Airtightness: Blower Door Testing

Excellent levels of airtightness are equally, if not more, important to the level of insulation you decide to put into your house. These really are (insulation and airtightness) the two pillars of an passive house and pretty well any other Eco-house building.

For our house, we’d gone with high levels of insulation in the range of 3x the typical amount for standard construction: R32 under-slab and basement walls, R56 walls, and R80 attic. However in deciding our insulation levels and our targeting goals for airtightness, we did try to strike a balance between cost-benefit and recognize the point of diminishing returns.

I have written about our insulation choices previously here and here, so I will not go into that as much, but in terms of airtightness there are some basics that are worth discussing. The fact is: air leaking into and out of a building is not efficient no matter how much insulation you have in the walls. Although insulation decisions, thermal bridging reduction, and solar gain can be designed into the house, airtightness can really only be ensured while actually constructing the building. Airtightness is tested with a blower door test and is rated based on “air changes per hour a 50 pascals of pressure.” Typical construction in Canada reaches about 3 ACH. The Canadian R2000, our high-efficient energy standard, is 1.5 ACH. While the Passive House standard is a whopping 0.6 ACH.

Although I was hoping we could target the extremely difficult goal of 0.6 ACH as per Passive House standard, the question was – how far ($$$) are you willing to go to reach this? As with insulation levels, there is a point of diminishing returns. Will 0.8 ACH versus 0.6 ACH be anymore noticeable in terms of user comfort? And over the lifespan of the building would you ever balance out these costs?

We decided to set an ambitious, but realistic goal, of 0.8 ACH.

The reason for this was four-fold:

  • 1. Our house is not big. It is a rectangular bungalow at 1240 sq.ft. The blower door test is an test of absolute air leakage from the building – not a relative test. By that I mean, that a large house can more easily meet a lower ACH level then a smaller house due to the greater volume of the house overall.
  • 2. We were not prepared to spend the greater amount of money on air sealing tapes, interior sheathing, and the labour to do this. A standard house is sealed with a 6 mil vapour barrier (cost is $50 per 8’x500′ roll) and Tuck Tape ($6 per roll). A Passive House is often sheathed with 5/8″ OSB ($25 per 4’x8′ sheet) on the interior to serve as it’s vapour barrier or high-end Intello Plus vapour barrier ($320 per 64″x164′ roll) with the seams sealed with Tescon Profil/Vana tape ($45 per roll). It does not take much in the way of math skills to see that the latter option can get extremely expensive. But if you really want to ensure you hit that Passive House 0.6 ACH target, that’s probably what you need to do (the Tescon Profil tape is often used on the outside walls as well to seal the air barrier and windows/doors).
  • 3. We were not pursuing Passive House certification, so really there was no point in ensuring we hit 0.6 ACH. If you’re spending the money to have a Passive House consultant work with you at the initial design stage and you’re spending the money on the high-end Passive House certified windows, the special tapes and the extra insulation, you better make sure you hit 0.6 ACH or all of that expense will be for nothing. For us, if we made 0.6 ACH, great, if we didn’t, oh well.
  • 4. We were installing a wood burning stove and chimney. Although the stove itself is very high quality from Morso in Denmark, I figured this extra hole in the wall would likely negatively impact our airtightness. But we were not budging on not having a wood stove. We also had another extra hole in the wall for the water cistern in the basement, but again this could not be avoided.

All that being said, we did make every effort to design the house to be as airtight as we could. The dense-packed cellulose in the walls itself provides a high degree of air sealing on it’s own. We limited the penetrations into and out of the house by selecting a condensing dryer from Bosch and having an electric boiler (the only penetrations are the chimney stack, the water cistern pipe, and the HRV). We used a standard 6 mil poly for the vapour barrier with acoustic sealant at every seam. Each seam was also taped with standard Tuck Tape to ensure another layer of added protection. Around the windows and exterior doors we purchased and used the Teson Profil air sealing tapes to attach the vapour barrier to the frames. Although this tape is very pricy, it made sense to me to use it here as the greatest area of air leakage is often at the window frames and doors.

Now it was time to test the house.

