Documenting the design and construction from start to finish of a Passivhaus (Passive House) in Ottawa, Canada. Insider info on what it's like working with an architect and costs associated with building.
Posted in: Build
Joists and hangers and LVLs galore
The joists and beams for the second floor are in! Today we start installing subfloor and railings. It's really exciting to see the views taking shape as we get higher!
This is the open space over the dining room, and the start of our tall south window
Getting closer and closer to the canopy of our silver maple!
This week our crew squared up the first floor walls, installed some LVLs (laminated veneer lumber) to support the floor above, framed some interior walls and started putting up floor joists for the floor above.
With the first floor framed in, it's starting to look and feel like a proper house :) Have a look at Mark's Periscope from this past Friday.
We can't believe our luck with the weather these past couple weeks. It has been positively balmy. If mother nature keeps this up, we can shave R-20 and a foot of insulation off our house. Just kidding...I have full confidence that Mother Nature will show up with a vengeance. As she always does for us here in Ottawah. We'll take what we can get.
Floor joists going in.
Our spectacular kitchen window. Deep walls = added counter top!
The sun sets over another week.
The last two walls went up this Monday. Here is a Periscope from the weekend with a special guest star appearance. Teaser: it was me. We put the final touches on the walls together.
We are counting our blessings lately for all this "warm" weather.
One of our wall sections being assembled and ready for lifting!
With the wood framed walls well underway now, I thought it was high time that I sat down to write a post about the design and theory behind the wall system we are using. When we set out to build our project, I spent a lot of time thinking about double stud wall construction. For those unfamiliar, a double stud wall is a wall made up of two seperately framed walls, one inside of the other, usually seperated by a space for insulation. The beauty of the double stud wall is that the overall thickness of the wall is very flexible: by moving the two stud walls further apart you can add insulation and increase the effective R-value of the whole assembly. The continuous insulation is also a great thermal break preventing thermal bridging through studs.
Still, there are a couple of challenges that the traditional double stud wall presents. First of all, the exterior wall is usually built first, and the interior wall much later once the house is enclosed. The main drawback of this is that the exterior wall necessarily becomes the load bearing structural wall. I'm a big fan of keeping structure as much to the inside of the thermal envelope as possible for two reasons: first, it keeps the structural elements warm and dry and protected from cycles of expansion and contraction, and second, it reduces the number of structural penetrations or complex structural details that interfere with a good air barrier.
When designing the system for our project, I set some key goals for myself. I wanted to have a system that hit all of these key points:
As discussed above, this is just the right place for structure to be. It also facilitates the next point below...
I wanted to use OSB with taped joints for the primary air barrier. In order to keep from having a messy transition at floors, the idea was to come up with a way to run the air barrier up straight past the floors without joist cavities to contend with
With all walls, and especially with high R-value walls, it is crucial that the wall has good drying potential, and that no opportunities for condensation are created within the assembly.
This could have been the first point. Super-insulated is Passive House's alternate code name.
I wanted to avoid insulation that would require scaffolding or lifts for installation, partly because of the limitations of the site, and partly for cost and labour savings. In terms of insulation type, I'm a big fan of mineral wool insulation. What's not to love? It's water resistant, mould-proof, fire-proof, high in recycled content, and has a good R-value that actually improves as it gets colder outside.
Wall section: Click to enlarge
Many hours of sketching and head scratching and I came up with the idea of creating a hybrid system. Taking some cues from Swedish platform framing, and some from the double stud wall approach, I designed a system using thermally broken wall trusses with wood fibreboard exterior insulation and 20" deep cavities for filling with Roxul. Here is how this system meets the design criteria from above:
The wall trusses are composed of a 2x6 stud and a 2x4 stud held together by a series of 5/8" plywood gusset plates. The 2x6 stud is the interior layer of the stud, and behaves very much like a standard 2x6 wall. The gussets support the 2x4 layer through shear resistance, and are engineered to support the siding and wood fibreboard insulation. These trusses align with the foundation below: the 2x6s bears down on the concrete, and the 2x4s are cantilevered out over the EPS foam. By building with these wall trusses, we end up with a double stud wall with an interior structural element, and the whole assembly goes together in one shot.
