Construction and Budget Information
Detailed information on the project budget and construction is provided on this page. Information will be added as construction progresses, with issues and solutions discussed.
The project architect is Greg Damant of Cascadia Architects in Victoria. The building program is a two-family residence for a young family of four, with active grandparents in a suite. As the front of the lot faces west, the building must maintain a suitable presence from the street while maximizing the southern orientation for solar heat gain in the winter. To provide separation of living spaces for two families on the sloping lot, the upper suite uses the front yard as outdoor space. The lot is on a quiet street and the yard can be landscaped for privacy. The secondary suite on the lower level is on grade, with the backyard as its outdoor living space.
Compared to most passive house designs, this project has a relatively complex form due to the lot shape & orientation, the program and zoning requirements. The complexity of the building form arises from the “T” shape, an enclosed garage outside the thermal envelope and a couple of other features incorporated to meet zoning requirements. PHPP calculations indicate that the building meets the passive house energy efficiency standard with increased insulation levels and some incremental construction costs. Meeting the required level of air tightness with all the nooks and crannies will challenge the construction team.
Given the goal of building within a budget typical of residential construction, costly design options are minimized and readily available building products are used.
The slab is a cold pour incorporating the footings, with walls formed on top of the slab
A significant portion of a building’s heat loss is through the concrete foundation and slab, creating uncomfortable cold spaces adjacent to the concrete. By placing insulation under the slab and on the outside of the foundation walls, those surfaces become warm in the winter and provide thermal mass to moderate daytime heating in the summer. Because the concrete slab will be warm in the winter, we contemplated finishing the slab to use as the finished floor, but for cost reasons have decided to install hardwood and tile. Our slab design calls for 16” of closed cell EPS foam under the slab and 12” on the walls. Structural EPS geofoam will be used under the footings. The slab will have a U value of approximately 0.11 (R value of approximately 50). Increasing foam thickness from 12” to 16” under the slab decreased energy demand significantly and will ensure a warm lower level even if the insulating value of the foam reduces slightly over time.
Bernhardt Contracting Ltd. installed the foundation and foam insulation.
Installing the sub-slab foam tray was more labour intensive than anticipated due to the amount of cutting required to form the footings and then fit blocks of foam in the remaining spaces. We look forward to the introduction of foam glass gravel to the Canadian market, allowing us to insulate below the footings and slab with recycled foam glass. It can trucked, moved and compacted like gravel, insulates and drains if becomes wet.
The complex building form arising from site and zoning requirements increases the buildings area to volume ration, requiring a higher level of insulation. We have chosen to add much of the additional insulation to the outside if the slab & foundation walls to minimize wall thickness, ensure a warm basement level and build in a design cushion to ensure we meet the Passive House standard. With construction almost complete, we have concluded we will use less sub slab foam in future projects. A simpler slab/footing design, and building form would significantly reduce costs. Part of this decision arises from how easy we found the rest of the construction to be – we now have the confidence of knowing the additional foam is not required to compensate for later “slips”.
The structural framing consists of a stud wall constructed with 8” studs, 24” OC sheeted with plywood on the exterior and OSB on the inside. A light 2” X 4” service wall inside the main structural wall provides the space for electrical and plumbing services. Both walls are insulated and will have an effective U value of 0.139 (effective R value of 35). This figure assumes 19% of the 2 X 8 wall is comprised of studs if sill plates, cripples, headers, etc. are counted. To ensure air tightness, the interior OSB will be continuous past the floor joists as the lower section of wall ends slightly above the upper floor. The floor joists are hung on a lintel mounted over the OSB. The ceiling will also be sheathed with OSB to ensure a continuous air barrier from the top of the concrete and across the ceiling. The wall is designed to ensure it is vapor permeable to the exterior, with a 3/4” air gap between the exterior sheathing and exterior cladding for ventilation.
The thermal bridge free design not only reduces energy consumption but improves building durability by eliminating condensation and mildew on interior surfaces. Thermal imaging and a blower door test will be undertaken by City Green Solutions prior to installing the interior service wall will detect any air leakage or cold spots which can be repaired before the walls are finished. Electricians and plumbers will be free to work in the service wall, but penetrations of the 8” structural wall are minimized.
Victoria Truss is providing trusses, joists and wall panels for the project. They have designed low profile roof trusses to keep the building within its height restriction while allowing room for insulation under the flat roof. Their service and pricing on prefabricated wall panels made them an attractive option, particularly when building during the wet season. The wall panels, joists, trusses and beams have been delivered & installed on schedule. The prefabrication of wall panels works well for high performance buildings. We will look into a higher level of prefabrication for future projects and are particularly interested in the advanced use of wood framing for larger buildings.
The framing is being done by Bernhardt Contracting Ltd. Although we tried to beat the wet weather, we managed to start framing just as the worst weather of the year arrived. The weather, and the fact we were doing this for the first time, slowed the process. Framing time and the foundation were the two areas we experienced cost overruns.
