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The greenhouse gas burden of weatherizing northern US homes and estimated lifetime energy savings
Weatherization retrofits are prioritized in plans to reduce greenhouse gas (GHG) emissions, as they decrease the energy needed to heat and cool residential homes. However, the materials used for weatherizing can be GHG-intensive, and it should be determined whether the GHG footprint of weatherization retrofits is higher or lower than the emissions from the amount of energy saved from heating and cooling a home. Our model revealed several scenarios with a clear net GHG benefit over time compared with simply using more space conditioning energy, where the GHG emissions per kWh of space conditioning energy avoided are lower than most renewable energy systems, and others where the GHG emissions per kWh avoided are higher than renewable electricity sources, including solar and wind. The type of materials used for insulating an attic especially influences whether the impact per unit of energy avoided is lower than that of renewables due to the amount of energy that can be saved over the lifetime. We also present the upfront GHG burden of these weatherization retrofits in a way that allows policy and decision makers to include these values in their GHG inventories to adequately plan for short-term climate goals.
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Alyssa Pfadt-Trilling
University of California, Merced, USA
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What motivated you to investigate the greenhouse gas emissions associated with weatherization materials and installation?
We were motivated to investigate the greenhouse gas emissions associated with weatherization materials after noticing in previous work on climate action policy that weatherization was one of the main ways that cities were planning on reducing energy-related GHG emissions. However, they were simply assuming that the benefit of weatherization was 100% based on the energy saved and not accounting for the actual materials needed, which in many cases are quite carbon intensive.
How do the materials used in weatherization impact the overall carbon footprint, and are there more sustainable options homeowners should look for?
There are a wide variety of materials used in weatherization, with a wide range of carbon footprints and lifetimes, so the material does strongly impact the overall carbon footprint. Recycled materials that can achieve the same thermal insulation over the same lifetime as petroleum-based materials have a much lower carbon footprint by reducing energy consumption without the need for new virgin-material production at all.
How do regional factors, such as climate, affect the greenhouse gas benefits and trade-offs of different weatherization strategies?
Regional factors, particularly climate, are hugely influential in determining the overall net greenhouse gas benefits of weatherization. For this analysis we looked at one climate zone—the very cold region of the United States—which has predominantly heating needs over cooling needs, as measured in heating degree days compared to cooling degree days. The other big regional factors are the local grid electricity mix, whether natural gas or oil is being used for heating, and where that is sourced (i.e., which basin).
What should homeowners and policymakers take away from your findings when deciding how to invest in energy efficiency improvements?
Energy efficiency improvements are great, but decision makers need to be aware of and transparent about how these improvements actually affect the overall greenhouse gas balance. Essentially, there is no way to "zero out" energy emissions without producing GHG emissions elsewhere. And the only way to know which option is going to be better from a greenhouse gas standpoint, either weatherizing a home or using more energy, is to do the math and figure out the balance. That's the main takeaway of this analysis, and a lot of life-cycle assessment work in this space, really.
As it relates to the individual homeowner, my personal philosophy is that these sort of responsibilities should fall far less on individual homeowners and more on policymakers to be using our collective funds more wisely.
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Global challenges, equitable solutions
Cell Reports Sustainability is a multidisciplinary, gold open access journal that publishes cutting-edge research across natural, applied, and social sciences that seeks to address the world’s grand challenges.
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