"You emply stone, wood and concrete, and with these materials you build houses and palaces: that is construction. Ingenuity is at work." - Toward An Architecture, Corb
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CLT Modular Housing
Understanding the efficiencies in Prefabrication, Cross-Laminated Timber, and Modular Housing - Where construction becomes an analysis of sustainable measures.
Cross Laminated Timber
A lot of the motivation for this post is coming from a current entry and a construction analysis paper that I put together in my freshman year of MArch back in 2015. Nevertheless, it is another chapter in this "blog-saga" that I find relevant to share.
In a time where our resources are becoming finite and our eco-system has proven to show some negative repercussions for our daily environments, as architects and builders we must understand and acknowledge the materials being used in our projects to their full influence and potential. When addressing materiality in any construction, it is important to emphasize on issues of sustainability and carbon emissions that our materials can and will have an impact on. For most of the 20th through the 21st Centuries, we have been using inorganic materials such as concrete, masonry and steel. Hence, the revolution and introduction of Cross-Laminated Timber, a wood panel product made from gluing layers of solid-sawn lumber together, in any project should be applauded and recognized as a building and structural material that works for an environmentally friendly approach.
Most of CLT construction projects, which are not too many, as this is a new way of construction, use a platform construction process. In which they set each floor on the walls below until reaching the final roof ceiling and in order to secure the joints and alignments of partitions-to-floors, screws and angles are positioned. Much like the system used with pre-fabricated wall panels. But today, our focus and interest is on modular housing which is prefabricated off-site and then brought onto site for an easy and quick assembly. The benefits are in this kind of construction material, CLT, and in the construction type, modular. Not only is CLT much easier to assemble on-site rather than poured concrete, it is a much greater structural property than steel and/or reinforced concrete and a much more sustainable property since it does not require the burning of fossil fuels during its production. This provides an advantage in cost of materiality taking away any massive need of steel or reinforced concrete for structural properties, while also providing the advantage of a quick construction process of about 3 times less the time of any other construction type.
Moreover, the materiality of Cross Laminated Timber, specifically solid wood panels have much more efficiency in carbon footprint than carbon masonry, in which studies have shown a 40% advantage of carbon emissions release than most commonly used material types. CLT also allows for an achievement in requirements of fire resistance, through the chemical process known as charring, where materials are heated to its maximum incomplete combustion providing a 60-minute fire resistant material. After installation of the CLT, plasterboard is always added for an interior finish and this adds a 90-minute fire resistance to the final wall property. This becomes extremely relevant and efficient when considering the building and fire codes that require significant materiality and layers to acquire the desired fire-resistance. The same way CLT can be manipulated for fire resistance it can be reused as a waste material, and therefore, is a significant sustainable material. It is also a great product of thermal insulation as it's thickness allows for the storage of heat for longer times than any other thermal property.
To be able to take this material property and use it through Modular Construction is just another benefit to the client, construction and building process. The design of sustainable architecture can be produced at a high level with CLT and off-site modules. Since the CLT exterior/interior walls and CLT slabs are angled when jointed, it is a relatively easy on-site construction and assembly. This makes the planning of electrical wiring, plumbing and mechanical features much easier to bring into the assembly of the total structure. Again we can consider the cost of labor, material use and the ability to provide an efficient architectural typology for building processes as shown in the related drawings. The use of modules can be applied to different architectural schemes and designs based on the building footprint and allowable design area on a site.