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The report analyses the embodied carbon 503 as-built low-rise homes in the Greater Toronto and Hamilton Area. Based on a A1-A3 analysis using the BEAM tool, the results ranged from a high of 90.7 tonnes of CO2e to a low of 9.5, with a mean of 42.9 tonnes. The material carbon intensity for heated floor area ranged from a high of 561 kg CO2e/m2 to a...
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... Timber framing, particularly for external walls, offers the opportunity to achieve high insulation thicknesses and thus reduce the operational environmental impact through reduced heating requirements during the cold seasons. However, the most commonly used mineral or plastic-based building materials for thermal insulation are currently responsible for approximately 26.1% of the total embodied CO 2 in construction [10]. Recent research shows that timber constructions with insulation that has a hygrothermal behaviour similar to that of wood are generally more robust and, therefore, more durable [11]. ...
The use of renewable building materials in construction is crucial to minimising the environmental impact of new buildings. Bio-based building materials have a wide range of positive properties, many of which are due to their hygroscopic behaviour. The purpose of this study is to investigate the hygrothermal performance of chopped straw, sheep’s wool, and cellulose insulated timber frame external wall assemblies in the presence of air leakage and high indoor relative humidity. For this purpose, tests with different moisture contents, overpressures, and defects in the airtight layer were carried out in an outdoor test stand over a period of 18 months. The results were compared with a conventional mineral wool insulated construction. Both sheep’s wool and cellulose are particularly fault-tolerant insulation materials in combination with timber frame constructions. All three bio-based insulations, despite defects in the airtight layer, showed no mould-prone moisture content. An installation level insulated with sheep’s wool can increase the fault tolerance of constructions with insulation made of hygric and more sensitive building materials. For chopped straw and cellulose, the measured U-value was lower than expected. Further in situ measurements of bio-based structures are important to gain confidence in their hygrothermal behaviour and to increase their use in multi-storey construction.
... However, insulation materials are one of the largest contributors to emissions and, therefore, to the environmental impacts of the construction materials. Research on 503 buildings found that 26.1% of total carbon emissions came from insulation material production [9], the largest after concrete production that represents 33% [9]. Nonetheless, with recent concerns to improve energy efficiency, more insulation tends to be used in buildings. ...
... However, insulation materials are one of the largest contributors to emissions and, therefore, to the environmental impacts of the construction materials. Research on 503 buildings found that 26.1% of total carbon emissions came from insulation material production [9], the largest after concrete production that represents 33% [9]. Nonetheless, with recent concerns to improve energy efficiency, more insulation tends to be used in buildings. ...
... However, despite carbon sequestration due to biogenic carbon, a thicker layer of the material might be needed to provide the same thermal resistance. A comparison between insulation material thickness and carbon dioxide emissions for a thermal resistance of 5 (m 2 K)/W can be observed, adapted from [9]. When it comes to building renovation, which is specially addressed in the latest European directive, EPBD recast 2022 [7], it is essential to understand that in the past, passive strategies, including the use of bio-based insulation materials, were the main principle to deal with thermal comfort. ...
Within the context of climate change and the environmental impact of the building industry, insulation materials contribute to improving the thermal performance of buildings, thus reducing energy demand and carbon emissions during the operation phase. Although most of them are responsible for significant carbon emissions during their production, bio-based insulation materials can provide good performance with low carbon emissions. This paper aims to investigate natural insulation materials' properties and environmental impacts through a literature review. Due to the growing importance of Environmental Product Declarations (EPDs) on specification requirements, many manufacturers already disclose environmental data related to their products, allowing for a comparison between thermal insulation solutions. In academic research, embodied environmental impacts are not as explored as physical properties. In addition, from the analysis of results, it is possible to conclude that the characterization of the physical properties of this type of material is normally focused on thermal conductivity. Nevertheless, most studies overlook other important parameters of these materials, such as the thermal capacity, lifetime, and environmental impacts. This is something that is necessary to overcome in future developments to allow for a comprehensive comparison between the properties of different (conventional and bio-based) insulation materials.
