Roof replacements: The impact on energy and carbon emissions

by arslan_ahmed | March 15, 2024 6:06 pm

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By Justin Koscher

With the aim of lowering greenhouse gases (GHGs) by 40 to 45 per cent by 2030 and achieving net-zero emissions by 2050, Canada is transitioning toward a clean growth economy. To meet these sustainability targets, Canadian policymakers are turning their attention to the built environment. As the country’s third-largest carbon emission source (responsible for more than 18 per cent of national carbon emissions),¹ the building and construction industry holds much potential for change.

Retrofits hold the key to climate-adaptive building envelopes

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While new construction can easily accommodate modern energy efficiency technology and adhere to the latest building codes, the existing building stock can also be addressed with cost-effective strategies to the aggressive energy savings and emission reductions necessary to mitigate climate change. After all, of the existing building stock in Canada, about 70 per cent is expected to still be in use in 2050.² While the structures may remain standing through the years, the rapidly changing climatic conditions, increasing requirements for energy-efficient building envelopes, and evolving building codes can require building improvements.

Since many of the structures in Canada’s existing building stock were built before the widespread adoption of modern building energy codes, many of them are under-insulated. This is concerning as the country is already experiencing the impacts of a changing climate.³

To further illustrate the severity of the situation, consider more than 85 per cent of building sector emissions come from space and water heating, as well as the extra energy required to heat and cool buildings with insufficient envelope performance.⁴ The elevated energy consumption can overwhelm a building’s heating and cooling systems, and escalate building utility expenses as well.

In such scenarios, retrofitting building components with high-performance insulation to maintain stable thermal temperatures can increase the energy efficiency of a building. Going one step further, roof replacements are one of the most common and effective envelope retrofits⁵ for existing buildings due to the relative size of the building component.

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Achieving energy efficiency through roof replacements

The Polyisocyanurate Insulation Manufacturers Association (PIMA) commissioned a third party-facilitated study⁶ to quantify the benefits of energy code-congruent roof replacements, in terms of lifetime energy and carbon emissions. The study considered generation-weighted national-level energy commodity prices, escalations, and emissions factors combined with building types and city-specific weather data to estimate the following impacts and benefits across Canada:

• Energy impacts—Building energy models were developed to represent the baseline and intervention or code-congruent scenarios.⁷ Both sets of models were simulated to produce estimates of whole-building energy use and their energy use was subtracted to produce incremental energy savings.
• Emissions impacts—Emissions impacts were developed directly from energy savings as the product of energy savings by fuel type and its corresponding national-level emissions factor.
• Economic benefits—Energy benefits (or cost savings) were calculated as the product of energy savings by fuel type and its corresponding national-level fuel price⁸ and then combined with secondary literature research on incremental material and labour capital costs to produce life-cycle economic metrics over a 30-year timeframe.

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With respect to the studied 30-year timeframe, anecdotal evidence suggests the average service life of a roof system is between 20 and 40 years. Various factors can influence the lifespan of a roof and systems may be rehabilitated or recovered to preserve the function of existing components. At the end of its service life, a typical roof system is removed and replaced with a new roof system, including insulation. The 30-year timeframe used in this study was selected as an average, conservative estimate for roof system and component service life for all building types studied.

Proof in results

The detailed analysis evaluates energy savings through code-compliant roof upgrades (during roof replacement) in commercial structures with low-sloped roofs located in Climate Zones 4, 5, 6, and 7A, as described in the National Energy Code of Canada for Buildings (NECB) 2020. Within these commercial structures, the building typologies in focus are primary schools, retail stores, strip malls, and small offices.

This independent analysis indicates energy-efficient roof replacements on commercial buildings located in Climate Zone 4 (mixed climate areas such as Vancouver, B.C.) can generate whole-building energy savings of 4 to 8 per cent annually. Those in Climate Zone 5 (cooler climate areas such as Toronto) stand to save 6 to 10 per cent annually depending on the building type. Commercial buildings in Climate Zone 6 (cold climate areas such as Montreal) and Climate Zone 7A (very cold climate areas including Edmonton) are positioned to generate up to 11 per cent annual energy savings by integrating code-congruent roof insulation in their existing building envelopes.

The study results reveal that by specifying increasing levels of roof insulation installed above the deck, specifiers can help building owners economically reach energy reduction goals. Whether the aim is to regulate temperature and control moisture to prevent mould growth (Climate Zone 4), or regulate cold seasonal temperatures and resist heat loss (Climate Zones 5, 6, and 7A), high-performing insulation materials such as polyisocyanurate (polyiso) can help meet performance goals for buildings and reduce energy consumption by 4 to 11 per cent annually when roofs are replaced.

