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What is a Passive House?

What is a Passive House?

A Passive House requires very little energy to maintain a constant, pleasant temperature. In this sense, such buildings are almost “passive” as they need hardly any active heating or cooling to stay comfortable year-round. Passive House reduces ecological impact and results in high-performance buildings that require little energy for space heating or cooling.

A Passive House design also allows for the building to use heat from natural heat generators, such as body heat and appliances, to heat the building; all while continuously feeding fresh air throughout. It has a super-insulated envelope encompassing all exterior walls, floors, and roof, ensuring that the ventilation system works as efficiently as possible. Perhaps more importantly, it is also key to preventing moisture damage and mould growth: in conventional buildings, gaps in the building structure allow air to pass through and thereby cool down. This can result in condensate that can put the building at risk. This is not a concern in Passive House buildings. Imagine wrapping a building up in a wool hat and scarf!

Advantages of a Passive House building:

Comfortable & Healthy

  • Summer and winter comfort
  • No draughts
  • No cold surfaces or downdraughts
  • Good indoor air quality
  • Silent ventilation

Affordable & Low energy

  • Lower running costs
  • Minimal heating
  • Efficient services, lighting and appliances
  • Addresses energy security


  • Focus on minimizing energy consumption
  • Can incorporate other environmentally friendly features
  • Helps raise awareness of general environmental issues

Project Context

YWCA Hamilton serves women, girls, and families in Hamilton and beyond, providing developmental, health and wellness, youth and childcare, workforce development, immigration and settlement services, in addition to women’s housing services. YWCA Hamilton is actively involved in issues related to our mission of empowering women locally, including racial and social justice for trans, non-binary, and gender-fluid folks, and domestic and gender-based violence prevention and education, victim advocacy, youth programming, and affordable housing for low-income individuals.

The new Putman Family YWCA, located in Hamilton, Ontario, is a 50-unit, mixed-use, affordable housing complex. The facility has 6 levels with approximately 4,695 m2 gross floor area. YWCA Hamilton identified the PHI Passive House Classic standard as the preferred pathway for achieving near zero operational emissions in new affordable housing buildings (and reconstructions). In addition to being designed and constructed to the Passive House Institute (PHI) Passive House Standard, the project also features sub-metering of the individual units to provide useful data on building operations as well as future learning possibilities.

Once complete, the complex will help to address the City of Hamilton’s affordable housing crisis by creating 50 affordable housing units for women and children – 15 of which have been specifically designed for women living with developmental disabilities.

Putman Family YWCA

Building Envelope

According to an interview with key staff on the project, both sustainability and fiscal responsibility were the primary guiding factors for the design of this project; the two are not mutually exclusive. By employing the use of prefabricated tilt-up construction, the YWCA was able to reduce the cost and time of construction as compared to a typical passive house building of this type and size. This efficiency was achieved primarily through prefabricated construction assemblies, utilizing precast concrete sandwich panels that integrate both the structure and the envelope into a single component.

Side view of Putman Family YWCA
Side view of Putman Family YWCA

The precast concrete sandwich panels did, however, result in shorter time on site, despite the longer than anticipated production lead times. The sandwich panels featured three layers of sealant; a face seal with secondary seal that moves to the exterior, the two forming a weephole at the bottom of the panel joints, and tape on inside, providing redundancy in air barrier and water management.

Finding suitable window and door frames (including hardware) on this project proved to be exceptionally difficult. Many products typically used in Passive House construction are not yet certified to Canadian standards, and in fact, most of these products originate from Europe. Window and doors frames, and their locking hardware, are a prime example of this.


Efficient detailing and redundancy are critical design features in Passive House buildings. The design team’s attention to detailing on this project created execution challenges for the construction team. Creating a triple seal at the precast concrete sandwich panel joints – part of the air barrier system – proved to be a challenge to install, and sourcing of certain high-performance components such as the fiberglass threaded rods used to secure the interior and exterior portions of the precast concrete sandwich panels added complexity to the procurement team’s efforts.

Air tightness is a key feature of passive house buildings, and the Putman Family YWCA is no different. The precast concrete sandwich panels serve as the primary air barrier, and redundancy at the panel joints is key to longevity in this system. At the exterior of the precast sandwich panel joints, a combination of two sealant joints create a rainscreen with weepholes at the base of every panel and serve as the exterior air barrier, while an additional sealant joint at the interior of the panel joints forms an interior air barrier. Finally, all precast concrete panel joints were taped at the interior to provide added redundancy to the air barrier system. Schilthuis (the general contractor) performed all air sealing and taping themselves to ensure the quality required for a reliable air barrier system. This is their approach to address another important QA/QC challenge of air sealing. Advance training and ongoing site surveillance are required to achieve the air tightness target.

