Final Blower Door Test – .3 ACH @ 50 Pascals

Drew McDowell, the Passive House Rater, came in on Saturday and performed the fourth and final blower door test.  The prior tests were all done manually (I believe they’re called “single source” tests); meaning that the Rater watches fluctuating readings on the meter and uses his judgment and observation to determine an average flow rate. In this fourth test, Drew used that method as a starting point, and came up with a value of about .28 or .29 ACH.  However he then followed up with a computerized test where the PC took dozens of readings in ten-degree increments (i.e. at dozens at 10 Pascals, dozens at 20 Pascals, dozens at 30 Pascals, and so on up to 70 Pascals) and then averaged and charted the results, and used the collective information to refine the computer’s 50 Pascal readings.   Also, unlike the manual test, this computerized test was performed in both directions; first while blowing air out of the house (i.e. depressurization), and then while pulling air into the house (pressurization).

The result came in at .3 ACH @ 50 Pascals.  Copies of the reports are visible below:

Download (PDF, 477KB)

Download (PDF, 259KB)

This was up a bit from the prior test (.24 ACH), which was performed before the installation of insulation.  I’m not sure how that happened, being that it seems to me the insulation and drywall should have made the house tighter, if anything.  But regardless, I’m very happy with the result.

Two observations worth noting.

First, as discussed in a (much) earlier post, we used a trio of products by Prosoco to seal the gap between the windows and sills.  The final product in the trio, R-Guard Air Dam, is essentially a very robust caulk that is used to seal the gap after the installation of a foam backer rod.

The windows were installed about a year ago.  We’ve been in the house now for almost two months, and I’ve been chipping away at the interior work as time allows.  Recently, when I began working on interior trim, I noticed a small gap in the R-Guard around one window.  That prompted me to inspect all of the windows, which led to the discovery on similar gaps at three others.   I suspect that the gaps were due to human error at the time of installation; the thickness of the application in those areas appears to have been very thin and the product appears to have simply shrunk.  Fortunately, the gaps were easy to find and seal because I hadn’t yet trimmed out any of the windows.  But the discovery caused me to think that my slow pace paid off.  Had the interior been finished by a hired trim carpenter, or had it been finished immediately after the drywall was finished (which was last spring), those gaps would have never been discovered.  To be clear, none of the gaps were deal breakers.  But collectively, get enough small gaps and I imagine it’s possible to break the .6 ACH limit.

The second point worth noting is that, during the final blower door test Drew and I went around the house with the thermal camera and smoke pen looking for leaks.  The only weak points we found were the exterior doors (all ThermaTru), which I’ve talked about extensively in a prior post.  Again, obviously the leaks weren’t deal breakers.  But frankly I expected much better given the amount of money those doors cost.  If I had the chance to do it over, I’d be looking at Intus for the doors as well as the windows.

Third Blower Door Test – .24 ACH/Intus Performs

Today we had the third blower door test; the first since completion of the mechanicals (the two mini-spllit lines, the electrical, plumbing, and ERV.  I was a bit concerned because those items required almost 30 penetrations to the building envelope.

Most were for wiring.  I’m not using any recessed lights on the second floor, and I’m using sconces wherever possible (2nd floor hallway, master bedroom, and bathroom mirror lighting).  But each of the three bedrooms will have a ceiling fan, and the two bathrooms and two walk-in closets will each two ceiling fixtures.  That’s eleven holes through the 2nd floor (Zip) ceiling.  In addition, there are four exterior outlets (front and back were required by code, but I also put one on each side), and four carriage lights (two for the front door and one for each of the side doors).

We placed the main electrical panel on the (detached) garage.  But we still needed a conduit that runs to a sub-panel in the house basement.  I ran two additional conduits; one to provide for a switch in the house that controls the outside garage lights and a second that will allow me to put a generator panel in the basement while allowing the generator to be plugged in at the garage.

We had penetrations for the two mini-split lines (which I ran through a PVC conduit, the power lines to both mini-splits, and the 7″ intake and exhaust vents for the Zehnder HRV.

And finally, we had penetrations for two hose bibs and for to waste vent pipes (that join in the attic and exhaust through a single stack in the roof.

But I made considerable effort to ensure that every penetration was a) as small as possible and b) sealed properly.  In the end, it all seemed to pay off because the blower door resulted actually decreased to .24 ACH from the .38 ACH result of the 2nd test.