Windows and doors are some of the most critical components of Passive House construction. Windows exposed to winter sun provide most of the heating for the home, but cannot provide the thermal performance of a wall. Glazing is therefore planned to maximize solar heat gain in the winter through south-facing windows that are shaded in warmer months, and minimize north-facing windows. East and west-facing windows require shading from morning and afternoon sun in warmer months. Where windows are not shaded by deciduous trees, roof overhangs or trellises are planned.
Although it is possible to meet the Passive House Standard with good, rather than great, windows & doors, we have chosen to install great windows. A true passive house standard of window not only performs better, but provides superior thermal comfort, assures long term air tightness, permits more design flexibility and larger window areas. It is possible to use lower quality windows by increasing insulation or reducing window size, but we believe the small incremental cost of quality windows is money well spent..
After looking at a variety of manufacturers we have selected EuroLine Windows Inc. as the project supplier. EuroLine is North America’s largest manufacturer of European-style tilt and turn windows and doors, and have just introduced a Passive House standard of window. This line uses a Passive House Institute certified fiberglass/UPVC frame having a U value of 0.79 and Cardinal 180 triple-glazing with Edgetech SuperSpacers, giving a glazing U value of 0.73. The performance and quality of the product combined with their staff expertise, short delivery times, installation support, and warranty service made Euroline the clear choice for this project. In addition, they are a local manufacturer and produce a no-waste window, recycling materials at their factory.
Doors and windows are installed in the centre of the thermal envelope, mounted with screws and brackets rather than a nailing flange. Mounting windows on the edge of the thermal envelope using a nailing flange diminishes thermal performance by compressing the thermal gradient on one side of the envelope rather than balancing it in the centre. To maximize thermal performance rod & calk is used on both the interior and exterior of the frame (another benefit of no nailing flange) prior to taping the interior with air sealing tape manufactured specifically for sealing windows frames to the rough opening. A nailing flange is a quicker and easier installation, but not worth the minor saving in labour.
EuroLine’s service and installation company, EuroServices, completed the installation of all doors and windows in less than 3 days. As they manufacture the windows, the glass or doors can be separated from the frames to allow all windows to be installed from the interior by hand. There was no need to work from high places installing from the exterior or to use lifting equipment, even for the largest patio doors with sidelights and transoms.
The air tightness standard for Passive House construction is 0.6 ACH at 50 pa. This compares to 1.6 ACH for an R2000 residence and up to 10 ACH for older homes. To achieve this level of air tightness, the air barrier must be simple and continuous, preferably on the inside of the thermal envelope. We are using a continuous OSB sheathing on the exterior walls and upper floor ceiling for this purpose. All joints will be sealed with SIGA air sealing tapes, as will all penetrations for electrical, plumbing, and mechanical services.
We selected SIGA as it is one of the major international brands of quality air and wind tight products that can be counted on to deliver long term performance. Tapes and other products performing at this level are more expensive than tapes commonly used in North America, but can be counted on to perform with superior adherence, ability to stretch and to create a complete air seal over irregular surfaces. They continue to perform over the long term, maintaining their adherence and flexibility. SIGA has invested in domestic sales support and distribution, making it an easy choice for us.
A few photos of interior taping are below. Several different tapes are used, with tapes made specifically for interior and exterior use and on base joints, corners, windows, etc. Having different tapes may seem complicated but actually simplifies and improves application. We were surprised how easily the tapes can be applied and how well they adhere compared to the tapes commonly used.
The airtightness of the building will be tested twice. City Green Solutions performed the first blower door test on February 8, 2013. With the air barrier exposed at that time, we were able to identify and repair any leaks prior to framing in the interior service cavity and partition walls. Despite the complexities in the building enclosure mentioned earlier, the air tightness was very good. The passive house standard requires a result of 0.6 air changes per hour at 50 Pascal’s pressure. We achieved 0.27 ACH on the pressurization test and 0.35 ACH on the depressurization test, for an average of 0.31 ACH. As far as we know, this result is the second best passive house blower door test in Canada, with Tim Nagler in New Brunswick holding the record with the Nagler house.
City Green will return upon building completion to perform a second blower door test, which is used to determine if the building meets the passive house standard for air tightness.
We used blown in cellulose in the wall cavities. It is an economical and sustainable option that breathes well. When installed to the correct density, cellulose does not settle, fills all gaps, eliminating air movement. The walls were scanned with a thermal imaging camera to check for missed areas. The pressure of the cellulose caused the OSB to bulge between studs, making more work in framing the service cavity. A different process for blowing in the cellulose can be used to prevent this, or a stiffer interior sheathing product could be used.
The final critical component of a Passive House building is a highly efficient Heat Recovery Ventilation system. Modern systems are able to silently provide a constant supply of fresh air while consuming a minimal amount of energy to operate. Windows and doors provide natural ventilation whenever solar heat is plentiful (most of the year), but the HRV will operate most of the time. One HRV will service both suites and will cost $3-4/ month to operate continuously. A Zehnder ComfoAir 550 HRV will provide continuous ventilation for the residence.