The testing is done through a Blower Door test. “A blower door is a powerful fan that mounts into the frame of an exterior door. The fan pulls air out of the house, lowering the air pressure inside. The higher outside air pressure then flows in through all unsealed cracks and openings.” The test is repeated in the same way by drawing air into the house. “The auditors may use a smoke pencil to detect air leaks. These tests determine the air infiltration rate of a building. Blower doors consist of a frame and flexible panel that fit in a doorway, a variable-speed fan, a pressure gauge to measure the pressure differences inside and outside the home, and an airflow manometer and hoses for measuring airflow.”

Essentially it simulates wind blowing against the house in all directions at the same time. The test takes about an hour to administer with the tester taking multiple readings at different fan speeds both while depressurizing and repressurizing the building.

IMG_3178IMG_3179

While the test was running we also used an infrared meter to look at any hot/cold spots.

IMG_3181

A couple days later he sent us the results: 0.8 ACH at 50 pascals.

Right bang on our goal. Not bad. The guy who tested it said it was the tightest building he’d ever tested before.

I was happy enough with it, but a couple days later I happened to be standing beside the chimney on a windy day and I could ever so slightly hear a whistle through the pipe. I looked closely at the seams and saw they were not fully sealed. Damn!

We’d also had some crappy construction locks on the doors and I put my hand against them. I could feel wind there too! Double damn!

After sealing these leaks and a few other tiny ones we found, we did another retest a couple weeks ago. This time, the results were 0.72 ACH at 50 pascals. Not too shabby.

After talking to the tester, though, he thought that given the higher than expected discrepancy between the depressurized and repressurized values that maybe the vents of the HRV had opened slightly causing a skew to occur. He’d like to do one more retest in a couple weeks, thinking this would take it down to 0.65 ACH or lower. At this point, he’s doing it at no charge as he’s simply interested to see what the truest level of airtightness is.

For me, I’m happy to know that we reached almost Passive House airtightness values while still being as economical as possible.

*** Please see the UPDATED BLOWER DOOR TEST POST for the redo test final results! ***

SUPER-insulation! Airtightness! The staples of a passive house.

There are seemingly innumerable weighs of building a super-insulated home. Once you venture outside of the conventional 2×6 walls with 1-2″ of EPS foam, there suddenly opens of a plethora of options. I won’t go into as I’ve talked about it before, in us choosing super-insulated walls system and the double-stud deep wall framing. Now what you put between those walls is just as important as how you construct those walls. In our case, we chose to use dense-packed cellulose.

Cellulose insulation is a made from recycled newspaper or other wastepaper and treated with borates for fire and insect protection (taken from GBA). Dense-packed cellulose is really, just what it sounds like: They pack it like crazy into the wall cavity – but not too crazy. In fact, the ideal balance between too loose and too dense is about 3.5 lbs per cubic foot. If it is too loose it will settle and result in poor insulation over time. The denser it is the more resistance to air leakage (the vapour barrier obviously reduces this further) and the better the insulation. However beyond about 4 lbs per cubic foot of density you are at risk of blow-outs (or the drywallers will not be able to work with your crazy wavy walls).

At 3.5 lbs per cubic foot and with 16″ thick walls, our R-value is a whopping R56 for the exterior above-grade walls!

We contracted a company, Westcan Insulators Inc., who has extensive experience with super-insulated homes and a wealth of knowledge in energy efficiency. At our preliminary meetings they provided us with so much valuable information (have preliminary meetings with all trades presents – it truly is invaluable). It was so reassuring to have them on board, as really in building an energy-efficient home, the insulation and airtightness are the most important aspects. If you don’t have this right, you really don’t have anything.

As Rob Dumont said: “Anything that has moving parts will fail; in fact, it must fail, because there is no such thing as a perfect bearing.” Therefore, passive systems are always better than active systems and insulation and air sealing, if done well, will have the greatest return (for the lowest cost) over the lifetime of the building.

So here’s how the process worked:

On day 1, the crew came in and wrapped the walls with InsulWeb, a mesh that holds the dense-packed cellulose in place while spraying. They go through a buttload of staples to hold this onto the studs. They have to put a staple every inch along every stud, so you can imagine how many staples that would be. Crazy.