Global environmental awareness pushes the building sector to achieve carbon neutrality and find low embodied impact solutions. The European Union has set a 2050 goal and is regulating the whole carbon life cycle (embodied and operational) as part of the Energy Performance of Buildings Directive (EPBD). In this scope, low-tech geo-bio-based materials can have an important role in reducing the embodied environmental impacts and carbon in buildings. Due to their low processing production, these materials fit in a circular approach since they can be easily recycled or returned to the natural environment at a minimal environmental cost. However, the lack of quantitative data on the life cycle environmental performance of some non-conventional techniques can hinder their use since professionals cannot compare the benefits of such versus conventional practice and comply with future EPBD requirements. This paper aims to contribute to the topic by presenting results on the life cycle environmental performance of earthen materials and bio-based insulation products versus conventional solutions based on data from Environmental Product Declarations or studies following the EN15804 standard. The results show that earthen materials can reduce the potential environmental impacts by about 50% versus conventional mansory walls. At the same time, bio-based insulation solutions offer the advantage of lowering operational carbon emissions and stocking carbon (e.g. straw has a Global Warming Potential performance about three times better than Expanded Polystyrene). The benefits of using earthen and bio-based materials are also discussed for the different building life-cycle stages, focusing on the possibility of reusing/recycling these materials in a closed-loop approach.
To create a resilient future, architectural design students must be trained to understand today’s challenges associated with quantifying embodied carbon and designing within a fledgling circular materials economy. In the Spring of 2022, interior architecture students at Sacramento State University were guided through an unexpected opportunity to deconstruct the defunct Solar Decathlon house. They spent the better part of the semester working as a team to remove, count, downcycle, and donate as much of the material from the building as was safely possible. The students then categorized and analyzed their results and considered what they had learned about the flexibility of each component for reuse. The house’s concrete foundation was also its largest embodied carbon emitter, but this was only part of the story. Like a thousand tiny papercuts, this project also revealed a multitude of materials that could not be readily removed, quantified, reused, or diverted from a landfill. The process of deconstruction exposed these elements and prompted questions about the connections between carbon, labor and design. The hands-on nature of this project was a practical and relevant way for students to begin to engage with calculating embodied carbon, understanding the economic system of reclaimed materials, and designing for deconstruction. Lastly, this project opens questions about immediate need and methods to teach students about embodied carbon in existing buildings and the challenges we face in designing a carbon-neutral and resilient future.
Summary of five studies of embodied carbon in low rise residential structures and insights based on these studies.
The building sector is responsible for a significant portion of global CO2 emissions and any attempt to meet global climate change mitigation goals requires dramatic reductions in CO2 emissions from building construction and use. Among the many green building certification programs intended to reduce the environmental impact of buildings, the passive house standards are one of the most stringent certifications with respect to reducing operational energy. While there is significant research demonstrating the reductions in operational energy use in passive house and passive house inspired buildings, there is comparatively little research into the embodied energy and embodied carbon emissions associated with these buildings. The aim of this research was to evaluate the relationship between embodied carbon emissions, operational carbon emissions, and overall carbon use intensity in passive house certified residential buildings, using a recently completed, multifamily passive house as a case study. First, the case study building was defined, and a partial life cycle assessment (LCA) was performed to evaluate the embodied and operational carbon emissions associated with this base case. Second, a catalog of alternative wall and roof assemblies were defined and the LCA of the case study was updated for each alternative assembly to assess the impact on the embodied carbon, operational carbon, and overall carbon use intensity. The results of this analysis indicate that the material composition of the exterior envelope assemblies can have significant impact on the overall, cumulative carbon impact of a particular building. Moreover, the results also indicate that there are clear scenarios in which operational energy efficiency should be sacrificed in favor of reducing upfront embodied carbon emissions, particularly when evaluated over critical time spans. Based on these results, this study recommends that green building standards and certifications, including passive house but also USGBC LEED, Living Building Challenge, and others, should place greater emphasis on embodied carbon and holistic carbon accounting in addition to operational efficiency.
