Musings on Passive House Standards and the Costs of New Home Construction, Part 3

If you have not yet read my posts (rants) in Part 1 and Part 2, maybe check those out first.

Have you heard of the Pareto Rule before? It’s more commonly known as the 80/20 Rule. It says that for many events, roughly 80% of the effects come from 20% of the causes.

I think that Passive House (PH) follows this rule to a T. It has certainly been our experience in building an extremely energy efficient home and following the principles of PH. I believe that 80% of the benefits of PH come from about 20% of the cost and effort (from Part 1 of these posts, I noted that our financial cost was about 8% more than a standard house construction). Whereas to get that last 20% to the hit the PH certified requirements, you’re going to have to spend 80% more… At least this was my assumption.

Still being the curious person I am and because I kept getting asked about it… I just had to know. How close does our house come to the PH standard?

The only way to find out would be to either track the house over the next year or to have someone run the house through the Passive House Planning Package software (PHPP) to predict our values.

As you may recall, we were never pursing PH certification, right from the beginning we were told the cost-effectiveness (80/20 rule) was just not there. Maybe if there was some incentive or rebate for going full-out, one could justify it. We were also told that there was no need to use the PHPP as it was too expensive. This latter statement however is simply not correct.

I decided to ask around and see who could put our house through the PHPP for us. Or at least get a price quote for it. Maybe it would be too costly and so I wouldn’t bother if it was. After a few emails, I was eventually referred to a very well-respected PH consultant out of Alberta – Stuart Fix at ReNu Building Science. I sent my email explaining that we’d already built the house and so really can’t change anything now, but due to curiosity I was wondering if he could run the house through the software. No problem he said. The price we were given was entirely reasonable and was actually less than what we had paid to run the house through the inferior HOT2000 software prior to building. Crap!

After a couple weeks we received the results, not surprisingly: we weren’t a Passive House. But the results on the various aspects of the house were very interesting and lead to some interesting points of discussion.

Based the three criteria for PH certification, recall:

  1. Space Heat Demand: max. 15 kWh/m2a  OR  Heating load max. 10 W/m2
  2. Pressurization Test Result @ 50 Pa: max. 0.6 ACH
  3. Total Primary Energy Demand: max. 120 kWh/m2a

Our results were as follows:

  1. Space Heat Demand: 37 kWh/m2a
  2. Heating load: 22 kWh/m2a
  3. Pressurization test result (assumed 0.6 ACH, prior to testing)
  4. Total Primary Energy Demand: 116 kWh/m2a

So, you can see that the only criteria we met was the Total Primary Energy Demand. The blower door test we did later came back at 0.72 ACH (we’d run the software assuming 0.6 ACH as a target). As a result of the actual pressurization value, this would correspondingly increase the other values, but, for argument’s sake, let’s simply say that the Total Primary Energy Demand we either met, or were very close to meeting, while for the Heat Demand and Heat Load, we were WAY above the German PH maximum values.

I won’t reiterate why this makes sense given the climatic and heating requirement differences of the Canadian prairies versus Germany (see Part 2). But I had to ask the PH consultant:

“If we were still in the planning stages of the house, what would be your recommendations to try and reduce these two values (Space heating demand and heating load)? Not that we would change anything at this point, but I’d be curious as to how we would have gotten those values lower – and if it would have been at all possible with our type of house and in our climate to feasibly meet the PH requirements as stated?”

​The ways to reduce the heating load & demand are as follows:
  • More insulation (you already have great R-values)
  • Lower airtightness (dropping from 0.6 to 0.3 has quite an impact, but you’re already doing tremendously well)
  • Add more south glazing, reduce all other glazing. (You already have a great balance of glazing)
  • Build a larger home (!?!?… small homes are the hardest to make meet an intensity based target, as they have the largest surface area to volume ratio. Meaning that a larger building squeezes more floor area into slightly more exterior envelope area, reducing heat loss per unit of floor area. The Germans do this to motivate one to build multi-family dwellings… but the result in North America has been a lot of larger single family homes getting certified).
​Your home is a great example of why you don’t see certified Passive House buildings taking off in Canada. It’s damn near impossible to design a compliant home, without either blowing the bank or ending up with a solar oven. I’ve designed many compliant buildings, and 99% of them end up backing off on insulation and glazing to be around where your home is. You’ll note that local Net Zero Energy homes have similar envelope performance to your home; it’s most cost effective from that baseline to invest in ​solar PV generation than to add more insulation.​

Under the section of the report on Energy Balance Heating, I asked, “I was surprised by the amount of heat loss through the walls as well as the windows – is that due to the size/number of south windows? Or does that relate to the number of windows on the east/west and north sides more so? How could we have changed that to reduce the heat loss?”

