Decarbonization Tool
ADRIEN GAUDELAS
ADVISOR, TRAINING CONTENT DEVELOPMENT, CECOBOIS
Biobased products provide an effective means of reducing the carbon footprint of buildings. While efforts have primarily focused on the use of structural wood solutions, biobased thermal insulation materials are also currently available.
Biobased insulation comes in several forms: Loose-fill, quilt, semi-rigid panels, and rigid panels.
- When used in loose-fill form, biobased insulation can be blown into wall cavities or enclosed floor cavities, allowing for density control. It can also be blown into roof spaces. Cellulose wadding, for example, can even be sprayed with water, which bonds the fibres together, as well as to the substrate.
- In quilt form, biobased insulation is used to fill wall and roof cavities. Here, it can replace glass wool or rock wool insulation. Although less compressible than fibreglass, for example, it has become especially popular with installers due to its flexibility, which facilitates installation.
- Available in semi-rigid or rigid panels, biobased insulation provides an alternative to similar insulation products made of rock wool, polystyrene, or polyurethane foam. It can therefore be used on OSB or plywood cladding, either as an underlay or exterior insulation. These panels can be purchased pre-coated with a vapour barrier or weatherproofing membrane. Similarly, these panels can feature tongue-and-groove edges to simplify installation.
Since most biobased insulation requires little energy to manufacture, using it as a substitute for conventional insulation helps reduce the building’s carbon footprint. Table 1 illustrates the embodied emissions of various insulation options for a light wood frame wall assembly (2x6) with an OSB bracing panel (Figure 1). The comparative analysis was performed using the GESTIMAT tool for building envelope configurations that meet the same thermal performance criteria, an effective RSI above 4.05 m2.K.W-1. These products all have a thermal resistance rating that allows for their use in zones 6 through 8, according to the 2020 Quebec Construction Code, which covers the entire province.
Figure 1 Typical Above-Ground Exterior Wall Composition
Source : Cecobois
Figure 2 Analysis Summary for Insulation Combinations
Source : Cecobois
Table 1 Carbon Footprint of Above-Ground Exterior Wall Compositions Based on Cavity / Rigid Insulation Combinations
Source : Cecobois
Compared to the reference scenario, compositions that contain wood fibre and cellulose wadding show the lowest values, along with GHG emission reductions ranging between 19.2% and 38.5%. The use of biobased insulation therefore has a significant impact on the environmental footprint of the building’s envelope.
What about the other performance metrics ?
Regardless of its form, the properties of biobased insulation either match or surpass those of conventional insulation materials in certain respects.
- Hygro-thermal comfort : Biobased insulation is known to contribute to occupant comfort by regulating humidity. In fact, this type of insulation can absorb excess relative humidity from the air in a room and release it during drier periods, without compromising its durability.
- Thermal mass : The specific heat capacity contributes to a building’s thermal inertia and helps increase occupant comfort. In winter, biobased insulation stores heat from the sun during the day and gradually releases it at night, which helps reduce consumption peaks while spreading out energy demands. Similarly, this also helps mitigate heat spikes inside the building during the summer months.
- Soundproofing : Biobased insulation can also be used as acoustic insulation, like any other conventional solution. Semi-rigid wood fibre insulation and rigid cork insulation, for example, are particularly effective for this purpose.
- Fire resistance : Biobased insulation may contain up to 15% additives (typically borate), which makes it fire-resistant while providing resistance to mould and pests.
- Water resistance : Biobased insulation is no less resistant when exposed to liquid water or excessive water vapour. In reality, conventional insulation materials like fibreglass do not show greater effectiveness in this regard. When exposed to water, for example, glass wool loses its structural integrity, collapses and fails to prevent mould growth.
For more information on biobased insulation, consult the Cecobois and FPInnovations fact sheets.
