I was going to write today about the range of energy efficient and sustainable housing standards and programs that are offered by organizations. But I got sidetracked by an article by Allison Bailes on his Energy Vanguard blog.

In it, he follows up on some harsh criticism of some work done by Alex Wilson of Environmental Building News. Alex had done some number crunching on insulation types and global warming potential (GWP) for an article in 2010. As Allison notes, Alex’s work on this study focussed on a single scenario, with a single material. Which, like anything else, doesn’t exist in the real world. The house exists as a system, in an infrastructure of systems and so, a whole raft of variables need to be considered to determine what’s effective in a given climate with a given set of energy sources, for example.

I’m not going to re-write or paraphrase either Allison’s or Alex’s articles here. If you’re geeky enough to care about the sordid details, you’ll do better to read those yourself. What I do want to point out is that there are no silver-bullet solutions to sustainability, and there are complicated challenges to determining what makes a material, a system, a house, a neighbourhood, a city, sustainable.

I have a couple of f’r instances myself (surprise, surprise).

A heat pump looks/feels/sounds like the best option for a retrofit heating system on a house with an older mid-efficiency oil furnace in Nova Scotia. But not really.

It depends.

Our electricity mix is primarily coal + fuel oil. The emissions are ± 1.1 kg/kWh. The generation and transmission losses across the grid means that less than 30% of the energy available in the fuel is actually usable electricity. This puts a high-efficiency single-processor heat pump at the same efficiency as a new code-compliant oil furnace. So in the big picture immediately, this is not necessarily the best solution in terms of GHG emissions with our current generation mix, but it does anticipate a higher renewables component supplied to the grid.

If, instead, we were looking at a new build, Net Zero Energy Ready project, then it’s a good long-term solution that will drop emissions dramatically, regardless of the generation mix, once the house has site-generated power.

If that new build has spray foam as one of it’s components, we need to know a lot about that material and it’s broadly defined lifecycle cost is to make a fully informed decision about whether it is a sustainable choice for this region with this energy mix or not. That’s a challenge. Who can/wants to crunch those numbers and who can/wants to pay for those numbers to be crunched? What parameters are we going to use? Who decided those?

There’s a great tool that I’ve used for crunching those numbers. The Athena Sustainable Materials Institute has suite of  lifecycle cost assessment (LCA) software tools that allows you to look at whole assembly or component LCA. All of these tools are FREE to use. Use ’em and make good choices.

The good news is that you really only have to do these kinds of calculations and analysis for each type of material in your own climate/utility service area for the specific scenarios you will be confronted with. For most designers/builders that’s going to be enough. It’s when you offer your services across several climate and/or utility service areas it’s more challenging.

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