DSC_0025

DSC_0028

The next day, they bring out a big 5 tonne truck and using a 3″ wide metal hose they make a hole at one-third and two-thirds of the way up each stud bay. They then proceed to essentially filling the walls with the entirety of the truck. In actual fact, they unloaded about 6000 lbs of insulation into the walls alone (holy crap!).

DSC_0031

Here is a close-up shot of the cellulose and penetration. You can nearly read the newsprint.

DSC_0032

The next day came the vapour barrier and air sealing. This actually took the better part of five days for them to complete, but they did an excellent job (by the looks of it – we will really find out when we test it with a blower door in the next few weeks).

Airtightness is really equally as important as the insulation – perhaps even more so. Air leaking into and out of a building is not efficient no matter how much insulation you have in the walls. They used 6 mil poly for the vapour barrier with acoustic sealant at every seam. Each seam was also taped to ensure another layer of added protection, though truthfully this is probably unnecessary (from what we have been told, with this insulation alone, without the vapour barrier, would surely pass the R2000 airtightness requirement of 1.5 ACH @ 50 pascals), but it’s not hard to do and once the drywall is up you can’t go back and add more.

Around the windows and doors though we spent a bit of money and purchased Tescon Profil tape from 475 Building Performance. The stuff runs at $45 per roll, which is certainly a premium price versus the $9 per roll of good ol’ Tuck tape (the latter of which we used around all other seams). However between the walls and the windows/doors, there isn’t the layer of protection of the dense packed cellulose insulation (although they did spray foam around each window and the rough opening), so we felt the extra price could be justified here (to do the whole house in the Tescon Profil tape would be simply cost-prohibitive [although some people do it]. For the marginal gains you “might” make in airtightness, you would never save enough money on the long-term to justify that huge upfront cost, in my humble opinion).

IMG_3029

DSC_0035

DSC_0036a
Expensive fancy tape.

Final house design

Well, after twelve revisions and eight months of planning, designing, redesigning, changing, scrapping, planning, and redesigning some more we’ve finalized the house design at last. It’s funny, we had been so sure of what we wanted and didn’t want before, but gradually this all changed. I’m super happy with the design. And although it is different in some ways from our original plan (i.e. basement, open kitchen/living/dining room), it is more true to our original vision then we had ever expected: a quaint, simple, modern farmhouse. It’s crazy to think about how far our design gradually strayed from this original vision before we finally were guided back towards the root of what we wanted.

In a lot of ways designing the house has been a full circle – as we meandered away from our vision, only to come back to it. It was also an evolution. The final product was far better than what we had ever originally envisioned. So I suppose you must go through the process. You are never going to get what you want the first time through, despite how confident we felt that we knew exactly what we wanted. We didn’t. We needed to explore. We needed to think about all kinds of scenarios and possibilities before finally discovering what it is that we really want.

And so, here it is. I cannot wait to see this become a reality.

IMG_2576

Is Passivhaus Appropriate for a Cold Canadian Climate?

This is something I’ve been wrestling with since we decided on building a super-insulated, highly energy efficient home. And really this is something that I think a lot of builders, architects, and designers of eco- and green homes have been debating about since the Passivhaus concept came to North America in the past few years. When we initially got going on our project I was pumped on the possibility of ‘not needing an active heating system’ – as Passivhaus enthusiasts have touted their homes on. However, that really is not quite true.

Although many of these Passivhaus homes in Europe don’t necessarily use a boiler or furnace as we do in Canada, they do still technically require some way of heating. Often that is a heating coil attached to the existing ventilation unit that warms the incoming ventilated air. For our house, the possibility of using such a system simply made no sense. Passivhaus often justifies some of its standards on “user comfort.” Certainly I agree that user comfort is critical, however, in order to meet some of the rigorous standards of Passivhaus, people have tended to sacrifice comfort to meet the certification. For example, in our project, indeed, we could have used this method of heating as a secondary option, but it would not be sufficient to meet all of our heating needs despite the super-insulation. Furthermore, we need a thermal mass (concrete floor) to take advantage of the solar gains to cut down on our heat load. Those of you who have walked around on a cold concrete floor know that this is pretty uncomfortable (as a physiotherapist, I cannot count the number of people I see who complain about knee, back and foot pain due to walking on concrete floors at work). That being said, a warmed concrete floor is very pleasant, and strangely comfortable. Given that we wanted a concrete floor for both thermal mass and aesthetics, it made no sense to me not to use in-floor hydronic heat. In this case, we had to choose user comfort over Passivhaus standards.

