By Randy van Straaten, PEng, PhD, John Straube, PEng, PhD, and C. Alexander Lukachko, MArch
In this paper precast concrete wall systems are compared to curtain wall and window wall systems in terms of durability and disaster resilience of multi-story buildings. Window wall systems are currently the enclosure system of choice for tall residential buildings in most parts of North America. Precast concrete wall systems can be expected to last the lifetime of a building with routine seal replacement. These are highly durable systems. Windows within precast concrete wall systems will require replacement in 25-35 years but represent a limited portion of the wall area and hence are less costly and have less impact on building use interruption.
The impact of façade choice on passive survivability and security are also considered. Maintaining livable temperatures in a space in Toronto, Ontario (a city with a climate similar to many Northern U.S. cities) during a power outage is shown to mostly depend on having little heat loss, reducing solar gains, and provision of thermal mass. A whole wall metric is also introduced which combines various vision and non-vision wall system heat loss components. A similar metric for solar gain is introduced. The most significant factor affecting this heat loss and solar gain (and thereby affecting thermal resilience) is to avoid high Window to Wall Ratios (WWR). This will apply for most wall systems but is most significant for systems like precast concrete where there is minimal thermal bridging through the insulation. In terms of security, precast concrete walls will protect occupants from projectiles and endure little damage during disasters. These impacts make precast concrete wall systems significantly more disaster resilient.
Note: This article was presented at the 2016 Annual Conference of the Canadian Society for Civil Engineering. Copyright 2016 by the Canadian Society for Civil Engineering. Reprinted by permission at buildingsciencelabs.com, for private use only. For more information about conference proceedings, visit https://csce.ca/publications/past-conferences.