Energy-efficient renovation and thermal comfort assessment of two Swedish single-family residential buildings from the Million Program

Abstract

The energy use in the building sector is increasing rapidly which contributes to the rise in global greenhouse gas concentration. Energy-efficient buildings are considered as healthy buildings due to the improved air quality and comfortable indoor environment. One million residential buildings were built in Sweden during 1965 and 1975 to minimize the acute housing shortage. This initiative was taken by the Swedish government was named as “The Million Program”. Since the residential buildings from the Million Program are old, the indoor temperature is often uncomfortable for the occupants. The occupants of these buildings suffer from health problems due to inefficient ventilation systems and poor indoor air quality. Energy-efficient renovation is important to ensure thermal comfort for the occupants and achieve sustainability in the built environment.

This thesis deals with the thermal comfort issues in two single-family residences built during the Million Program. The research question addressed in this thesis is, What is the influence of energy-efficient renovation on energy use and thermal comfort in Swedish single-family houses built during the Million program? The objective is to evaluate different energy-efficient renovation strategies and their impact on thermal comfort for the occupants. A comparative analysis of the thermal comfort condition before and after renovation was explored in this study. Two case study buildings and pre-determined boundary conditions were simulated. Thermal comfort analyses were performed based on the current scientific methods.

This study contributes to the existing knowledge on energy-efficient building design. The results in this study showed that if all the energy-efficient strategies are considered, it is possible to reduce the energy usage up to 70%. Therefore, energy-efficient renovation can bring significant reduction to the energy use. Maintaining a satisfactory comfort level was found challenging. The results revealed that the renovation strategies improved the indoor thermal environment and enhanced the comfort level of the occupants. The findings of this study would be useful to achieve thermal comfort in the single-family residences from the Million Program.

Popular Abstract

Technological advancements, population and infrastructure growths are the reasons for the rapid energy consumption all over the world. The energy consumption gives rise to the CO2 emission. The energy use from building sector is approximately 40-50% of the total energy use in the European building sector. Each year the building sector emits around 678 million tons of CO2. Energy-efficient renovation measures can reduce the CO2 emission significantly. This study addresses the key issues of energy-efficient renovation and thermal comfort.

One million single-family and multifamily residential buildings were built in Sweden during 1965 and 1975 to minimize the huge housing shortage. It was as an initiative by the Swedish government and the initiative was named as ‘The Million Program’. In Sweden the buildings built during the Million Program constitute 25% of the present building stock which are in need of renovation as they are more than 30 years old. Since the traditional single-family and multifamily residential buildings built during the Million Program are old, the indoor temperature is often uncomfortable for the occupants. Since people living in northern climates spend most of the time indoors, it is important to ensure thermal comfort for the occupants. Therefore, energy-efficient renovation measures should be considered for the comfort of the residents and to ensure the efficient energy use.

In this study, the relationship between energy efficient renovation and thermal comfort have been investigated. The purpose of this study is to examine the influence of energy-efficient strategies on energy use and thermal comfort in the single-family residential buildings built during 1965 and 1975. The experiments carried out in this study focuses on evaluating the thermal comfort condition before and after renovation in single family residences.

The proposed methods in this study for assessing the thermal comfort condition can be useful in determining the actual indoor thermal environment in single-family residences. The results in the study showed that if all the energy-efficient strategies are taken into consideration, it is possible to reduce the energy usage up to 70%. Therefore, it means that energy-efficient renovation are beneficial in terms of energy use. The results of this study shed light on linking the energy-efficient renovation and thermal comfort. The thermal comfort condition was examined before and after renovation in two case study buildings from the Million Program. The results revealed that the indoor temperature during winter in a non-renovated house was extremely low due to the heat losses through the building envelope. On the contrary, in a renovated house the indoor temperature often exists in a comfortable range as the building envelope was airtight and well insulated. During summer the implementation of shading device cut down the overheating hours efficiently and kept the temperature within the comfort range. The renovation measures improved the indoor thermal environment and enhanced the comfort level of the occupants. A few contributing factors such as orientation and window-to-wall ratio can influence the dissatisfaction level of the occupants. The maximum glazing area situated towards southwest can be beneficial for receiving more daylight during winter. However, the results showed that the zones suffered from overheating period in spite of having external shading. Therefore, careful considerations are necessary while designing the layout of the buildings to ensure satisfactory thermal comfort level for the occupants.

The findings are applicable for any single-family residential buildings built during the Million Program. This study shows the variation in thermal comfort level between a renovated and non-renovated building. The findings can motivate the residents’ decisions to adopt different energy-efficient strategies as the strategies can positively influence the thermal comfort level.

• author: Bhattacharjee, Shimantika
• supervisor: Åke Blomsterberg
• organization: Division of Energy and Building Design
• course: AEBM01 20161
• year: 2016
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Energy-efficient renovation, thermal comfort, energy use, indoor thermal environment, The Million Program.
• language: English
• id: 8886295
• date added to LUP: 2016-07-04 11:17:17
• date last changed: 2016-07-04 11:58:01