Another major criticism of Passivhaus standards is both the annual energy consumption and annual heating/cooling consumption standards. These standards are very strict at 120 kWh/m.sq./yr and 15 kWh/m.sq./yr. I’ve previously written about these as well. But is this actually possible to attain in a very cold Canadian climate? Indeed this has been shown to be possible in a handful of projects in Canada. But not that many. Why is that? Recently we’ve run our numbers through the HOT2000 software, which is a Canadian software for energy efficient homes to calculate energy consumption. It’s not as thorough as the PHPP Passivhaus software, but it’s pretty good, and a lot cheaper to have done.

Ok so here are our numbers:

House size 1240 sq.ft (main floor) + 1240 sq.ft (basement) = 2480 sq.ft of treated floor area = 230 m.sq of total treated floor area.

Estimated Annual Space Heating Requirement: 7159 kWh / 230m.sq. = 31.13 kWh/m.sq/yr

Estimated Annual Electrical Space Heating (minus expected wood stove use): 2342 kWh / 230 m.sq. = 10.18 kwh/m.sq/yr
Estimated Annual DHW Heating: 3409 kwh
Estimated Annual Appliance: 8760 kWh
TOTAL ENERGY CONSUMPTION: 19,328 kWh / 230 m.sq = 84.04 kWh/m.sq/yr
First let me explain a couple things. One, we expect to use our wood stove a lot in the winter. I love a wood fire, there is something incredibly comforting about watching wood burn. Two, I do think that the annual appliance use is on the high side and I would also argue that our total space heating is also a bit high when comparing it to the Mill Creek NetZero house, an eco-house project using the same wall system in a similar climate. Nonetheless, let’s give these numbers some context:
Our House Projected Annual Space Heating = 31.13 kWh/m.sq/yr
Our House (minus wood stove heat) Annual Space Heating = 10.18 kWh/m.sq/yr
vs.
Passivhaus Annual Space Heating Standard = 15 kWh/m.sq/yr
Ok, so you can look at the comparison numbers I’ve provided above for Passivhaus and the average Canadian home versus our place at 31.13 (overall heat requirement) and 10.18 (electrical space heating requirement). Both of these numbers are A LOT less than the Canadian average. I’ll use the 31.13 number because it is the highest possible use we would need in an extremely cold year without using any wood heat. That is 77.3% less than the average house in Canada! Pretty awesome! And yet, it is twice as high as the Passivhaus standard!!
I’ll remind you that we are using the following: R100 ceiling, R56 above grade walls, R32 below grade walls and R32 under slab insulation. We are also having significant south glazing and minimal north glazing. We will be installing the highest efficient fiberglass windows and we expect the airtightness of the house to meet the Passivhaus standard of 0.60 air changes per hour at 50 pascals. So, WTF?
The bottom line here is that Saskatchewan is a lot friggin’ colder than Germany. The number of heating degree days in Germany in 2014 was 3100. The number of heating degree days in Saskatoon in 2014 was 6035. Well, that’s about twice as much, which would account for our need for twice the heating load – makes sense! Therefore, I have a hard time understanding how the standards of German Passivhaus can be applied to a very cold Canadian climate.
If we look at the overall Total Energy Consumption (84.04) however we are actually significantly lower than the Passivhaus standard of 120. This begs the question of, in Germany, what is accounting for the 105 kWh/m.sq/yr difference of energy if not for heating? Is their appliance and hot water use that much higher? Or is this particular standard higher to account for the larger homes and buildings that are typically built with Passivhaus? (This brings up another criticism of Passivhaus penalizing smaller homes. Check out this article for an exhaustive list of criticisms of Passivahus in North America. Passivhaus US and Canada have recognized the limitations of the European standards and are taking steps to try to modify these to be appropriate in North America. However at this time, the standards are still up for debate).
Anyways, what do these numbers really mean, except to compare apples (Germany) to oranges (Saskatchewan)? We weren’t going to be pursing Passivhaus certification anyways (at an approximate $10,000 price tag for certification, I’d rather put that money into solar panels). But I think it provides an interesting discussion. In the end we will be building a highly efficient, super-insulated house that will consume about 75-80% less energy than the average Canadian house. We truly won’t know our overall energy consumption until we actually live in the house so all of these numbers are a bit arbitrary.
Yes, you can build a “true” Passivhaus on the prairies, but you’d be looking at making huge financial investments and sacrificing comfort to meet the standards.
I’m reminded of a discussion I had with a local energy efficient home builder recently. He said: “Anyone can build an extremely energy efficient house with enough money. But to build one on a budget, now that is something impressive.”
In the end, we are building on a budget, which should come in at or below the cost of building your average stick framed house and our energy bills (100% electric) should be in the range of $100/month. I think I can live with that.

