A side effect of the increasing drive for energy efficiency in houses is that walls just keep getting thicker. As we seem unable to make our heating and fuel supplies more efficient than they already are (and they are pretty efficient) it has fallen to insulation strategies to advance us further. The problem with this is that to get a more insulated wall you have little choice but to thicken it. Walls that a couple of decades ago were around 350 or 300mm thick are these days closer to 400mm. So what you might think but consider for a moment that that means a 30% increase in volumn for each external wall. That is not extra air but extra stuff. All that stuff has to be manufactured and transported which are both significantly polluting activites – particularly in the case of many insulating materials. No one has considered this as a whole process. Just how much energy is used and how much pollution caused by building in this way and is that balanced by a greater reduction in terms of the building during it’s lifetime? Given the efficiency that we strive to attain now in buildings I would not be suprised if the point of zero return was approaching. Who knows? No one as we have yet to get to grips with pollution as a process rather than at individual points in the economy.