Life Cycle Inventory Data for Life Cycle Assessment (LCA) of Highly Energy Efficient Case Study House in Dillingham, Alaska

This life cycle inventory data is used to conduct a life cycle assessment of a case study house. While energy efficiency features can significantly reduce the greenhouse gas emissions during a building’s operational stage, extra materials and processes associated with these features typically involve higher greenhouse gas emissions during the construction phase. In order to study this relationship, a case study of a highly energy-efficient house in rural Alaska was performed. For the purposes of this case study, a theoretical counterpart home was designed that has the same interior space, but insulation values close to the code minimum requirements. Using computer simulations, LCA was performed for the case study home as well as its conventional counterpart. The extra greenhouse gas emissions associated with the construction of the case study home were compared to the annual savings in greenhouse gas emissions achieved thanks to the energy efficiency features, and carbon payback was calculated to be just over 3 years. The house is located in Dillingham, Alaska. Net living area of the house is about 54.8 square meters, outside dimensions are 7.3 m by 7.3 m with 71 cm thick walls. The house falls into the category of a net-zero energy ready building, consuming roughly 3,000 kWh annually for all energy needs. Air tightness was measured at 0.05 air changes per hour (ACH) at 50 pascals. The case study home was built utilizing a “box-in-a-box” technique with a continuous polyethylene vapor barrier surrounding the interior “box”. This construction method allowed for a continuous vapor barrier with minimal thermal bridging. The vapor barrier is on the outside of the interior framing so that the wiring for the interior of the house does not puncture the vapor barrier. The 60 cm cavity between the interior and exterior wall was filled with blow-in cellulose insulation. There is fiberglass insulation within the interior framing. The walls have an RSI value of about 16 K·m2/W. The ceiling of the house has an RSI of about 25 K m2/W. The theoretical conventional counterpart home model has the same interior dimensions of 5.9 m by 5.9 m. The wall structure is a frame with 38 mm x 140 mm studs (referred to as 2x6 frame in the U.S.) with RSI of 3.7 K·m2/W fiberglass insulation and 25 mm polystyrene foam board on the inside, giving the walls an RSI 4 K·m2/W value. The ceiling is a frame with 38 mm x 286 mm ceiling joists (referred to as 2x12 frame in the U.S.) with RSI 6.7 K·m2/W fiberglass insulation and 25 mm foam on the inside giving it an RSI 7.2 K· m2/W value. The air tightness of the house was modeled at 1.0 ACH at 50 Pascals. The conventional model has a 45.7 cm crawl space to create room for the plumbing structures.

本生命周期清单数据用于开展某案例住宅的生命周期评估（Life Cycle Assessment，简称LCA）。尽管节能设计可显著降低建筑运营阶段的温室气体排放，但此类设计相关的额外材料与工艺通常会在施工阶段带来更高的温室气体排放。为研究这一关联，本研究针对阿拉斯加州乡村地区的一栋高节能住宅开展了案例分析。为完成本案例研究，研究人员设计了一栋理论对照住宅：其内部空间与案例住宅一致，但保温性能参数接近当地规范的最低要求。借助计算机模拟，本研究对案例住宅及其传统对照住宅分别开展了LCA分析。研究人员将案例住宅施工阶段产生的额外温室气体排放，与节能设计带来的年度温室气体减排量进行对比，计算得出碳回收期仅略超过3年。该住宅位于阿拉斯加州迪林厄姆（Dillingham）地区。其净居住面积约为54.8平方米，外部尺寸为7.3米×7.3米，墙体厚度71厘米。该住宅属于净零能耗预备建筑范畴，全年各类能源消耗约为3000千瓦时（kWh）。气密性在50帕斯卡条件下测得为每小时0.05次换气（Air Changes per Hour，简称ACH）。本案例住宅采用“箱中箱”建造工艺，内部箱体外侧包裹连续聚乙烯蒸汽阻隔层。该施工工艺可实现连续蒸汽阻隔，同时将热桥效应降至最低。蒸汽阻隔层设于内部龙骨结构外侧，避免住宅内部布线刺穿该阻隔层。内外墙体之间的60厘米空腔填充了吹填型纤维素保温材料。内部龙骨结构内部填充玻璃纤维保温材料。该住宅墙体的热阻RSI值约为16 K·m²/W。该住宅天花板的热阻RSI值约为25 K·m²/W。理论对照的传统住宅模型内部尺寸为5.9米×5.9米。其墙体结构为龙骨框架，采用38毫米×140毫米的龙骨（美国俗称2×6龙骨框架），内部填充热阻RSI值为3.7 K·m²/W的玻璃纤维保温材料，并在内侧铺设25毫米厚聚苯乙烯泡沫板，最终墙体热阻RSI值为4 K·m²/W。其天花板采用38毫米×286毫米的吊顶龙骨（美国俗称2×12龙骨框架），内部填充热阻RSI值为6.7 K·m²/W的玻璃纤维保温材料，并在内侧铺设25毫米厚泡沫板，最终天花板热阻RSI值为7.2 K·m²/W。该传统住宅模型的气密性在50帕斯卡条件下模拟为每小时1.0次换气。该传统模型设置了45.7厘米高的爬行空间，用于容纳给排水管道设施。