Planning and designing the house

Well, I’m about done with planning and designing. About 3-4 months ago we thought we were close to being done designing the house. Like really really close. However even though it was “close” to being done. It was not feeling right. There was something off about it and we weren’t really sure why or what it was. It was tough to admit that as we had already spent a considerable amount of time and money getting the house to the point that it was in mid-October. We’d done eight designs by that point, which is quite a few to not have it complete or at least feeling good about it. The pressure was also mounting as we were getting close to our first time frame – to have construction drawings started by December. But the fact was we were not feeling good about it and we were a bit discouraged.

In the back of my mind was also the price tag of this place. It was creeping up and up. There were some costs that we had not accounted for when we first put together the budget, such as, septic system ($18,000), well-hook up ($8000), water treatment system ($10,000), kitchen appliances (not sure how that was forgotten – $10,000-$14,000). Also, the footprint of the slab foundation on pilings was also increasing. We really wanted to keep it to less than 2000 sq.ft. But that was just not happening and the rooms that we didn’t care about as much but needed (mechanical room, storage) were really taking up a large chunk of the space – taking away from the spaces we really wanted to be a certain size (living room, kitchen, bedrooms).

My mother is an interior designer and we had been a bit reluctant to ask her to give us feedback on it… Well, Darcie had been a bit reluctant. Understandably, who wants their mother-in-law to design their house? However we thought we better ask her what she thought and what changes she might suggest.

“Be honest.” We told her. Now, the one thing you have to know about my mother is that she is one of the kindest and most caring people in the world. Everyone who has met her agrees (not just me). After awhile of looking at it she said, “I’m sorry to say this, but this is just… bad.”

Ouch. Our hearts sank. We’d spent so much effort on this and, well, it sucked, I guess. Though this was followed shortly by an overwhelming sense of relief. We knew it was not good, but we were too close to it to see the truth.

Over the next few days we spent pretty much every moment that we weren’t either at work or sleeping (there was not much sleeping though) brainstorming, thinking, and redesigning the space. There were some very important things we needed to figure out: 1. How could we make this space smaller? 2. How could we save money? 3. How could we make it more functional? 4. Still keep the views of our land and the river valley focused? 5. And still maximize the Passive House efficiencies and principles of the home?

There were no easy tasks here.

We needed to start to question the things we thought we wanted (an office, 3rd bedroom, vaulted ceiling, several large windows to the east, kitchen separate from the living spaces) and those that we had adamantly refused to consider beforehand (basement, open kitchen).

Initially we had not wanted a basement. Basements are very popular in this part of Canada. It is highly unusual for a house not to be built without one. In a lot of other places, basements are not common due to high water table or rocky land. But that’s not the case here. Still basement can be a problem due to the lack of light compared to spaces above ground and you still have to be careful to grade and landscape properly to make sure that water doesn’t want to find it’s way inside. But really why were we so against it? These problems could be rectified. A basement is more expensive then a slab or a crawl space of the same size, but if we reduced the main floor size and put those things that didn’t need to be upstairs in the basement, we could thereby reduce the overall footprint making the extra cost of a basement justifiable. We started crunching some numbers. The slab with piles and grade beam was going to be ~$37,000 for 2000 sq.ft. I figured if we could reduce the main floor size by 200 sq.ft. at the anticipated cost of $250/sq.ft. then this would balance out the extra cost of doing an ICF (insulated concrete form) basement.

Ok, but how do you make a basement nice, comfortable, bright, and inviting?

