Socio-Technical Dimensions for a Sustainable Housing Transition
6.3 Physical Attributes
improved building quality and performance outcomes, and low energy bills, this approach has been allowed to continue. However, in the con- text of rising energy bills and the climate emergency, it is an approach that is no longer suited for housing.
The physical elements of new housing and renovations of existing housing tend to be similar to previous housing unless otherwise specified (and paid for) by a knowledgeable client, or if regulatory changes require it. Using similar practices for each construction project is perceived to offer financial and logistical advantages, such as buying materials in bulk, building trusted relationships with supply chain stakeholders, and knowl- edge of working with the technologies or materials leading to controlling some of the variables involved in the construction (or renovation) of a dwelling [1]. While there may be a perception that the dwelling owner has significant opportunity to engage in the design, material, and techno- logical decisions, this is often limited by what the industry (or specific stakeholder) offers. Subtle variations to a dwelling design can often add significant costs (and time) for a dwelling owner and they are often struc- tured this way to dissuade consumers from wanting things outside the normal provision of standard housing.
As Smith [1] and others found, the existing housing industry is not typically focused on how to improve design, quality, and performance (e.g., life cycle considerations). There is often little consideration for materials used in construction in terms of where they come from and what their inclusion means for the building or household. The focus is mostly around cost and ease of access. A just in time structure by many industry stakeholders to the ordering and delivering of materials also means that the construction industry needs certainty on product avail- ability and costs, which has created familiar supply chain relationships that entrench practices. When sustainability elements are included, it is often the “bolt on” options (e.g., adding solar PV to a dwelling), rather than make deeper design and construction changes (e.g., improved insu- lation) to significantly improve the overall quality and performance of the dwelling.
Stakeholders involved in delivering sustainable housing think more holistically about the dwelling and centre on occupant needs. For the sus- tainable house (or renovation), designs typically begin from the ground up
rather than trying to take standard designs and add sustainability elements to them [17]. In this way, sustainable housing providers can ensure they are maximizing key sustainable building technology and design principles such as orientation, passive solar, insulation, advanced window glazing, rainwater collection and storage, the use of local materials, and more.
Incorporating these ideas from the start generally helps to reduce costs, both capital costs and through-life costs. To date, these sustainable hous- ing stakeholders often have specialist sustainability design knowledge and/
or have learnt by doing and experimenting with what works (or does not work). As the number of sustainable houses being constructed or retrofit- ted increases, key ideas around what design, material, and technology ele- ments work means that future projects can build upon those that have come before without having to re-invent the design each time.
The scale of sustainable housing has changed in recent decades. Earlier sustainable housing examples were seen as unique, one-off small-scale designs that were so far removed from the typical housing market that they were not considered feasible for many housing consumers. The use of things like mud bricks, inclusion of off-grid renewable energy systems, or composting toilets were not seen as appropriate for the average hous- ing consumer, nor were these approaches easy to scale up. As knowledge, understanding, and technologies have improved, there are increasing examples of sustainable housing that looks and feels like standard hous- ing. In addition, with more evidence becoming available about the life cycle of various design decisions, materials, and technologies, there is a shift in focus from reducing occupancy impacts (e.g., heating and cool- ing) to reducing embodied energy impacts and considering what happens at end of life.
6.3.1 Cross Laminated Timber
An increasing area of physical attributes focus within the sustainable housing field has been on material innovations in order to make sustain- able housing scalable, reduce costs, and improve quality and performance.
Cross laminated timber (CLT) is an example of such innovation [27].
CLT is an engineered timber product composed of multiple layers of
two-dimensional lumber glued together perpendicular to each other and compressed tight. As a naturally fire-resistant product, CLT was first used for walls, floors, and roofs in both residential and non-residential con- struction. The benefits of using CLT include a high degree of prefabrica- tion and off-site assembly, and compared to light-weight timber construction, CLT has less air permeability and more capacity for humid- ity and thermal energy. CLT is also able to act as a load-carrying element, which makes it applicable as a stand-alone structural element, and it is being used as a substitute for reinforced concrete. This makes it an appro- priate substitute for reinforced concrete, helping builders reduce their carbon footprint as CLT is much less carbon intensive than concrete and steel. More recently, CLT has been used to construct tall timber struc- tures of up to 18 storeys. Examples include “Treet”, a 49.9 metre-high apartment tower in Bergen (Norway) design by architectural office ARTEC [28]; “The Toronto Tree Tower”,2 a 62 metre-high residential tower in Toronto (Canada) designed by Penda (now Precht); and
“Carbon12”,3 a 26 metre-high mixed-use building (residential and retail) in Portland, Oregon (USA) designed by Kaiser+Path. At the time of writ- ing, there are proposed residential towers of 90 and 100 metres tall using CLT in Toronto and Switzerland, respectively. If built, these buildings would be the tallest mass timber structures in the world.