Wood in Canadian Construction
CASSANDRA LAFOND
ENGINEER AND SCIENTIST IN THE BUILDING SYSTEMS DEPARTMENT, FPINNOVATIONS
In 2018, FPInnovations, in collaboration with 475 High Performance Building Supply and the Canadian Wood Council, launched a pilot project that could illustrate the use of wood fibre insulation (WFI) in various climate regions across Canada and collect data regarding its hygro-thermal performance through building monitoring.1 Data was collected over more than two years and across two buildings.
Both buildings are located in cold, relatively dry climates: One in Collingwood, Ontario (Climate Zone 5), the other in Saskatoon, Saskatchewan (Climate Zone 7A). The first is a large single-family home, and the second includes nine townhouses.
Both projects were designed to meet the Passive House (Passivhaus) standard, thanks to highly insulated and airtight building envelopes. Both were originally designed to use other types of exterior insulation (e.g., plastic foam) but were modified to incorporate exterior WFI.
For the Collingwood house (Figure 1), 80-mm-thick WFI was installed on the exterior of a double-stud wall assembly filled with blown-in cellulose insulation, and the exterior surface was covered by a weatherproofing membrane and a 38-mm-deep ventilated cavity. For the Saskatoon project, two WFI products (one 240-mm-thick WFI panel and one 40-mm-thick exterior WFI cladding) were installed on the exterior of a wood frame assembly filled with mineral wool. The exterior WFI cladding was exposed to a 19-mm-deep ventilated rain screen cavity, with no protective membrane.2 These two exterior wall assemblies present effective R-values above 42 and 56, respectively, which far exceed the R-24.5 value required for homes in both climates, according to the Quebec Construction Code, Part I.1, Energy Efficiency of Buildings.
To monitor hygro-thermal performance, four locations, including two replicas of north- and south-facing walls, were selected in each building for the instrumentation. At each monitoring location, a set of sensors was installed to measure relative humidity (RH) and temperatures within the wall assembly, as well as the moisture content (MC) of the intermediate cladding (i.e., the plywood) and a single stud. The monitoring system was set to collect and transmit data once per hour.
Figure 1 Illustrations montrant les assemblages muraux et l'emplacement des capteurs
The monitoring of two buildings in different Canadian climates has shown that exterior walls containing WFI perform well in the Canadian built environment.
The following provides a summary of the exterior WFI walls’ hygro-thermal performance in both buildings.
The exterior walls belong to the building’s envelope and effectively serve to separate the environments of both buildings. Indoor temperatures and humidity levels remain well within comfortable ranges under climates characterized by cold winters and hot summers; these levels remain below the Passive House threshold of 10% hours per year at temperatures exceeding 25°C.
- Indoor humidity levels also remain comfortable. For the Collingwood house, humidity levels range from 30% in winter to roughly 60% in summer. By comparison, RH levels are slightly lower at the Saskatoon house (typically around 25% in winter), which is located in a colder and drier climate than the Collingwood house.
- Measurements confirm that the intermediate cladding and the studs remained dry throughout the monitoring period, indicating that the exterior walls are functioning properly at the monitored locations.
- The vapour pressure differences measured at various points on the exterior walls confirm that vapour tends to move outward in winter due to the warmer, more humid indoor environment. WFI’s high vapour-permeability, along with its other components (including vapour-permeable membranes), would allow moisture to dry outward if, for example, the wood was accidentally exposed to moisture during the building’s construction or usage phase. This positive characteristic inherent to WFI may contribute to the long-term durability of the exterior walls for both buildings.
1. (Knudson and Thomas, 2018)
2. According to the manufacturer, this WFI panel is highly water-resistant. According to Part 9 of the National Building Code of Canada, a secondary protective layer, most commonly a type of water-resistant membrane, is required to protect moisture-sensitive materials from water penetration (e.g., wind-driven rain). In a humid climate with a humidity index greater than 1 (such as a coastal climate), a rain screen cavity is required to provide a capillary break and ensure drainage. It is thought that a 19-mm-deep rain screen cavity, which is not necessary in Saskatoon’s dry climate, significantly reduces wind-driven rain loads on the exterior WFI cladding. It is also recommended that any untreated WFI panel be protected with a water-resistant membrane to ensure its long-term durability, particularly in humid climates.