Everyone suggested a walk-out basement. I don’t know why, but “walk-out” makes me cringe. I think it’s all of the fancy snobby acreages and suburban houses that have a “walk-out”. Everyone is all like “Oooo a walk-out.” It seems like it’s a pretentious thing that people with a lot of money do. Maybe that’s an unfounded statement (probably) but something about it just felt too… pedestrian. Too upper class. Too suburban. It reminded me of a perfectly manicured lawn, or maybe even an astroturf lawn, on a 1 acre “acreage” and a 7000 sq.ft. house for two people and their chihuahua. Gah.

I had to prove it to myself that a walk-out would be OK. We went on a house tour to some middle aged hippy folks’ acreage across the river from us. They had built an Eco-house about 20 years ago and on their land, with a natural hill, they tucked the house neatly into it. You still entered the house on level ground but then it opened to the south from the other side. The rooms in the basement were bright and airy and there was a nice little courtyard out the basement door. Hmm. Maybe… Maybe we could do this.

Trimming off a mere 200 sq.ft. from the main floor turned out to be super easy – one bedroom and the laundry room. Done. But why stop there? The smaller we made the footprint the more money we would save.

Weirdly enough as we made the main floor smaller it seemed to make the rooms and spaces more functional. Suddenly a lot of our issues with flow and function on the larger basement-less bungalow were being solved by simplifying and making the house tinier.

Finally we got it down to I think as small as we could at 1240 sq.ft. of interior space (including the 16″ thick walls the total was 1440 sq.ft.). Interestingly though that gives 2480 sq.ft. of conditioned floor space with the basement and main floor combined. So, making the house “smaller” and therefore cheaper, actually made it larger overall. That seemed like the best of both worlds! It kind of felt like cheating.

Making the main floor the size we did also allows us the option to leave the basement unfinished. I know that’s pretty lame, but it allows us flexibility now that we didn’t have before with the one level house (which would have all needed to be finished). This way if the budget gets overran in other areas then we can wait to finish the basement until later. The main floor has everything that Darcie and I need. The basement allows room to grow when required.

The sense of relief that came over us was immense. Although it set us back in the process by a month I’m so glad we took the time to analyze this more and really figure out what our needs were and where we want to spend our money.

Now we needed to figure out if this crazy walk-out basement idea was going to work or not (yes, more money is needed. Sigh).

Heating a super-insulated airtight house in a cold Northern climate

The biggest question mark for us up to this point was, “How the heck are we going to heat this place?”

First there are a couple of caveats:

  1. We had no natural gas to our site. This is probably a moot point anyway because even if we did have ‘natural’ gas we would not have used it. We did have a neighbour ask us if we would consider bringing it in. But this just seemed ridiculous to me. For a cost of $20,000 you can pipe in a non-renewable resource, then pay monthly fees for it for as long as it is available. And given the rising energy prices this cost is only going to go up and up.
  2. We do have power to our site, but we intend to be Net Zero or Net Positive if possible. The power delivered to our site comes from the Queen Elizabeth power station, which is a natural gas burning. This is a big reason why people in places where you “must” choose from grid-tied power (which is often still coal-based) or ‘natural’ gas will often select the apparent lesser of two evils and choose natural gas for heating/cooling and appliances. Still, there is a third option that people seem to forget – SOLAR POWER! For less than or equal to the cost of bringing natural gas to our site, we can put up solar panels and generate not only our own electricity for heating, but also our own power for running everything else in the house.
  3. We are putting in a wood burning stove as a back-up heat source. Now, I know Passivhaus purists think that this is a bad idea and Wolfgang Fiest, the Passivhaus guru in Germany, has outright said that there are no wood burning stoves that meet Passivhaus standard, but we don’t care. I know of nothing more comfortable than sitting next to a crackling fire. Also, wood is considered to be a renewable resource, cut down a tree for firewood and plant a tree in its place.

Ok, so now that we have the prerequisite information out of the way, there were still huge decisions to make. Over the past few months I’d read innumerable articles on heating options for northern climates and in particular, super-insulated houses, as well as received everyone else’s biases on the optimal heat source. I soon realized that there are dozens of different options and all of them have their own pros and cons.