After the walls are stood up and insulated, the interior gets clad with OSB sheathing. At the top of the walls, the floors are installed on hangers that mount to the face of the OSB and through to the floor header installed into precut notches in the 2x6 layer. The hangers will use a self-sealing nail tape during install. The result is that the OSB air barrier runs in a perfectly straight line from the foundation up to the roof (with window and door openings being the only exceptions). Easy to tape, easy to seal.
The entire assembly to this point is extremely vapour open. The OSB is the most vapour resistant element so far, and it is on the warm side of all of the insulation. The mineral wool and wood fibreboard both allow water vapour to move through and dry to the exterior. This was one of the main reasons we chose to use the wood fibreboard exterior cladding over a foam material.
With a 20" deep cavity and 2-5/8" of wood fibreboard on the exterior, the nominal R-value of the wall is roughly R-96!
As the walls are framed, they are squared and stabilized with let-in t-braces on the exterior 2x4 layer. Coupled with temporary bracing, we are able to frame all of the exterior walls, floors, and roof prior to installing the OSB sheathing. This leaves the wall cavities open to the interior for easy installation of batt insulation. Adding the OSB after insulation is complete adds the final permanent racking strength to the house where it belongs, right against the structural framing.
We had all of the wall trusses manufactured off-site, and delivered pre-cut and labeled as a complete framing package. We have framed and lifted three wall segments so far, and although progress is slower that hoped for as we figure out the nuances, things seem to be working well! We rented a set of wall jacks to help lift the walls into place, as they are far too heavy to lift safely by hand. Here's today's timelapse showing the process.
We are starting to pick up some steam as we go. Three more sections to go on the main floor and we will be almost ready to install the second floor deck. It is really exciting to watch as the rooms of our home take shape!
There are many other details and considerations that went into this and all of the other construction methods being used in the house, so I welcome any questions or comments!
Mark's broadcast from site this morning.
Periscope removes the videos after 24 hours, so I'll start posting them up here for those who may have missed them. (You won't see the questions and comments from viewers, but the content is still all-good).
This week, the team finished installing the ledger boards, hung our floor joists (supplied by Kott), finished the interior structural framing, and set a floor on top of the floor joists. Construction is starting to resemble a more traditional site-framed home. Over the weekend, we had a family picnic in the house and even had our first official guests over to join us (of course we all wore hard hats).
We forgot to mention on the blog that last week was International Passive House Days. There were several events and tours happening around the city. There is rising interest. Mark also gave a couple tours of our place (outside of the PH week events). One to a group from NRCan (Natural Resources Canada) and one to a group of fine folks taking a Passive House course. Seeing as how our build has been garnering interest and tour requests, we will post a sign-up form (eventually) and open them up to the public. We are all-for raising awareness for Passive House...we are also pretty proud of what we’re building and happy to show it off. We'll get that going soon.
Next week, work will be geared towards the main floor walls.
In the new toasty basement
Welcome to the main floor
Last I wrote, I left us on a cliffhanger, didn’t I? Wood and hammers and nails — oh my!
Oh no.
I jumped the gun. Much prep was yet required before framing could begin in earnest. Those tasks included:
1. Glued the last few stacks foam to the outside of our basement walls
All that foam combined (R-4/inch) should have an R-value of 74. (Ontario Building Code requirements for a foundation are as low as R-12 on the walls only).
Last layers of foam held in place while glue sets.
2. Installed the frost skirt
Because the bottom of our foundation isn’t quite deep enough to guarantee that it will be below the frost line on any given winter, we needed a frost skirt. (This is a standard detail for shallow foundations in Canadian construction). It’s a thin layer of foam installed horizontally around the permitter of the building at foundation depth. Typical frost penetration is around 4 feet in Ottawa, but last years' exceptionally cold winter brought that to 6’. A frost skirt is used on shallow foundations to extend the path that frost must travel to reach the bottom of a foundation. Bad news if it were to happen — expansion, contraction (heaving) leads to cracks and structural damage.
Frost skirt and overlapping and waterproofing membrane.
