Passive House in Canada

While Passive House remains a mystery to most, and a misnomer to many in the building trade, here is some news of steps in Canada. And why wouldn't you?

Tree hugger reports here on a Canadian charity building social housing to Passive House standard.

CBC News​ reports here ​h​ow Canadians are constructing North America's biggest green buildings​.​ And perhaps the greenest big buildings too.

​And here's an article from High Performance Building Supply about why smart cities need passive house buildings, which is not really about Canada​, but they do mention a project in Toronto.

Carbon payback in a month not three days: Check those facts!

It looks like a simple arithmetic mistake has struck again.

In preparation for my lesson, I noticed my slides proudly announcing that five jerry cans of paraffin will put out two hundred times more carbon emissions than ten square metres of glass wool insulation. I had the carbon emissions for paraffin at a quarter of a tonne, which at first seems like a lot, but it's pretty much all carbon, and each one of those atoms is going to bond with a couple of oxygens from the atmosphere as they set of heating up the planet in their cosy little threesomes. You have to remember that fossil fuels are worth more than their weight in carbon dioxide emissions! Adding this to the extra density of the paraffin, a factor of two hundred is reasonable.

To give a little extra support for my students who are good with numbers but less good with foreign languages, I wanted to add a more precise weight of carbon equivalent to the glass wool. I could have just divided the quarter tonnes by two hundred, which would have given me one and a bit, but I wanted to get a more precise figure.

My first port of call for fact checking, as usual, was google. I assumed I could just ask it how much embodied carbon was in glass wool, and it would tell me.

I quickly found this greenspec.co.uk, which doesn't have any actual numbers, but has a few graphs. Very sensibly, it starts with different thicknesses of insulation to reach a respectable wall U value of 0.15 W/m²K, which would be about 23cm for glass wool. Then it has the embodied carbon value for a square metre of wall. If my I've read the graphs right, and my sums are correct, this gives 25 kg of carbon dioxide equivalent for my ten square metres of glass wool. Not two hundred times less than the paraffin, but ten times less.

I started looking for my own workings or references, but didn't find any. Usually I add a reference somewhere nearby, in the last few slides of a presentation or as a footnote of a blog post. At least it's good practice to do that, and I always expect it from my students!

So back to google again for a second opinion. I found a carbon footprint of 1.35 kgCO₂/kg for glasswool in table 4.3 on page 118 of Sustainable Construction Processes: A Resource Text, by Steve Goodhew, which is the same as the University of Bath figure I wrote about before. The density is 25 kg/m³ here on engineering toolbox, which gives a slightly higher figure. But if I go with the spec on google shopping of 10kg/m³, I get to about 13 kg of carbon dioxide equivalent for the roll. Twenty times less, not two hundred times less.

There's a factor of ten error somewhere, but since I didn't keep my original workings, I can't see exactly where it is. I've checked a few times, and I'm pretty certain that the roll of glass wool is 10 square metres, and since it's 100 mm thick, it's going to have a volume of one cubic metre. I can well imagine a factor of ten error sneaking in somewhere around there.

Anyway, in terms of the return on carbon investment, instead of a three day carbon emissions payback for switching from paraffin to insulation, it's actually a month. Still seems like a pretty good idea!

This does go to show that it's always a good idea to double check calculations.

When I prepared the lesson two years ago, I was comparing an 11-metre roll of 910-mm wide, 100-mm thick glass wool with five 18-litre cans of paraffin, both of which cost 6000 yen. I'm not sure if it's a trend, or there is some fluctuation, but now the glass wool is a thousand yen cheaper, and the paraffin a thousand yen more expensive.

Lesson 10: Take 3: Standards

It's a challenge making building standards interesting. The topic seems as dry as a highly insulated house in the middle of winter with heat recovery ventilation and no humidification. As I started brushing the cobwebs off last year's presentation, my first thought was that I should teach this lesson later, and tackle the altogether more exciting topic of energy generation first. I stopped myself, thinking that I was just trying to put it off, and I've just noticed now that I'd moved it two weeks later last year. A lesson on comfort had been added to the original plan, and Windows 2.0 came after the lesson on standards the first time.

This lesson should really work as a revision of what I've been telling them about low energy building, since standards ideally reflect the essence of low energy building, and promote improvement.

I followed the plan at the beginning, giving them several reasons for low energy building. An obvious reason is to reduce environmental impact, although unfortunately this is a relatively low priority for a lot of people. Money is often a higher priority, and the fact that low energy buildings are cheaper to run, long term, is perhaps a more powerful incentive. Even then, a lot of people are concerned with the immediate costs, and less worried about possible future savings. Grants or tax breaks are another reason people may build low energy, but the most powerful reason is probably where there are laws that oblige people to build low energy.

Then I tried to introduce the idea of standards, with a few examples and their logos, including the JIS (Japan Industrial Standards) logo, which they all knew, and the logos for European Standards, British Standards, and Forestry Stewardship Council (FSC), which they did not.

In order to breathe some air into the topic, I put them into groups and had them imagine they were government committees who had to come up with their own standards to ensure low energy buildings.

First they had to brainstorm for things they could look at. I had to steer them away from things like giving grants, which is a good idea but not actually a standard.

Their ideas mentioned insulation materials, windows, form factor and solar power.

After some brainstorming, I got each group to choose two or three ideas, and come up with some details of what exactly they would stipulate.

They came up with a few concrete suggestions, such as using wood rather than aluminium for window frames, and a minimum percentage of glazing to frame. Other ideas were a bit vaguer, like making the air gap thicker, and having "really thick" walls. There were very few actual numbers, and nobody mentioned U-values, which makes me think I haven't talked about that enough times.​ Also nobody mentioned ventilation.​ One group came up with the two ideas of adding solar panels, and adding a battery to store the power. These are both interesting ideas but have absolutely nothing to do with what we've been talking about for the previous nine weeks. That did make me think I should have done the lesson on generation first.

The lack of detail also made me wonder whether I should have given them that task later in the lesson, after I had given some examples of actual building standards. As often happens in teaching, there is a difficult balance to reach between giving students information and getting them to come up with their own ideas. Perhaps I should start off by introducing some of the early low-energy building standards and then get them to think about what is missing, how they could be improved, and what they would do now.

This may have been a good lesson to produce a multi-dimensional gap fill, or jigsaw activity for. There is a smartphone app called Quizlet Live that lets you add several questions and their answers, which are then scrambled for students to match. The teacher gives students an access code, then the app puts students into groups of three or four, so they have to go and find their partners. Then each student gets around four answers on their screen, and the questions come up in turn. The student with the correct answer must select that, then they will all get the next question. If someone gives the wrong answer, it goes back to the beginning again, shuffling the answers. This may not make the content any less dry, but it could socialise its delivery.

​ ​