Image Credit: Kent Earle
More Guest Blogs
Editor’s note: Kent Earle and his wife, Darcie, write a blog called Blue Heron EcoHaus, documenting their journey “from urbanites to ruralites” and the construction of a superinsulated house on the Canadian prairies. The blog below, originally published in April, is the last in GBA’s series documenting the project, but there is still lots to read at their website. A complete list of Kent Earle’s GBA blogs can be found below.
Have you heard of the Pareto principle 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 follows this rule to a T. It has certainly been our experience in building an extremely energy efficient home and following the principles of Passive House. I believe that 80% of the benefits of Passive House come from about 20% of the cost and effort. (In Part 1 of these posts, I noted that our financial cost was about 8% more than for standard house construction.) Whereas to get that last 20% to hit the Passive House certification 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 (PHPP) software to predict our performance.
What the test results said
As you may recall, we were never pursing Passive House certification. Right from the beginning we were told the cost-effectiveness (80/20 rule) was just not there. Maybe if there were 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.
BLOGS BY KENT EARLE
Adding It All Up, Part 2Adding It All Up, Part 1Blower-Door TestingInsulation, Air-Sealing, and a Solar ArraySoffits and Siding at the Blue Heron EcoHausPlacing the Concrete FloorsAdding Walls and RoofDealing With Really Bad WaterMaking an ICF FoundationLet Construction BeginPicking High-Performance WindowsHow Small Can We Go?Choosing a Superinsulated Wall SystemHeating a Superinsulated House in a Cold ClimateIs Passivhaus Right for a Cold Canadian Climate?
I decided to ask around and see who could put our house through the PHPP — or at least to see if we could get a price quote for it. Maybe it would be too costly and so I wouldn’t bother.
After a few emails, I was eventually referred to a very well-respected Passive House 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 might lead to some interesting points of discussion.
Based on the three criteria for PH certification, recall:
Our results were as follows:
You can see that the only criterion we met was the total primary energy demand. The blower door test we did later came back at 0.72 ach50. (We’d run the software assuming 0.6 ach50.) Inputting the actual air leakage value would correspondingly increase the other values, but, for argument’s sake, let’s simply say that we either met, or were very close to meeting,the total primary energy demand, while for the heat demand and heat load, we were way above the German Passivhaus maximum values.
What would have to change
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 Passive House consultant: “If we were still in the planning stages of the house, what would be your recommendations to 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?”
Here was his reply: “​The ways to reduce the heating load and 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 builders to build multifamily 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?”
His reply: “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 would 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 maximize your return on investment. For example, adding 1 inch of cellulose in the attic is much cheaper than adding 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 R-10, 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 as a energy modeling tool because of its ability to accurately predict overheating.”
Would earlier consulting made a difference?
I also asked, “Did you have any thoughts or considerations you would have given us had we run these numbers off the bat with the house planning?”
He said, “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 unjustifiable cost. The PHIUS criteria are 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 in the Passive House standard as the be-all and end-all (even 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 Passive House in Saskatchewan.
Finally, the question of windows
Even still, there was one last thing that I just had to know. It kept coming up again and again, 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.
Some people say that German (or Polish and Lithuanian) Passivhaus-certified windows are the crème de la crème of windows. They are attractive, heavy, thick (6 inches 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 Passivhaus-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. I was actually surprised that the cost of the Passivhaus windows was only $17,000 CDN more than the windows we had purchased from Duxton Windows.
Although they certainly would have been way outside our budget, 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 fiberglass, triple-pane windows we got? The U-factors and solar heat gain coefficients were not that much different. Maybe 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 bottom line, of course, 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.
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22 Comments
Shutters.
Ask the modeller to add r-30 exterior shutters to every window and see if that does the trick to hit PH standard. Have them closed 16 hours per day and the north ones closed through the winter. Then see if you can withstand the temptation to have them locally built and installed.
Ven
I know you have had good experiences with the shutters at your centre, but do you think many homeowners would be content to only have their windows uncovered for eight hours each day? Similarly, north windows have usually been included after careful consideration that they are serve some useful function. Why would this function disappear during the winter?
Windows
I'm with Malcolm- Shut all north side windows all winter? To save a few bucks, when the house already costs next to nothing to heat? And who will slog through the snow twice a day to open and close the other shutters?
PGH is more than good enough. As Kent clearly points out, PH makes little economic sense in really cold climates.
Ven is digging in the right direction
The Sakatchewan Conservation House used insulated shutters and double-pane windows to meet what are essentially Passivhaus targets back in the 70's. The designers and engineers of that groundbreaking building also used much fewer windows. It’s unfortunate that Mr. Earle's consulting team advised him to dig in the passive solar direction, and not towards the conservation direction. His building is way too over-glazed and not air tight enough for this challenging climate and therefore could not meet the Passive House Standard. (Both design choices.) No harm, no foul. Passive House is still an optional and voluntary standard and it sounds like the building is still a lovely building in a pristine, unspoiled area of natural beauty.
