In order to determine the payback of the various design decisions needed in a new build (or even a renovation), you need to first determine the most likely lifespan of the dwelling you are designing. Many Europeans would say a home should be around for hundreds of years because many of theirs have been.
How is this possible?
Most are built with brick or stone and are in OLD cities. How old? Well the Romans were around when many of them were in their infancy.
Why is the age (maturity) of a city important?
To answer that we need to look, in contrast, to cities like Vancouver and its surrounding neighbours which are all very young in comparison and changing rapidly. Single family dwellings on small parcels of land still represent the majority of the housing built and available (when looking at land use and not just total numbers of dwelling units). As such there is a huge potential for redevelopment as the city matures and grows.
I live in a large single family neighbourhood 10 minutes from downtown Vancouver. North Vancouver has predominately been a single family neighbourhood since the early 1900’s. But it is rapidly changing (many would say for the worse due to the traffic congestion that has developed and really does not have an easy cure due to the geographical challenges of the region). The District and the City of North Vancouver are both looking to and have been dramatically increasing density in our region with the misguided goal that doing so will make accommodation in our cities affordable. This has been attempted over and over again in Vancouver, and the facts are that these high density ‘villages’ become sought-after-hot-spots that have some of the highest rental and real estate values in the country if not all North America. Cole Harbour comes to mind.
I digress, why is the age or maturity of a city important?
Well, the fast growth of urban areas in my region dramatically shortens the life span of what I feel will be the soon defunct urban single family dwelling. While my current house was built in 1954 and has had a good run until now, I highly doubt that the house I plan to build next year on this property will come even close to 60 years before it is torn down to make way for a low to mid-rise multi-family housing. In fact, I would be surprised if it was still around in 25 years. With its proximity to the Down Town core, Lions Gate Bridge, and Upper Levels highway, it is prime land for re-development; development that is already underway at several nearby locations. A single family neighbourhood less than 5 minutes from me is slated to become the new Lower Capilano Village. Another single family neighbourhood within 7 minutes drive has now been bulldozed and is slated to become part of the Lower Lynn Town Centre.
The point I am making, is that it is unreasonable to expect that a single family dwelling built today will still be around in 50, 30, or even 20 years in many neighbourhoods in growing urban centres. Like the cities that have a much longer lineage than those in North America, there will be a forced march to densification and an abandonment of the single family home on a small distinct plot of land. Does it therefore make sense to model a home that would have a 50, or worse, 100 year payback in energy savings or carbon reduction in these types of neighbourhoods? Before coming anywhere close to cancelling out the costs to build or embodied energy of the dwelling, it would be torn down and end up in a land fill.
So often logic is not part of our design decision making process. We want something so badly that we will fabricate a way to make that decision sensible. Designing a home that is SO energy efficiency that it would take 50 or more years to pay back may not actually be helping the planet if that dwelling is only around 20 years. I hope that more discussions like these will encourage a greater uptake on what makes sense in the larger picture, and start allowing informed well thought out designs that are defensible.
For my part, I believe it will be sensible to apply a 25 year life span when calculating the break even point on the various design decisions I have ahead of me. If the dwelling is torn down earlier, I will not have left too much on the table, and if it has a longer run, the payback will have already occurred and it will then be providing dividends in carbon reduction and utility bill savings.
As always, thanks for reading and please let me know your thoughts.