One note that I consider important: Given that I hadn’t made any adjustments to the Intus windows since the 2nd test, it now seems clear to me that they exhibited extraordinary performance.  In a previous post, I noted that there was some leakage through the windows during the 2nd blower door test.  But I’ve now concluded that, despite the fact that there was some leakage, the windows were responsible for a very small portion of the .21 ACH increase (it went from .17 ACH in the first test to .38 ACH in the second test).  I believe this because I made no adjustments to the windows after the second blower door test.  Therefore, the .14 decrease in the 3rd blower door test must be attributable to adjustments I made to the doors (I corrected the weather stripping on two of them) and the sealing of the electrical conduit (which fit tightly through the rim board, but had not been calked when we did the 2nd test.  Given all of this, at worst the windows could only be responsible for leakage of .07 ACH (.24-.17).  But that’s highly unlikely because some of that leakage must be attributable to the three doors, and some must be attributable to miscellaneous small leaks that are inevitable, and impossible to identify.  Considering the significant cumulative length of the window seals (only one two are fixed, the other 21 function) the amount of leakage that appears to have resulted (something less than .07) is, in my estimation, extraordinary.  Kudos to the folks at Intus!

So we’re now ready for insulation (which should occur this week) and drywall (which is scheduled for next week.  Hopefully, things will start moving more quickly..

Blower Door Test #2

A few weeks ago, we conducted the second blower door test.  Our number increased to .38 ACH @ 50 pascals. This was still comfortably under the .60 limit.  Interestingly, it appears that the bulk of the increased air leakage (over the 1st blower door test) resulted from the windows (actually, maybe that’s not so interesting, given that the only change since the first test was the installation of the doors, windows, and blocking for the pent and porch roofs).  While under negative pressure (we were pulling air out of the front door opening), some of the sashes exhibited leaks that could easily be felt and easily seen with a smoke pen.


I visited the guys at Intus in Washington DC the day after the test.  They were incredibly helpful, and explained how to (easily) adjust the windows for a potentially tighter fit where necessary.  Of course, they also cautioned that I double check the installation (plumb/level/square).  While I’m confident that the installer took great care with his work, I also know that few things in life are perfect.   They also pointed out that that the numbers are still incredibly positive.  And they added that, when getting down to the numbers we’re at, even high performance windows may have limits.

The next test will be performed after the mechanicals are installed.  If it becomes necessary, I will examine the installs and adjust the windows to see if it results in any performance increase.

Choices in Window Installation

The window installation has been one of the more difficult issues to deal with.  The first part of that issue was deciding which product/method to use to flash the windows and achieve the necessary level of air-tightness.

We tested three products/methods on the basement windows.  The first was Tremco’s ExoAir Duo Membrane.  This is basically a flashing tape that is applied to both the inside and outside of the window jamb gap.  Half adheres to the window, and half adheres to the jamb, thereby completing the seal.  Spray foam is applied in between the two (before the second side is applied.  This product seemed to be the least favorable.  First, it was difficult to get the tape to seal to both surfaces without undesirable waves.  But the bigger issue was that it seemed almost impossible to get the spray foam to fill the gap without pushing the tape outward.  It was obvious that this would make it difficult to properly trim out the window box; at least not without significant difficulty.  We estimated that it would have cost approximately $750 for enough of this product to do all 19 windows in the house.  Here’s the best and worst of what it looked like:

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The second product that we considered is also made by Tremco.  It’s called the Exo Air Trio, and seemed to be a much more effective product.  It basically consisted of a a compressed foam band with adhesive on one side.  It is applied to either the window or the jamb.  Once unrolled, it begins to expand, so you have to plan out the installation a bit.  But the expansion rate is rather slow, so it’s not a mad rush.  Once fully expanded, the foam completely seals all of the gaps between the window and the jamb.  It looked pretty effective, if not a bit amazing.  The biggest downside was the estimated $1800 price tag to do all of the windows.  Here’s what the installed product looked like:


