January 30, 2020
by Ted Winslow
Canada is a vast country with drastic differences in topography, rainfall, and humidity—all factors influencing the decisions of builders and architects when they are creating comfortable and energy-efficient structures. With nearly all of Canada sitting north of the 45th parallel, insulating homes, businesses, and industrial applications to achieve thermal efficiency is a persistent challenge. Thanks to long winters and cold temperatures, many of Canada’s structures are in a constant battle against energy loss.
There are many reasons for building professionals to be concerned about proper insulation. According to a recent report, Canada produces more greenhouse gas (GHG) emissions than any other G20 country. While a great deal of that is attributed to oil and gas transportation, much of it stems from the costs of heating and operating buildings in colder climates. For example, commercial buildings account for over 50 per cent of the country’s total electricity consumption and roughly 28 per cent of the nation’s GHG emissions, according to the National Science and Engineering Research Council of Canada (NSERC). According to Natural Resources Canada (NRCan), 80 per cent of residential energy consumption can be attributed to space and water heating alone. Canada is a vast country with drastic differences in topography, rainfall, and humidity—all factors influencing the decisions of builders and architects when they are creating comfortable and energy-efficient structures. With nearly all of Canada sitting north of the 45th parallel, insulating homes, businesses, and industrial applications to achieve thermal efficiency is a persistent challenge. Thanks to long winters and cold temperatures, many of Canada’s structures are in a constant battle against energy loss.
Proper insulation is crucial in mitigating long-term operating costs for building owners. It also goes a long way toward helping Canada meet its ambitious national goal of reducing GHG emissions to no more than 511 million tonnes by 2030 (down 70 per cent from 2005 levels).
Designing for thermal control
Temperatures vary widely from region to region. For instance, the average January low for Toronto is –10 C (14 F) while Winnipeg is –23 C (9 F). In Yellowknife, N.W.T., the average January temperature is a frigid –31 C (24 F). Designing for maximum thermal control should be top of mind for every builder and architect.
Additionally, it is critical to have a good understanding of heat transfer and thermal efficiency. Heat flows naturally from areas of high to low temperature. The bigger the temperature difference, the more the heat flows (or transfers) through an assembly. For example, a heated building will lose heat to its colder exterior in the winter, and in the summer, an air-conditioned building will draw heat from its warm exterior. In the makeup of walls, pipes, and other mediums, certain materials speed up the rate of heat transfer or hinder it. Conductors like metal transfer heat very well, while insulators like fibreglass have a high resistance to heat flow.
Conduction, convection, and radiation—the three modes of heat transfer—occur simultaneously and play an important role in balancing the thermal performance of a building. Conduction, or the transfer of heat energy through a substance or material takes place when a material separates an area of high temperature from a space with low temperature, such as a wall. Convection, forced or natural, happens when a liquid or gas moves over a surface, such as wind blowing against a building. Natural convection occurs when the movement of liquid or gas is caused by density differences. In forced convection, the movement of the liquid or gas is precipitated by external forces. Radiation involves the transfer of electromagnetic heat waves from one object of higher temperature (e.g. the sun) to another of lower temperature.
Structural components in buildings are highly conductive and create thermal bridges. For instance, metals conduct 300 to 1000 times more heat than most building materials. This means a metal stud has an exaggerated effect on heat transfer that is out of proportion to its physical size—even greater than the material’s actual surface area—making the selection of proper insulation assemblies crucial. To create a more energy-efficient and comfortable building, design professionals must find ways to ‘break’ thermal bridges to reduce the transfer of heat energy through the wall (or roof).
While heat transfer cannot be stopped entirely, it is possible to significantly slow down the process by placing appropriate obstacles in its path. Here are some ways to design with insulation in mind in various scenarios.
Home is where people spend the majority of their time and want to feel most comfortable, so it is important residential insulation systems successfully address airtightness, thermal performance, and moisture management.
Airtightness is a commonly overlooked aspect of heat transfer and can become a greater challenge as buildings age. For new homes, spray foam insulation that expands to fill potential air gaps can be a suitable solution for open spaces like attics, and can help create a more energy-efficient living environment. In many cases, more of the cost-efficient solutions chosen incorporate a combination of different types of components, such as housewraps (for large exterior areas), tapes (for sealing seams and protecting window and door leaks), caulks, and sealants. Entry and exit points of pipes and wires are potential areas of heat loss. Using caulk and sealants on the outside (and inside) of the home and spot treating with spray foam around plumbing and electrical penetrations can address porous areas where heat can escape. Even simple solutions like including gasket covers on all outlets and light switches can make a big difference in preventing the outflow of heated air. The baseboards where walls and floors meet tend to be drafty, so special care must be taken to ensure those junctions are properly caulked and sealed.
While less common in modern residential buildings, crawl spaces are still used by builders for convenience and upfront cost savings. Levelling a sloping lot for a concrete pad can be expensive, and a crawl space eliminates that need. It can also be a convenient place to route HVAC, water, and sewer connections. Crawl space insulation is not a big deal in hot climates. However, in colder regions, uninsulated crawl spaces can be money pits where heated air could exfiltrate the building. Despite the inefficiency, there are many homes in the United States and Canada with dirt-floored, vented crawl spaces. Insulating crawl spaces ensure a tighter building envelope, and places significantly less stress on heating systems. Additionally, fibreglass batts between floor joists (where pipe and wire conduits are located) help prevent heat loss between the floor and anything below it.
