As part of a seminar on how to avoid building envelope failures, a speaker at Construct Canada drew rough parallels with the building practices and codes of Ancient Babylon.
Of the 282 laws of the Code of Hammurabi, named after the King of Babylon from 1792 to 1750 BC, several dealt with the built environment, said Jon Juffs, a director at McIntosh Perry Consulting Engineers Ltd.
There were severe penalties for ignoring those laws, such as one which decreed that if a poorly constructed house was to fall and kill the owner: “then the builder shall be put to death.”
Present day builders don’t face that same fate, but they need to understand, plan, deal, and resist air, wind, vapour, and other elements which can negatively impact building envelopes, he said.
Consisting of slabs, roofs, walls, and other components, their purpose is to “keep the outside out and the inside in.”
When water freezes it gets bigger and with the force to burst concrete
— Jon Juffs
McIntosh Perry Consulting Engineers Ltd.
And keeping them in good shape is expensive. Residential condominiums in Ontario spend approximately $2,800-per unit on repair and maintenance, of which about 35 per cent is for envelopes, he said.
Not designing and building them properly can lead to failures which are costly to repair and sometimes can have disastrous consequences, he pointed out.
His presentation included a photo of London’s Grenfell Tower fire which killed more than 70 people earlier this year. In a post-seminar interview he cited the case of a young woman in Montreal who was killed in restaurant when a piece of cladding fell through its window.
Topping the list of deleterious forces is water penetration which can enter the building in a number of ways including gravity, air pressure, or openings within or between materials. The source of those leaks can be ground water, rain, or melting snow.
“Controlling water penetration is of paramount importance,” said Juffs, who stressed that not achieving that goal simply negates efforts to protect buildings from other elements, of which there are many.
And it isn’t just liquid water designers and contractors should be concerned about.
“When water freezes it gets bigger and with the force to burst concrete.”
Next to controlling water, managing air flow in buildings is important because air carries a lot of harmful substances such as vapour, contaminants, pollution, spores, and particles of combustion. Air movement is driven by several factors including wind/barometric changes, temperature differences, and ventilation fans, he said.
“Where does the wind come from? In Ontario it comes primarily from the northwest,” said Juffs, noting that even simple measures, such as changing the orientation of roof ridge caps, can lessen the prospect of wind driven rain damage.
Controlling vapour is also critical because it causes condensation. But it can be easily controlled, “as long as wind and air movement are both handled properly.”
Other critical measures include controlling heat flow, solar and other radiation. Ultraviolet radiation is a “particularly destructive force” to plastics, urethanes and bitumens.
Building envelope performance requirements also demand controlling noise and fire. Noise is the “the human perception of unwanted sound.” It can be greatly attenuated by mass construction techniques, distance and masking, he said.
In summing up his message, Juffs said three main criteria come into play when designing and constructing buildings: durability, esthetics, and economics.
“These requirements are difficult to reconcile, like quality, speed and cost. Choose two at the detriment of the third.”
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