Most Passive houses that I read about used a “Mini-split heat source”, the majority of which were made by a company called, “Fujitsu” out of South Korea. These are pretty cool little devices. The popular choice with most houses I read are the ductless mini-split. In a Passivhaus, the heat load is so low (usually between 10,000 to 15,000 BTUh – as an aside most standard furnaces are 60,000+ BTUh) that usually two of these little systems are sufficient for heating a 2000 sq.ft house with ease. As the name implies, they do not use any ductwork, and essentially function like a space heater mounted on the wall. There is a pipe with refrigerant that passes through the exterior wall to an outdoor unit that draws air in, preheats it and delivers it to the indoor unit for distribution. In the moderate climates of Asia, Europe and the US these are great. A major appeal for these is that in the summer they act in reverse providing air conditioning. However, in a northern climate, such as Saskatchewan, though these are likely not the best option. Previously these units would be able to preheat air as low as -5°Celsius (23°F). Fujitsu has recently come out with a new model for “Extreme Low Temp Heating”, which will heat up to -25°Celsius (-15°F) outdoor temperatures. Unfortunately, this is still not sufficient for our cold Canadian prairie winters. Last year we had a record number of cold days for the winter: 58 days of -30°Celsius (-22°F) or colder. A couple years ago for the entire month of December it did not get above -25°Celsius (-13°F) for a high! There will be a few days, every year, when it is -50°Celsius (-58°F) in the morning. That is insanely cold. If you have never experienced cold like that, it is really something to behold. Fujitsu would have to come out with a “Super-Duper Ridiculously Extreme Low Temp Heating” mini-split to cope with that I’m afraid.

If we were to use the mini-split system then we would need to have back-up heat sources in each of the rooms of the house such as radiant wall panels or baseboard heaters to manage the cold whenever it dropped below -25°Celsius (-13°F). Although these radiant heaters are relatively cheap at less than $100 each, I must admit that I think they are kind of ugly. Well, uper ugly. Even the fancy ‘modern’ ones are ugly. I KNOW, that shouldn’t be one of my criteria, but it is, I’m extremely particular and I think they’re ugly and cheap looking. And I think the mini-splits are ugly too! Gah, the truth comes out.

You see, we like minimalism, our house was going to be simply designed, no casing around doors and windows, no crown moulding, no baseboards. Adding BASEBOARD HEATERS just seemed like a mortal sin to our minimalist aesthetic.

Ok, breathe…

Another option that was brought forward was to use an electric reheat coil. Basically how this worked was like a typical forced air ducted system, but a little bit different. A no-brainer must-have for an airtight house is a ventilation system. If you don’t put one of these in then you are going to have serious problems from moisture build-up, mold and air quality. We had already decided that we would use a Vanee HRV (this was developed by Dirk Vanee through the University of Saskatchewan who is credited with developing the first widely available and mass produced HRV systems) in our place, which as with all other ERV/HRV systems, uses ductwork to each room or area of the house to deliver fresh air and draw out stale air. How the reheat coil works is by being mounted in the mechanical room at the outlet to the fresh air thereby preheating the air before it is distributed to the house. The cool thing about this is that you can use the ductwork already present for the HRV system, but only because it is a super-insulated house, in a conventionally built house you would need separate ductwork. For this reason, this leads to the claim by some that in Passive Houses “conventional heating systems are rendered unnecessary throughout even the coldest of winters” (a fairly misleading statement) as it uses the pre-existing ventilation system.

There are a few downsides with this system however, the longer the ductwork, the greater the heat loss prior to reaching its end point. We are a building a long narrow house and have one length of wall that is 48 feet. Secondly, this is basically a forced air system. A HRV flow rate is a lot less than a true forced air system, but essentially you are just heating the air, not surfaces as is the case with “radiant” heat. Thirdly, this system cannot be well-controlled, it is one system for the whole house. So in our living/dining room and master bedroom that get more solar gain, they would also get the same air heating, which could lead to overheating concerns. Fourthly, we would likely still need to supplement the system… and we’re not going to talk about that again.