Ideally, if the insulation in all areas of the building cost the same, you’d want to balance the R-values so that the heat loss intensity rate is the same through all envelope elements. Your exterior above grade wall has the highest relative rate of heat loss, so that’d be the place to add more insulation first if you want to improve performance. If you want to optimize R-value ratios this way, it’s smartest to add in the cost/ft2 of each insulation type, then you can maximise your return on investment. For example, adding 1″ of cellulose in the attic is much cheaper than an inch of foam outside of a wall.
The glazing of course has the highest rate of heat loss, but that’s just because you max out at around R10, where your opaque assemblies are R50+.
Your North, East, and West windows are NET losers of heat, while the South windows offer a net gain. This is as expected, and is really the basis of Passive Solar design, that a South window can actually HEAT a building throughout the heating season, with the right recipe. If you wanted to optimize the glazing further, you can add more South glazing while removing glazing on the other elevations (North being the biggest drag on efficiency), which will continually reduce the annual heating demand (how much energy is consumed to heat). This is a Red Flag area though, following this path of more South glazing will eventually cause overheating throughout the year. Prediction of overheating / discomfort is an area where the PHPP is very poor, and I’ve been burned in the past on some projects where we pushed the Passive solar too far in an attempt to reach certification. I now use IES<VE> as a energy modelling tool because of its ability to accurately predict overheating.
“Did you have any thoughts or considerations you would have given us had we run these numbers off the bat with the house planning? “
I’d honestly say you’ve done a great job on your home. It’s pretty much impossible to meet the PHI Passive House criteria for a small single family home in Saskatchewan, without significant and typically unjustifiably cost. The PHIUS criteria is based on a more climate-specific analysis, which attempts to stop investment in conservation at the point a little bit beyond where renewable generation is more feasible. Meaning it’s more realistic to meet the PHIUS+ targets, though we’re not seeing much uptake in the Prairies.​
All of this was very interesting and at the same time reassuring to me. Like many others, I had put a lot of credence on the PH standards as the be all and end all (even still despite reading and appreciating the issues I’ve previously discussed). It was good to hear that the assumptions we’d made were in the end in line with the reality of trying to build a PH in Saskatchewan.
Even still there was one last thing that I just had to know… it kept coming up again and again. It was one of those pesky assumptions we kept getting asked about. And one of my recently reposted blogs on Green Building Advisor brought it back to my mind again… German windows.
It is regarded that the German (or Polish and Lithuanian) Passive House certified windows are the creme de la creme of windows. They are attractive, heavy, thick (6″ wide!), and expensive. But if you want to reach Passive House standards, you gotta have ’em! (Or at least that’s what they say).
I felt a little bit guilty asking for quotes on windows that we were never going to buy, but my curiosity just couldn’t be helped. I wanted to know how expensive PH-certified windows would have been for our place. We’d heard outrageous prices of up to $80,000 for some homes.
We tendered a couple of quotes and received a reply from Optiwin of Lithuania. The salesperson was exceptionally thorough and I was really impressed with his communication (which made me feel more guilty). After a couple of weeks I received the pricing back. I was actually surprised that the cost of the PH windows was only $17,000 CDN more than the windows we purchased from Duxton Windows. Although they would have been certainly way outside our budget anyway – they weren’t 400% more than the price we paid by any means (just a measly 75% more). Nonetheless, I really had to pause again and wonder, why? What would make these windows $17,000 better than the fibreglass, triple pane windows we got? The U-factors and solar heat gain coefficients were not that big a difference. Maybe the the locking mechanisms of the windows could get you a bit lower on your airtightness – but $17,000? How long would it take you to save on heating bills to justify that “investment”?
All this being said, I’m happy to have answered my lingering questions and to confirm some of my assumptions. The bottomline, of course, though is that you want to be able to sit back and be happy with what is around you. To know that you did the best you could in building a sustainable home for the future.
I can’t complain.

Musings on Passive House Standards and the Costs of New Home Construction, Part 2

If you have not read Part 1 yet, please go back and read it first. 

In mid-November of 2015, just prior to us moving into the house, we were asked to be apart of the Passive House Days tour (a world-wide weekend of awareness of Passive House and energy efficient building). Well, not “officially” – we were asked to be apart of the tour by the event organizer in Saskatchewan who is the Passive House (PH) consultant on what should become the first certified PH in the Saskatchewan. Even though we did not build a PH, we did follow their standards as closely as I could justify, but from the beginning we were not pursuing certification.

Although all of the visitors on the PH Days Tour were very interested in our house, our process, and why we did the things we did, one question we got a lot was, “If you were following the PH standards why not go all the way for certification?”

First, let’s back-up a little bit. Indeed the principles of a PH are second to none. From Passipedia: “Passivhaus is a building standard that is truly energy efficientcomfortable and affordable at the same time.” So simple. Brilliant even. I wanted to build a PH. Who wouldn’t?

Strangely, if you visit Canadian Passive House Institute (CanPHI) website there are total of 5 projects that have received Canadian PH certification. If you look up the PH Project Database there are a grand total of 23 houses in all of Canada that have received certification.

Why the discrepancy you may ask? Why so few certified projects?

