Life cycle assessment of a CAV, a VAV, and an ACB system in a modern Swedish office building

anglais. Energy use in buildings contributes significantly to the global energy demand and environmental impacts. Among all building services, heating, ventilation, and air conditioning (HVAC) systems consume the most energy. HVAC systems are as well one of the largest consumers of natural resources and materials in the building sector. Studies have shown that the manufacturing and operation of HVAC systems have a significant impact on the environment. With a constant growing awareness towards thermal comfort and energy use, the question remains, which HVAC system has a better environmental performance. This thesis presents a comparison between the life cycle impacts of three different HVAC systems — constant-air volume, variable-air volume, and active climate beam systems — designed for a Swedish modern office building. The system boundary of the life cycle assessment was set to be cradle-to-grave with options, over a 20-year period. SimaPro software was used for the life cycle assessment (LCA) of the systems. The CML IA (baseline) method was used for the life cycle impact assessment and the results were weighted based on the shadow cost Dutch method. Initially, a base case scenario was set for all three HVAC systems, using Copper material for the hydronic system and using Swedish electricity mix. Varying the material used for the hydronic system and the electricity type, a parametric study was then conducted comparing the environmental impacts of the systems. The results of the Base case scenario showed that, from a life cycle perspective, the ACB and VAV systems have similar environmental performance. During the life cycle of the CAV and VAV systems, the operational phase showed to have the highest environmental impact. Whereas, for the life cycle of the ACB system, the manufacturing phase exhibited the highest environmental impact. The biggest reduction in environmental impacts was observed when PVC pipes were used instead of copper pipes, in the ACB system. A slight reduction was seen when 100 % renewable-based electricity was used by the systems instead of the Swedish electricity mix. Under all case-scenarios, the CAV system showed to have the highest environmental impacts. Further research regarding the impacts of the maintenance phase and life span of the systems would be relevant for the comparison of life cycle impacts of the systems.

anglais. Life cycle analysis comparison of three different heating, ventilation, and air conditioning systems designed for a modern office building, in Sweden: In the modern industry, product-related activities, including production, manufacturing, and disposal processes, have worldwide environmental consequences. The purpose of a full-scale environmental assessment is to trace those impacts from a life cycle perspective and help identify areas of improvements. In this thesis, the environmental impacts due to the life cycle phases of three different heating, ventilation, and air conditioning systems were evaluated. Activities causing environmental burden vary depending on the industry. However, the built environment is well known for being one of the largest contributors to harmful emissions, making up around 50 % of the carbon dioxide emitted globally. While in the European Union, the building industry accounts for approximately 40 % of the total environmental burden. This is due to not only construction-related activities but as well as activities occurring during the building´s manufacturing phase and operational phase of indoor climate control systems. Therefore, when accounting for climate change, there is a need for a reassessment of the environmental impacts that building materials induce. This is especially true for climate control systems due to the rising focus of improving indoor air quality along with the high complexity and usage of materials. A review of previous environmental assessment studies has indicated that climate control systems have been, in most cases, evaluated based on their carbon emissions, with disregard to other harmful environmental factors. Additionally, due to the high energy use of those systems, studies have usually focused on the environmental effects of climate control systems during their operation period. This calls for an evaluation of climate control systems considering different life cycle phases and other environmental factors, in addition to carbon dioxide. Therefore, different environmental factors, such as the depletion of natural resources, impacts on sea-life, etc, were considered in this thesis. The results of the thesis showed that the operation period of climate control systems with high energy usage was the highest contributor to the total environmental impacts. The use of completely clean electricity did not significantly reduce the impacts of the systems as was hoped. However, in systems with lower energy use during their operation time, materials such as copper showed to have a more adverse environmental burden. Life cycle analysis is an effective tool in assessing the environmental performance of systems and services. However, there is a need for more standards sharing the same goal and scopes that would enable direct comparison of the environmental performance of similar products.