Energy Efficient Stuff , Net Zero Energy Homes
Sustainability Is Not A One-Size-Fits-All Label
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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Deep Energy Retrofits , Energy Efficient Stuff , Indoor Air Quality , Stuff that makes me crazy
Damp basement season. It’s coming
What are you going to do about it? Hopefully not install an exhaust only system to pull more humid air into your humid basement.
Don’t. Do. It.
I’ve been discouraging these systems forever, here in Nova Scotia. They don’t reduce humidity levels in basements, but that’s what the marketing infers. What they do is exhaust the humid air from the basement while bringing in humid air from the outside. There is no way to reduce relative humidity levels and stop condensation without a) increasing the ambient air temperature so that it can carry more moisture while at the same time increasing the temperature of all exposed (or first condensing) surfaces or b) stripping moisture out of the ambient air (that’s what a dehumidifier does — oh, wait, that’s the market these exhaust only systems are muscling in on). In reality, the best way to deal with humid basements is to #1 Find the moisture source(s), and #2 Eliminate them. That’s the straight up, bottom line, end of story.
Moisture sources like open sumps are the problem — sealing this off before doing anything else will go a long way to reducing the moisture level in your basement or crawlspace. Note the white efflorescence on the wall — that’s salt crystals left behind from moisture migrating through the wall.
Open sumps, cracks in concrete that allow bulk water into the basement, these are pretty obvious sources. Less obvious sources include crappy drainage at the foundation, damaged or non-existent drainpipe leaders, high water tables.
Then there’s the fact that cooler surfaces cause moisture to condense out of warm, humid air. Concrete or masonry, present in most basements, are terrific first condensing surfaces. Insulating concrete and masonry can help to reduce the extent of condensation. But only if all moisture sources are dealt with so there’s trapping of more moisture in the basement…so back to #1 above.
Read this blog post by Allison Bailes at Energy Vanguard if you want more details about the pitfalls of exhaust-only systems and a fantastic in-depth explanation of why they won’t, don’t, can’t work in basements. Although he references New Orleans specifically, the physics that lead to problems with humid air and cold surfaces, along with the need to eliminate moisture sources in basements and crawlspaces are the same everywhere. The severity of the problem is related to the climate zone and the condition of the basement.
Energy Efficient Stuff , Stuff that makes me crazy
Sir, Ma’am: Step Away From the Foil Faced Bubble Wrap!
So Martin Holladay at Green Building Advisor blogged about foil faced bubble wrap last week. Will that stuff and the ridiculous claims around it in regards to insulation ever ever ever go away?
And here’s a recent 4-pager from NAIMA
I see that Allison Bailes at Energy Vanguard also blogged about it back in 201o.
And here’s a bunch of info I posted in October 2007. Note that even then, I couldn’t believe that it was **still** something that had such bandwidth. This was posted on the old Green Building Listserve…but the whole article is available as a pdf here.
There’s a good discussion going on in the LinkedIN RESNET BPI – Energy Audit & Home Performance Group, instigated by Chris Laumer-Giddens.
One comment sums it up: “The fact that Mr. Holladay felt compelled to write this article is troublesome because it just goes to show how many unqualified, willfully ignorant contractors are out there. Not only do these people offer their clients little return on their investment, it’s likely they diverge from code and protocol, causing property damage and potentially endangering lives.”
The stuff of nightmares…litigation and very unhappy householders.
More excellent discussion has come up today, courtesy Arlene Zavocki Stewart in regards to the issue of ‘effective’ R-values. R-value, U-factor = measurement of conduction. Building envelope materials all have properties that impact heat transfer via convection and radiation as well as conduction, but mere mortals using standard issue energy modelling software acceptable to home performance, DSM, and other incentive/funding programs, can only measure or model the conduction portion with any vigor. Engineers, physicists and fans of complex spreadsheet building (she raises her hand sheepishly) may be able to do otherwise, but it doesn’t count for your client if you can’t plug it into the modelling program and have it make sense with what’s already being calculated. I have bumped into this challenge in terms of modelling thermal mass for cold climate passive solar design, but it’s the same issue: how much heat gain does a material or assembly absorb or reflect from a radiant source, and how much does that contribute to the heating or cooling regime of the building?
Arlene brings a great point to the discussion: “Codes allow ‘cutting edge’ products but our ways of measurement and communication on their features often can’t be quantified in existing conventions. Developing accurate ones is very expensive and takes years for widespread adoption, a funding line item that investors just don’t seem to account for.”
In the meantime, we have ‘snake foil’ salespeople out there, talking up effective R-values that defy all the laws of thermodynamics. I will stop short of banging my head against the wall now.
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