duxton – Blue Heron EcoHaus

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

Posted on April 2, 2016April 2, 2016 by kent

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:

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

Our results were as follows:

Space Heat Demand: 37 kWh/m2a
Heating load: 22 kWh/m2a
Pressurization test result (assumed 0.6 ACH, prior to testing)
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.

Drywall (the least romantic part of building) and Paint

Posted on October 8, 2015October 8, 2015 by kent

Ok, none of it is really romantic, but drywall has got to be the most unappealing stage in building. Despite what everyone says about it making a space “look bigger”, I didn’t get that impression at all. I just thought: this is gross.

I had been taking a tonne of pictures up until this stage, but truthfully, I didn’t want to remember this drywall stage (I think I took 3 photos total). I was glad when it was finally over, but it ended up that the contractor took 4 weeks longer than anticipated and ended up setting us back a full month in construction.

In the end, they did a “good job” from a boarding/mudding/taping point of view. Our house was actually pretty complex, as we realized, for the drywallers. A few things I will share.

First of all, we did not want any baseboards, crown mouldings, or trim around the windows. Why!? Why would you do this?? You may ask. And I will tell you: we like the look of the clean lines of the materials sharply bumping up against the next – drywall to concrete, drywall to pine ceiling, black window framess to walls. If you want to get philosophical (who doesn’t?), this transition for us of moving, building, giving up our city life, has been an experience of pulling back the layers of ourselves and exposing who we really are. And the non-philosphical reason: I just think it looks cool.

Now, this added a couple of significant dimensions of challenge to the drywallers, how do you finish the drywall where it meets the concrete floor (main floor and basement), where it meets the concrete walls of the basement, and where it meets the window/door frames (a whole challenge in itself)?

After much debate, we elected to use a product called a “tear-away bead”. Basically they stick this bead on the bottom edge of the drywall, mud overtop of it, and then simply tear away this little tab on the bottom giving a nice clean line at the drywall edge. Most people use this for butting drywall up against exposed timber framing. We ended up using it extensively, about 2000 linear feet, on all bottom seams where the drywall met the concrete floors and the exposed concrete walls in the basement.

Now the windows were another challenge altogether. As you know, we built 16″ thick walls, which made for a significant 14″ return on the windows from the interior wall (2″ for the window thickness). On the window sills, we will be installing douglas fir sills, but to do that around the whole of windows would be too much wood (in my opinion, as we will be installing pine ceilings throughout the whole main floor). So instead we wanted to do a drywall return on the top and sides. Now, I’m not sure how other people do this, but there is a drywall return channel on the window frames that the drywaller will simply slide the drywall into and then you’re done and ready to proceed with adding your trim.

For our windows, it was not that simple at all. We had asked them to remove all of the drywall return channels prior to the shipping the windows so that we could add our fancy air sealing Tescon Profil tapes to the windows (if we hadn’t have done this there would have been no way to secure the vapour barrier to the window frame – how do people normally do this, I asked? Most people don’t secure the vapour barrier to the window at all, was the answer I received. No wonder people have drafty windows!).

Ok so that was one thing, but it had a cascade of effects, namely that you had to get a reasonable overlap onto the window frame to secure the tape, which was approximately 1/2″. Remember too that there is spray foam that is sprayed in between the rough opening of the window and the actual window frame – about 1/2″ as well on all sides. Drywall is only 1/2″ thick… see where I’m going with this? The numbers were not adding up. Our only option was to double-up (two sheets) of drywall at each window return. As there was now no way to use the drywall return channel for the windows (and we weren’t putting on trim anyway to hide it) we ended up using the tear-away bead here too to give a tight clean line between the window frame and the drywall.

Problem solved!

Not quite… the whole house had been designed for 1/2″ drywall throughout, which you may not think would be a problem, except for the two corner windows (between the main entry door and kitchen/dining room).

Frick.

This was not going to work. After coming up with some preliminary dumb ideas, I removed the second piece of drywall, which made the corner flush again, but it exposed too much of the Tescon Profil tape on the windows, that cutting it away would expose the vapour barrier. I ended up shimming out the side closest to the window, at 14″ in depth, you can’t visually notice the 1/2″ transition that occurs, allowing the corner to be flush and the tape to be covered at the window frame. I’m so smart! (I humbly told myself). (Though my woodworker doing the sills will be cursing me).

Unfortunately the corner window with the main entry door, would not be so simple. The only option here was to build out the entire one wall and to make it two sheets thick. Oh well.

Once the mudding was finally done, we spent the next two weeks painting like madmen. We decided to use Benjamin Moore Cloud White for the entire house (except for the basement doors, which we will paint in Oxford White). I do like the colour white and there are seemingly an infinite number of whites to choose from. Cloud White though is a favourite of one of the design duos we follow: Mjolk. So that made the decision easy for us.

