Cladding
Cladding is defined as any material that covers an exterior wall from the outside. In a building envelope, the cladding is identified as the first plane of protection. The planes of protection are systems within the wall assembly that work together to protect the assembly from bulk water penetration. The planes of protection must be designed and constructed to minimize the ingress of precipitation (rain and snow) caused by the kinetic energy of raindrops, surface tension, capillarity, gravity, and air pressure differences. The first plane of protection intercepts moving rain drops, while the second plane of protection is a water resistive barrier to prevent water moving into the cavity. Within the effective R tool, there are a variety of cladding options to choose from including brick, siding and EIFS systems. Each of these cladding options have unique properties that help to define the performance of the wall assembly.
Brick is a common building material that is often applied as a non-structural veneer to clad wall assemblies. Brick is a porous, absorptive material which can act like a sponge; moisture can be absorbed into the brick and stored and re-released later. A vapour pressure differential can drive stored cladding moisture into the assembly. The vapour pressure differential, sometimes referred to as solar driven moisture, is a phenomenon that occurs when the sun heats a saturated cladding material and drives the moisture in the form of water vapour inwards, potentially into the wall cavity. This can be mitigated by the installation of a low permeance material inboard of the brick, or by the provision of a vented cavity or air space immediately behind the brick. Assemblies without a low permeance exterior material or vented cavity may at times have elevated relative humidity levels within the cavity.
Brick veneer cladding must be installed with a one-inch air space behind it. The air space generally, provides some relief for the brick veneer wall, where the backup wall is not perfectly plumb and straight and allows for the inevitable mortar droppings, which could completely block the air space. Within the Effective R Tool, when selecting brick cladding, only assemblies with an air space of more than 3/4 inches (20 mm+) are available. The air space creates a drainage plane that allows any moisture that gets past the brick to drain out of the wall assembly. The space allows water to drain down the inner brick surface and out at the bottom by means of flashings and weep holes at the bottom of the cavity. The air space, when constructed with weep holes at the top and bottom, also functions as a vent, which helps to remove any moist air and direct it away from the interior. The air space is also useful at intercepting incoming solar driven moisture, preventing it from being driven into the wall assembly by flushing or ventilating it away through weep holes at the bottom and openings at the top, connected to the outside air. It also provides, a separation or “capillary break”, intercepting any liquid water coming up through the brick veneer. In some cases, where approved by municipalities, drainage mats or other proprietary materials can sometimes be used in the cavity to maintain the air flow, drainage and to keep mortar droppings from filling and clogging the space and weep holes. For an example of how a wall assembly with brick veneer, and its corresponding information, is displayed on the Effective R Tool, please see Wall ID 8309.
Siding is a common building component that is used as an exterior wall covering. Siding is typically considered a non-absorptive and rain shedding cladding material. This means that water is not absorbed and stored. Best practice is to install most siding materials over vertical furring strips, thus creating an air space for drainage. The air space also allows drying by air circulation and provides a capillary break. Some vinyl sidings are designed with a profile to create the cavity without the need for furring strips.
There are a variety of different siding options available on the Effective R Tool, including vinyl, fibre cement, wood, and metal. Each of the siding options depicted on the tool perform similarly and should be installed to the manufacturer's specifications. For wood and fibre cement siding, it is imperative that all cut edges of the siding are painted or sealed to the manufacturer's directions. This ensures that there is no potential for water absorption which could diminish the durability of the siding and compromise the cladding. The Effective R tool assumes the use of wood and fibre cement sidings that have been treated or coated in the factory on all four sides. This is a fundamental assumption that is built into the tool. Non-coated wood (on-site stained or unstained/untreated wood) and non-coated fibre cement sidings do not follow the assumptions that are embedded into the Effective R Tool. For an example of how a wall assembly with siding, and its corresponding information, is displayed on the Effective R Tool, please see Wall ID 6257.
Exterior Insulation and Finish Systems (EIFS) are non-load bearing composite cladding systems. They are composed of a water-resistant barrier (often liquid applied) over a substrate. An insulation board, which is often either attached with adhesive and/or mechanically to the substrate. Over the insulation an integrally reinforced base coat with a texture protective finish coat is applied. EIFS provide a continuous layer of insulation across the exterior wall surfaces, which significantly minimizes the instances of thermal bridging and increases the effective R-value of the assembly. These systems are available in a variety of insulation thicknesses from one inch to three inches or more; the specific R value of the system will vary by manufacturer.
It is critically important to install EIFS in accordance with the manufacturer’s specifications and instructions. This is because EIFS are tested as a whole system, not as individual components. Due to the nature of the product, the drying potential of the wall towards the outside is significantly reduced and care must be taken to avoid interstitial condensation within the wall assembly. Detail and care regarding water management and weather resistant barrier detailing and application will be required, including preparing all openings with integrated flashing and drainage details. The long-term performance of the EIFS system derives significantly from the drainage plane and air gap that is used. For an example of how a wall assembly with EIFs, and its corresponding information, is displayed on the Effective R Tool, please see Wall ID 7666.
References
Brick. (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
Cladding. (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.
E.I.F.S systems: ADEX - Architectural Coatings. (n.d.). Retrieved April 27, 2021, from https://www.adex.ca/eifs-system/
National Research Council Canada. (2015). National Building Code of Canada 2015 s. 9.27.2.2.(1)
Ontario Building Code, O Reg. 332/12, s.9.27.2.3.(1)(a)(ii)
Siding. (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