The Langley Passive house is a ‘split-insulated’ wall assembley pioneered by RDH Building Engineering for the BC climate. This strategy is described in the Building Enclosure Design Guide (HPO 2011) and Guide for Designing Energy Efficiency Building Enclosures (FPInnovations 2013) both by RDH. The wall design borrows from the North Shore Passive House in construction by the Econ Group (http://www.econgroup.ca/north-shore-passive-house/) and progress photos of the North Shore home are available at http://www.econgroup.ca/north-shore-passive-house/.
The schematic roof – wall – foundation diagram shows the component parts for the Langley Passive house. The wall assembley consists of a 2×4 structural and service wall with a plywood vapour barrier at the exterior. An air barrier is taped to the rigid plywood backing. Two layers of rigid roxul provide exterior and continuous exterior insulation which in turn is held in place by 2×4 strapping on flat anchored with long screws.
The roof assembley consists of a truss roof with OSB vapour barrier attached to the underside and a 2×4 drop ceiling for services. Blown in insulation blanket the attic space.
A raft slab concrete foundation sits on 2 layers of rigid insulation which abut the rigid roxul of the wall assembley ensuring continuous insulation without thermal breaks.
The Langley Passive house is currently largely framed with roof membranes in, rigid roxul and wall strapping mostly present, and raft slab foundation installed and backfilled. The image shows the blue roofing membrane on the lower granny suite, staging is shown, double layer of rigid roxul at wall, 2×4 strapping, and south facing sunshades at the right-side of image.
The chosen assembley is a relatively vapour open system allowing any moisture that finds its way into the wall from condensation or through gaps in the assembley a way to dry out. The plywood vapour barrier has a permeance range of 115 – 252 ng/Pa*s*m2 above the prescriptive requirement of 60 ng/Pa*s*m2 (BCBC). This in addition to the vapour open air barrier and roxul insulation allows for drying to the outside. Similary the roxul in the stud wall cavity allows for drying to the inside. This contrasts with the relatively vapour closed passive house systems such as structurally insulated panels (SIPS), closed cell spray foam, EPS or XPS exterior wall insulation, and to a lesser extent systems using a traditional poly vapour barrier. The team including the passive house consultant Dale Mueller have chosen this strategy to best contend with British Columbia’s temperate rainforest climate.
Subsequent posts will go into more detail regarding the roof – wall- foundation assembley, exterior window and door installation and their construction sequencing. There are some nonconventional methods used in the all these areas which may be of special interest
Triple pane window is installed over sill flashing & weather resistant membrane and then taped.
Then there is a 2×4 ripped to the thickness of 1 layer of rigid roxul around the window offset about 3″. This holds a layer of rigid roxul tight against the window frame and provides a nailing & flashing surface. The second layer of rigid roxul covers up the 2×4 resulting in a thermal bridge free detail. Borate treated 2×4 strapping on flat hold the 2 layers of rigid roxul in place. Also shown here is the wall connection to the foundation. You can see the dimple board drainage layer with a self adhered flashing at the top and the rigid roxul over top. On the left of the lower picture (above) you can see how the rigid roxul is held in place with temporary bracing via leaning 2x4s before the install of permanent strapping and long screws.
You can see the head flashing at the top of window. This is nailed into the 2×4 ripped strip offset above the window. Wood trim is installed at jambs and sill flashing with end dams. What is left is the siding nailed into the strapping (not shown).
On the inside headers are installed at the floor joist level. Air barrier wrap can be seen surrounding the window head and jamb.
The windows are installed through the interior side of the window frame rather than with the common flange. Sill self adhered flashing can be seen with the air barrier membrane properly lapped. Tape from the window frame to the structure and rod & caulk will be provided in future (not shown).
The head and jamb are shown here.
Compared to a typical window installation there are some differences here. The membrane wraps are similar but the air barrier membrane needs to be taped at all seams. The window is flangeless and is mounted with side-mounted screws. There is a 2×4 nailing strip offset at head and jamb and the 2 layers of exterior rigid roxul is a new addition to the conventional sequence of installation. The 2×4 strapping on flat is larger than the standard and the required extra long screws must penetrate the 2×4 strapping, 2 layers of rigid roxul, plywood sheathing, and at least 1.5″ into the stud. This takes some skill as the studs can’t be seen and must be hit. Also, the screws should be angled upward slightly. This is due to the nature of long screws which tend to sag from the weight of the siding if installed horizontally. The angled installation slightly up mimics the final resting ‘sag’ of the screw such that there is no movement of the siding after install. Any screws that miss their mark are to be left in place. This avoids penetrations of the air barrier if these screws were removed.
We’re so excited to see this new house project completed in Nanaimo, BC! This modern spec home sold already half way through construction. There will be two more to come on the subdivided lot.
We created lofty spaces to capture the beautiful views of the Marina. The house is designed with simplicity and flexibility in mind. The bottom floor converts into a secondary suite with separate entrance for those who need a mortgage helper, or it can easily become a studio or office for the growing population of creative professionals that work from home.
