One of the issues cities across North America are grappling with (at least those that are not yet moving on progressive housing legislation, such as California’s SB 828) is the fact that, with single family home zoning, the only thing a ‘teardown’ can be replaced with is another single family home.
Mathematician, data analyst and notorious census mapper Jens von Bergmann points this out, noting that which is dominating the political landscape in Metro Vancouver these days — that when we look at single family home (SFH) development from an affordability perspective, it doesn’t look good.
And from an emissions perspective too — things look mixed at best for entire swaths of SFH neighbourhoods, all across the region.
If replacement homes are built to current, minimal energy standards, we come out carbon negative. If we build to City of Vancouver 2025 standards, or even ‘passive house’ (often referred to in Europe as passivhaus), we recoup the energy debt accrued during teardown/rebuild within about 30 years. But that only works for the first iteration in the teardown cycle.
Frequent Price Tags contributor Ian Robertson illustrates this with a handy analogy:
It is often quoted unthinkingly that ‘the greenest building is the one that still exists’ … to which the only reasonable response is yes, but perhaps only in the very short term. Just as it is reasonable to replace an old dirty car with a new efficient one, so it is with houses.
Essentially, teardowns have a carbon footprint that cannot be ignored, even if, as von Bergmann concedes, “we ignore affordability concerns, [that] we are the centre of a growing metropolitan area.”
(And we can do this, academically at least, and only until October 20th.)
So yes, we know we have to get better about how we accommodate our growth and allow more density. Let’s park that.
But what to do about the fact that from an emissions perspective, as Robertson and von Bergmann calculate, the payback for a code-minimum house in BC is 164 years, more than five times that of the aforementioned CoV or passive house standards?
In a new paper recently published by von Bergmann, with Joseph Dahmena and Misha Dasc, entitled, “Teardown Index: Impact of property values on carbon dioxide emissions of single family housing in Vancouver“, the de facto standard should be to require passive house building standards for all new single family homes.
And that, considering we currently tear down 1 home for every 5 we build in CoV (1 in 7 in Metro Vancouver), we should begin this practice now.
But according to Robertson:
The press talking about the article immediately took exactly the wrong impression of the article, that it suggests we shouldn’t replace existing SFH with multi-family units, whereas the point intended by the authors was specifically that replacement should be done well (and yes, dense).
Robertson extended the car analogy — that the energy used by a typical BC single family house is almost identical to that of a typical car, so the scale of energy savings can also be similar.
An older house is a Hummer, and a passive house is even better than a Prius. And nobody would say ‘the greenest car is the Hummer that still exists’, and thus should they not necessarily say the same for houses. Replacing Hummer Houses should be a virtue, not a vice.
He goes on to note that Vancouverites tend to venerate pre-1940 houses, “as if they were built only with old growth timber by unfathomably skilled hands, and the sine qua non of houses. The reality is that many were quite simply bought from Sears and have been damaged by illegal/unpermitted renovations and rot over the years, and are very likely to have significant structural and other life-safety issues.”
You can read more of Robertson’s thoughts on this topic on the blog Dynamic Cities Project.
And if you’ve got a head for CO2 emissions payback and statistical analysis of energy modeling for residential buildings, check out the UBC paper by von Bergmann et al; once the free version if locked down by Elsevier, it will still be available for purchase.
But the abstract alone is worth a read, by just about anyone interested in building efficiency and the true costs of new construction.
Or you could just consider the following, again courtesy of Robertson:
Keep what is good, replace what isn’t with that which is much better, and if you’re replacing something good, make sure the replacement is the best you can make it. This shouldn’t be a bitter debate.