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.


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


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.



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!).


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


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).



Expensive fancy tape.

The septic hits the fan

Oh boy, the excitement and speediness of the week prior came to a screeching halt when our project manager called notifying me that the septic contractor had not realized the depth of our basement. He would have to recalculate the cost of our septic system and get back to us. But he estimated the cost of this “mistake” (basement being OVERDUG) would be $12,000!!

I felt immediately sick to my stomach. The next three nights were completely sleepless. Over those days (and nights) I read more and learned more about septic tanks then anyone ever should. As the septic contractor told me, the maximum depth of a septic tank is 9′ (meaning 9′ of soil coverage). Our basement was 11′ and then with the clear out drain from the house this would put it at 12′. Three feet deeper then the maximum depth. This meant that he would have to get a “deep burial tank” specially fabricated to twice the thickness of the standard fiberglass walls. It would have to be structurally reinforced to withstand the pressure and he really couldn’t guarantee that we wouldn’t have problems with it.

All of this just sounded terrible to me.

But beyond this I was pissed off that this was NOW being discussed. Why did we not know this before? Why did no one discuss the depth of the basement of a potential issue? Unfortunately (for us) it was a total breakdown of communication. We had in fact had a meeting, reviewing a previous drawing of the house with the septic contractor. The depth of the basement was in there. But there was no discussion of maximum depths of septic tanks and no mention that the depth of our basement was an issue at all.

Nonetheless, we had to figure this out. I got on the phone with the owner of EcoSmart (and it’s parent company, Integrated Designs), Murray, and explained the issue to him. He is a stickler for lean construction including target cost design, planning and communication (in fact, he gives lectures around the country on avoiding these types of problems), and he was shocked by the issue, but assured me he would help to figure this out. There has to be a solution, he told me.

So over the May long weekend, myself, Murray, Taylor (the builder), and the house designer, spent hours trying to figure out alternates to this septic problem. Possibilities ranged from reasonable to crazy:

– Fill in the hole with three feet of dirt and move the foundation over – redoing all of the piles and structural slab (No, this would be more costly then the deep burial tank).

– Replace toilets with composting toilets (No, this did not solve the problem of the basement clear out drain for laundry, showers, sinks in basement)

– Build the structural slab up by 36″ (Possible, but costly and would need to take back to the Structural engineer to have this approved and redesigned)

– Use an effluent pump (Literally pushes shit up hill. Unfortunately this is against building code)

– Move the tank

The latter option was discussed immediately with the septic contractor, but he adamantly refused that this would be possible as the drain still had to pass under the 11′ basement. However, we had had a topographical study down several months ago which detailed the build site area and natural slopes of the land (which were impossible to see because of the mountain of dirt piled all around the house). However with the topographical study we could see that in fact there was at least two possibilities of alternate positions. The best option being to the east of the house.


As you can see in the picture above, a little old outhouse (about 70′ from the house) sits 10’6″ lower, which is nearly the same depth of the basement. We were going to grade and excavate from the east side of the basement anyways for the basement windows, so if we graded out a bit more then certainly we could make up the 36″ and then some.

However we needed the septic contractor to agree to this and then would need approval from the health region inspector.

So on holiday Monday morning, we met at 7:30am at our site with the septic contractor, house builder, building company owner, and Darcie and I. After about two hours of walking the site, talking, debating, and going over the drawings, the septic contractor finally agreed that we could probably make it work.


“However,” he said, “We are going to have to do something about this dirt. This is just too much to work with. We’ll have to move it a couple times to get in here.”

“Oh God, how much is that going to cost?” Is all I could think…

3D sneak peek

Our house designer, Crystal Bueckert at BLDG Studio, uses a program called “BimX” to transfer her CAD drawings from 2D format to an awesome 3D virtual reality extravaganza! Some people are naturals at being able to read a blueprint and imagine the space. I can get a sense of that, but having it in 3D and being able to do a virtual walk-through is a totally different experience.

Here are a few screen shots of the 3D walk-through on the final construction drawings:

This is the “front entrance”. I always call this as the backdoor (my wife calls it the front door) as it is on the north side of the house. There are only three windows on the north. One narrow window beside the “back” door so we can see who is there. One at the end of the hallway for ventilation. And one in the bedroom for fire safety and ventilation.


This is the west side of the house (opposite of the river side). The side door leads to the chicken coop and yurt. Yes, that is an outdoor shower beside the door (one of my favourite features).


This is the southwest corner of the house. The deck is 20’x30′ and faces south.


The “Great Room”. This room faces south with the large (almost 6 foot tall windows) bringing in a lot of light and  passive solar gain in the winter months. The overhangs of the roof completely block the unwanted heat when the sun is higher in the sky in the summer (this BimX program allows you to put in your GPS coordinates and perform solar studies to track the light coming into the house at different times of the year – so cool). The ceiling will be finished with whitewashed tongue and groove clear pine. The floors will be either a polished concrete or troweled and sealed (still deciding how much work we want to do on that). The window sills, door trim and miscellaneous wood finishing will be in whitewashed Douglas fir. The windows sills are about 14″ deep, and about 16″ from the floor, meaning there are natural window seats throughout the house. We are not having any baseboards and instead will have a “gallery” finish in which the drywall slightly floats off the bottom of the floor.


The kitchen seems pretty stark in this photo, but you can get the idea (our kitchen cabinet maker is doing his own 3D rendering that will be a bit more true to the final product). The tall cabinets and entire island (including butcher block countertop) will be wrapped in white oak and finished in a whitewash lye with clear coat overtop. The upper pantry cabinets will actually go the full height of the 9′ ceilings and we won’t have open shelves, but instead will have upper cabinets as well. The lower cabinets will be a white slab with a white concrete countertop. We found a pretty awesome fireclay farmhouse apron sink to sit under the east window overlooking the river. I do the dishes and do not want to be staring at a wall while doing them. The east wall will be tiled from counter to ceiling in either a white subway tile or white square tile (yet to be decided).


The master bedroom faces south and overlooks the river. Yes, eye masks will be a necessity.


It was tough to get a decent shot of the master bathroom, but this room is going to be pretty awesome I think. It will have a large shower, double sink vanity, water closet for the toilet and a vintage clawfoot tub. Darcie is currently refinishing one that we found on kijiji for $75 last year. It is turning out really well and I will post some photos of it later. The bathroom will have a tiled wainscotting that I cannot wait to install.


It’s time to make this place a reality. Construction starts now.