A PassiveHouse Wall Designed for Canada

Designing a Passive House can be a daunting task. We can get easily overwhelmed by the overall goal that is in front of us, or get lost in the detail too early on.

As a project manager, I simply break down a grant goal into smaller manageable bites. Here is one such step: Choosing a wall that will work for a passive house in Ontario, Canada.

In this post you will get: 

  • Design of the wall, incl: sectional drawing

  • Which materials will work

  • Why do we recommend the materials

  • Considerations on how to practically build the wall

  • Where to purchase the materials

  • Example Photos of a Passive House built in Canada (Alberta) with this wall design

Objectives: What does the wall need to accomplish

Must haves (#passivehouse requirements):

  • thermal bridge free [Ψ ≤ 0.01 W/(mK)]

  • airtight [not quantifiable when looking at this component alone]

  • high R-value/ low u-value (U < 0.15W/m2K)

  • longevity 

Great to have: Service cavity, corner detail that will work for offsite manufacturing, ability to increase or decrease r-value of the wall easily, material cost optimzation, ease of air tightness control, use cellulose (great CO2 saving, very cost effective), use mainly standard materials on the market

Must haves from a building physics point of view:

  • rain screen

  • breathable exterior

  • vapour retarding interior

  • great control of vapour retarding layer (lets you easily make it tight)

  • high thermal time lag and maximum thermal phase dampening

  • vapour retarding layer in interior 1/3 of the wall

What will this wall achieve

  • Great thermal performance: insulation for the cold, heat protection for summer

  • Very high sound insulation

  • (the obvious:) structural requirements for building code

 Download a PDF by clicking on the image.

Download a PDF by clicking on the image.

Design of the wall

This is the design we suggest, that accomplishes all the above objectives. The inside is a weight bearing structural 2x4 wall. It is basically the same as any standard wall (code minimum for Canadian building code).
It also lets you increase or decrease the r-value, according to your PHPP calculations by increasing or decreasing the thickness of the main insulation layer. This is simply done by chosing defferent depths of TJI joists. You can also substitute TJI joists with larson trusses.

Which materials will work

Regular dimensional lumber, TJI joists*, OSB, cellulose, mineral wool. We recommend you use OSB rather than plywood. OSB is more consistent for airtightness and also less expensive. Using plywood as your vapor retarding layer may result in higher air leakage.
Insulation: we recommend you use either cellulose or mineral wool.
Agepan DWD or Ampatex Aero for external vapour open layer
Tapes: Ampacoll XT (exterior vapour open layer) + Ampacoll INT (interior OSB), or just use Ampacoll XT for inside and outside

Why did we use these materials

The design of this wall will give you very high time lag and very high temperature phase dampening, virtually eliminating any fluctuations of the exterior temperature on the inside. This is particularly good for summer heat protection. In order to support the dense pack blown-in cellulose, we recommend you use Agepan DWD on the outside. This sheathing material is vapour open, which will avoid moisture related issues (condensation in the insulation cavity, which can lead to rot and mould).

Agepan DWD also acts as your 2. WRB, and doesn't need any extra water repelling membranes such as Ampatex Aero or Tyvek. If you prefer to use mineral wool main insulating layer, you can also use a membrane such as Ampatex Aero on the exterior. It will give the necessary support to the mineral wool. In this case no sheathing is needed on the outside of the TJI's.

TJI's will reduce thermal bridging to the bare minimum. Using dimensional lumber in the insulation cavity will still leave you with thermal bridges. (there are other technical solutions in this instance, but will leave this for another time)

Two choices for insulation material:

When to use Cellulose:

  • If you have access to a contractor with a proper machine.

  • When you have access to the cavity, after the wall is set up.

  • When you want to save on insulation material

When to use Mineral Wool: 

  • no access to contractor that can properly dense pack cellulose ATTENTION: dense packing requires a special cellulose blower. A contractor that says he can dense pack cellulose (50kg/m3) with a regular machine, has never dense packed cellulose. You will end up with cavities in your insulation cavity. 

  • in tricky spots, that cannot be reached after the wall is set up

  • if you want to insulate the wall before transporting it (you may actually use mineral wool and Agepan DWD. Ampatex Aero may be wrecked during transportation)

Considerations on How to build the wall:

Think about layering the wall properly. You have to tape the OSB on the inside, when you have access to it.
We recommend you built it in layers on the ground. Start with your TJI's, lay the OSB over the top, tape the joints, add the 2x4 layer, flip it over and add the DWD (or fill main insulation cavity with mineral wool, and then add

On-site vs. Off-site

The discussion about On-site vs. off-site is more complex than what we can cover her. It depends on so many factors of your business, your abilities and the state of the construction site. Do you have the indoor space for off-site assembly? Do you have the necessary equipment to flip and handle the pre-built walls, do you have the necessary transport equipment for finished walls? Do you have construction site restrictions that will not let you use a telehandler? Can you use a crane? Do you have to use a crane? Sorry folks, this is a bit of a non-answer, but hopefully some pointers of what you need to consider.

Where to purchase the materials?

Lumber, OSB sheathing, TJI-joists, Larson trusses: at any of your local lumber yards or trussing manufacturers

The rest of the materials are available right here at Pinwheel:

Ampatop Aero
Ampacoll XT
Ampacoll INT
Agepan DWD

Example Photos of a Passive House built in Canada (Alberta) with this wall design

This exact wall system was used by Tom Gyimesi of www.5thC.ca for a building (workshop and apartment) in Alberta. Here are photos of the actual build:

We want to hear from you: Are you planning a PH and would like to use this wall system? Do you need flooring and ceiling details to work with it? Do you need more design services to go along with it or even pre-manufacturing of these walls for your project?

*A note about TJI-joists: All TJI-Joists available in Canada at this point are reated for horizontal load bearing, ie: floors, ceilings. It is becoming more and more common to use vertical TJI-joists in the main insulating layer, but that's usually not what they are designed for. Europe and scandinavia they have created/rated beams for vertical applications. So use this method with caution and talk to your structural engineer, so you don't have any surprises in hindsight.