Other builders and designers in this region of Canada have been able to rise to the Passive House challenge, and meet its targets. Lukas Armstrong shared these examples in his recent presentation at NAPHN16 here: http://nypassivehouse.org/wp-content/uploads/2012/06/LukasArmstrong.pdf.
Rob Dumont's study outlining Saskatoon path to Passivhaus
Here's the article I was referencing that outlines how the Saskatchewan Conservation House points to Passivhaus: https://www.greenbuildingadvisor.com/sites/default/files/Passive%20Solar%20Heating%20-%20Rob%20Dumont%20-%201978%20.pdf
Bronwyn
You wrote: "Passive house is still an optional and voluntary standard". Where do you stand on the standards being made compulsory and incorporated into building codes? I have asked you this before, but you didn't reply.
Ven
I think shutters are often a good idea, I just didn't think it as worth modelling their influence assuming such long use. More realistically, they will be opened when the occupants get up, and closed when it becomes dark outside - much as curtains are.
i completely missed that this was a weekend house. I assumed they lived there.
Malcolm on shutters.
I only ask that he model them and see what the results are. Then I will leave the choice open, if he prefers the energy savings and minor inconvenience of closing them, that will be a certain personality tendency. Others will not go for it. But shutters have a long history on houses, and of course people have blinds and drapes which require closing if they are to be effective. On the north side if the savings are trivial he can have interior shutters which he leaves closed at his whim since there is no direct sunlight which can crack glass. It may be hard to design easy closing shutters at this point but not all windows need them. He also uses his house only on weekends which means the shutters could be left closed 5 days a week when the house is vacant.
Malcolm
I'm for voluntary standards but for requiring the architect and builder to pay the first year of energy bills over an agreed threshold. That way you'd never need to mandate Passive House standards. Everyone would voluntarily build to them.
Response to Bronwyn Barry
Bronwyn,
It sounds like your proposed regulation would encourage architects and builders to build net-zero houses, not Passive Houses.
Response to Martin
If BB's "agreed threshold" is agreed between buyer and builder/architect, it might not encourage any particular standard, whether Passive, Net-zero, or PGH. More likely architects/builders would simply set easy thresholds to exceed; the "under-promise, over-deliver" paradigm.
Another issue might be that one is essentially providing "conditioning insurance" for a year: if any excess conditioning is paid by someone else, why not keep a couple windows open all year? I've actually met folks who do this on their own dime, although only in a 2000 hdd climate..
Compulsory Passive House Standards
Bronwyn,
I asked because although you deflect worries that the standards may imposed on the larger building community by saying they are voluntary, that isn't the position Passive House International. Their 10 Point Plan includes mandatory adherence for any buildings with municipal involvement and the incorporation of the standards into local building codes.
So these aren't as you have put it "just another standard you can choose to use", and for me that's why the intransigence of Passive House in adapting or modifying their practices is so important.
Leed is full of silly requirements, but that didn't matter until they managed to get many municipalities to adopt it as the default environmental standard for their projects. From my persecutive the result has been a series of buildings adhering to a standard which encourages largely meaningless modifications.
As it stands today meeting Passive House standards is a direction appropriate for a small sub-set of the buildings being constructed. If I thought it was content to remain that way, and allow those who found it useful to choose to follow it, I wouldn't spend as much time arguing against it.
German PH Standard?
Would this home pass the German PH modeling? We know it can't pass the US version but what about the German version?
Peter,The German standard is
Peter,
The German standard is tougher to meet from an energy perspective, I believe Calgary is the closest PHIUS climate set to Kent's house and the annual heating demand limit is 7.8 kbtu/sf which should equate to 24.54 kW/m2.
We live here full time
I'm glad this post has stimulated some good discussion. I will clear up a couple things:
1. I'm not sure where the confusion came, Ven, but we live here 100% of the time.
In regards to the question about shutters, I wouldn't personally go for them. I would be interested in modeling them for curiosity but I wouldn't use them. We tried to follow a design principle (not a PH principle) to have light on two sides of every room. This makes a very comfortable space for visiting and conversation.... to the downside of PH. However, in building and designing our house, energy efficiency was just one part of the picture. We had 3 priorities: i) maximize the view (we live on a beautiful stretch of river, valley and trees), ii) maximize the energy efficiency, and iii) be cost effective.
After nearly a year of living in the house, I have no regrets and no complaints. I wouldn't change any of the choices we made.
