零净值在建筑行业意味着什么

有关整个建筑物生命周期评估的更多信息, 生物碳和碳储存, 以及环保产品声明, 访问我们的 可持续性的页面. 查看可持续性资源的完整列表 在这里.

什么是净零? 

“净零”这个词在建筑行业已经很常见了. 最近建造的建筑被吹捧为净零, 设计师和业主努力实现净零排放, 和 policies are in place 和 being created that require net-zero construction. 每个人似乎都想要一个净零的结果, but t在这里 is lack of consensus on what the term means 和 how to get t在这里.

在不久的过去, net zero within the 建筑 industry was a term associated with operational energy—i.e., used during a 建筑’s operation to power, heat, 和 cool the structure. 随着能源效率的提高, 可再生能源选择, 以及更高效的设计技术, 许多建筑已经能够实现 净零运行能耗，不需要场外能源的标准性能，和 净零运行碳, w在这里 associated carbon emissions are zero through the use of renewable energy sources. 这些建筑经常被称为 净零能耗建筑 or 零的建筑. 偶尔, 净零也被用来描述性能目标, 例如建筑物居住者对水或废物的使用. 例如，在a 净零水建筑; the amount of water from alternative sources plus the water returned to the original source is equivalent to the amount of water used during operation of the 建筑 in a year. 同样,一个 零浪费 建筑 不会导致废物进入堆填区或焚化炉.¹

最近，“净零”一词已被讨论与 整体 碳的影响 一个建筑物，包括两者 运营的碳 和 体现碳.² Embodied carbon refers to greenhouse gas (GHG) emissions associated with the manufacturing, 运输, 安装, 维修保养, 解构和处理结构内的材料.^3,4 Embodied carbon is often counted separately from 运营的碳, so it is possible to set 净零隐含碳 目标. When considering operational 和 体现碳 together, the goal would be 净零总碳.

净零碳讨论的另一个复杂之处是 碳补偿 (也称为 碳抵消信用额 or 抵消学分)，可以购买以补偿碳排放.^5,6 These offsets are then subtracted from the carbon total in order for the structure to claim 零碳排放.⁷

木制品如何有助于降低隐含碳

One of the most straightforward ways to reduce the 体现碳 of a structure is to utilize materials that have low 体现碳. This means finding materials that emit less GHGs into the atmosp在这里 during production, 安装, 和解构. 再三, it has been shown that wood materials have lower 体现碳 than functionally equivalent alternatives.⁸

部分原因是可再生生物质燃料的使用.e., bark 和 other residual wood fibers) in place of fossil fuels during product manufacture. 在美国木材委员会(AWC)成员设施, 它们代表了超过86%的结构木制品行业, more than 70% of the energy used in wood product manufacturing comes from biomass.⁹ Based on the “-1 in/+1 out” biogenic carbon accounting framework outlined in ISO 21930¹⁰ 源自可持续管理森林的生物基材料, 生物质能被认为是碳中性的, so the associated carbon emissions don’t contribute to the 建筑’s 体现碳.¹¹

此外，由于木材是一种可再生的生物基材料，它含有 生物碳,¹² which is carbon that was removed from the atmosp在这里 through the process of photosynthesis during the tree’s growth. 这些碳继续被储存在木材中, 在木制品的整个生命周期内使其远离大气. 在执行整个建筑生命周期评估(WBLCA)时, it is helpful to account for 体现碳 和 biogenic carbon separately since they represent different sources of carbon. 然而, 当考虑到一栋建筑的全部碳影响时, the negative biogenic carbon value is often summed with the positive 体现碳 value. If t在这里 is at least as much biogenic carbon stored in the wood products as t在这里 is 体现碳 released throughout the 建筑’s life, 结构可以考虑 净零隐含碳. 对于净零的定义, 记住这一点很重要, although the product will indeed store biogenic carbon over the lifetime of the 建筑, 最终, 在这栋楼的寿命结束时, 部分或全部储存的碳将从系统中“释放”出来,¹³ at which point it is no longer available to offset the 体现碳 emissions.

净零碳的真正目标

因为“净零”这个词有很多用法, 建筑 owners 和 designers should be clear which type of net zero they’re aiming for, both during the design phase to ensure their efforts are focused appropriately, 和 in sharing their accomplishments with the public to eliminate confusion. 无论是讨论操作碳还是隐含碳, 在一天结束的时候, the goal in 零碳排放 construction is the same: to create a built environment that is less carbon-intensive. 这可以通过多种策略来实现, 包括木质建筑材料的使用. WBLCA的使用 can help owners 和 designers analyze 建筑s through a carbon-conscious lens 和 make material choices that lower carbon emissions. 虽然净零是一个崇高的目标，没有简单的方法来实现, 在建筑中使用木材是一种行之有效的减碳策略.

额外的资源

大厅,E.S.(2020年9月). 如何计算建筑物的木材碳足迹.

KL&A工程师和建筑商., Adolfson & 彼得森. (2021年7月). 普拉特15生命周期评估.

木制品-木制品委员会. (2021年10月). Building Sustainably: From Forestl和 Management to Carbon-Positive, Healthy Buildings.

认为木材. 净零楼宇.

¹ U.S. 能源部. (2017年8月). Federal Existing Buildings H和book for Net Zero Energy, Water, 和 Waste. 

² O ' conner J. 2月(2020). 我们能对隐含碳做些什么呢? 加拿大建筑师. 

³ 现货UL. (2020年8月). 实际碳与操作碳. 

⁴ 碳领导力论坛. (2020年12月). 隐含碳101. 

⁵ 碳补偿指南. 什么是碳补偿? 

⁶ CarbonCredits.com. 如何通过生产和销售碳补偿来赚钱. 

⁷ T在这里 is also an emerging interest in the sale of credits for carbon stored within mass timber 建筑s. 有关更多信息，请参见:Ta, K. (2022年9月). Aureus Earth 和 the University of Washington Execute Ground-Breaking Carbon Offset Transaction for a Mass Timber Building. 绿冠节点. (2022). 开创了第一个大规模木材碳去除方法. 

⁸ Sathre R.奥康纳，J. (2010年10月) 木制品研究综述 & 温室气体影响2^nd 版. 

⁹ 美国木材协会，(2020年12月). 环境、能源 & 安全报告行业进展报告. 

¹⁰ 国际标准化组织. (2017). ISO 29130: 2017 可持续性 in Buildings 和 Civil Engineering Works – Core Rules for Environmental Product Declarations of Construction Products 和 Services, 第七节.2.7. 

¹¹ 在关于这个主题的资源中, a US EPA Policy Statement “reflect[s] the carbon-neutrality of forest bioenergy 和 recognize[s] biomass as a renewable energy source, provided the use of forest biomass for energy production does not cause conversion of forests to non-forest use.” U.S. 环境保护署. 美国环保署生物源性二氧化碳(CO)的处理₂) Emissions from Stationary Sources that Use Forest Biomass for Energy Production. 

¹² 有关木制品中碳储存的信息，请参见 这 木制品的文章. 

¹³ 如何在LCA中包含生物碳将在 这 木制品的文章.