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My Leap to Passive House Pre-Fab

– Posted in: Explainer

It took 12 years in the green building sector and two dozen LEED projects before I discovered Passive House, now my sole choice for designing and building for energy efficiency. I saw how Passive House offered the crucial elements – simplicity, rigour, and cost effectiveness – to enable large-scale uptake of ultra-low energy buildings. This was the first stepping stone of a new path for me, a path I’d like to share some insights on…

The first step:

Passive House is the optimum methodology for energy AND cost effectiveness. Simple math is sufficient to show that, even at today’s low Canadian heating fuel prices, a Passive House owner can enjoy lower total monthly house ownership costs from the day they move in. The main reason that passive homes can “tunnel through the cost barrier” is that they are much simpler buildings, trading active, expensive, energy-sucking heating/cooling systems for cheaper, passive approaches like better envelope and windows and thermal bridge-free details. At its heart, Passive House is an economic solution developed to minimize life-cycle cost and cost of ownership, optimizing return on investment for improving building envelope to reduce heating loads.

HOP over barriers:

After forming my consulting practice, I quickly discovered that Passive House is a tricky niche for a design professional, especially within the residential sector. Although design fees represent a small percentage of the overall build cost, these fees occur up front, before a construction mortgage is secured, leaving private clients feeling that they’re ‘speculating’ on the consulting effort necessary to deliver a Passive House project. Bundling the build costs with the design fees is easier and more palatable to clients. Design/build under one roof offers the client greater convenience and lower risk. It also eliminated barriers to engaging in Integrated Design, a process considered a pre-requisite to designing a high performance building in a cost-effective way.

SKIP the cost premium:

The cost premium for Passive House is perhaps the largest barrier to widespread uptake in North America. Despite the strong argument for Passive House based on lowest overall cost of ownership, the housing market primarily focusses on upfront capital costs and cost-of-entry.

Most providers today will concede that there is an upfront premium to design and build a Passive House building.  CANPHI suggests a 10% premium as being a good conservative estimate for a single family home, less for a multi-residential project. Any premium less than 10% is a small price to pay for deep energy efficiency, durability and comfort. Unfortunately, even this small premium is a barrier for most buyers. This was especially the case for my first Passive House project, an affordable 44 unit townhouse project in Welland, Ontario called Cordage Green (, which is aiming to be the first certified Passive House affordable housing project in Canada.

JUMP to pre-fab shells:

To ensure affordability, we had to take it one step further and utilize a model based on pre-fabricated, panelized construction. In fact, the pre-fabrication process presented itself as the solution to many issues:

  • Build quality. Although the sector is growing, there is still a scarcity of builders who understand how to achieve the air tightness standard required for Passive House. With a pre-fab approach, the air barrier is integral to the panel, with factory-installed taped & sealed OSB air barrier and panel gaskets that are protected from damage during subsequent fit-out construction. Pre-fab removes the uncertainty of builder-related quality issues and optimizes worker productivity, by standardizing the construction process.
  • Weather control. Factory-building reduces the potential for weather-related damage that could occur using a site-framed build. The construction crew enjoy the indoor working conditions. Site installation takes mere days, allowing us to pick a good weather window for the install.
  • Staying Lean and green. Using a factory setting allows a Lean production method, and a pre-fab install minimizes the transport of workers and equipment between job sites.
  • Speed. Fabrication of panelized sections occurs off-site, concurrent with site preparation, thus reducing overall construction time and construction loan financing costs. Weather delays are factored out.

We supply the Passive House building shell only, allowing the client to finish the house with a non-specialist builder and local trades. This reduces our time on a project, allowing us to increase the number of Passive House structures built. Thermally-broken, insulated slab/foundations are still the exception rather the rule, so Leap House provides foundation design and site supervision, with concrete work subcontracted locally. We also team up with local builders during installation, providing training and supervision as required to ensure a quality product that we can guarantee. Reducing our time on site from months to mere days means that we can extend the geographical area we serve.

How are we doing so far?

It’s still early days for Leap House. We’re in the design phase for three residential projects. Our pricing strategy is to achieve passive house shell on par with a typical Energuide 80 or EnergyStar house shell cost – in around $95-$110/sf, depending on building-specific factors. Our multi-res project, Cordage Green, is presently in pre-sales, with construction cost estimated to come in under $150/sf (full fit-out, including landscaping but excluding land purchase), which is below typical multi-res development cost.

Partnership discussions are ongoing with PassivStructures LLC, a firm founded by Adam Cohen, an internationally recognized leader in the Passivhaus movement (and Passive Buildings Canada member). PassivStructures has developed a panelized wall system – “a very simple snap-together system” – that will revolutionize the industry. Modules consist of wall panels in 2-foot length increments and with two height options for 8’ and 9’ ceilings; building corners; six windows that can be ganged in varied ways; and three-door types (see sidebar). This produces 64 custom panel options that can be configured in any number of ways, offering designers a great degree of flexibility. Custom panels can also be produced, making the system fully customizable. To make the process accessible to any designer, the panel drawings are made available as SketchUp ‘components’ which can be inserted and configured easily with a few mouse clicks.

Wall panels consist of a traditional stick frame (2×4, 2×6), insulated, sheathed, air-sealed, and covered with rigid EPS foam, with foam thickness varied to suit local climate zones. Panels are joined on site with an expanding foam gasket (for vertical connections) and liquid-applied sealant (for horizontal joints). Super energy-efficient tilt & turn windows from Klearwall are pre-installed in the factory, so the walls are true “plug & play”. As one contractor commented, “You’ve turned Passive Construction into Ikea® Legos®!” Systemizing the design and production process greatly reduces cost.

PassivStructures finished its first factory-fabricated project this past spring, with three more scheduled for completion by early 2015. We plan to market this system to architects and builders in 2015, so stay tuned.

Putting it all together…

Pre-fabricating and panelizing walls to Passive House standard is a game-changer. Combining design/build with pre-fabrication allows us to leap over barriers and deliver Passive House quality at market costs. It’s modular, repeatable, standardized, and simple. Removing risks and eliminating the need for Passive House trained builders means that we don’t have to wait for a seismic shift in the industry, we can begin rapid uptake of affordable Passive House buildings here and now.

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