3. Waterproofed the foundation
Using a Nudura waterproofing membrane, which is a peel-and-stick rubberized sheet. This required some patience because the foam had to be cleaned and dried prior to application. It wasn’t adhering as snugly as we’d have like to see, either. Some temporary strapping helped with this. A dimple board, held on place with metal fasteners, was layered over top of the membrane. Bam. Waterproofed.
4. Set up drainage
Water shall not pass (our membrane) and will weep if it dares to encroach. Weeping tile was placed around the perimeter of the foundation and connected to the storm sewer. There is a filter sock around it to prevent it from filling up with sand. (Am I the only one who finds the term weeping tile odd? There is no porcelain or ceramic whatsoever. It’s a plastic pipe with some nylon around it. Weeping tile does sound dramatic, however. I therefore think it sticks).
Dimple board and weeping tile.
5. City inspection
Our city inspector wanted to check things out prior to back fill. So he paid a visit. He decided he wanted to throw in an additional check, which threw a bit of a wrench in to our coordination efforts (see next step).
6. Backfill
There were two steps to the backfill process. First we covered the drain tile with clean gravel (as to not clog the nylon with sand and silt straightaway). Cue city inspector – who gave us the thumbs up. And then we filled up the hole with native fill (some of which has been sitting around and taking up precious room on site and some that was stored off-site).
My oh my. What a difference this back fill has made. Now that half of the foundation walls lie underground, it actually looks and feels like a basement from the outside.
Backfill stage 1: clean fill
Backfill stage 2: native fill
7. Sill plate leveling and installation
This sill plate is what our first floor walls rest on. It’s a 2 x 6” piece of lumber that’s installed on top of the concrete, leveled with grout.
8. Ledger board and air barrier prep
The ledger board is what our first floor floor rests on. Remember those ledger bolts that were screwed into the concrete? These hold up the 2 x 10” ledger board. But out air barrier goes up first – Siga MAJPELL 5 membrane. Mark had a Periscope broadcast on this last week. They installed it with excess available to overlap once the second/main floor goes up. (Gotta keep that air barrier line as clean and streamlined as possible!)
Air barrier detail over ledger bolts
Ledger board install
That’s the house up-to-date. Additionally, we had a few deliveries made and spent some time shuffling our construction materials around as we suddenly had a lot more room with the backfill out of the way. Our neighbours were no doubt pleased to regain their front lawn. And we lost a couple days due to bad (wet) weather.
Lotsa stuff out front.
Behind the scenes, there was a bit of good news. We applied for our first construction mortgage withdrawal. Mark explained our house build to the appraiser, and why our breakdowns/allotments should be different. The appraiser accepted Mark’s breakdowns — whoot! We have been reimbursed for Phase 1. Foundation complete. This helps alleviate some of our financial pressures.
For next week: wood and hammer and nails — oh my!
Exterior rendering of Casey and Natasha Grey's Passive House in Manotick
[Post written by Casey Grey of Cornelis Grey Construction]
Working with Mark, Meghan and PLOTNONPLOT was a must for us. Since we had already built a Passive House for ourselves, we obviously knew we had values that aligned. This partnership was meant to be. Ultimately, the building industry needs to change and there’s no way one person can do it alone. We all have to work together if we’re going to have any sort of impact in this life.
Although the term “Passive House” is widely unknown, “saving money” is something we can all relate with. In a world where everything seems to become more and more expensive, it’s about time we start saving some money. That is what Passive Houses do. They save energy which, in turn, saves money.
As a Builder who lives and works in a Passive House, I can vouch for all the benefits. It was the smartest decision (other than marrying my wife, of course) that I have made in my life. With solar panels on the roof that are a part of the MicroFIT program, we actually make money every year instead of paying energy bills. I’m also giving my family healthier indoor air quality and a more comfortable place to live. To top it all off, all these decisions help the environment in more ways that I can count.
I’m sure you’re all tired of hearing about saving the environment so I ask you to think of it differently. A way that actually makes more sense. It’s not the environment we’re trying to save, it’s humanity... The environment was here long before us and will be here long after us. No matter what we do, it will adapt. Even if that adaptation requires getting rid of humanity. Let’s work together towards a future that costs less money, betters our health and saves lives. The decisions you make today could make you a hero for generations to come. That’s why we decide to build Passive Houses.