2. It's an interesting thought about conservation vs. passive solar. Obviously a very tight closed box with 24" of insulation surrounding it would be very efficient but I don't think many lay people such as myself would want to live there. From the post above, I think bronwyn is referring to over glazing on the north, east and west sides, as the south windows are a net gain. But this brings me back to the point above of light on two sides of every room - and the fact that we needed Windows on those sides for passive cooling in the summer.
Also, in regards to conservation vs. passive solar- I've had the impression and nothing I've read and no one I've spoken to has convinced me otherwise - there's a point where conservation loses cost effectiveness and investment in PV solar becomes a better way to invest funds. This cut off was something we tried to find and I think we came pretty darn close - this is why we spent $24,000 CDN in solar panels rather than the same amount in higher end German Windows, more insulation or greater airtightness.
If our goal is to build attractive homes, reduce our energy use and be cost effective so that others will be encouraged to do the same, who really cares then whether they follow net zero principles or PH principles? Or some hybridized version of the two (as we did).
If you live in a climate and location where you can meet PH targets and be cost effective - awesome. If you live in a climate where you can't meet PH targets and/or you location doesnt suit it (for example the home owners best view is north - our best view is south so we are lucky) then why not maximize what you can do following PH and then invest in PV solar or wind renewables? Finding a balance is best. I'm no expert but as a commoner this makes sense to me.
Kent, about shutters.
Shutters are only closed at night, so it does not affect day light at all. They are usually only closed during the 4 coldest months and left permanently open 8 months per year. All they are is super insulated curtains really. North side windows if aesthetically pleasing can be left open in the day...it is merely a matter of taste.
The inside of the shutters can be painted white, and at night they brighten the house rather than having jet black windows, as naked windows appear through the long winter night.
Response to Peter L (Comment #13)
Peter L,
Q. "Would this home pass the German PH modeling?"
A. Re-read paragraphs #9 and #10 of this blog. In those paragraphs, Kent Earle summarized the three targets that one has to meet to achieve the German Passivhaus standard, and goes on to report that his house met only one of the three targets -- resulting in a Fail.
My mistake.
I had this house confused with the Quebec house which was near passive. That was a weekend off grid house. This, is the Sask. house.
Ven
I know - these damn Canadians with their energy efficient houses sprouting up all over the place like mushrooms.
Malcolm and Martin
I believe you'd both be surprised to learn that I'm not so orthodox about rigidly adhering to the Passive House Standard. From my personal interactions with PHI and with Dr. Feist himself, I don't believe they are either. Dr. Feist showed one of Carter Scott's projects as an exemplary building at the last International conference plenary and has applauded project teams who have made divergent choices for various reasons that meant they missed the PH metrics.
That said, I still believe the Passive House standard offers one of the best methods (and modeling tools) for consistently delivering outstanding comfort and performance at the lowest possible price. Measured results from my own projects confirm that the PHPP is a reliable and useful tool. Our designs and assemblies just keep getting better, smarter and cheaper. Whether you actually hit all the target metrics or not, that's the part I'm less fixated upon. The ability to make an informed decision on which measures to choose/use is way more important. I believe this is what Mr. Earle has done and I applaud him for it.
We can all get super-geeky about whether shutters or better and fewer windows would have enabled his Haus to meet the PH standard. From my own modeling of this design, I'm convinced it could have been done more affordably and comfortably if different design choices were made. Plenty of natural light - from two sides - and views would remain. Given that other choices were made, my opinion is quite literally academic.
Martin - my regulation of choice would certainly offer builders the option to build to Net Zero or PGH. However, once builders start integrating super-insulation, better windows, HRV's and air-sealing into their regular practice, then getting to Passive House is the same cost. From numbers I'm seeing collected by the DOE on PGH and Net Zero builds, they're in the same cost premium range as Passive House: 5-10% above code minimum. I've yet to see a hue and cry over those projects?
Malcolm - I agree there is plenty of stupid already embedded into our building codes. (Vented crawl spaces being my own pet peeve.) If you're worried about the Passive House Standard becoming required by code, you may want to consider shuttering your practice before the next code cycle... (it will be warmer that way too!) More rigorous energy codes are coming soon everywhere. If it makes you more comfortable to call them something other than 'Passive House' my personal regulatory preference will allow you to do so. (And don't worry - as a foreign born citizen, I'm not eligible to run for President. :)
Bronwyn
Don't worry, I'll be alright. It's worth remembering that both the house we are discussing and my practice are in Canada under different codes. Our latest version here in BC has already addressed increased levels of air sealing and insulation. It also requires full-time balanced mechanical ventilation, including crawlspaces. Past iterations have brought us rain-screens for cladding and new seismic requirements. The results are on their way to what I would call Pretty Good Houses, and I'm all in favour of any future incremental code changes that my occur.
Excellent article and great comments.
I so appreciate this qualified and thoughtful dialogue!
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