Dedicated to sustainable,
high performance building

Materials selection elevates buildings

By CaGBC

A healthy building is made of healthy building blocks. Using sustainable materials that comply with building codes today – and those decades in the future – really help a project stand out.

Over the last decade the building sector has been redefined by innovations in building materials and an increased interest for materials transparency. Occupants are concerned about their exposure to the chemical components of the building materials; owners want to understand what materials are present in their building; and designers and architects are no longer content to simply specify a product without understanding the holistic attributes of that product. Where design and budget constraints traditionally determined materials selection, now a growing awareness and interest in sustainability is driving new behaviours.

Increasingly, manufacturers are offering more sustainable, durable, and resilient materials. By pursuing the highest sustainability standards, manufacturers are diversifying their products with greener alternatives to classic building materials. As a result, more project teams are able to earn credits towards certification for rating systems and standards such Leadership in Energy and Environmental Design (LEED®) or CaGBC’s Zero Carbon Building (ZCB) Standard®.

Today, architects and project teams can access detailed information about building materials and products. This allows them to weigh their options against the building’s sustainability goals and keep LEED Building Product Disclosure and Optimization (BPDO) credits in sight. Information like that included in Environmental Product Declarations (EPDs) or Heath Product Declarations (HPDs) provides full disclosure of any potential areas of concern in a product, helping projects limit potential negative impacts on the environment and building occupant health.

SUBSCRIBE TO THE DIGITAL OR PRINT ISSUE OF SABMAGAZINE FOR THE FULL VERSION OF THIS ARTICLE.

Decarbonizing cement

By Jeff Ranson, Senior Associate, CaGBC

As we move towards 2050 targets for green building, embodied carbon is increasingly important to staying under the emissions budget and limiting global warming below 1.5 degrees Celsius. What is embodied carbon? It’s the product of the materials and construction methods we choose. This value is often stretched over the life of the building to reflect durability, the idea that a building built to last is likely better than one that will need constant repairs. However, the reality  is that those emissions are all fully released up front. Like net-present value in the financial world, a ton of carbon emissions today is worth more than a ton of carbon emissions tomorrow.

Of all the opportunities to reduce embodied carbon, the most significant is in concrete. Concrete is the most widely used building material, cutting across both buildings and infrastructure. And despite strong and promising market growth of alternative low-carbon materials including wood and biomaterials, concrete will continue to be a critical material for construction.

Potential as a climate solution

Reducing greenhouse gas emissions from concrete is a national priority. Natural Resources Canada and the Cement Association of Canada have committed to develop a decarbonization roadmap for the industry. For the designing construction industry, there are a few significant ways to reduce emissions today, and some very promising opportunities emerging.

In the immediate term, there are two opportunities to reduce emissions from concrete. The first is simply to minimize the amount of concrete projects use. This involves looking at how much concrete is required for the project and optimizing its use. This requires designers be conscious of how design choices such as massing impact material requirements. In many cases, designers are evaluating alternative low-carbon materials like mass timber to replace concrete, but nothing is as effective as just using less material.

One area in relation to embodied carbon that has been overlooked is the impact of land use planning. Infrastructure like roads, sewers, and transit require concrete.  There is no realistic substitution. Low-density suburban development oriented around the automobile results in huge amounts of embodied carbon, seldom considered in any municipal carbon strategies. CaGBC has been in discussions with researchers at the University of Toronto to better understand the relative carbon impacts of different development patterns, but at present there isn’t a well-established practice for evaluation. With more research we hope to understand the impact of embodied carbon from infrastructure and the importance what we build and where we build it.

SUBSCRIBE TO THE DIGITAL OR PRINT ISSUE OF SABMAGAZINE FOR THE FULL VERSION OF THIS ARTICLE.

Design practice: Buildings as a Climate Change Solution

By Chris Magwood 

The focus of green building has long been on reducing impacts… doing “less bad” to the planet and ourselves by shrinking our ecosystem, chemical and climate footprints through conscious design and material selection. But when it comes to our current climate crisis, doing less bad is simply not going to be good enough. The climate science is clear: we collectively need to get to net zero emissions as soon as possible AND remove carbon from the atmosphere in order to meet the targets in the Paris Accord1. The building industry is now tasked with doing “more good” by reducing net emissions to zero and actively contributing to carbon drawdown. 

Fortunately, there is a clear roadmap for the building sector to move from being a leading cause of climate change to becoming a key part of the solution. Unlike many sectors, climate change does not force builders to face an existential crisis because it is possible for buildings to become a climate positive industry.

The starting place on the roadmap is for all designers and builders to understand the nature of the issue. Collectively, we’ve done excellent work to address the operational emissions from buildings and have helped move the bar on better codes and created a proliferation of voluntary systems to achieve near zero emissions from high performing new buildings and renovations.

But operational emissions are only part of the problem. A building that achieves zero emissions during its operation is an important step. The other half of the problem now needs to be addressed: material-related emissions.

By recent estimates, the production of building materials accounts for approximately 21% of all emissions globally. We cannot adequately address climate change through operational improvements alone; we cannot “net zero” our way out of this. The “embodied carbon” side of the equation needs equivalent focus and action. We need to take responsibility for all the emissions we cause through harvesting, manufacturing, transporting and installing building materials because of the sheer scale of these emissions.

Tackling these “material emissions” may be easier than you think. The data and tools available to make carbon-smart materials choices is growing rapidly and the evidence of the emission reductions that can be achieved is encouraging.

In a study I completed in 2019, a small (930 m2) multi-unit residential building was modelled with a range of different materials that are all comparable in terms of code compliance, cost and practicality. Material selection was found to have a remarkably broad range of potential results (See graphic top of page 59).

