In the last issue of the Canadian Design & Construction Report magazine, Rob Dembo, Founder & CEO of Zerofootprint, wrote about re-skinning – or re-cladding – the exterior envelope of older, existing buildings to improve energy efficiency.
Continuing along the same themes – building envelopes and energy efficiency -- whether wrapping or replacing an existing envelope with a new system, or designing a new building altogether, the challenges to maintain technical integrity and improve energy efficiency remain the same for the design and construction industry.
For example, one major challenge is avoiding thermal or cold bridging, where heat or cold strays into or out through the building’s enclosure by means of a conductive, non-insulating material or a mix of materials touching each other. The heat or cold, naturally, wants to run along the path of least thermal resistance, decreasing both energy efficiency and technical integrity along the way.
Bridges are usually found repeating themselves, such as metal ties in a cavity wall, or the window frames; or non-repeating bridges such as lintels piercing cavity walls; and geometrical bridges, where two planes meet, such as at a corner or roof.
Thermal bridges not only allow heat and cold to pass through building enclosures and reduce energy efficiency, but also rot enclosures from the inside out. For instance, warm air from the interior runs along the thermal bridge to meet cold air from the exterior, or vice versa, creating condensation -- water that over time eats away at brick or metal or whatever else it meets along the way.
Breaking thermal bridges, however, takes more than merely wrapping them in insulation. There has to be a clean, or near clean break.
One solution is to research, find and use materials with low or no thermal conductivity between the parts making up the bridges. A second strategy is to detail a wall with double layers, which minimizes the elements that bridge the entire wall.
The design and construction industry faces another challenge having to do with energy efficiency when deciding on windows: How many? What size? Which technology? And in what location?
High performance windows are expensive. They pay back, however, in three ways: First, with energy efficiency; second, with greatly increased occupant comfort and satisfaction; and finally, through decreased ductwork because they do not require a supply of heat directly at the window location.
It is also important to ensure that windows are located as close to the centre of the insulation as possible (given that they must also connect with the structural elements).
Airtightness is also an area in which we need great improvements. This does not mean buildings with little or no ventilation, but buildings where, when we know the points in which air works its way in, we are able to heat or cool it. Buildings which leak air not only lose heat that could have been captured, they force moisture into the walls causing all manner of problems, as we have seen across our industry.
Finally we have to be willing to prove the quality of our work through such measures as blower door tests, and through creating more reliable thermal models. These tests need to be positioned as tools for improvement. For example, a blower door test should occur before finishes are installed, so that cracks can be found and corrected.
The design and construction industry fronts the responsibility for building envelopes. They play a large part in a building’s performance. And since buildings are our biggest asset and one of the major contributors of green house gases, we can play a major role in increasing energy efficiency and decreasing overall emissions.
Continuing along the same themes – building envelopes and energy efficiency -- whether wrapping or replacing an existing envelope with a new system, or designing a new building altogether, the challenges to maintain technical integrity and improve energy efficiency remain the same for the design and construction industry.
For example, one major challenge is avoiding thermal or cold bridging, where heat or cold strays into or out through the building’s enclosure by means of a conductive, non-insulating material or a mix of materials touching each other. The heat or cold, naturally, wants to run along the path of least thermal resistance, decreasing both energy efficiency and technical integrity along the way.
Bridges are usually found repeating themselves, such as metal ties in a cavity wall, or the window frames; or non-repeating bridges such as lintels piercing cavity walls; and geometrical bridges, where two planes meet, such as at a corner or roof.
Thermal bridges not only allow heat and cold to pass through building enclosures and reduce energy efficiency, but also rot enclosures from the inside out. For instance, warm air from the interior runs along the thermal bridge to meet cold air from the exterior, or vice versa, creating condensation -- water that over time eats away at brick or metal or whatever else it meets along the way.
Breaking thermal bridges, however, takes more than merely wrapping them in insulation. There has to be a clean, or near clean break.
One solution is to research, find and use materials with low or no thermal conductivity between the parts making up the bridges. A second strategy is to detail a wall with double layers, which minimizes the elements that bridge the entire wall.
The design and construction industry faces another challenge having to do with energy efficiency when deciding on windows: How many? What size? Which technology? And in what location?
High performance windows are expensive. They pay back, however, in three ways: First, with energy efficiency; second, with greatly increased occupant comfort and satisfaction; and finally, through decreased ductwork because they do not require a supply of heat directly at the window location.
It is also important to ensure that windows are located as close to the centre of the insulation as possible (given that they must also connect with the structural elements).
Airtightness is also an area in which we need great improvements. This does not mean buildings with little or no ventilation, but buildings where, when we know the points in which air works its way in, we are able to heat or cool it. Buildings which leak air not only lose heat that could have been captured, they force moisture into the walls causing all manner of problems, as we have seen across our industry.
Finally we have to be willing to prove the quality of our work through such measures as blower door tests, and through creating more reliable thermal models. These tests need to be positioned as tools for improvement. For example, a blower door test should occur before finishes are installed, so that cracks can be found and corrected.
The design and construction industry fronts the responsibility for building envelopes. They play a large part in a building’s performance. And since buildings are our biggest asset and one of the major contributors of green house gases, we can play a major role in increasing energy efficiency and decreasing overall emissions.
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