Polyiso, as a rigid foam board insulation, has one of the highest thermal resistance (R-value per inch or RSI per mm) compared to other insulating options. As a result, it provides excellent resistance to heat transfer, which lowers space heating and cooling requirements, and minimizes energy consumption to maintain consistent and comfortable indoor temperatures.

Moreover, polyiso panels are manufactured in incremental thicknesses typically ranging from 25 to 115 mm (1 to 4.5 in.), with greater thickness options available from manufacturers. The long-term thermal resistance value for polyiso insulation is 1 RSI (R-5.7) for 25 mm (1 in.) boards, and polyiso roof insulation boards are typically manufactured with a labelled compressive strength of 138 kPa (20 psi) or 172 kPa (25 psi). The sheets are easy to handle and lightweight, enabling building teams to achieve the desired thermal performance in a multi-layered system of polyiso boards with joints staggered. Polyiso’s proven thermal performance makes it a popular choice in residential and commercial applications to insulate roof assemblies, as well as wall systems and below-grade applications.

Within roof assemblies that have been tested and evaluated for fire performance, polyiso can be attached directly to steel decks, without needing an additional thermal barrier product such as gypsum board. In addition, a wide range of roof assemblies that include polyiso insulation have been evaluated to meet the requirements of the National Building Code of Canada (NBC). Building designers will find energy-efficient roof assembly options that meet the NBC requirements for interior and exterior fire exposure, as well as other critical performance metrics such as wind uplift. By specifying code-congruent levels of polyiso insulation during roof replacement retrofits, building designers and specifiers can deliver resilient, energy-efficient building envelopes, and simultaneously reduce carbon emissions and operating costs for owners.

Increased energy savings in colder climates and larger buildings

In addition to outlining potential energy and cost savings through roof retrofits, the detailed study points to several nuances that can change the way Canadian building industry stakeholders achieve energy savings in different climate zones. Some of the key findings shed light on the relationship between energy savings and colder climates, the size of the building footprint, and building performance.

• Relative energy savings tend to be greater for larger buildings. Commercial buildings with large footprints spread across one to two stories have a greater roof-to-wall area ratio compared to their high-rise counterparts. If the roofs on these buildings are not thermally insulated, they will typically require more energy to heat or cool. However, with appropriate roof insulation, the building envelope effectively minimizes heat transfer and consequently provides greater energy savings.
• Roof retrofits in colder climate zones can reduce energy consumption. Naturally, heating an under-insulated buildings in cold climates typically consume more energy and increase associated energy costs. Sidelining this challenge, integrating roofs with high-performance insulation (i.e polyiso with a high thermal resistance) can bolster the thermal performance of the envelope and reduce energy consumption by a substantial margin. For instance, by adding code-congruent insulation during roof retrofits, a strip mall in Vancouver can save up to 6 per cent on energy costs, whereas a strip mall in a much colder climate area such as Edmonton can save up to 11 per cent on energy costs. It is important to note that more stringent envelope insulation requirements in colder climates contribute to this increased savings potential.
• Roof replacements support building performance standards and carbon reduction goals. Roof replacements can be a cost-effective tool to help building stakeholders reduce their carbon footprint to meet emission reduction goals and building performance standards (BPS) by locking in energy savings at the time of replacement. Adopting such practices can help building owners comply with forward-thinking policies such as the Annual Greenhouse Gas and Energy Limits Bylaw,⁵ which was adopted by the Vancouver City Council to meet the city’s aggressive 2030 sustainability goals. Starting in 2024, commercial buildings in Vancouver larger than 9,290 m² (99,996 sf) will have to submit an energy and carbon report (also called a benchmarking report) to the City for the 2023 calendar year. Data collected from the benchmarking reports, which will need to be submitted annually for each subsequent calendar year, will be used to confirm compliance with Vancouver’s BPS. Commercial buildings larger than 4,645 m² (49,998 sf) and multi-family buildings larger than 9,290 m² (99,996 sf) will begin reporting in 2025, and multi-family buildings larger than 4,645 m² (49,998 sf) will begin reporting in 2026. In establishing a BPS, Vancouver joins a wider movement of jurisdictions in North America that are supporting climate goals while improving the overall performance of their building stock.

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Government initiatives to support change

To take additional strides toward energy and carbon emissions savings, the Canadian government has developed bold and immediate actions to fight climate change and ensure a clean growth economy. Under the Canadian Net-Zero Emissions Accountability Act and as part of the 2030 Emissions Reduction Plans, the federal government is spearheading the mission to minimize building carbon through forward-thinking, science-based efforts.