The third option (the option that we went with) uses a three-part solution by Prosoco.  Unlike the other two products, the Prosoco solution seals the gap and flashes the window.  The first part of the process involves the application of Prosoco R-Guard Joint and Seam Filler, which is described as  “a fiber reinforced fill coat and seam treatment.”  It basically appears to be a pink, fibrous, rubber caulk.  It’s applied to all of the seams in the rough opening.  After that, the R-Guard Fast Flash was applied to the entire opening (and the exterior of the opening).  Like the Joint and Seam Filler, it’s applied with a caulk gun.  But then it’s smoothed out with a spatula to create a consistent rubber-like covering over the entire area.  Once dry, it really leaves one with the impression that the opening will be impervious to water and moisture:


Then the window is installed, and an appropriately sized backer rod is installed in the gap surrounding the window on the interior surface.  The final step is the application of the R-Guard Air Dam product to the face of the backer rod:

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All in all, it appears to be a pretty bullet proof system that interplays well with the Zip System sheathing, and should serve us well.  On top of it all, we estimate that it will cost us somewhere around $500 to cover the installation of all of the windows.


The First Blower Door Test

The first blower door test is now history.  Results came in at approximately .17 air changes per hour @ 50 Pascals, well below the Passive House requirement of .6 ach @ 50 Pascals.  Here are a couple of photos from the test:

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The reading (in cubic feet per minute) actually fluctuated between the high 40’s and high 60’s at roughly 50 Pascals (the photo above is showing 49.9 cubic feet per minute @ 51 Pascals).  Although the house contains approximately 29,000 cubic feet of interior space (when including the basement), the Passive House rating system uses an adjusted cubic feet computation, which reduces the total to approximately 23,600 cubic feet (only 60% of the basement is counted) and makes the target standard more difficult to attain.  Had we been able to use the entire 29,000 cubic feet in the computation, the test results would have been lower yet.

External Framing Completed

The basic frame and all Zip sheathing was completed on September 16th.

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In the two photos below, you’ll see how the Zip is being wrapped over the top of the second floor walls.  Once we prep for the future attic insulation (we need to install some type of baffle to retain the 18″ of cellulous),  Zip will be installed on the rest of the second floor ceiling and the seams will be taped.  As can be seen in the following photos, the finished side will face down.  It could have gone either way, but since the tape will be placed on the bottom, this seemed to make most sense.

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That’s 1/2″ Zip in the photos above.  The same thickness we used on the exterior walls (we used 5/8″ Zip on the roof).  Looking back, we could have saved a bit of weight and money by using 7/16″.  I was a bit concerned with the ability of the roof trusses to hold the weight of the drywall, zip, and 18″ of insulation.  But they’re engineered to support 10lbs/sqft, which provides a reasonable margin of safety, as the weight of the drywall, Zip, and insulation amounts to less than seven.

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The combination of perspective, background lighting, and lack of windows and porch make the house look mighty small.  Hard to believe that its over 2,000 square feet.


The rest of the Zip was taped a couple of days later.  The Zip tape dispenser/roller proved difficult to use effectively.  The roller seems to have a slight crown that makes it difficult to seal the edges and causes the roller to drift.  But the job was completed:

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The First Floor Decking and Backfill

On August 5th and 6th the framers came out and framed out the first floor decking.

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The sill plate went on over the sill gasket with two beads for caulk, and the rim boards, I-Joists and subfloor followed.

We used Weyerhauser 1 1/8″ TJ Rim Boards.  I don’t like them.  We’ve been experiencing a lot of rain, and some of them swelled to anywhere from an-inch-and-a-quarter to an inch-and-three-quarters.  Everyone tells me that it’s fine. But I’m still convinced that I want to use 1 3/4″ LVLs for the 2nd floor  rim boards.  They’re three times as expensive (about $1.50/lf vs. $4.50/lf).  But that only amounts to a few hundred dollars.  And since the porch roof will be cantilevered off of the 2nd floor rim boards with blocking (more on that later), I’ll feel a lot better about the connection.

It took a bit of effort, but I got the building inspector to OK the use of Weyerhauser Flack Jacket I-Joists (for the first floor).

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This allowed me to avoid having to drywall the basement ceiling to achieve the fire protection rating required by the 2009 International Residential Code (IRC).  In addition, it actually appears to be a money saver.  For instance, considering the 360 Series 11 7/8″ I-Joists, when we checked on pricing, we found that the Flack Jacket version runs about $3.40/lf, while the regular version runs about $2.53.  Figuring that we had about 500lf of I-Joist in the first floor, that amounted to an increased cost of approximately $565.  However using the Flack Jackets would preclude the need for drywalling the basement ceiling, which I am told would be about $42/sheet installed, or about $1,300.  So we figure that use of the I-Joists will result in a savings of approximately $700.

