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June 13, 2018
At the recent CaGBC Greater Toronto Chapter Gala, I was pleased to accept the award for Innovation in a Residential project on behalf of Derek Seaman of Seaman and Sons Builders. Of course, it was extra special that it was a vacation home Derek built for my family and me. When Derek and I sat down exactly 3 years ago to hash out the particulars of the house, we came up with almost 30 different technologies or strategies that we wanted to try in the project and thus I think the "Innovation" title of the award was appropriate. Having now a couple of years in the house, I thought you might be interested in hearing "the good the bad and the ugly" of how it turned out, or perhaps better stated, the "great, the annoying and the funny" of the adventure.
I need to start by saying it was a great build experience. The last time we had a house built was 25 years ago and that went well enough, but Derek and his great crew exemplified the best of what we all know homebuilding can be. The craftmanship that you would expect from a third generation builder combined with the professionalism of proper budgeting and scheduling, topped off with application of the best of what a true understanding of building science can bring to modern housing.
You will undoubtedly want to know about the insulation levels. It's a modest 1.5 storey home, 1450 sq.ft. on the main floor, but 26,000 board feet of pink extruded foam sheathing surrounds the house to effectively create a beer cooler. Six inches under the slab on grade. Yes, slab on grade that I love, perfect for sandy soils with a high water table near the lake. That 6" lines up with 3" of foam set into the foundation stem wall that provides a thermal break at the slab edge and brick ledge. What seemed like a great idea, that is used regularly in barn construction, but turned out to be an annoyance for the guys tying-in the extensive rebar structure outlined by the engineer who had to stamp it for a skeptical residential building department. That 3" in the foundation wall lined up with the 3" of exterior foam sheathing on the 2 x 6 walls. The framers were quick to point out that you can't get button cap nails at that length in a nail gun so they had to hand nail the insulated sheathing and that was annoying. No surprise that the Net-Zero homes that most builders now use includes 2" insulated sheathing. The 3" of wall foam lined up with 4" of XPS on the roof deck. A 2 x 8 rafter to form the cathedral ceiling, then the 4" of foam, then 2" strapping for a vented roof assembly. This roof assembly shows up in Joe Lstiburek's building science guide as ideal for high snow load areas. When I told Joe how annoying it was for the guys to build it, given the 8" long screws needed for the strapping, Joe said he drew it, never expecting anyone to actually build it. That was kind of funny, but it does make for a very forgiving roof assembly and an extra 550 sq.ft. of living space under that simple gable end cathedral. I find it funny that when the sun shines on the south facing room the foam expands and you get this subtle popping noise in the upstairs room. Then you get a slightly different noise when the sun goes down that sounds like a squirrel running on the roof. Make a note to include spacing and a slip plane to allow for the expansion or use a lower expansion sheet foam such as polyiso foam. Finally all the cavities (walls and ceilings) are filled with high density spray foam, just because I wanted the highest possible R-value. The walls end up with an Effective R value of 36 (partly due to advanced framing), the ceiling has an Effective R value of 59.
The fun part for Derek and I was to make the house as tight as possible, tighter than Ron Seaman's house, Derek's dad, whose house I tested 28 years ago at 0.35 ACH@50 Pa. We made it down to 0.19 for great bragging rights. The tightness was achieved partly by detailing the Tyvek as an air barrier, that got it down to 1.1 ACH, then the XPS was taped and gasketed as per the OC's codeboard air barrier details. That got us to about 0.7 ACH and the foam and drywall got us that final air tightness. Consider the insulation, the triple glazed windows, the incredible air tightness combined with the vanEE Gold Series with HEPA filtered fresh air directly to each bedroom. As a result the house is so quiet, the bedroom air so fresh and clean all our guests sleep in like never before. It is actually fun to see the difference that makes. Not to mention that I can leave the house for weeks in the winter without any heat on with no danger of freeze ups.
Here are a few other interesting lessons learned:
Although we all know energy savings aren't all that important to us or our customers when it comes to making house decisions, I can tell you that with 2 full years of data, the house has generated 10% more energy than I have used (yes it is a vacation home that we use sporadically in winter) so it is comforting to know that when we aren't there the utility is sending us checks.
Overall a wonderful build experience and I would be pleased to discuss it further with anyone interested.
Written by Gord Cooke.
This article originally appeared Winter 2017 edition of Better Builder (Issue 24).