CREJ

June 2020 \ BUILDING DIALOGUE \ 21 emitting unconscionably large amounts of CO2, archi- tects and developers need to lead the way toward a car- bon positive future. We must strive to eliminate all GHG emissions from the built environment by 2040 to meet the Paris Agreement targets. American Institute of Architects recent Resolution for Urgent and Sustained Climate Action mandates that “un- til zero-net-carbon practice is the accepted standard of its members, AIA prioritize and support urgent climate action as a health, safety, and welfare issue.” While various approaches can decarbonize buildings, I would like to close out this series with two relatively new, albeit very different concepts that we will be hear- ing and seeing a lot more of going forward: 1. Building electrification 2. Mass timber construction Each has its limitations and counter arguments as to their benefits, here are why they make sense: Building electrification. Because natural gas and fuel oil are fossil fuels, and their combustion for space heat- ing and heating hot water not only results in CO2 emis- sions but also has localized negative air-quality impacts. While going all-electric, including culinary, we have the opportunity to meet nearly all our buildings’ ener- gy needs from an increasingly low-carbon electric grid, eliminating direct fossil fuel use in buildings and mak- ing obsolete much of the gas distribution system – along with its costs and safety challenges. Forward-thinking cities from coast to coast are already heading down this path. In support of this transition Xcel Energy, Colorado’s largest utility, has one of the most ag- gressive utility clean energy goals in the country (Fig:2). Except for the coldest climates, electric heat pumps are currently the most efficient available technology for space heating and making hot water in the commercial and residential sectors. Although heat pumps have high- er initial capital costs, high efficiency and minimal main- tenance make air source heat pumps a positive financial investment over 20 years (Source: Decarbonizing U.S. Buildings, Center for Climate and Energy Solutions). To promote widespread adoption, this technology is being increasingly incentivized in Colorado. Mass timber construction. Because wood is a renew- able resource, it can have clear advantages over steel and concrete in terms of its total embodied energy. This refers to the primary load-bearing structure being made of either solid or engineered wood. There are multiple and complementary motivating factors for the rise of this trend: response to context, environmental and bio- philic (connecting people to nature) benefits and eco- nomics. Many in the building industry want nothing less than to turn the coming decades of global commercial con- struction from a giant source of carbon emissions into a giant carbon sink by replacing concrete and steel con- struction (China being the world’s majority, by a large margin, producer of cement and steel) with mass timber (potentially sourced in North America). This would avoid the CO2 generated in the production and transporta- tion of those building materials and sequester massive amounts of carbon by tying up the wood in buildings for decades or even longer, perhaps in perpetuity. We must ensure that mass timber drives sustainable forestry management, otherwise a lot of the benefits may be lost. To this end, builders and architects should use wood products certified by the following organi- zations: Sustainable Forestry Initiative, American Tree Farm System, Canadian Standards As- sociation, Forest Stewardship Council and Programme for the Endorsement of Forest Certifica- tion standards. On Dec. 23, the city of Denver voted to adopt the 2019 Denver Building Code, which includes the tall mass timber code provi- sions approved for the 2021 In- ternational Building Code. Key takeaways. First, when it comes to carbon, CO2 or GHG emissions, it is one planet, one health. We are all connected in a world that is hot, flat and crowd- ed. And if you are looking to de- carbonize your next project, con- sider “building electrification” and mass timber construction. \\ It’s All About the Carbon Figure 2: Xcel Energy’s carbon reduction trajectory – part of its commitment to clean energy transition by 2030 and 2050. Source: https://www.xcelenergy.com/environment/carbon_reduc- tion_plan