Policy Context

Canada has committed to a goal of reducing greenhouse gas emissions to net zero by 2050, with a 2030 target of emissions reductions to 30% below 2005 levels (Canadian Institute for Climate Choices, 2020). In alignment with the Paris Agreement within the UN Framework Convention on Climate Change to keep increases in average global temperature below 2℃ above preindustrial levels, Ontario has also committed to reducing its emissions by 30% below 2005 levels by 2030. Ontario’s building sector is responsible for 19% of its energy use, equating to 14% of its total greenhouse gas emissions (Province of Ontario, 2019).  In 2017, The Atmospheric Fund (TAF), in partnership with the City of Toronto supported the creation of The City of Toronto Zero Emissions Buildings Framework, defining global best practices and energy efficiency policy, and evaluating the implications of passive design strategies for building construction (Provident, Morrison Hershfield, Integral Group, 2017).


Specifically, for the Putman Family YWCA, the capital cost premium has been calculated to be 3%. With the significantly lower operating costs anticipated, the capital investment will be largely reimbursed in a few years.

Numbers of studies support this finding. Here are a few examples.

In 2014, Pennsylvania adopted an approach to provide points to passive house (PH) projects in the evaluation of affordable housing project proposals, many affordable housing project proposals were submitted that showed little to no extra capital costs compared to other proposed projects (McDonald, 2015). In 2015, they received 85 multi-family project proposals, of which 39 were awarded funding and 7 of those projects (totaling 422 units) were passive house.  Overall, costs of the proposed projects showed negligible difference between PH and non-PH projects:

  • 32 PH projects (37.6% of projects) – Average cost = $1,825/m2 ($169/ft2)
  • 53 NON-PH projects – Average cost = $1,780/m2 ($165/ft2)

A similar experience was also reported in Philadelphia:

  • 7 PH projects (30.4% of projects) – Average cost = 2,300$/m2 ($213/ft2)
  • 16 NON-PH projects – Average cost = $2,200/m2 ($204/ft2)

According to data from the Pennsylvania Housing Finance Agency (PHFA) on low income housing tax credit (LIHTC) applications awarded 2015 through 2018, the first year of passive house projects showed a 5.8% cost premium over the agency’s conventional construction affordable housing projects, the second year a 1.6% cost premium over conventional construction, and the third year PHFA projects designed with conventional practices cost 3.3% more per square foot than the passive house projects (Legere, 2018).

Based on PHFA’s listing of projects awarded LIHTC’s during these years, cross-referenced with projects registered in the Passive House Institute US (PHIUS) database, the majority of PHFA’s 2015 passive house projects receiving low income housing tax credits were designed to the PHI Classic Passive House Criteria. PHFA’s 2016 passive house projects were an even mix of those designed to meet PHI Classic criteria and PHIUS+ 2015 criteria and PHFA’s 2018 passive house projects, which cost 3.3% less per square foot than their conventionally constructed affordable housing projects, were all designed to meet PHIUS+ 2018 criteria (Klingenberg, 2019).

(Steffen, 2019) examines the costs associated with different phases of a multi-family housing project and found that 68% of cost was spent on construction cost. The remaining costs were distributed between developer fees, consulting, and other fees. (Steffen, 2019) recommends using Cost Efficient Design and Construction (CEDC) approach which utilizes standardization, repetitions, and prefabrication. The objective of this approach is not to rush the construction project, but rather to reduce cost to generate substantial savings through efficient layout and optimization. The approach suggests standardizing components such as foundation system, structural, MEP systems, and typical interior finishes, just to name a few. Customized components include building plan/layout, building form/massing, and a few select unit plans, amongst other components.

Aside from capital costs, there are other cost benefits associated with adopting passive house design. Schweitzer and Tonn (2003) conducted a literature review to examine non-energy savings cost-benefits of weatherizing low-income homes (CMHC, 2018).  Savings were divided into three major categories and each with subcategories: ratepayer benefits (payment related benefits, service provision benefits), household benefits (associated with affordable housing, and those related to safety, health and comfort), and societal benefits (environmental, social or economic). The study found a total lifetime non-energy related benefit of $3,346 (2001 dollars) per household, with societal benefits much larger than the ratepayer and household benefits. Non-energy cost-benefits were estimated to be higher than the net-present value of energy savings value of $3,174.


