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 Boor 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.

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

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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 high then 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.

 

Turning a house into a home

House: (noun) def. 1. a building for human habitation.

Home: (noun) def. 1. the place where one lives permanently, especially as a member of a family or household. The family or social unit occupying a home. A place where something flourishes, is most typically found, or from which it originates.

We’d spent nearly all of the past year, a stress-filled 2015, planning, designing and constructing the house. I certainly have never had so much stress and anxiety in my life (in fact, if you combined all of the stress in my previous 32 years of life, I think this past year alone would have surpassed momentously). But now, over the past four weeks we have actually gotten to live in this place – and experience what exactly we’d been working toward. But during the initial couple of weeks of December, I continued to call it the house. As in, “we are at the house now,” instead of “we are home now.”

I realized that the house had been associated so much with work and stress and was not “a place where something flourishes” for me – yet. I suspected that this would gradually change once we moved our furniture in and started hanging things on the walls. But really, this still didn’t change my terminology. Forcing myself to call it “home” just seemed weird to me. Even though we were living in the house, it wasn’t home yet.

I suspected this would gradually change – at least I hoped it would. I’d heard that building a house is like child birth (being a dude, I doubt I will have the experience to draw on direct correlation here) but from what I’ve been told, a woman goes through some of the worst pain imaginable in labour and delivery but at the end has a baby that she loves dearly. And suddenly, by some evolutionary trick of the mind, she essentially forgets or does not care how painful the process was. Often she will go through this same pain again more than once, knowing full well that the pain to get there was so terrible – but the reward so great.

For me, in the initial three weeks of being in the house, although it is beautiful and exactly what we had been hoping for, I still wasn’t at the forgetting the pain part yet.

But as it was in the last week, just before our Christmas break, I said to my friend, “We will be at home tonight.” And just like that, without any intention or forethought about it, I stopped referring to it as the house and started to call it home.

On New Year’s Eve, my wife and I decided to reminisce and read back through the blog posts I’d made here in the past year (yes I know – we are crazy crazy party animals). And wouldn’t you know, it was amazing how many things we’d forgotten already! We kept saying “I can’t believe that happened!” or “Oh man, I forgot about that – that sucked!” or “how did we get through that?” Truthfully we did not read through all of the posts… I think we made it to September 2015, at which point my wife said she couldn’t handle reading anymore as it was giving her anxiety!

A friend of ours, who has also built a custom house, recently said to us, “I’m so glad you are at the living in and loving it stage.” Indeed we are.

I can now look around the house and instead of thinking of my to-do list, I just think, “this is my home.”

 

Alchemy of a Concrete countertop

As if we didn’t have enough concrete and thermal mass in the house already, we decided to install a white concrete countertop in the kitchen. We’d priced out quartz as an option as well – a machine-made product that has the benefits of durability, scratch-resistance, stain-resistance, heat-resistance, and being made from some recycled products. But the reality is, because of all of these benefits, it also is very expensive, shockingly so, in fact. We needed 14’x24″ for the long counter. I don’t know what I expected the price to be, but it certainly wasn’t the $8000 price tag they quoted. Ouch.

As an alternative, our kitchen cabinet maker, Ryan Unger with Rhine Artisans, suggested a concrete counter. He was building our butcher block counter for the island in rift sawn white oak and he’d also done a few concrete counters himself before as well. Perfect!

He’d never made a white concrete counter before but he was game to try it. It probably helped that he and I have been good friends for a number of years and he’s been willing to try a few “different” woodworking jobs for us on this project..

Although I’d had in my head that I wanted a crisp white counter for whatever, I was excited for the “handmade” benefits of the concrete counter. True, concrete can stain and scratch, but being hand-made, we’d get something completely unique and special.

On a balmy October Saturday the guys came out to build the concrete form and pour the counter. It took them nearly 6 hours alone to make the form, which they would pour in three sections, due to the size, weight, and need to form around the under-mount farmhouse sink. It had to be perfectly level, square and flush. They used white MDF for the form to make it as smooth as possible. For structural support, they used wire mesh, which they smartly spray painted white in the event that it would “shadow” through when poured.

For the concrete itself, they were able to source white portland cement, white aggregate and white sand for the mixture.

We covered the counter with a tarp and placed two heaters in there for the next 3 weeks. The temperature was dropping and these would need to be sitting in our shop for the next three weeks.

It was mid-November and above freezing still, which is bizarre for our area. It was terribly fortunate as had it been below freezing we would have had to haul the counters to the basement of the house for them to polish there. That would have sucked.

As it was they were able to polish the counters outside – only slightly as too much polishing would bring out the aggregate. We still wanted these to be as white as possible.

Once the sun went down though, it was freezing and what we had was what we were going to have. The three of us then needed to carry these in through the front door.

It was SHOCKING how insanely heavy each piece was. I don’t think I’ve ever tried to carry something so heavy before. We nearly died, but miraculously we were able to get them up the steps to the door and placed on the cabinets without any serious injury or damage.

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The counters were not a crisp white, which I had originally wanted, but instead are a creamy white, which actually looked amazing against the creamy white oak cabinets. Plus the organic, handmade, imperfections of the counter really added a nice feel to the whole space. Very wabi-sabi.

After another couple weeks, we sealed them with an acrylic sealer (we tried a food safe, water-based sealer but this did nothing, as we found when a single drop of red wine left our first stain – Grrr [vinegar and elbow grease made it less noticeable]). We then added a topcoat of beeswax to finish it.

But before we would seal this, I’d need to finish my tiling work on the backsplash.