Passive Approaches to Low-Energy Affordable Housing

Canadian Property Valuation Magazine

Search the Library Online

2017 – Volume 61 – Book 3

Passive Approaches to Low-Energy Affordable Housing

CMHC

Share:

PDF

Passive approaches to low-energy affordable housing

An introduction to the benefits, technologies, costs and best practices

Submitted by Canada Mortgage and Housing Corporation (CMHC)

Affordable housing providers are increasingly interested in energy-efficient housing models that can achieve improved levels of building performance in support of lower cost housing and better quality living environments. For many, the rising cost of utilities can make even the lowest-cost housing unaffordable, or force them to make hard choices between utilities, groceries and other basic needs. For housing providers, high energy bills or operating and maintenance costs can significantly reduce the money they have available for other much-needed expenses, like repairs or client services. Fortunately, in recent years, innovations and experience in more sustainable affordable housing development have made it more accessible and financially viable.

One of the most promising ways to meet both affordability and environmental goals is through a better building strategy that uses ‘passive’ approaches to design and construction to significantly reduce energy consumption, while creating a comfortable, attractive and healthy living environment. To help affordable housing providers explore this new approach in affordable multi-unit residential buildings (MURBs), Canada Mortgage and Housing Corporation (CMHC) carried out a comprehensive literature review of existing research and projects in the field.

The goal of the review was to:

• Identify promising passive design strategies and technologies for low-energy and affordable MURBs;
• Identify real-world projects that have successfully implemented passive low-energy approaches in their design and construction; and
• Identify some of the challenges, costs and benefits associated with passive low-energy affordable homes.

What is ‘passive design?’

‘Passive design’ refers to any technologies, construction methods or other strategies that increase energy-efficiency, reduce operating costs and improve indoor environmental quality, without the need for expensive and overly complex mechanical or energy systems.

This includes relatively simple and inexpensive improvements like increasing the amount or performance of a building’s insulation, reducing thermal bridges, creating air-tight building envelopes, using high-efficiency space conditioning (heating and cooling) systems and incorporating Heat Recovery Ventilators (HRVs) to maintain comfort, provide good indoor air quality and control moisture.

Existing high-performance labels, programs and standards

There are a number of high-performance and energy-efficiency labels, programs and standards in use today, which incorporate passive low-energy design features and technologies. These include such industry-leading initiatives as:

• Leadership in Energy and Environmental Design (LEED) certification programs developed and delivered by the U.S. Green Building Council (USGBC) and Canada Green Building Council (CaGBC);
• Passive House Standard by the international Passive House Institute;
• Net-Zero Energy Home initiatives like the CHBA’s Net Zero Energy Housing Labelling program, the US DOE Zero Energy Ready Home program and CMHC’s EQuilibrium™ Housing Demonstration Initiative; and
• Living Building Challenge by the International Living Future Institute (ILFI).

Numerous affordable housing projects across Canada and the U.S. are using these programs to achieve extremely high levels of energy performance at a minimal additional cost. Some of the examples outlined in the report included:

Table 1: Canadian and U.S. construction and retrofit projects outlined in CMHC report: Passive Approaches to Low-Energy Affordable Housing.

Passive design technologies and design practices

As the project examples show, passive low-energy design principles can be used with a wide range of construction practices, methods and materials. The ‘best’ choices often depend on where a project is located, the building type and design, current material prices as well as the experience and preferences of the builder or developer.

In general, however, many of the passive, low-energy affordable housing projects tended to feature common design elements and attributes, such as:

• High-performance wall systems with high levels of blown or sprayed insulation; 38 x 89 mm (2×4-inch) or 38 x 140 mm (2×6-inch) wood-frame construction with significant exterior rigid foam insulation; or Structural insulated panels (SIPs);
• A focus on eliminating thermal bridges through the building envelope to minimize heat loss;
• Strategically-placed, high-performance triple-glazed windows with inert gas fill, thermally-broken and insulated frames, warm edge spacers, low-emissivity coatings, multiple airtight seals and external shading;
• An airtight building envelope with a minimum airtightness of 0.6 ACH₅₀; and
• Heat Recovery or Energy Recovery Ventilators (HRVs and ERVs) to improve indoor air quality while saving energy and lowering costs.

The costs and benefits of passive design

The incremental cost of integrating passive low-energy design practices can vary considerably from one project to the next. For the projects reviewed in the study, the additional cost was found to be from 5-10% of the total cost of construction.

Affordable housing projects tended to have a slightly higher incremental cost, since they often have a lower base cost to begin with. Instead of focusing solely on incremental costs, however, the projects identified tended to look at how the costs and benefits of the affordable passive low-energy design projects compared to the cost of similar projects that don’t have these features.

To offset the upfront investment, it is important to remember that passive low-energy design features can achieve significant long-term energy and operating savings throughout the entire lifecycle of a building. This includes both reduced energy consumption and lower utility bills, as well as a variety of non-energy-related benefits to affordable housing providers, such as:

• the avoidance of rate subsidies;
• lower bad-debt write-offs;
• reduced carrying costs for arrearages;
• fewer notices and customer calls;
• fewer shutoffs and reconnections due to delinquencies; and
• an increase in overall property values.

Interviews with key experts

As part of the study, a series of interviews about passive low-energy design approaches were conducted with leading affordable housing providers, experts and stakeholders from across Canada and in the U.S.

Table 2: Stakeholders interviewed by CMHC about Passive Low-energy Housing.

As a result of those interviews, the study was able to identify some of the main needs, challenges, benefits and trends of passive low-energy housing approaches from some of the foremost experts in the field. Their responses were then grouped into five key categories:

1. Reasons to pursue low-energy affordable housing:

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

2. Requirements to implement successful passive design measures:

• Have few or no occupant controls.
• Address the lack of trained building operators and high turnover.
• Accommodate occupants who open windows in winter.
• Be simple to design, commission and operate.

3. Tenant education initiatives Introduced after project completion:

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

4. Benefits of low-energy passive design:

• Lower utility costs.
• Better indoor air quality.
• More comfortable and quieter living environments.
• Lower tenant turnover.

5. Barriers to adoption of passive low-energy design principles:

• Lack of examples of larger passive low-energy MURBs to demonstrate lower construction costs, lower utility and O&M costs, and tenant feedback.
• Management commitment to other rating systems which 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 turn-around 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.
• Developers are often reluctant 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.

Find out more

For more information about the benefits, features, costs and best practices of incorporating passive low-energy design principles into your next affordable housing project – including an in-depth look at the leading techniques and technologies, interviews with affordable housing providers and other stakeholders, as well as dozens of real-world case studies from across North America – download your free copy of the CMHC Research Report:

Passive Approaches to Low-energy Affordable Housing Projects – Literature Review and Annotated Bibliography at www.cmhc.ca or call 1-800-668-2642.