From the outside the house exhibits a professional, clean look, with simple lines and low-maintenance materials. There are 2 bedrooms on the main floor for those who prefer a one-level living style. There is also a master suite on the top level with direct access to a luxurious rooftop patio!
The whole house is designed and sited using passive solar principles. South facing clerestory windows provide lots of natural light into the living spaces. The South facing rooftop patio is a great space to suntan or grow some vegetables! The overhangs are sized so that the home will not overheat in the summer, preserving a comfortable feel in the interior year round.
The whole package provides appeal and adaptability to wide audience, whether they be starting a family, looking to downsize, run a home business, or just live in simple clean style!
This artist’s residence on the Gibsons Waterfront is now complete! The original home was in disrepair but the new owners saw a lot of promise and great structural bones. We were enlisted to surgically alter the interior spaces and give the outside a much needed facelift. Here is the result!!!
We paid a visit to our project site in Powell River this December and how pleased we were to see the progress!
The project is for a Main House and Studio/Workshop space for a couple from Vancouver. And what a beautiful waterfront setting this is! Breathtaking waterviews can be seen from virtually every room in the house. The cozy Studio at the back of the property doesn’t lose out on the view either, perched above it looks over the roof of the Main House to the ocean beyond.
It was so great to see how warm and bright the whole house and the studio feel bathed in winter sunlight! Access to light was a big concern for the clients and the house is sited and designed to take maximum advantage of solar gain.
A nice grove of trees surrounds the buildings, the clients were adamant about preserving as many trees as possible on the site and the trees do add to the feeling of peaceful and secludedness of the property, in contrast to the expansiveness of the water view on the opposite side.
Can’t wait to see the final product! I would settle down in a heartbeat!
We are so excited to see this home renovation project of ours in West Vancouver getting near completion! We just dropped by for a site visit and were so pleased with what we saw! It is hard to believe it is the same house. Absolutely beautiful construction and attention to details! The owner wanted to stay very true to the original design and did not settle for less. It’s amazing to look at the rendering next to the construction photo and how close they are to each other! It is certainly a treat for us architects each time to see something manifest in reality just as we had envisioned in the drawing, it makes our work worthwhile! And the part that is even more gratifying is seeing our clients so happy and proud of their new home! The landscaping will be going in next, and then it will be time for some beautiful architectural photography to document the project. Stay posted!
This was a feasibility study that we were commissioned to do in order to demonstrate the potential of a lot for sale in West Vancouver. It is often worth investigating the site and its possibilities early in the process to ensure that the site is right for its owner. Topography and sunlight access are just some of the elements that will influence the final design.
When anyone first enters the Rockhouse, after a moment of disbelief, they invariably ask, “How on earth did you manage to enclose a rock bluff inside a living room?!”
So we decided to share what we learned from this experience in the blog, from the conceptual, practical and technical sides.
I have to say that the largest barrier we had to overcome was the problem of perception rather than technical difficulties. Before we could get anywhere with the idea of enclosing a rock inside a living room in the rainy climate of BC, we had to believe for ourselves that it was possible. I will not underestimate the importance of this first step because nothing could have been accomplished without it. This proved to be very challenging at times when everyone and everything around us seemed to suggest that it could not be done. So the next big step was to convince others of our vision. This included everything from having the support of our family and friends, to having the support and expertise of fellow professionals to work with us towards that vision, convincing builders that they already had the skill to do something they had never attempted before and getting their input on how it could be done, convincing municipalities that together we were a competent team that could successfully bring this vision into reality.
Another big part of this learning experience for us was understanding our relationship to the building site. Our first desire was to have the entire back wall of the house exposed to the rock. But there were problems with this idea. Although most of the rock face was smooth and dry, there was a big crack on the lower portion of the rock face we wanted to expose where water was constantly draining out of. We contemplated various ways of dealing with the water drainage problem, including plugging the crack with epoxy. One day we were standing at the construction site already well underway, like two little specs in front of this massive rock bluff surrounded by the footprint of the house foundation, and we understood for the first time our place in the whole picture. We could not impose our will on nature. Plugging that crack on the rock face would likely generate leakage unpredictably elsewhere. To succeed we had to work with what was already there. So we studied the rock face more closely. We observed the parts of the rock that were naturally kept dry and how the water naturally drained. We went back to the drawing board to reformulate our strategy. Instead of exposing the entire rock face we decided to strategically expose only the portion of the rock that already “wanted” to be exposed. From that standpoint, the design evolved smoothly into what came to be a very special “picture framing” of the rock, as well as a cozy seating space where we could hang out by the rock.
The conceptual lesson the Rockhouse taught us was twofold – That it is important to have the confidence to believe in our ideas and to be able to bring others along with our vision. But that it is equally important to be humble in the understanding of our place in that vision – to understand that we cannot impose our will on others and much less on nature. The best we can do is to bring out the full potential of what is already there.
