The passive house building standard requires the envelope to have a maximum heating and cooling demand of 15 kWh per sq. metre per year.By Bruce Nagy
Vancouver is arguably one of the most overachieving cities in Canada, where they are consistently looking to push boundaries. Apart from the 44 per cent chance of rain on any given morning, the crazy cost of real estate, and the Canucks; Vancouver is just about perfect. (Sorry to any Canuck fans out there).
In the last few years, one of Vancouver’s (and B.C.’s) focus has been on setting an example when it comes to environmental policy and green buildings. While Ottawa grapples with selling its carbon tax to some provinces, B.C. has had one in place since 2008 and has managed a steady GDP growth ever since.
In 2015, Vancouver created a new policy targeting 100 per cent renewable energy and then in 2016 added rules requiring new builds to produce zero emissions by 2030. All buildings in the city are set to do the same by 2050.
The original No. 17 Firehall was built in 1955This year it created a net-zero energy program that provided design and construction funding to help developers become cleaner. A new industry training program was also developed regarding passive housing. The passive house building standard requires a super-insulated envelope with a maximum heating and cooling demand of 15 kWh per square metre per year. This dramatically lowers the code for already built homes in most places. In addition, buildings must not leak more air than 0.6 times the house volume per hour (n50 ≤ 0.6 / hour) at 50 Pa (0.0073 psi). There are additional requirements and minor variations between the German Passiv Haus Institute and the USA group.
Reduced load calculations
The term “passive house” is mentioned increasingly in news out of Vancouver and is part of a Bellwether fire station retrofit now under construction in the city. The Firehall No. 17 project in south Vancouver started with the ambition to make the build a passive house and use geothermal. “People thought we would have to give up something to go green,” says Tyler Moore, deputy chief. “But as it turns out we didn’t.”
The retrofit is basically a rebuild involving the creation of a fire station, training, and emergency centre that will be about twice as big as the seismically unsafe 1955 building that previously stood on the site. Since a temporary station is continuing to operate during construction, and the new building will cover most of the lot, project manager Scott Ghomeshi of Integral Group in Vancouver was concerned that they would have difficulty squeezing enough geothermal into the available space to hit net-zero energy for an 18,000 sq. ft. building.
“The building would require 70 boreholes if built conventionally, which would not have worked within the existing site’s context. But given the Passive House high-performance building envelope required by the city, 12 wells are all we needed, which coincidently just fit within the limited space available on-site. We only need 12 but we’re drilling 15 to make sure we mitigate constructability concerns and allow for added field capacity in the face of climate change.”
Emergency resilience
The reality of life on the west coast is that the area has been deemed highly vulnerable to earthquakes and other natural disasters. In addition to accommodating emergency services and training, the new building will serve as a post-disaster emergency hub. It is being fitted with backup power, advanced IT, radio, SCADA, and traffic control communications equipment.
The building will be heated and cooled using ground-source heat pumps with four-pipe coils for terminal units and six-way valves that modulate.These compounded the complexities of designing for net-zero, and the city website says the project is “being used as a demonstration project to develop a new zero-emissions building standard for future City of Vancouver owned buildings.” The project is under a public microscope, the goals are ambitious, and of course, aspirations are occasionally changing.
“Eventually we came up with a design that adds to our resiliency,” says Moore. “It’s environmentally sound without any impacts on operations and we were able to add the training centre, which previously was in a remote location.”
How it works
“A geo-exchange field coupled with ground source heat pumps is the primary heating and cooling system, with four-pipe fan coils for terminal units utilizing changeover coils and six-way valves that modulate accordingly,” says Ghomeshi. The goal is to effectively condition the space while keeping carbon emissions at zero. They would be about 33 tons in an equivalent code-built structure. Energy use will increase about 25 per cent for the special communication equipment.
“We worked with the architect to locate the heat pump water heater next to the data communications rooms, so that waste cooling energy from the water tanks can help with conditioning the data/communication rooms. Our rough calculations land us in the realm of reducing the cooling energy consumption for these spaces by 20 per cent.”
A conventional build on the site would normally require around 70 boreholes, but since the city was looking for Passive House accreditation, they were able to design the project using only 12 boreholes and drilled 15 to ensure constructability concerns.In addition to coils, geothermal is used for some radiant heating in the slab of the turnout area. This is oftentimes a very wet section of the station, where fire and emergency workers remove, decontaminate, and hang clothing and gear after returning from a call.
Quick response to emergencies
Geothermal is quite common for us, but it is not always the answer,” says Jay Lin, project architect for Firehall 17 with HCMA Architects. “The selected system has to continue to perform for our client and provide value down the road. We don’t just chase LEED points. Operations were an overriding concern in this case. We created a whole new firehouse design that, for example, makes turnout time-optimal when the alarm comes in. They want to get out there fast, in a safe manner, from wherever they are in the facility – that is the paramount goal.”
He notes that most of the passive house projects designed by HCMA have been residential, but there seems to be a push into commercial, institutional, and public education building types.
The fire station retrofit project is under the microscope as the city looks to develop environmentally sound projects.Bells and whistles
The dynamic glass windows offer both glare reduction and energy savings, which can change the heat gain co-efficiency by about 60 per cent, reports Ghomeshi. This translates to around a 14 per cent reduction in overall HVAC load.
In addition, the electro-chromatic window shading is integrated into the controls function. Sensors pick up shading and heat requirements, and the sequencing allows for the glass to activate or deactivate to mitigate or harness heat as required, he adds.
The fire station is expected to be certified gold under LEED version four and to reach its goal of net-zero.
Green building
The building will save 40 per cent on water with low-flow plumbing and drought-resistant, low-maintenance landscaping. It is expected to exceed the city’s standard for green demolition, diverting about 85 per cent of construction waste to recycling rather than landfill.
“I think the most important achievement is that there is no gas whatsoever being used in normal operations,” says Moore. “Climate change is important, and this building implements a very robust strategy that sets the tone for what the city of Vancouver stands for.”