts to do it with.
There were lots of exhibitors at Ecobuild telling us that their products are the best. I met a small-scale installer of solar panels and asked him how he chooses which to use. He said he deals with a big and reputable supplier and lets them make the decisions! Everybody needs to concentrate on the areas where they can hope to make a proper judgement, and rely on others for help where they can't.
Still, it is worth remembering that sometimes things are simpler than they seem. The man who did the carbon footprint analysis reminded me that it is almost always a decent proxy for overall environmental impact. So most of the time, we can concentrate on carbon and ignore the rest - not because the rest is unimportant but because it usually follows along.