A lot of conventional builders, and I’ll say “lay-people”, suggested in-floor heat. Actually they said if we didn’t use in-floor heat then we were idiots (OK, they didn’t quite call us that, but I felt their judgment). In-floor radiant heat is certainly appealing for a lot of reasons. We planned to install a 1.5” concrete slab topper on the main floor of the house for passive heating purposes as well as the required 4” slab for the basement. And we also really like the aesthetic of nicely finished concrete floors (remember we are modern minimalists). But there was one problem: concrete floors are cold. When we told people that we might not use in-floor heat in the concrete, this is when their judging eyes showed themselves.

Second, in-floor heat is indeed very comfortable. We have several friends who have in-floor hydronic heat and walking into their house and feeling the warmth in the winter is very pleasing.

Third, you don’t actually see the heat system. It is imbedded in the floors. No wall panels, no horrendous baseboard heaters.

Fourth, it can be zoned and controlled. Each room or area can have a thermostat installed individually with piping running specifically to each room with a sensor in the floor that allows for it to be controlled. This was a big bonus, because rooms like the master bedroom and living/dining room do not need as much floor heat because the thermal mass and solar gain will heat these areas passively, whereas the north rooms and hallways do not have solar gain and so would need to have a higher floor temperature.

Ok, so you can begin to see where my bias was leaning. That is until I started to read about radiant floor heating in super-insulated and well-built houses:

“Radiant Floor Heating: Why radiant-floor heating systems don’t make sense for new, energy-efficient houses”

“All About Radiant Floors”

“Heating a Tight, Well-insulated House”

Damn. The basic argument was that radiant in-floor is nice and makes sense, in crappy houses. I don’t want a crappy house! Also the general agreement was that these systems were overkill. Passivhaus is called “passive” for a reason – reduce the use of non-passive, mechanical systems. The heat load, as mentioned of 10,000-15,000 BTUh, does not require a big system like a boiler, pump, and in-floor piping. In fact, when we talked to a couple friends who had built well-insulated houses with passive solar orientation they told us that overheating in the winter did happen and they would have to open their windows in the dead of winter. This seemed crazy!

Another concern was how we would deliver this heated water through the floor. Most systems use solar thermal panels that have water pumped to the roof to be heated through copper piping, then brought down to a storage tank and boiler that heats the water to upwards of 100°Celsius. This is then pumped through the floor in a closed loop system. As we found out from our recent well water testing, we unfortunately needed to use either a whole house reverse osmosis (RO) system or have water brought in by truck and stored in a cistern. The ramifications of this being that RO water is highly corrosive to copper piping. Crap! So what were we to do?

I had no straight answer and everything that I read either did not seem appropriate for our climate’s peak loads (coldest times of the year) or was apparently overkill. Sleepless nights were the result.

However, as I talked to others in the Passivhaus field, they admitted some problems with the Passivhaus model for a northern climate with frigid temperatures like ours. Passivhaus was really designed for moderate climates in Germany and a lot of the articles I had read were discussing moderate climates in the US. Indeed radiant floor would be overkill for those climates, but they do not get down to extremely low temperatures like us.

It was decided the best means of make this difficult decision was to sit down as a team and discuss. We had a meeting with our team of four engineers, all trained in LEED building, one with Passivhaus certification and one with R2000 and extensive energy modelling experience, the mechanical contractor and my wife and I. We went through made a list of advantages of each system – which essentially is what I wrote above.

In-floor hydronic heating was the clear winner.

All of my questions of setting up this system and concerns of overheating were alleviated in this meeting. We would use our solar PV system to power a simple, small 2-element, 100% efficient electric boiler by Argo. (We did briefly play around with the idea of an air-source heat pump hot water heater from Germany for both in floor heat and domestic hot water, but due to the high capital cost and potential issues of no one knowing how to service it here, we canceled this. Although the thought still seems intriguing, in another few years this may have been the best solution. Check out this article for more information). On the domestic hot water side, we selected a fairly straight-forward, 47-gallon Bradford White high efficient electric hot water heater. We also planned to insulate this with its own extra insulated jacket. Really, in the end, it came down what is the simplest, most cost-effective solution to meet our needs.

As for overheating, the engineers would design the system so that areas hit with solar gain would not overlap with those of the in-floor system, while those not receiving solar gain could be controlled separately to deliver us the best of both worlds. On the extremely cold days, our little Norwegian wood burning stove would take the edge off.

Boom. Decision made. Now I could sleep again.

PS. This post was edited from its original version on Nov. 23/2015.