This is a bit complicated and took me awhile to figure out. But here are the basics as I understand it: the Passivhaus standards were developed in Germany for German buildings in the German climate (obviously). However, when other builders in other countries tried to build a “Passivhaus” in say the USA, England, or Canada, they realized something profound: Hey… wait a second… I don’t live in Germany!

Maybe trying to build to German PH certified standards in Minnesota or Saskatchewan is going to be really difficult? Maybe impossible? Or maybe possible but really expensive? Or maybe possible but a really uncomfortable building to actually live in?

Still PH institute satellites started to spring up in most countries around the world. Slowly, Passive Houses, built to the German requirements, started to be built in other countries with the first certified Canadian building being built in 2009. The uptake, however, was certainly not rapid nor widespread. Why? Was it not as the PH Institute of Germany said that these buildings are “truly energy efficientcomfortable and affordable”? Or is it just that we are too cheap and/or lazy and/or complacent to meet those strict German requirements elsewhere?

It seems like this is something that these PH satellites were struggling with as discussed herehere and here.

A few years ago though, some people started to say, this is silly – why are we following German standards and requirements for our buildings when we don’t actually live in Germany?

The German PH standards are as follows:

  1. Space Heat Demand: max. 15 kWh/m2a  OR  Heating load max. 10 W/m2
  2. Pressurization Test Result @ 50 Pa: max. 0.6 ACH
  3. Total Primary Energy Demand: max. 120 kWh/m2a

Simple enough right? Hit these numbers using the PH planning software and your building can be certified as a PH. Where’s the problem?

The Pressurization Test for 0.6 ACH is strict, but not impossible. There had been many houses built to this level of airtightness before PH came around. Rob Dumont’s own home in Saskatoon in 1992 tested at an awe-inspiring 0.47 ACH.

Jumping to the third requirement, the Total Primary Energy Demand of 120 kWh/m2a ensures essentially that you are not wasting energy or are at least using it wisely. It forces you to use energy efficient lighting, appliances and mechanical systems. I don’t think anyone can argue with that as being important to green building.

The real problem though, in my opinion, is the Space Heating Demand of 15 kWh/m2a or heat load of 10 W/m2. These numbers dictate the maximum space heating allowed for each square meter of a building. Remember – this is based on a German climate.

In Germany the number of heating degree days (HDD) is around 3100 compared to over 10,000 HDD in Saskatoon. So that means there is over three times as much heating requirement in Saskatoon as compared to Germany. Besides that, who really cares what your heating demand is? With the maximum energy demand of 120 kWh/m2a already stated, what difference does it make whether you use 50% of that to heat your house or 10% in terms of your overall efficiency? This is my real beef with PH and the one that most others working towards PH in countries that have climates other than a German one tend to struggle with too.

Recently the PH Institute in the USA (PHIUS) split off (or was banished – depending on what you read) from it’s affiliation with the German PHI. This allowed them to develop their own standards and specific requirements for climate zones in the USA (Minneapolis also has different heating needs compared to Miami) and also to use North American calculation values instead of European. As a result it is now easier – ok, let’s say, attainable – to hit the PH targets for your Minneapolis house using a Minneapolis climate to calculate your requirements. Now that makes sense to me.

Sadly, the Canadian PH Institute has been resistant to following their American counterparts and has continued to align itself with the German requirements. Thus making it darn near practically impossible to meet the PH standard and become certified by the Canadian PH Institute.

There is a small loop-hole of sorts though, a Canadian house can pursue certification via the PHIUS, which is somewhat closer to our climate in the northern States. Although the conversion is not exact, the Space Heating Demand requirement for the northern USA is about 30 kWh/m2a (or double that of the German standard maximum). That’s better, but still the maximum heating degree days in Saskatoon are more than any other place in continental USA. Nonetheless, there have been a few of PHs in Canada that have used the US system to become certified (ok, like maybe 10 or 12).

I told you this was complicated…

Anyway, let’s try to bring this full circle, back to my original question of why don’t we just build all new houses in Canada to the PH standard?

I hope that I have presented the argument that it may not be realistic to build a certified PH in Canada and follow the original edicts of the German Passivhaus Institute of “energy efficientcomfortable and affordable.”

From Part 1 of this post, you may be able to see that there is a HUGE chasm between how most new homes in Canada are currently built as a result of our pathetic building code allowing inefficient homes to perpetuate, and the extremely difficult PH standards currently set in Canada.

Unfortunately, I think the CanPHI has done itself a disservice in not distancing itself from the German PH Institute. By not developing it’s own Canadian climate specific standards for the unique climate zones of our country, which maybe (just maybe) one day could be adopted on a large nation-wide scale.

Until such a time that the CanPHI recognizes this and modifies their requirements appropriately and regionally, I doubt that PH will ever gain much more than a very small handful of faithful followers willing to spend, at all costs, to meet an arbitrary set of values developed on the other side of the world.

That being said, I do KNOW that you CAN in fact build a house in Canada that IS energy efficientcomfortable and affordable.

But it isn’t a Passive House. 

Because that’s what we’ve done.