Cavity Insulation
Cavity Insulation refers to the insulating material that fills the spaces between studs within a wall assembly. Insulation must be applied to the full length and width of the space between framing members. Cavity insulation can be batt, densely blown, loosely filled, or sprayed foam. These different cavity fill material options are represented on the Effective R Tool.
Glass Fibre Batt insulation is composed of glass fibres that are formed into lightweight batts of uniform thickness. These are one of the most common traditionally used cavity insulations in residential design. The batts are available pre-sized to certain depths so that they can easily fit in the wall assembly depending on the framing dimensions. These batts can be compressed to fit into the cavity; however, compression in some cases can decrease the thermal performance of the insulation. Care must also be taken when placing these batts in the cavity to ensure that there are no large gaps as these can create convection cells. A continuous primary air barrier system should be installed to reduce air leaking into the cavity. Recognize, that envelope components can variously contribute to the resistance of air movement for the entire assembly. For example, where sealed polyethylene is the primary air barrier, the drywall interior finish and the plywood sheathing installed on the exterior of the assembly both contribute to the overall air tightness of the assembly. In this instance, the resistance to air movement provided by the plywood reduces the potential for wind washing of the air permeable cavity insulations. Glass fibre batt is highly vapour permeable (greater than 60 ng/Pa.s.m2) and will not impede the drying of the wall to the outside. Typically, this material would require a vapour control layer such as polyethylene or vapour retarder paint inboard of the insulation. For an example of how an assembly with glass fibre batt, and its corresponding information, is displayed on the Effective R Tool, please see Wall ID 14150.
Dense Blown Fibre Glass is a densely packed, glass fibre insulation that can be installed into attic spaces, walls, and other areas. It can be used as an alternative for batt insulation in both new construction and retrofit applications. The thermal resistance of this material is based both on the insulation thickness and its blown density. The density must also be appropriate to avoid insulation settlement. Dense blown insulation, when installed properly, can reduce gaps in the insulation that can result when the insulation is improperly installed. A continuous primary air barrier system should be installed to reduce air leaking into the cavity. Recognize, that envelope components can variously contribute to the resistance of air movement for the entire assembly. For example, where sealed polyethylene is the primary air barrier, the drywall interior finish and the plywood sheathing installed on the exterior of the assembly both contribute to the overall air tightness of the assembly. In this instance, the resistance to air movement provided by the plywood reduces the potential for wind washing of the air permeable cavity insulations. This insulation is highly vapour permeable (greater than 60 ng/Pa.s.m2) and promotes reasonable drying potential towards the outside. Typically, this material would require a vapour control layer such as polyethylene or vapour retarder paint inboard of the insulation. Blown-in insulation options are more commonly seen in double stud wall applications and are used to fill the large cavity between the stud walls. For an example of how an assembly with dense blown fibre glass, and its corresponding information, is displayed on the Effective R Tool, please see Wall ID 16476.
Dense Pack Cellulose is a blown-in insulation material that is packed into the wall cavity until it achieves its required density. Cellulose, a paper-based material, has been chemically modified to provide fire, fungal, and corrosion resistance. When correctly installed, dense pack cellulose can reduce gaps in the insulation that can result from improper installation. A continuous primary air barrier system should be installed to reduce air leaking into the cavity. Recognize, that envelope components can variously contribute to the resistance of air movement for the entire assembly. For example, where sealed polyethylene is the primary air barrier, the drywall interior finish and the plywood sheathing installed on the exterior of the assembly both contribute to the overall air tightness of the assembly. In this instance, the resistance to air movement provided by the plywood reduces the potential for wind washing of the air permeable cavity insulations. This insulation is highly vapour permeable (greater than 60 ng/Pa.s.m2) and promotes reasonable drying potential towards the outside. Typically, this material would require a vapour control layer such as polyethylene or vapour retarder paint inboard of the insulation. Like the dense blown fibre glass option, dense pack cellulose is more commonly seen in double stud wall applications to fill the large cavity between the stud walls. For an example of how an assembly with dense pack cellulose, and its corresponding information, is displayed on the Effective R Tool, please see Wall ID 16602.
