Two months ago, the World Green Building Council issued a report advocating that every building in the world should be “net zero energy” by 2050, as a key strategy in climate change mitigation.
I began wondering whether this is even a worthwhile goal, let alone possible. According to the report, the world’s building stock will nearly double from 223 billion square meters in 2017 to about 415 billion square meters by 2050.
As a reference point, the United States right now has about 87 billion sq. ft. (8.1 billion sq.m.) of nonresidential space and about 250 billion sq.ft. (23.2 billion sq.m.) of residential floor space, about 14% of the global total.
The report further states that we must triple the rate of building retrofits immediately from 1% to 3% of the building stock. For every year of delay in reaching this goal, the objective for future years would have to correspondingly increase.
If you do a Google Earth look at the layout of any major city, you’ll find out that putting solar on every rooftop is just not a feasible idea, given the amount of shadowing from taller buildings around it.
Leaving aside the sheer impossibility of making EVERY building in the world “net zero energy” from onsite solar or similar resources, in ANY time frame, let alone 2050, shouldn’t we ask if this is even a worthwhile goal, however aspirational?
In the same time frame, we are actively moving toward 100% renewable energy in most of the world’s higher-energy-using economies. Sweden has set a 2040 goal for achieving this result, for example. The United States has enough solar resources to power the entire country from a small portion of the southwestern deserts, given cheap battery storage, which seems just around the corner, and adequate transmission capacity, which is also quite achievable.
If all buildings are going to be supplied by 100% renewable energy, should we care about the energy use of any particular building or group of buildings, other than that greater energy efficiency will reduce the amount of renewables needed to achieve the “net zero” goal of eliminating the contribution of buildings to global carbon dioxide production?
I think before everyone signs up to the idea of “net zero energy” for all buildings or even a large subset of them, it would make much more sense to have a focused retrofit program that would aim at the 25% of buildings that could deliver 75% of all possible savings, wouldn’t it?
If we have renewables powering everything electric, should we care about the energy use of any particular building? It seems to me that solar and wind power are the only renewables that can scale quickly enough to the Terawatt level to make a global difference. Shouldn’t that be our primary focus? What do you think?