The advantages of building to the PH standard are undeniable and positive. As an affordable housing provider, the YWCA Hamilton offers a wide range of services for tenants and the community, and takes pride in the new Putman Family YWCA recently built. Indeed, passive house buildings are more comfortable with a steady temperature throughout, are quieter and the indoor air quality is better than in regular building. Because the population the YWCA serves is in general more prone to have a sensitive health, all of these benefits provide an additional level of comfort to the tenants. Additionally, passive house buildings are more climate resilient and can provide shelter in case of heat wave or winter storms. Additionally, the aggressive energy efficiency targets are appealing to the YWCA Hamilton as it aligns with the vision of providing quality and resilient housing to the vulnerable population accessing their services.

According to a study published by Canada Mortgage and Housing Corporation (CMHC, 2018) on building affordable housing using passive house design, interviews were conducted with housing providers and stakeholders from the Canada and the US. The following responses were gathered:

Reasons to pursue low-energy affordable housing:

  1. Meet the requirements imposed on affordable housing providers.
  2. Achieve higher levels of performance to meet future code requirements.
  3. Lower utility bills for tenants and/or affordable housing providers.
  4. Reduce maintenance and replacement costs.

Requirements to implement successful passive design measures:

  1. Have few or no occupant controls.
  2. Address the lack of trained building operators and high turnover.
  3. Accommodate occupants who open windows in winter.
  4. Ensure measures are simple to design, commission and operate.

Tenant education initiatives introduced after project completion:

  1. How to reduce overall energy consumption.
  2. How to operate an HRV/ERV.
  3. How and when to open windows for passive cooling.
  4. How to adjust to the slower response time of ground source heat pumps.

Benefits of low-energy passive design:

  1. Lower utility costs.
  2. Better indoor air quality.
  3. More comfortable and quieter living environments.

Lower tenant turnover.

Risk and Challenges

As with any design project, there are barriers that present themselves along the way. Some challenges specific to passive house design as discussed with housing providers and stakeholders include:

  • Lack of examples of larger passive low-energy multi-residential buildings to demonstrate lower construction costs, lower utility and operations and maintenance costs, and tenant feedback.
  • Management commitment to other rating systems that may make it difficult to adopt different approaches.
  • Lack of awareness of innovative technologies and practices by authorities having jurisdiction over building design approvals.
  • Short turnaround time from when projects are awarded funding to when finished designs are required (approx. three months on average), which doesn’t leave enough time to support new design approaches, conduct performance modelling, or try new things.
  • Frequent reluctance of developers to build passive low-energy housing if they have limited availability of key components and need to sole-source products such as high-performance windows or HRVs.
  • Additional risks and challenges will be detailed in the final report, along with strategies for mitigating risk that have proven useful on other affordable passive house MURB’s.

Lesson Learned

Staff, Consultants and Contractors

Engaging the right staff, consultants, and trades on a passive house project of this type was key. Without buy-in from all parties, the Putman Family YWCA could have gone much differently at several points in the project. Contractors with previous passive house experience are key, as otherwise the learning process will take additional unnecessary time that the project may not be able to afford.

Engaging sub-contractors early in the process is helpful. This can ensure trades receive the proper education on Passive House principles, and how they relate to their work. Schilthuis chose to perform air barrier detailing themselves, rather than engage a subcontractor for this work, to provide a higher degree of confidence in the quality of the air barrier detailing. This also allowed for quicker rectification of deficiencies.

In addition, involving the precast concrete manufacturer and ordering windows and doors earlier in the process would have reduced production delays significantly.

It was noted that Passive House specific training for the Contractor was also not readily available locally. Without a widely available training program, contractors with experience become even more important to the process. Passion from all parties was key, you get what you pay for. Cultivating the patience and persistence to collectively find solutions was critical. The impetus to rush and an ‘us vs. them’ mentality does not work well on these projects.

Construction Process

Setting clear design requirements from the beginning of the project is very important. As are clear expectations, lines of responsibility, and lines of communication. Continuity with consultants from project start to finish is also an important factor, as less time is required for onboarding of new consultants.

A contract administration software was proposed by the Architect (Rform), through which all project information flowed including submittals, drawings, change orders, etc. This software greatly simplified the review process and provided a high degree of clarity throughout the project.

