RESILIENT INFRASTRUCTURE June 1–4, 2016 MAT-734-1 INCREASING THE DURABILITY AND RESILIENCE OF TALL BUILDINGS WITH PRECAST CONCRETE ENCLOSURE SYSTEMS Randy A. Van Straaten RDH Building Science Inc., Canada John F. Straube RDH Building Science Inc., Canada C. Alex Lukachko RDH Building Science Inc., Canada ABSTRACT 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. Keywords: Precast, Concrete, Durability, Disaster Resilience, Passive Survivability, Solar Gain, Heat Loss 1. INTRODUCTION Buildings are products that provide spaces for human use and, in most cases, occupancy. The building enclosure is the element which physically separates these spaces from the outdoors. The enclosure has support, control, finish, and sometimes distribution (e.g. electrical, plumbing, etc.) functions. How and/or how well these functions are fulfilled directly affects in-service performance and other attributes of the building (beauty, sustainability, etc.). This paper will explore how precast concrete wall systems contribute to two important attributes, durability and resilience. Precast concrete has been used successfully to provide durable building enclosures for many decades. As requirements for thermal performance, air leakage and rain penetration control increase in modern buildings, designers are often considering precast concrete to provide a low-maintenance, durable, high-performance solution. There are three broad categories of architectural precast concrete wall system: Conventional panels use precast concrete as large format panels on the exterior acting as the exterior finish and providing the enclosure support function. Double wythe insulated precast concrete wall panels (sandwich panels) incorporate thermal insulation between an exterior finish