Open Cell Spray foam insulation is an insulating material made from polyurethane which is sprayed into the building assembly. This material consists of insulating gas "cells" that have not been completely encapsulated in the polyurethane. This results in a softer and more flexible spray insulation. This material has a high vapour permeability (greater than 60 ng/Pa.s.m2) and would typically require a vapour control layer such as polyethylene or vapour retarder paint inboard of the insulation. However, the high vapour permeability facilitates drying potential to the outside. Open cell spray foam can be part of an air barrier system, but this would need to be verified with the manufacturer and must be CCMC approved to demonstrate this characteristic of the system. Care must be taken when designing the details of the assembly around penetrations and proper flashing and sealant must be used to prevent the entry of water. Open cell spray foam is often found in 1/2 lb and 3/4 lb densities as seen on the Effective R Tool. For an example of how an assembly with open cell spray foam, and its corresponding information, is displayed on the Effective R Tool, please see Wall ID 13000.
Closed Cell Spray foam insulation is an insulating material made from polyurethane that is sprayed to a building assembly. Closed cell spray foam consists of an insulating gas that is retained because it is completely encapsulated in the polyurethane. The resulting foam is rigid and dense. This material has a high R value per inch compared to other insulating materials and is designed to expand up to one inch per application. It may be applied in multiple layers to achieve the desired R value. Typically, closed cell spray foam has a low air permeability and provides water vapour diffusion resistance (less than 60 ng/Pa.s.m2), which eliminates the need for an additional vapour control layer. Please check with the foam manufacturer. If this material is intended to be used as an air barrier system for the assembly, it must be CCMC approved to demonstrate this characteristic of the system. Care should be taken around penetrations to avoid rainwater leaks and follow proper manufacturer recommended detailing, flashing, and sealing procedures. Closed cell spray foam is most often used at a 2 lb density, as seen on the Effective R Tool. For an example of how an assembly with closed cell spray foam, and its corresponding information, is displayed on the Effective R Tool, please see Wall ID 13010.
References
Blown Insulation. (2013). In Glossary of housing terms (Rev. ed. of: A glossary of house-building and site-development terms, 1982 ed.). Ottawa: Canada Mortgage and Housing Corporation.
Cellulose Insulation Manufacturers of Canada. (2009). GENERAL INSTALLATION GUIDELINES FOR CELLULOSE FIBRE INSULATION (C F I). Retrieved from http://www.thermocell.com/wp-content/uploads/bsk-pdf-manager/cimac_installation_guidelines_112.pdf
Glass Wool Insulation. (2013). In Glossary of housing terms (Rev. ed. of: A glossary of house-building and site-development terms, 1982 ed.). Ottawa: Canada Mortgage and Housing Corporation.
National Research Council Canada. (2015). National Building Code of Canada 2015 s. 9.25.2.4.(4)(a)
National Research Council Canada. (2015). National Building Code of Canada 2015 s. 9.25.2.3.(4)
Open cell vs closed cell foam: Which should I choose? (2018, June 28). Retrieved April 27, 2021, from https://tigerfoam.com/sprayfoaminsulation/open-cell-vs-closed-cell-foam-which-should-i-choose/
Owens Corning. (2018). ProPINK® Fiberglas®Blown Loosefill Insulation. Retrieved from https://dcpd6wotaa0mb.cloudfront.net/mdms/dms/Residential%20Insulation/501104CA/501104-ProPink-Blown-Insulation-Data-Sheet-Canada-EN.pdf?v=1542268901000
Spray Applied Foam Insulation. (2013). In Glossary of housing terms (Rev. ed. of: A glossary of house-building and site-development terms, 1982 ed.). Ottawa: Canada Mortgage and Housing Corporation.