by Bohdan Rewko (Bo of T.O.)

Created on: November 18, 2011

The construction industry is notorious for slowness when it comes to change. It is partly understandable, given that real estate development involves major capital investment and few people are willing to take chances with their money. We have seen the folly of rushing into new and cheaper ways of doing things only to pay the price later. Aluminum wiring and toxic ureaformaldehyde insulation are just two examples.

At the same time, we keep repeating mistakes in the industry because of traditionally ingrained practices that were acceptable on a small scale, but not on modern large scale projects. When it comes to high rise buildings, the most glaring of these involves the way in which we enclose structures and enable thermal bridging to take place, that is, allowing cold to get into our buildings unimpeded. In southern climes it does not matter too much how buildings are enclosed. But in Canada and the northern United States where temperatures routinely dip below freezing, this poses a significant problem.

Thermal bridging is not only a comfort issue; it can have a major impact on the cost of maintaining buildings and it can shorten their life span. Uncontrolled freeze-thaw action on the surface of buildings contributes to the deterioration of building facades and even adjacent concrete floors within buildings. This can happen whenever water is able to penetrate and remain in porous materials such as brick or concrete. The practice of forming concrete floor slabs and using them to support brickwork is not as prevalent as it used to be. Still many architects like to use concrete floor slabs in a sculptural way as they create sweeping horizontal fins and balconies that unite exterior and interior spaces of their buildings. In the process they create thermal bridges that have adverse effects on buildings for as long as they keep standing.

The best way to enclose buildings in colder climates is to put a jacket on them. In other words, we need to cover them up so that there is as little interior structure exposed as possible. One of the best ways to do this is through a curtain wall system, as typified by buildings that are predominantly glass. There are new curtain wall systems that create a virtually complete separation between the exterior skin of a building and its interior structure. Even the bridging portion of frames where double-sealed glazing units are attached, are made of an insulating material that slows the migration of cold into a building. Where there

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