deep wall system – Blue Heron EcoHaus

Ok, none of it is really romantic, but drywall has got to be the most unappealing stage in building. Despite what everyone says about it making a space “look bigger”, I didn’t get that impression at all. I just thought: this is gross.

I had been taking a tonne of pictures up until this stage, but truthfully, I didn’t want to remember this drywall stage (I think I took 3 photos total). I was glad when it was finally over, but it ended up that the contractor took 4 weeks longer than anticipated and ended up setting us back a full month in construction.

In the end, they did a “good job” from a boarding/mudding/taping point of view. Our house was actually pretty complex, as we realized, for the drywallers. A few things I will share.

First of all, we did not want any baseboards, crown mouldings, or trim around the windows. Why!? Why would you do this?? You may ask. And I will tell you: we like the look of the clean lines of the materials sharply bumping up against the next – drywall to concrete, drywall to pine ceiling, black window framess to walls. If you want to get philosophical (who doesn’t?), this transition for us of moving, building, giving up our city life, has been an experience of pulling back the layers of ourselves and exposing who we really are. And the non-philosphical reason: I just think it looks cool.

Now, this added a couple of significant dimensions of challenge to the drywallers, how do you finish the drywall where it meets the concrete floor (main floor and basement), where it meets the concrete walls of the basement, and where it meets the window/door frames (a whole challenge in itself)?

After much debate, we elected to use a product called a “tear-away bead”. Basically they stick this bead on the bottom edge of the drywall, mud overtop of it, and then simply tear away this little tab on the bottom giving a nice clean line at the drywall edge. Most people use this for butting drywall up against exposed timber framing. We ended up using it extensively, about 2000 linear feet, on all bottom seams where the drywall met the concrete floors and the exposed concrete walls in the basement.

Now the windows were another challenge altogether. As you know, we built 16″ thick walls, which made for a significant 14″ return on the windows from the interior wall (2″ for the window thickness). On the window sills, we will be installing douglas fir sills, but to do that around the whole of windows would be too much wood (in my opinion, as we will be installing pine ceilings throughout the whole main floor). So instead we wanted to do a drywall return on the top and sides. Now, I’m not sure how other people do this, but there is a drywall return channel on the window frames that the drywaller will simply slide the drywall into and then you’re done and ready to proceed with adding your trim.

For our windows, it was not that simple at all. We had asked them to remove all of the drywall return channels prior to the shipping the windows so that we could add our fancy air sealing Tescon Profil tapes to the windows (if we hadn’t have done this there would have been no way to secure the vapour barrier to the window frame – how do people normally do this, I asked? Most people don’t secure the vapour barrier to the window at all, was the answer I received. No wonder people have drafty windows!).

Ok so that was one thing, but it had a cascade of effects, namely that you had to get a reasonable overlap onto the window frame to secure the tape, which was approximately 1/2″. Remember too that there is spray foam that is sprayed in between the rough opening of the window and the actual window frame – about 1/2″ as well on all sides. Drywall is only 1/2″ thick… see where I’m going with this? The numbers were not adding up. Our only option was to double-up (two sheets) of drywall at each window return. As there was now no way to use the drywall return channel for the windows (and we weren’t putting on trim anyway to hide it) we ended up using the tear-away bead here too to give a tight clean line between the window frame and the drywall.

Problem solved!

Not quite… the whole house had been designed for 1/2″ drywall throughout, which you may not think would be a problem, except for the two corner windows (between the main entry door and kitchen/dining room).

Frick.

This was not going to work. After coming up with some preliminary dumb ideas, I removed the second piece of drywall, which made the corner flush again, but it exposed too much of the Tescon Profil tape on the windows, that cutting it away would expose the vapour barrier. I ended up shimming out the side closest to the window, at 14″ in depth, you can’t visually notice the 1/2″ transition that occurs, allowing the corner to be flush and the tape to be covered at the window frame. I’m so smart! (I humbly told myself). (Though my woodworker doing the sills will be cursing me).

Unfortunately the corner window with the main entry door, would not be so simple. The only option here was to build out the entire one wall and to make it two sheets thick. Oh well.

Once the mudding was finally done, we spent the next two weeks painting like madmen. We decided to use Benjamin Moore Cloud White for the entire house (except for the basement doors, which we will paint in Oxford White). I do like the colour white and there are seemingly an infinite number of whites to choose from. Cloud White though is a favourite of one of the design duos we follow: Mjolk. So that made the decision easy for us.

I do not like painting at all, but we are lucky enough to have an amazing neighbour who came and helped us paint for two long days on the weekend. Having the extra hands was such a blessing to us. Over the next week we were able to finish the painting and were ready for the next step: exposing the concrete floors and the nightmare that followed.

The day following the completion of the excavation, backfill, grading and dirt hauling, Taylor and Curtis with EcoSmart got to work framing the double-stud exterior walls. We had chosen to use the “deep wall system” originally developed by Rob Dumont, a local Saskatoon engineer who is widely recognized as one of the pioneers of super-insulated green building. He has been a major inspiration to the owner of EcoSmart Developments, Murray Guy.

Rob Dumont had been one of primary engineers in creating the Saskatchewan Conservation House – which is one of the original homes that inspired the German Passivhaus movement. This is a fantastic article about Rob Dumont’s own home that he built in 1992 using his deep wall system (it was considered to be the most energy efficient house in the world at the time!).

Rob Dumont developed this super-insulated wall system and Peter Amerongen from Edmonton AB has been perfecting it over the past few years, using it in the Riverdale NetZero and the Mill Creek NetZero homes, amongst others. To my knowledge, no one since Rob Dumont himself, has built another home in Saskatchewan using this type of wall system. I’ve written about this wall system previously, but now we were going to see it come to life before our eyes.

Taylor and Curtis had of course never built this type of wall before, but they had done extensive research and were very motivated about it. This wall system utilizes two 2×4 walls, spaced 16″ apart thereby creating an 8″ void between each 2×4 wall. There is no need to offset the studs as the large void, which will be filled with dense-packed cellulose (recycled newspaper), has no thermal bridging whatsoever. We elected to space the 2x4s at 16″ centers for both the interior and exterior walls. It is possible to space the non-loading bearing wall at 24″ centers, but when attaching the wood siding to the exterior wall (our non-load bearing wall) this might be a little more tricky.

Of course this wall system takes a bit longer to construct then your typical stick-framed house, as each wall needs to be built twice. What the guys did was to lay the lumber one on top of the other to ensure that the spacing was appropriate. The studs were nailed together with a double bottom plate (we will be pouring 1.5″ of concrete for the main floor so you another bottom plate was needed in order to secure the drywall to it) and a double top plate. The two walls were then secured to a 16″ wide 3/8″ OSB header and footer and tipped up into place using wall jacks. The walls were then glued and nailed into place and sheathed on the outside.

The first day they framed the west wall which is 30′ in length. Honestly, the excitement of seeing a wall could not be contained that day.

Day two they framed the north side which is a longer 48′ wall with minimal penetrations – one window in bedroom, one in the hall for ventilation and the back door.

Day three was the west wall, again 30′, which included three large windows (energy efficient geeks will note that there is minimal benefit to large windows on east side and there is risk of overheating in the Spring and Fall) however these windows look onto an amazing river view that we had to enjoy. The windows will be glazed in a special coating to reduce heat gain (more on that later).

Main entrance and foyer corner window (tricky detail)

Day four they ambitiously completed our southern wall, our primary 48′ wall, with three MASSIVE windows – all of which are more then 10′ wide – and a patio door to the deck. This side of the house looks onto a beautiful southern view across the river valley, but also will be a source of heat gains in the wintertime.