The inspector’s initial concern was that, while the evaluation report that I provided him said that Flack Jacket I-Joists were approved under the 2012 IRC, it said nothing about the 2009 code, which is still in force in Pennsylvania.  His thinking seemed counter-intuitive to me.  So I contacted one of the Tech Reps at Weyerhauser, who was extremely helpful, did the research, and provided me with the following explanation:

“I dug into this a little and it is an interesting issue. PA is enforcing the 2009 IRC code with a couple of legislative changes. The base 2009 code does not require fire protection of floors over basements. This is new requirement in 2012 IRC. The base 2009 IRC does include a controversial requirement for sprinkler systems in residential construction. The PA legislature decided to add the fire protection requirement- based on the 2012- while allowing the sprinkler requirement to be waived . So while it is true that our code report does not comply with the 2009 IRC, it is only because membrane protection was not required in the 2009 BASE code. I have attached the bill related to this issue. It begins on the bottom of page 10. Our code reports list only the base codes and do not include special state provisions or amendments. Flack jacket does provide the 2×10 equivalence as the provision intends. Ultimately it is up to the code official in each jurisdiction to determine what he will accept, but we are certainly willing to work with him and address any concerns.

Based on the above explanation, I provided the inspector with a letter of explanation together with the Pennsylvania legislation, and he gave his approval.

I should also note that, prior to giving his approval, the inspector suggested that I use a product called No-Burn.  It’s a spray-on coating that achieves the same purpose.  But it just seemed like more work, and more of a mess, than the Flack Jacket alternative.

When it came to the sub floor, I was particularly concerned with its ability to hold up in the rain (given that we’ve had a particularly wet summer and things were moving forward rather slowly).  I was also concerned with floor bounce, which we had experienced in our last home and just seemed to detract from a feeling of quality.  To combat the latter problem, I’m certain that I over-killed the issue by using the 360 Series 11 7/8″ I-joists for the longer (16′) spans (we used the 210 series for the shorter spans, and their specs showed that it would have been fine to use them throughout).  But to avoid any issue that might be caused by the rain, and to provide double insurance against bounce (particularly since the I-Joists are 24″ on center) I decided that I wanted to use Advantech flooring.  The floor is rock solid, and looks like it would support an elephant.  And since it was installed, we’ve had at least a half-dozen days of rain.  But it looks like it’s holding up well.

The Advantech sub floor (we used 1″) ran about $41 per sheet, while the 2nd choice, 7/8″ Weyerhauser EdgeGold, came in at about $34 per sheet.  At approximately 80 sheets,that resulted in an increased cost of approximately $560.

Once the decking was on, we had the precast Bilco well installed.  It’s a $3,200 unit (with primed steel doors), and bolts to the foundation in four spots (two high and two low).  In our case, we had it bolted right to the exterior foam, ensuring a complete thermal break.  The only issue encountered was a couple of pieces of rebar right where the fourth hole was to be drilled.  After several hours of struggling, they were able to cut through it and get the well installed. We then covered the seams with Resisto peel and stick, and wrapped the dimple board around the inside corners, and we were ready for back-filling.

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I still don’t quite understand how Bilco sizes these wells.  We ordered (and received) a size “E” well, which is supposed to be used for applications where the distance from the footer (i.e. the bottom of the well) to final grade is anywhere from 83″ to 91″.  But given that the outboard edge of the well casting is only about 5″ inches thick, that simply doesn’t seem possible; particularly when considering that the grade should fall away from the house.  Our final grade will be about 4″ above the dimple board (which is about 86″ from the footer). With a bit of creative landscaping, I’m sure we can make it all work out fine.             IMG_0073

It took three of us a day-and-a-half to backfill; using a jumping-jack tamper for every two-foot layer.  We didn’t bring it all the way up to final grade because the EFIS still has to be installed everywhere other than under the porch.


Then we sealed every seam, inside and out, with Sica Polyurethane Caulk.  I think it took somewhere around two dozen tubes at just under $6 each:

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