A key lesson learned is that windows and doors must be ordered as early as possible in the construction process. Although interviewees noted that this seems to be getting better with time, limited local availability of key materials for Passive House projects is a common problem. One suggestion made by interviewees was to ensure specifications are performance-based and broad enough to allow flexibility in system and product selection.


For Passive House project, the contingency should be higher than usual in case of key change orders. Additionally, a long approval process can delay construction, if possible, streamline this process ahead of time. A clear decision-making process has to be in place before the start of the project to avoid delays.

Hiring a cost consultant at the beginning of project incentivized to predict lower costs. Clarity, transparency and realistic expectations should be delineated when starting the project.

Ultimately, a high initial investment and operations provides long term benefits.

Tenant Education/ Post-occupancy Evaluation

The following sections summarize key information and findings from post occupancy evaluation discussions with the Facilities Team.


Consultations with the Facilities Team identified various gaps in residents’ understanding on the differences between a conventional building and a Passive House building. Many residents do not understand passive heating and cooling strategies, and the length of time required to heat or cool a space within a Passive House building.

Many residents have a low understanding of how to operate their thermostat and how the use of the thermostat impacts their space. Thermostats in each unit have a 4°C range of operation, giving residents a limited range of temperature control from 18°C to 22°C. This is a problem for many residents, as there have been complaints about the temperature being either too warm or too cold. Many residents are not accustomed to Canadian temperatures and require more temperature control within their unit to suit their needs.

Putman Family YWCA have distributed operation guides to educate residents on how to operate their thermostats, and strategies to maintain a comfortable temperature within their units. Moving forward, Putman Family YWCA plans to review opportunities for widening temperature range parameters and resident surveys will help to better understand resident comfort levels.


Through consultation with the Facilities Team, it was discovered that residents have minimal understanding of how to operate windows in their units during different weather conditions. Various complaints about temperature were due to windows being open when they should have been closed and vice versa.

Putman Family YWCA have distributed operation guides to educate residents on how to operate windows during different weather conditions to control for comfort, and how they impact overall building systems and conditions. Putman Family YWCA plans to conduct monthly audits to determine the frequency of windows being opened and closed, and to conduct biannual in-suite checks to ensure windows are operating effectively.

While most tenants find it comfortable to operate windows, those with larger sized operable window panels as well as those with some forms of disability are experiencing difficulty opening/closing windows. Facilities staff find maintaining the windows to be difficult, noting that larger, heavier windows seem to fall out of alignment the more they are used, requiring realignment of the latches that hold them closed. This is resulting in penetration of air, water (leakage) and sound, with some residents experiencing outdoor sounds as if the windows were open. In the future, procurement of specialty items, specifically windows and doors are noted as a longer-term concern due to both costs and lead times.

Air Quality:

Through discussions with the Facilities Team, it was discovered that residents are unaware of how to control the humidity levels in their units, and how the building system works to filter air and maintain air quality.

Putman Family YWCA has distributed operation guides to educate residents on the impacts of outdoor pollutants, how to maintain indoor air quality, and how the building system cleans and filters air. Putman Family YWCA plans to conduct biannual in-suite checks for signs of high humidity and the development of mold. Surveys distributed to residents will help the Facilities Team understand the levels of humidity and air quality within each unit and determine modes of action.


The newly installed condensing dryers take twice as long as conventional dryers, and the dryers installed are smaller than the washing machines. This resulted in people overloading the dryers, which affects the drying time even more. For future projects, the dryers should have the same capacity than the washers, and should cost less per cycle so tenant can run them twice if needed.


From a facilities side, while there is a strong response for overall design and staff note operating the building as easy to average, maintenance staff find it difficult to maintain HVAC systems. Although the equipment is new, some components have failed requiring complete replacement, and system issues have sometimes caused complete system failures for an entire floor. Staff note a desire for further training in building systems for better understanding of operations.

The interim report available from UofT and CMHC highlights the various issue encountered with the mechanical system. The commissioning has been a long and challenging process mostly because of the air balancing. It’s been found that there might be an air leakage in ducts substantial enough to unbalance the system. As a reminder, this system has been designed in 2018. The mechanical equipment currently available has already improved significantly and the trades have received more training.

An informative session explaining the basics of PH has been held for tenants and staff and educational material has been distributed to tenants as well. While helpful, having these in place at the time of occupancy could help in mitigating some early resident complaints.

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