If over 90% of the heat in the exhaust air is transferred to the incoming fresh air, the building requires only occasional heating from an active source. The main HRV supply duct will have a hot water heating coil in it to provide space heating through the ventilation system. A thermostatically controlled three-way valve will direct hot water to the hydronic coil if space heat is required. Given the quality of the ventilation and even temperatures through the building, an occasional supplemental heat source should keep all parts of the residence at 20 degrees Celsius. Some electric heat mats will be installed under the floor tiles in the bathrooms, which is an unnecessary luxury. Natural gas is the energy source selected for hot water and space heat due to its efficient heat production.
FortisBC is our natural gas supplier. They recognize the importance of energy-efficient construction as a key to a healthy future and are collaborating with the project team to offer innovative energy solutions for the passive house standard. Our plumbing & mechanical contractor, City Service Plumbing and Heating, have an interest in high performance construction and are pleased to be involved in the project. They have selected an Eco King condensing combi boiler with an indirect hot water tank and have worked with FortisBC and ourselves to fit all of the mechanical systems into a space the size of a closet. Electricity could have been our energy source for hot water and space heating. An electric hot water tank and heating coil costs less than gas to purchase and would not reduce thermal comfort. We chose gas because of its efficiency, lower life cycle costs and superior hot water production. A boiler and indirect hot water tank is perhaps the most expensive system to install, but it eliminates the “cold sandwich” effect of a tankless heater and ensures an adequate flow of hot water for two families.
The use of gas also helps to limit “primary energy” consumption. Primary energy is the term used by the Passive House Institute for the total energy required to provide a kilowatt of energy, including extraction, generation and transmission losses. Because gas is more efficiently extracted and delivered, using gas reducing the primary energy demand of the building. The PHPP energy model for this project indicates the primary energy demand will be 76 kWh/(m2 a), well within the 120 kW limit. The model also indicates our specific heating demand and heating load will be 11 kWh/(m 2a), again well within the 15 kW limit for the passive house standard. We have deliberately designed and constructed the building to fall well within the limits set by the passive house standard on our first project to provide a margin for error or adjustment during the certification process. With experience, costs can be reduced by designing to meet the passive house standard rather than exceed it.
Plumbing for a passive house is similar to any other residence, but some care is required to minimize building envelope penetrations and ensure the system design has all heat sources inside the thermal envelope.
The electrical system will be familiar to any electrician, with a few design differences designed to minimize penetrations of the thermal envelope. LED light fixtures will be installed in most locations and energy efficient appliances will help to minimize the electrical load. Given the budget objectives of the project, features such as computerized lighting control systems will be avoided. With energy efficiency being the core of this project, Canem is the logical electrical and building systems partner. They have sourced simple monitoring equipment to allow us to monitor electrical usage in real time and manage the information on mobile devices.
Finishing the Building
As the budget document linked to the text below illustrates, most elements of constructing a passive house are identical to any other building and need not be outlined on this website – there are many other sources of such information. The text above is intended to provide an explanation of the choices made for passive house specific features in this project. Other choices are appropriate for other projects. The standard does not dictate how energy efficiency is achieved, leaving it to owners, designers and builders to identify the best solutions in each situation. The partners in the Bernhardt Passive Home hope the information has been useful and would be pleased to discuss specific issues with you. Links to each partner’s website are found on the Partner’s page of this website.
The project is now (May, 2013) substantially complete and we are waiting for the results of our final blower door test before beginning the passive house certification process.
Photos of the (almost) finished residence …..
The Budget & Cost Details
With the exception of a few basic elements, construction costs are identical for passive house and conventional construction. The elements that differ are design, insulation, framing, doors & windows and mechanical. More design is required, more insulation, better windows and doors, and slightly more wood framing is used. The mechanical costs are, however, significantly less. To replicate the thermal comfort of a passive house, high quality radiant heating (usually hot water) is required in the floors and under windows. An HRV is still required to ensure air quality, although a less efficient model is adequate for conventional construction.. Passive design remains slightly more expensive than conventional, but is more affordable because of reduced operating costs. If the incremental construction cost is amortized with a mortgage, the energy and maintenance savings make the residence immediately cheaper to live in, without waiting for a payback period
A comparative budget of this project as a passive house vs. conventional construction can be found here. Click Here. This budget reflects our costs on this project. As outlined above, we have learned a number of lessons in this, our first passive house project and can reduce the incremental costs from those shown on this budget.
Does Passive House construction cost more? Depends. The simple building form favored by passive construction may reduce costs more than what a customer may have spent creating the same amount of living space with conventional construction. There are many factors and ways of looking at the issue. Whatever method of analysis is used, it is clear Passive House is affordable and, in almost all cases, cheaper to own and operate than conventional construction of comparable quality.
“The energy that buildings use for heating, lighting and cooling is the major component of their environmental impact – approximately 85% of the total life cycle impact for typical office buildings.”
- LEED; Cole & Kernan, 1996; Winistorfer and Chen, 2004;
Trusty & Meil, 2000; CORRIM, 2004