Properly insulating homes is all about finding balance. As insulation materials have improved in quality, moisture and mould prevention has become an increasingly important issue—the more energy efficient and airtight a home is, the less efficient it is at being able to dry out when moisture gets in. As builders have pushed for tighter building envelopes and lower Home Energy Rating System (HERS) scores, manufacturers have responded by developing thicker and more effective insulating materials. These additional insulating layers and new materials, however, have not managed to keep moisture from rain and vapour out of walls. Over time, trapped water can damage wall assemblies, create mould, and degrade critical framing assemblies. Employing continuous exterior insulation with interior cavity fibrous batt insulations in combination with a smart vapour retarder—one that ‘breathes,’ becoming more porous as humidity increases—allows trapped wall moisture to dissipate into the conditioned air space.
Due to an especially cold 2017 winter season, Canada’s GHG emissions actually went up that year—far short of its reduction targets under the Paris climate agreement. As Canada takes steps to become more energy efficient and eco-conscious, developers must pay close attention to commercial building designs that burden power grids and contribute to air pollution via energy generation. Using insulation products made with plant-based/organic binders (as opposed to formaldehyde and harsh acrylics and dyes) and containing high-levels of recycled content supports green construction, and helps buildings achieve Leadership in Energy and Environmental Design (LEED) certification and other sustainability credits.
Commercial buildings—typically built from concrete and metal—are rife with thermal bridging. Both concrete and metal offer poor heat flow resistance between exterior walls and the outside. Metal stud framing, common in commercial construction, is a major source of heat loss due to the material’s conductivity. Incorporating appropriate amounts of thermal insulation into the wall assembly is a good first step toward an effective thermal control strategy. Commercial thermal insulation options include cavity insulation, which occupies space inside the wall cavity, and insulating sheathing, which is installed over the exterior walls.
A steel stud cavity wall with a masonry façade is the most common type of wall assembly for commercial buildings. In cold climates, designers can improve thermal performance and control cavity condensation by:
These are cost-effective ways to achieve thermal performance while managing moisture and reducing the saturation of substrate materials.
Insulating sheathings can be installed inside or outside of concrete block and tilt-up walls. A common insulating material for this construction is foam plastic insulation board. The location of the sheathing varies based on climate and material type. Interior non-loadbearing steel-framed assemblies can support cavity insulation. Fibreglass batt insulation inside the cavity increases the thermal efficiency of commercial buildings. It is moisture resistant and eliminates heat loss when combined with structural insulated panels. Since thick concrete has insulating value, some building codes have reduced insulation requirements. However, it is advised to exceed code requirements to achieve the highest level of energy efficiency.
Exterior insulation systems typically resemble traditional stucco and create a thermal break between exterior walls and the surrounding environment. If an exterior finish does not accommodate insulation, a continuous insulation (ci) board inside of the wall assembly is a good option.
ASTM C518, Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus, is used to measure the thermal properties of building materials. A heat flow apparatus measures heat transfer through homogeneous materials such as insulation. The performance of those materials is rated according to thermal conductivity (K), thermal conductance (C), and thermal resistance (R-value). Every region of Canada mandates a different mix of techniques and insulation requirements based on the annual rainfall, moisture, elevation, etc. For that reason, the Canadian Wood Council (CWC) sponsors a building product calculator, which displays the latest thermal-resistance code requirements in a selected climate zone and suggests the most appropriate materials.
Mechanical insulation, including thermal protection for HVAC systems, mechanical piping, and marine and industrial uses, is overshadowed by traditional building insulation. However, the insulation is just as important in mechanical equipment and boats as it is in buildings to combat energy loss and control operation costs.
In cold environments, fibreglass blanket insulation is an effective and inexpensive method of reducing heat flow. Blanket insulation keeps structures warm, decreasing the stress on furnaces and other heat sources. In warm environments, blanket insulation blocks heat transfer into the structure and can reflect heat outward if a radiant barrier is attached, making it quite versatile. When installed at the proper thickness, a foil scrim kraft (FSK)-faced, flexible fibreglass blanket insulation placed around the exterior of rectangular and round HVAC ductwork reduces unwanted heat loss or gain. It also eliminates ductwork condensation problems that can lead to mould and microbial growth.
Semi-rigid fibreglass board can be used in a variety of new and retrofit construction to provide thermal and acoustical insulation in exterior wall cavities where framing is not present. This is useful in large, open structures such as parking decks, mechanical rooms, theatres, sports arenas, shopping centres, and utility plants. When used in the exterior envelope of steel-framed buildings, fibreglass board minimizes temperature fluctuations that can occur in the winter and summer through heat loss and gain.
For voyaging boats and other marine vessels, natural condensation can be a frustrating problem. When temperatures reach the dewpoint, condensation can form on interior surfaces of an uninsulated, or under-insulated, hull or deck. This can be uncomfortable for sailors, who already face a wet and unforgiving world above deck. Condensation can be prevented by adding a sufficient layer of insulation and sizing so the surface temperature will be above the dewpoint.
Hulls and decks are made of wood, fibreglass, metal, or a combination of materials, each with various degrees of thermal conductivity. Boosting the thermal resistance in the form of insulation decreases thermal loss, reduces heating costs, and lowers fuel demands. For boats, weight is often an issue when it comes to insulation. Boats operating in cold waters need adequate insulation to keep their crews warm and protected while not limiting freight capacity, so opting for a lighter insulation product offering similar benefits to other options can be a smart investment.
Builders and architects working in Canadian markets have their work cut out for them when it comes to specifying proper insulation. However, the right tools and knowledge can help builders design structures that punch above their weight in efficiency and comfort.
Ted Winslow is the brand product manager of building science, systems, and technical marketing for CertainTeed Insulation. He serves the company as a technical resource on topics ranging from code reviews to sustainability programs, and oversees development of CertainTeed insulation systems. Winslow holds a bachelor’s degree in mechanical engineering from Temple University. He can be reached at firstname.lastname@example.org.
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