Building retrofits have great potential to reduce CO₂ emissions since buildings are responsible for 36% of emissions in the United States. Several existing studies have examined the effect of building retrofit measures on CO₂ emission reduction. However, these studies oversimplified emission factors of electricity by adopting constant annual emission factors. This study uses hourly emission factors of electricity to analyze the effect of building retrofit measures on emission reduction using U.S. medium office buildings as an example. We analyzed the CO₂ emission reduction effects of eight building retrofit measures that related to envelope and mechanical systems in five locations: Tampa, San Diego, Denver, Great Falls, and International Falls. The main findings are: (1) estimating CO₂ emission reduction with constant emission factors overestimates the emission reduction for most measures in San Diego, while it underestimates the emission reduction for most measures in Denver and International Falls; (2) The same retrofit measure may have different effects on CO₂ emission reduction depending on the climate. For instance, improving lighting efficiency and improving equipment efficiency have less impact in emission reduction in cold climates than hot climates; and (3) The most energy efficient measure may not be the most efficient emission measure. For example, in Great Falls, the most energy efficient measure is improving equipment efficiency, but the most efficient emission measure is improving heating efficiency.

建筑物改造在减少 CO ₂排放方面具有巨大潜力，因为建筑物占美国排放量的 36%。现有的几项研究已经检验了建筑改造措施对 CO ₂减排的影响。然而，这些研究通过采用恒定的年度排放因子，过度简化了电力的排放因子。本研究以美国中型办公楼为例，利用电力的小时排放因子分析建筑改造措施对减排的影响。我们分析了 CO ₂与五个地点的围护结构和机械系统相关的八项建筑改造措施的减排效果：坦帕、圣地亚哥、丹佛、大瀑布和国际瀑布。主要发现是： (1)用恒定排放因子估计CO ₂减排量高估了圣地亚哥大多数措施的减排量，而低估了丹佛和国际瀑布大多数措施的减排量；(2) 同样的改造措施可能会因气候不同而对CO ₂减排产生不同的影响。例如，提高照明效率和提高设备效率与炎热气候相比，寒冷气候对减排的影响较小；(3) 最节能的措施可能不是最有效的排放措施。例如，在大瀑布城，最节能的措施是提高设备效率，但最有效的排放措施是提高加热效率。