An Alternative to Purchasing Blinds for Tilt-Turn Windows

The tilt-turn Intus windows that we installed in our house are excellent products.  They’re robust, airtight, and extremely efficient.  Nearly everyone who visits offers positive comments on them. However, from our perspective here in the U.S., they do have two drawbacks.

The first is that they open to the inside of the house, rather than to the outside, which could cause unanticipated problems.  For instance, a tilt-turn window over the kitchen sink our counter could be problematic.  It could be blocked (from opening) by the faucet, or it could interfere with a person who is standing at the sink and trying to access to the upper cabinets that are to the left or right of the sink.  Tilt-turn windows in other rooms could also be troubling if the homeowner doesn’t consider furniture placement and natural walkways.

Fortunately, this issue hasn’t been a problem for us.  Over the kitchen sink, we almost always use the “tilt” or venting option rather than opening the windows.  But I did take great care when installing the kitchen cabinet to ensure that the faucet does not interfere with the windows if we choose to open them.

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But the other issue…one that I didn’t give as much thought to…is providing privacy shades, particularly at night.  Tilt-turn windows require unique blinds. The blinds must be attached at both the top and bottom to keep them from swaying away from the window at the bottom when the window is tilted.  In addition, the blinds must be attached to the window, rather than the wall or trim surrounding the window.  Otherwise, it would be impossible to use the “turn” function to open the window or the tilt function to vent the window, when the blinds are “down.”

To my knowledge, only one U.S. company currently makes blinds for tilt-turn windows; RS-Sylco.  So the blinds can be purchased.  But there are two problems.  First, the blinds are far from cheap; typically in the area of $300-$500 per window.  That problem can be easily solved by those with enough money.  But then there’s still the second problem.

The tilt-turn blinds attach to the windows in two ways.  Either they can be attached directly to the glass with a special double-backed tape, or they can be attached to the frame that surrounds the glass by drilling holes and using screws.

I don’t like the idea of drilling holes into the window frame, so that option was out.  But I thought that the second option would do, particularly given that I only needed blinds on two windows (the second floor bathrooms).  But the problem is that our windows have a (simulated) divided light option, with the “mullions” adhered to the face of the glass. These mullions stick out about a quarter-inch, making it impossible to adhere the blinds to the glass.

Fortunately, after giving it a bit of thought, I was able to come up with an economical solution.  What I did was make a narrow frame out of poplar.  The frame is large enough to cover two-thirds of the window and is 1″ wide by 5/8″ thick (so as not to interfere with the window lever).  I gave the frame a beveled profile with a router to lighten it up a bit, mitered the corners, and assembled it with glue and small biscuits.  I then purchased a roll of shoji paper to use as the shading material, which I cut to size and stapled to the back of the frame.  There’s a lot of different shoji material out there.  I purchased mine from esojhi.   It has a durable laminated coating and can be wiped clean with a damp cloth without damage.

The shoji frames are incredibly light.  So I was able to attach them to the window frames using four one-inch squares of velcro fasteners, one in each corner.  The frames fill the need perfectly.  They move with the window, don’t permanently affect the glass or frame, and can be removed or replaced in seconds.

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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..

Window Extension Jambs

Because of the four inches of exterior foam board and full one-inch-thick strapping to hold it on and provide a nailer for the siding, we needed to create extension jambs for the windows and doors.  As with most tasks, there are a number of ways in which that task could have been handled, and the solution is partially dependent upon the location of the window within the exterior wall.

In our case, the architect decided that the windows should be installed within the 2×6 framing (i.e. flush with the Zip sheathing), rather than even with the exterior plane of the wall/siding structure.  The architect did this to achieve better thermal performance, and also to provide a more appealing exterior by providing depth and shadow lines.

Given that position, we had to come up with a method for extending the window (and door) jambs five inches to place the exterior jamb surface to a place where it could be properly trimmed out; trimming the jambs out that far, would put them in the same plane as the surface of the 1×4 strapping.

Rather than building plywood extension jambs that extend into the rough opening and attach to the wide surface of the 2x6s that form the opening, we decided to use Azek, and build the boxes so they would attach to the outside of the building structure, with screws driven through the sheathing and into the 2x6s that form the rough window opening.

The jamb extension boxes are glued and tacked together.  We cut a 3/8″ wide by 7/16″ deep rabbet into the inside rear edge of the sides and top of the boxes.

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This allows the Intus windows (which don’t use a flange) to be installed 1/2″ proud of the wall sheathing and fit into the extension jamb and over the sill.  We also put a 5 degree pitch on the box sill, and made the sill a half inch wider than the sides and top to allow water to drain over the trim sill.

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Attachment flanges (1 x 1 3/4″ Azek strips) are tacked and glued to the sides of the boxes to allow the boxes to be screwed through the sheathing and into the studs.  On the smaller windows, we only put these flanges on the sides of the boxes (as shown above).  On the larger windows, we also put them on the top and bottom for added support.

Here are a couple of photos of the boxes installed (no nailers or trim yet):



Once the box is attached to the house and the 4″ of foam board is applied to the exterior of the walls, we glued and pocket screwed 1×8 Azek “nailers” to the sides and top of the boxes to serve as an attachment point for both the trim hoop and the siding. A 1 x 3 “nailer” is attached to the bottom.

Here’s what the nailers look like when attached:

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And here’s what they look like on the house:

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Once the nailers are attached, we’re ready to attach the trim.  The trim, which will be in the “Arts and Crafts” style, will look like this:

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The sides are 5/4 x 4 1/2.  The top is 6/4 x 5 1/2, and the sill is 1 1/2 x 2 1/2, with a 15 degree pitch. The inside dimension of the sill is 1/8″ wider than the sill on the box.  When installed, the trim sill is pushed up against the bottom of the sill on the box.  The trim hoop is sized to result in a 3/8″ reveal all the way around.

All in all, it’s an extremely sturdy structure, and they’re very quick to build (much quicker than this explanation conveys).  However, care must be taken to ensure that they’re installed square (as we built them, there is about a quarter inch of play each way that can result in an out-if-square installation if you don’t pay attention).  Also, the Azek is flexible enough that variations in the sheathing (e.g. where the wall bows slightly) can result in a bowed front edge on the box.  If the bow is in the sides or the top, the 1 x 8 nailers will take it out when they’re attached.  But if the bow occurs in the sill, the 1 x 3 nailer may not provide enough rigidity to remove it.  The easier solution might be to shim between the attachment flange and the sheathing if necessary.