As Canadian specifiers know, one part of the approach is developing increasingly stringent, performance-based model building codes. The Canadian federal government does this by proactively working with the stakeholders within the building and construction industry, as well as local governing bodies. These policies bring the codes for retrofitting existing buildings into the spotlight.

Roof upgrades and replacements can seem resource-intensive to building owners. To ease their concerns and help drive high-impact renovations, the federal government has laid a foundation of progress by mobilizing funds and resources promoting green construction methods. Some programs such as the Deep Retrofit Accelerator Initiative (DRAI) and the Commercial Building Retrofit Initiative by Canada Infrastructure Bank (CIB) cater to energy efficiency-focused retrofits in commercial buildings. In fact, the latter has already committed $2 billion to cover the upfront costs on commercial building retrofits.

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NECB requires roof insulation and provides a prescriptive compliance pathway for new construction opaque roof assembles, but it does not cover roof replacement projects that can support existing building policies and regulatory building performance standards. So, the responsibility of delivering energy-efficient building envelopes falls with the building teams and specifiers.

Roofing retrofits for an energy-efficient built environment

Canadian specifiers stand at the forefront of transformation and can play a pivotal role as changemakers by strategically implementing the use of high-performing polyiso insulation during roof retrofits. As demonstrated by the comprehensive study on the benefits of Canadian roofing retrofits, taking this approach has the potential to significantly reduce energy consumption in Canada’s commercial buildings by 4 to 11 per cent annually and reduce associated building operations costs.

Further, by creating resilient and adaptive structures through roof retrofits, specifiers can help combat the effects of climate change, such as temperature fluctuations, and consequent implications, such as power cuts. This reduces the vulnerability of building occupants against extreme weather conditions and lowers the cost of living, while ensuring compliance with the latest energy code requirements. By prioritizing energy savings and reducing carbon emissions, specifiers can meet the challenges of the moment and stay true to national and personal sustainability goals. As such, the time to act is now.⁶

Notes

¹ When direct emissions from fossil fuel energy, non-energy emissions, and indirect emissions from electricity use are included. For details, see the Environment and Climate Change Canada, Canada 2030 Emission Reduction Plan, gc.ca/collections/collection_2022/eccc/En4-460-2022-eng.pdf[7].

² Visit this resource for more statistics, www.pembina.org/op-ed/zero-carbon-buildings-2050[8].

³ As per Canada’s Changing Climate Report (CCCB) commissioned by Environment and Climate Change Canada.

⁴ To learn more, visit www.blg.com/en/insights /2022/04/2030 -emissions-reduction-plan-and-canadas-journey-to-net-zero[9].

⁵ Refer to Table 1 in the conference paper, “The application, benefits and challenges of retrofitting the existing building” at https://iopscience.iop.org/article/10.1088/1757-899X/271/1/ 012030/pdf[10].

⁶ To know more about the methodology and calculation process, see the Polyisocyanurate Insulation Manufacturers Association (PIMA) to view full study report at www.polyiso.org/page/CanadaRoofEnergyCarbonSavingsAnalysis[11].

⁷ These values were selected to be representative of climate zone roof insulation code requirements, but in practice code adoption and compliance with National Energy Code of Canada for Buildings (NECB) 2020 vary by local jurisdiction and province.

⁸ National-level energy prices were developed by separately weighting electricity and natural gas provincial prices and forecasted escalation rates by the provincial’s corresponding system demand, or capacity, from the Canadian Energy Regulator. They were used to be congruent with the recently conducted similar U.S.-based study where select cities were used to represent impacts and benefits for their corresponding climate zone. For details about the U.S. study on the Insulation Saving Opportunity for Residential, Commercial and Industrial Buildings, see https://www.polyiso.org/page/InsulationSavingsExistingBuildings[12].

⁹ As per the Institute for Market Transformation (IMT), “Vancouver Adopts First Building Performance Standard in Canada,” www.imt.org/news/vancouver-adopts-first-building-performance-standard-in-canada[13].

Test your knowledge! Take our quiz on this article[14].

[15]Author

Justin Koscher serves as president of Polyisocyanurate Insulation Manufacturers Association (PIMA). In this role, he is the principle staff member for the board of directors and steering committee. His responsibilities include the implementation of the association’s strategic vision, management of finances and administration, and supervision of various PIMA work groups. Koscher joined PIMA in January 2017. He previously served as a director at the American Chemistry Council’s (ACC’s) Center for the Polyurethanes Industry (CPI). Koscher obtained his B.A. from Illinois Wesleyan University and J.D. from DePaul University College of Law. Visit polyiso.org for more information.

Source URL: https://www.constructioncanada.net/roof-replacements-the-impact-on-energy-and-carbon-emissions/

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