Travelling through Italy last summer we were reminded of Michelangelo’s famous quote: “I saw the angel in the marble and I carved him until I set him free.” Never before had that famous quote resonated with us so deeply. We understood that just as we cannot impose our own will on our clients, we also cannot impose our will on our building sites. Our building sites are in a way also our clients. We have to work with the clients’ ideas to bring out the best in them, just as we have to work with our building sites to bring out the full potential of what we already see in them.
On the practical side, we also had to deal with the nagging question, “But how much is enclosing a rock inside a living room going to cost? And is it worth it?”
This question comes hand-in-hand with other questions like, “What is the relationship between “design” and “money”?, and “Does innovative design need to cost a lot of money?”
Our understanding is that whenever we dive into any project, there is already an existing flow and logic to it. We always have the choice to go with the flow or to go against it, but going against the flow will always take more effort. In the same way, working against the building site will always cost more money. Lots of money could have been spent blasting away the site to impose a pre-conceived design on it, or in trying to control the water drainage pattern of the rock. On the other hand, lots of money was saved by working with the land and what was already there, instead of imposing our will on the site.
If a design becomes prohibitively expensive, we have to pause and ask ourselves, “What are we working against here? And how can we reformulate our strategy to turn this around and swim with the current instead of against it?” If all the options are considered and the design still proves to be prohibitively expensive, it is important to have the courage to ask, “Is this site right for me?” A relationship between a house and a building site is not unlike a relationship between people. If after doing everything to try to make a relationship work it is still not working, letting go may be the best option. On the same token, if the site proves to be not right for the house you envision, it is important to have the courage to either let it go, or to adjust your vision to work with the site. In the case of the Rockhouse, we chose the latter.
Having said that, it is very important to pick a site that works for you. If you are someone who can’t handle too many stairs, don’t pick a steep site to build your house on. If you have to work against your piece of land to impose your own needs and desires on it, it will inevitably cost you more money in the end. Pick a site that resonates with you. A site that already brings you closer to what your needs and desires are, and work along with it, not against it. We have learned that this attitude in itself can not only make the design more affordable, but will also go a long way in bringing out creativity and innovation in the design without prohibitive extra costs.
Another side of the relationship between “design” and “cost” worth mentioning is that it is also important to understand that you cannot accomplish something great unless you invest yourself in it. If a creative feature of the design is important to you, if it is something that you feel will really enrich the space and make that space more special and unique to you, understand that you will have to invest some money into that portion in order to express that feature well and fully. In other words, you want that special part to be done right. But this does not mean you need to go above and beyond your means to accomplish it. We often advise our clients to weigh their priorities and put their money where it means the most to them. Perhaps another feature of the design that is not as important can be cut back to make room in the budget to more fully express an important feature. The exposed rock wall was a very important feature of the Rockhouse to us, and to make room in the budget for that we ended up eliminating a few items from our ‘wish list’, such as a wood fireplace, an outdoor tub, and a green roof over the bridge entrance, with the understanding that these features could be added in the future when our budget allowed. In some cases we even made provisions for the future addition of these items.
Finally on the technical side, the solution to enclosing the rock in the living room ended up being fairly simple once we realized that we could take advantage of the dry portion of the rock face. The decision was made to cast a concrete frame around the perimeter of the rockface to be exposed, leaving the crack out of the exposed portion so that the rock could continue to drain out naturally. Within the concrete frame we embedded bentonite rope as a natural sealer. Bentonite is a natural clay material that expands when it comes in contact with water, creating a flexible seal against the uneven rock face. On the top portion of the concrete frame we created a gutter against the rock face to collect and drain the rain water away to one side. The gutter is built up with roofing membrane and metal flashing against the rock face. We insulated the concrete on the inside face with rigid insulation and covered it with drywall, creating a nice color contrast between the grey rock face and the white walls. The inner edge of the concrete frame was skillfully crafted in bamboo, using the carpenter’s technique of scribing to cut the bamboo edges to closely follow the uneven surface of the rock face. This visually created a warm frame around the rock, and also a nice seating space.
The other technical question we are often asked is, “Is the rock face cold?” If we consider the rock as a massive object, it is easy to see that it would take a long time to heat or to cool such a massive object, so its temperature cannot vary much. We find that the rock stays at constant temperature of about 15 degrees Celsius all year long. So it gives a nice cool feeling to hot summer days, and in the winter it is still warmer to stand by the rock face than it is to stand in front of a window. There is in fact a lot more radiative heat loss through windows than through the exposed rock.
On a final note, I have to admit that even though I am used to seeing a rock in my living room everyday, from time to time when I enter the Rockhouse I also stare at it in disbelief… The disbelief comes from the feeling that there is more at work here than anything we could have originally conceived – the confluence of the site’s influence and the efforts of all the people that have believed in the vision and had a hand in bringing that vision into reality created something that is really outside of our hands, it has a life of its own. And again we humbly stand as little specs in front of this massive rock bluff.