Energy renovation packages for the decarbonisation of Swedish multifamily buildings

Abstract

Sweden and Europe aim to be carbon neutral by 2045 and 2050 respectively. Upgrading the existing building stock has been identified as having great potential in assisting to realise these goals. This aged, energy inefficient building stock is poised for renovation towards carbon neutrality, and the investigation of the cost-effectiveness and possibilities for these were the main aim of this study.

Popular Abstract

Half of Europe’s building stock was built before energy performance was a focus resulting in a large share of the current building stock being energy inefficient while 85-95% of them will still be in use by 2050. Sweden’s building sector accounts for one fifth of its greenhouse gas emissions, while 20% of Sweden’s buildings constructed in what is commonly known as the “The Million Home Programme” this is also sometimes known as the “post-war” housing boom in Europe, which is in an urgent need for extensive renovation. Renovation provides an opportunity to reduce greenhouse gas emissions, through reducing typically high energy use in these buildings, and is further beneficial when it aids in avoiding high impacts associated with building new buildings were possible.

This study aimed to analyse a series of cost-effective renovation packages for buildings in the Million Home Programme, with achieving carbon neutrality as a key driving factor. Carbon neutrality is the process of balancing emissions of carbon dioxide with its removal or by avoiding its emissions in certain processes. The study investigated more environmentally conscious and innovative renovation options along with the more typical renovation measures currently used in the Swedish market. Furthermore, parametric analysis was used to ensure that every combination of the 30 inputs parameters were considered, resulting in thousands of possible solutions. The renovation measures considered (input parameters) ranged from installing various insulation types on either the façade or roof in various thicknesses, improvements to the windows, along with active measures such as a balanced ventilation system with heat recovery or an exhaust air heat pump. All these options were also coupled with various levels of photovoltaics on the roof resulting in 11 292 packages assessed.

The holistic overview of the results was broken into two main categories. The first was profitability against the base case of undertaking the required maintenance that these buildings required due to age and potential neglect. The second criteria, which is the key focus of the study is what packages achieve a good level of decarbonisation or achieved carbon neutrality. Only 8% of results proved to be both profitable and below a threshold value considered to be suitable for decarbonisation.

A common Swedish carbon neutrality definition called NollCO2 was adapted to suit the renovation project in this study. The reliance of the NollCO2‘s definition on offsetting coal from renewable electricity overproduction meant that careful consideration needed to be taken for the various inputs of the photovoltaic system in order to not have over exaggerated results. Through this the results for decarbonisation clearly showed that the most favorable results were those that incorporated high levels of photovoltaics. This also rang true on the profitability scale together with having the incorporation of storm windows was also very favorable and generally not having too high levels of insulation achieved a good balance for decarbonisation, profitability and energy reduction.

The study concluded that it was possible to renovate the existing building stock and achieve carbon neutrality in a cost-effective manner. However, NollCO2‘s definitions possible overreliance on renewable electricity meant that even well performing measures that reduced the ability to sell back electricity appeared less favourable even if it performed well from an energy and cost perspective. Assessing the current state of a building and addressing the weakest points regarding heat loss is crucial for achieving a high decarbonisation rate within fair costs. Furthermore, intensive renovation that focuses on energy reduction alone may not be beneficial from a carbon neutrality and cost perspective. Rather conscious renovations that assess the tri factor of cost, carbon and energy are paramount in order to achieve a high level of decarbonisation.
Factors such as increased thermal comfort were not considered in this study, but could influence decision making. If budget limitations were a factor, many of the envelope only renovations came close to achieving carbon neutrality, and on a project specific level could be altered to achieve such. Finally, a renovation specific definition for attaining carbon neutrality will be necessary to guide renovation projects to align with European and Swedish carbon neutrality targets. Such a certification system could also boost the desirability for property owners to renovate towards carbon neutrality.

• author: Daya, Bhavik and Nolan, Hugh
• supervisor: Ricardo Bernardo
• organization: Department of Architecture and Built Environment; Division of Energy and Building Design
• course: AEBM01 20221
• year: 2022
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Decarbonisation, Renovation, Multi-family homes, Life Cycle Assessment, Life Cycle Costing
• language: English
• id: 9086172
• date added to LUP: 2022-06-13 11:23:31
• date last changed: 2022-08-26 15:41:13