I do not like painting at all, but we are lucky enough to have an amazing neighbour who came and helped us paint for two long days on the weekend. Having the extra hands was such a blessing to us. Over the next week we were able to finish the painting and were ready for the next step: exposing the concrete floors and the nightmare that followed.

High Performance Windows

Posted on May 12, 2015February 16, 2016 by kent

One of the things I am most excited about in our house are the windows. We have a lot of windows in the house, 25 to be exact. And they are not terribly small. Even before knowing anything about energy efficient building, I’d always loved homes with large expansive windows overlooking a beautiful view. However, when building an extremely energy efficient home, the placement, size, glazing, window to floor ratio, and type of window matter a lot.

First, and perhaps most important, is which direction your windows should face. Obviously in the northern hemisphere, the sun is in the south. Therefore, the majority of your windows should face south and be able to take in the sunlight through the winter months when the sun is lower in the sky to provide some passive heating. Conveniently the sun is higher in the sky in the summer, so as long as you have properly sized overhangs or shading in the summer then you can prevent overheating. Recently we were in a neighbour’s house that was not designed with energy efficiency in mind. They have large south windows that are completely exposed, as well as some larger east and west facing. Even though they would (theoretically) have a great view, they had the interior blinds drawn on almost all of the windows! Interior blinds and shades do very little to prevent overheating as the light/heat has already entered the space and will simply heat the blinds and radiate inside anyway.

For us, we maximized our southern exposure (but not too much as you can still overheat in the winter – even at minus 40° Celsius). And minimized our northern, eastern and western windows. Fortunately for us our best view is to the south and east. We do have a couple large windows on the east side of the house to take advantage of the river valley and our unobstructed view of the sunrise (to not put windows there would be foolish). We would have liked to have put more windows on the east, but in order to do so that would require shutters on the exterior, thus obstructing the view anyway. Shutters are really the only way to “shade” light from the east and west as the sun is too low in the sky throughout the year (at sunrise and sunset) to actually “shade” it. As for the north we don’t have much of a view, and so only have two windows. One in a bedroom for ventilation and fire safety and the other in the hall for ventilation. Northern windows really don’t provide any benefit in energy efficiency and are actually an energy penalty.

As for glazings, these are really amazing and can help with heat gain or blocking unwanted heat.The glazing does not at all block the view. I think of it like sunscreen. On the east and west windows, you want more sunscreen because you don’t want to overheat. On the south you want minimal sunscreen because you want that good passive heating in the winter (as long as you account for passive shading in the summer).

Ok so what type of windows do you buy? Wood, PVC or fiberglass? We had really hoped that we would be able to afford fiberglass windows. These are simply the best for energy efficiency, durability and quality. The frames themselves are made of 60% glass (fiber-glass) and so they move with the expansion and contraction from the heat and cold of the windows. Consider -40°Celsius outside and +20°Celsius inside. That is a 60° change that occurs through about a one inch space. PVC and wood will flex and bend at a different rate then the glass, leading to more air leakage, reduced air seal, and eventual failure of the window over time. Fiberglass however does not have the same issues. Duxton Windows has some excellent information on their website.

Now that we had an idea of what we wanted, we needed to determine which supplier to go with. We priced out Duxton (fiberglass), Accurate Dorwin (fiberglass) and Plygem (PVC/wood). We did not consider any of the crazy German imported windows. Shockingly, people actually do this (this is where the economics of Passive House and extreme energy efficiency clash with reality and sustainability, as I’ve written about before). I was actually talking to a house designer the other day who was raving about some German windows they’d started to import. Indeed they are impressive windows – but they are coming from fricking Germany! My thought when building a “sustainable” home is that we should be really considering if we are spending our money wisely or if it could have a better effect elsewhere (for example, spending $15,000 more on windows to get a marginal energy improvement versus $15,000 in solar panels). AND if you are importing your high performance windows from 4000 miles away and shipping them on a cargo ship across the ocean… well… is that sustainable?!

Anyways, I knew that the fiberglass windows would be more expensive than wood/PVC – but how much more was the question? When we received the quotes back I was pleased to see that the fiberglass windows came in only 20% more expensive then PVC. For the added efficiency, durability, warranty and, not to mention the larger viewing area of the window (fiberglass is stronger therefore can have a smaller frame and more glass) it was a no-brainer to go with fiberglass. We ended up choosing Duxton over Accurate Dorwin due simply to the fact that our designer had recommended them. The price difference between the two companies was marginal.

In designing the house and choosing the windows I tend to think about what Christopher Alexander of the Pattern Language says: “light on two sides of every room.” I loved reading this book because it was all about aesthetics. Written in the 1960s, it did not give a crap about energy efficiency. It was a nice reality check against all of the energy efficient dogma that in some cases can really get out of control. You still need a home that you actually want to spend time in.