We asked Bryn Davidson, principal of the integrated design/build company Lanefab, to describe how they are taking the Passive House Movement and applying it to Vancouver’s laneway houses.
What are super-insulated walls and why were they necessary, considering Vancouver’s mild winter?
In a broader sense, super insulated means anything beyond the code-minimum requirement. In most places, code minimum is 2×6 construction, which has a nominal R-Value of 22 but an ‘effective’ value of ~R16 (once you account for all of the heat that leaks out through the wood framing). Vancouver, Montreal, and many other jurisdictions are increasing the minimum requirement – because R16 is not very good. In Vancouver, all builders will soon be required to meet R22 ‘effective’.
At the other end of the spectrum is the Passive House movement, which is aimed at creating homes that are so air tight and insulated that they don’t require a central heating system.
Passive houses will have walls with effective R values between R35 and R60, and roofs from R50 to R100 (depending on the climate). The passive house energy targets are aimed at reaching the ‘sweet spot’ where you’ve spent enough on insulation that you can save on the cost of a furnace or boiler.
When it comes to having that extra level of insulation for your home or commercial property, it is important that you have the right amount so that you have the potential to save on your energy bills. Some owners may even take a step further by deciding to use something like flat roof sprayed polyurethane foam (if your property has a flat roof) to maintain the right amount of insulation that you want to be able to live or work comfortably.
For our lane house projects we wanted to adapt the ideas from Passive House to a lane house context, and create a system that was competitive cost wise so that we could use it on every project. After some experimentation we arrived at a system with R40 walls and R48 roofs. For full size houses we typically use a higher R value for the roof, but for lane houses – which can only be 20′ tall – every inch counts and a thicker roof could make the project less livable.
We arrived at our specific R40 wall assembly (12.5″ thick) from a few different paths:
It allows us to have a flush interior wall without a weird ‘bump out’ to insulate the foundation. With standard 2×6 construction the framing sits on top of the foundation, but you also have to provide insulation against the foundation wall. In a lane house, this ~6″ bump out can eat up a lot of valuable real estate. Using a thicker wall allows us to hide the foundation insulation (3.75″ of polyiso spray foam) inside of the wall. The city of Vancouver doesn’t make us count the full thickness of our wall as floor area, so the thicker wall actually allows us to have more usable living space because the bump out doesn’t impinge into our floor area.
It gives us enough space for proper slab edge insulation. Most ‘normal’ houses are only required to use a small piece of wood (R1) to separate a home’s warm floor slab from the cold foundation and ground outside. This detail is pretty bad, as most of the floor slab’s heat loss is out the edge. With in-floor radiant heating the situation is even worse. Conventional homes are literally pumping heat right out the foundation wall. By contrast our thicker wall allows us to use a minimum of 3″ of rigid polyiso board (R18) at the slab edge.
It allows us to run plumbing and ductwork on exterior walls. The thick walls give us 4″ of space where we can run plumbing stacks, ventilation ducts etc. In lane houses, where there are tons of services (including HRV ducts and fire sprinkler piping) crammed into a small area it’s helpful to have more options.
We can downsize the heating system, or use a cheaper heating system. With the thicker walls we can always achieve at least an Energuide 82, even if we use low cost electric heating and hot water. In some cases, where the heating load is low enough, we can use a hot water tank to provide both space heating and hot water. Not all clients can afford a solar powered home, but if they have a good building envelope they can always upgrade their mechanical systems at a later date.
The thicker walls provide a distinctive architectural look. Our prefab panel system, and thick walls, allow us to have header-less windows, and deeper exterior window recesses, which give the more contemporary projects a different look and feel vs. standard 2×6.
The overall build costs are similar. Our R40 wall system, using prefab components, has a higher material cost vs. 2×6 but it goes up quickly and so we can save on labour costs, and mechanical system costs. At the end of the day, our build costs for the overall project are quite similar to other custom builders who are using conventional methods.
We often get comments from people living in other Canadian cities, but the fact is that Vancouver homes are heated for much of the year, and Vancouver – while relatively warm by Canadian standards – isn’t as different from Montreal when you look at how they each compare to a city much colder (Fairbanks, Alaska) or much warmer (Los Angeles) – see below. In both cities most people have chosen to spend money every month on GHG intensive heating fuels vs. putting those same dollars each month toward a more efficient, and more comfortable home.
Describe how the house functions during the winter and during the summer?
In most cases when designing a laneway house we don’t have the luxury of being able to orient toward the sun. The laneway house guidelines are very strict, and require the larger windows to face the lane, independent of solar orientation. For the E.57th project we were lucky that the corner site, and the lane house rules, lined up to allow us to put the large glazed doors and patios facing south. In the summer the 3′ overhang blocks most of the sun, and the solar panels produce excess energy which is sold on to the utility grid. In the winter the sun warms the living spaces, and the house draws power back from the grid when it’s dark and the days are short.
The newer solar panels on the market do a good job of harvesting energy even on cloudy days, and it’s even better because you can store this energy in a battery to use at off-peak hours. Battery sizes vary depending on the solar battery supplier. Perhaps it’s something to look into if you’re looking to conserve energy. Vancouver’s sun is quite similar to Germany – one of the world’s leaders in solar installation – but we lack the financial incentives to make solar photovoltaics cost effective.
For our projects we always start with a well insulated building envelope with an HRV, from there we add on LED lighting, drainwater heat recovery, and potentially a high efficiency heat pump or gas-fired system for heating and hot water. After we’ve done all of those things, the last thing we add is solar PV panels.