The model with the worst results was responsible for over 240 kg of emissions per square metre of floor area. There is no way that climate change is going to be adequately addressed if new buildings are adding emissions to the atmosphere at that rate.

Some simple material swapping reduced this carbon footprint by over 60%, getting it down to 90 kgCO2e/m2. This is an excellent example of our ability to do “less bad,” and to do so with minimal effort and no undue cost or scheduling issues.

But we can do better. A model for doing “more good” also emerged from the study. It resulted in no net emissions from its materials, but instead recorded a small amount of net carbon storage. At the end of construction of this building, there would be less CO2 in the atmosphere than before it was built. 

How is it possible for a building to have net carbon storage? To get to the answer, we need to understand a bit about the global carbon cycle. Every year, the earth’s plants draw down billions of tonnes of CO2  from the atmosphere and through photosynthesis absorb carbon and release oxygen. In a natural cycle, the carbon thus stored in plants is released back to the atmosphere when the plants die and decompose or burn. (See graphic next page.)

Builders can interrupt this carbon cycle by taking carbon-rich plant material and locking it up in buildings, preventing its return to the atmosphere for the lifespan of the building. We have been doing this unintentionally for millennia, incorporating wood and other biofibers into buildings. Conventional building practices include a range of widely available and affordable plant-fiber materials, including products like cellulose insulation, wood fiberboard and many kinds of timber products. By combining these carbon-storing materials with other low-emission materials, results like the 11 kg/m2 of net stored CO2  from the MURB study are entirely feasible with no disruption to the design process, supply chain or construction methodologies. 

The use of biogenic materials in buildings can be increased and our carbon positive impact on the climate further improved. There are biogenic material options for every part of a building’s enclosure and finishes. By intentionally choosing appropriate biogenic materials, the amount of net carbon can be amplified so that buildings can actually become a measurable carbon sink on the planet.

The final model in the study (graphic top right) used this approach and was able to offer over 130 kg of net CO2  storage per square metre. None of the materials used in this model are unattainable and all can (and have) met Canadian building code requirements, but many of these are unconventional materials and not currently available through typical supply chains. There is work to be done to make this kind of change, but the result would be a construction industry that actually helps the climate to heal. 

Chris Magwood is  a director at The Endeavour Centre in Peterborough, ON,  which offers two full-time, certificate programs: Sustainable New Construction and Sustainable Renovations and hosts many hands-on workshops annually.

SUBSCRIBE TO THE DIGITAL OR PRINT ISSUE OF SABMAGAZINE FOR THE FULL VERSION OF THIS ARTICLE.

 

VIEWPOINT

Making building performance a selling point, and moving on from the glass tower

By Richard Witt, Executive Principal, Quadrangle & Michelle Xuereb, Director of Innovation, Quadrangle

Sustainable building design is not a new concept. With the development and implementation of LEED in the early 1990s, sustainability became mainstream but has struggled to effect real change in the way we think about building performance, requirements or aesthetics. Economics and sustainable building design are at odds – sustainability is an extra cost, weighed against budget and relative value.

The Council of Tall Buildings and Urban Habitat concluded in their study Downtown High-Rise vs. Suburban Low-Rise Building that recently completed buildings significantly underperform in comparison to their counterparts from 50 years ago. The days of the glass skyscraper are coming to an end. Passive systems direct the way forward, as opposed to compensating for inefficiency with active systems.

Buildings are the key contributor and solution to climate change mitigation and adaptation.

According to the latest inventory release (2017) by The City of Toronto, 52% of GHG emissions in Toronto come from buildings, predominantly from burning natural gas to heat indoor spaces and water. Consequently, buildings must also be a climate change solution. The City of Toronto recognizes this in its Zero Emissions Building Framework, which is why the Toronto Green Standard (TGS) has us on a path to net zero buildings by 2030. What about the code? There is a plan to move Toronto to net zero by 2030, but it is not clear, given the current political climate, whether this proposal will be executed. Passive design solutions increase durability and climate change resilience while lowering energy usage, embodied energy from maintenance, and GHG emissions.

Passive solutions allow us to both mitigate and adapt to changing weather.

Based on the Climate Driver Study completed for the City of Toronto, we know that days are getting hotter, there are more of them and there are more of them strung together in heat waves. We are also experiencing larger storms, with heavier amounts of precipitation falling at once. The main issue we will have with our buildings is overheating and flash flooding – both in combination with power outages. This again reinforces the need for passive design solutions.

These power outages generally happen on our hottest and coldest days as a result of people cranking their AC or heating. The higher the total effective R-value of the building, the better they are able to maintain the indoor air temperature in the case of extreme temperatures without power.

The City of Toronto recommends that people be able to function independently for a minimum of 72 hours without power. In a residential building, maintaining indoor temperature is key to allowing people to shelter in place within their homes.

• At a basic level, a building is meant to shelter people from the weather – to keep people warm when it’s cold and cool when it’s hot. Glass is a very poor insulator, leaving residents feeling physically uncomfortable and paying high energy bills.

• As architects, the best thing you can do is reduce the amount of glass and increase the amount of well-insulated walls. We understand that keeping windows to about 40% of the wall area is the single most effective way to reduce the energy footprint of a building. Real walls with windows may seem old fashioned, but they don’t need to be. Our focus is on creating a thoughtful, well-designed building with an aesthetic that lends itself to real walls and windows.

• Unlike glass, insulation slows down the movement of heat. This allows you to hold onto heat during winter, making people more comfortable and more likely to actually use the spaces at the perimeter of their unit.