Optimization based on LCA with stages A and B for a DCV ventilation system for a preschool

Abstract

In pursuit of sustainable development within the building industry, there is a shift towards design strategies that are energy efficient and environmentally friendly. The European Commission has a goal of becoming climate-neutral by 2050 and the United Nations has also developed Agenda 2030 to aid in the reduction of the environmental impact. The city of Malmö has also developed a local plan for achieving a climate-neutral construction and infrastructure sector in Malmo by
2030 – LFM30.

The ventilation system accounts for a significant percentage of the environmental impact caused by a building. With previous studies placing weight on individual stages of a life cycle of the ventilation system being either the production and construction stage A or the use stage B, this study aims to investigate the combination of these stages by evaluating different design strategies while considering the economic factor. Evaluating the performance of the implemented strategies was achieved through conducting a comprehensive analysis involving Life Cycle Assessment (LCA), Life Cycle Cost (LCC), and an integrated life cycle assessment (ILCA), following LFM30:s guidelines and climate staircase. LFM30:s climate staircase includes the traditional level representing the base case, the Base level includes improvements without additional costs, BATNEEC involves efficient measures with a reasonable cost increase, and BAT approach where cost is flexible allowing for multiple measures. The potential environmental impact category taken into consideration for the LCA was the Global Warming Potential (GWP) measured in kg CO2 equivalents.

Two preschools in Sweden based on a standard model being constructed in different cities were used as a case study to determine the environmental impact of their current ventilation systems and the potential design strategies implemented. The ventilation system in these preschools consisted of two air handling units, LA01 supplying airflow to the whole building and LA02 only designated for the kitchen area which is a special trait in this project. The design strategies implemented in this study were a Demand Control Ventilation system (DCV) system for the BATNEEC approach and the use of recycled steel for the duct system for the BAT approach in addition to the DCV system, with the Base level considered a limitation. For the installation of a DCV system, a ventilation schedule with a reduced designed airflow volume was created based on the occupancy level provided by interviews and measurements conducted. The study findings indicate that a Demand Control Ventilation system regulated with carbon dioxide sensors could lower the designed airflow volume to 80%-65%.

Considering the special trait related to these preschools, system LA02 has a higher kg CO2e emission per m2 gross floor area (GFA) while having a lower amount in total kg CO2e emission compared to system LA01. The AHU accounts for the largest percentage of the total environmental impact of the ventilation system with the duct system accounting for the second largest. The study shows potential in placing weight on both the construction and production and the use stages of a project. The results indicate that measures related to installed material choice such as the use of recycled material have mainly a direct impact on stage A and not B while measures related to energy efficiency have a direct impact on stage B without affecting stage A negatively. The implementation of a Demand Control Ventilation system reduced the energy demand by 55% and thus the environmental impact due to Global Warming Potential impact (GWP) by 55%-67%. The implementation of any of these measures had a higher investment cost for installed material but made savings in considering the cost of the operational energy use. It was also concluded that the best-performing case could vary depending on results from the ILCA with whether a greater weight was placed on LCA or LCC.

Popular Abstract

Demand Controlled Ventilation is an energy-efficient and environmental design

The study evaluates the performance of design strategies on a ventilation system through a life cycle assessment and costing regarding the production, construction, and operational energy use stages.

A product’s life cycle assessment consists of different stages where a greater weight in previous studies has been placed on either the production and construction or the operational energy use of the building. For a ventilation system, the operational energy use stage is considered to be the one with the significant environmental impact in comparison to the production and construction stage accounting for a larger percentage.

In pursuit of sustainable development within the building industry, there is a shift towards design strategies that are energy efficient and environmentally friendly. The study findings indicate that a Demand Control Ventilation system regulated with carbon dioxide sensors could lower the designed airflow volume to 80%-65% based on conducted interviews and measurements in a preschool. This reduces the energy demand by 55% and the environmental impact due to Global Warming Potential impact (GWP) by 55%-67%.

The study shows that focus can be placed on both the production and use stages by the implementation of efficient design strategies in the early stages to reduce the overall environmental impact of the system. The results indicate that measures related to installed material such as the use of recycled steel for the duct system in this study had a direct impact on the production and construction phase without affecting the operational energy usage of the ventilation system. However, measures related to energy efficiency such as the implementation of a Demand Controlled Ventilation system, had a direct impact on the operational energy usage without affecting production and construction stages.

Regarding cost, these design strategies have an additional investment cost for installed material. A Demand Controlled Ventilation system has an additional investment cost but results in energy cost savings, while the use of recycled material mainly impacts the environmental aspect but adds to the investment cost. Upon considering both the environmental and cost aspects the best-performing case varies depending on whether more weight was placed on the environmental or economic perspective.

Considering that there is a greater importance placed on either the production and construction or the use stage the aim of this study is to emphasize the importance of connecting both, considering the environmental impact and energy usage. This is relevant since the European Commission has a goal of becoming climate-neutral by 2050 and the United Nations has also developed Agenda 2030 to aid in the reduction of the environmental impact. The city of Malmö has also developed a local plan for achieving a climate-neutral construction and infrastructure sector in Malmo by 2030 – LFM30 that includes guidelines followed by this study.

• author: Mahfoud, Hala and Zhou, Lijin
• supervisor: Ulla Janson
• organization: Division of Energy and Building Design
• course: AEBM01 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Life Cycle Assessment, Life cycle costing, Integrated life cycle assessment, DCV system, Global warming potential.
• language: English
• id: 9165047
• date added to LUP: 2024-06-24 15:25:52
• date last changed: 2024-06-24 15:25:52