Net-zero builds: How masonry leads the way

The need to maintain an acceptable wall thickness coinciding with the increased depth of exterior insulation now needed to meet the National Energy Code for Buildings (NECB) requirements has made adhered masonry veneers a popular material option.
The need to maintain an acceptable wall thickness coinciding with the increased depth of exterior insulation now needed to meet the National Energy Code for Buildings (NECB) requirements has made adhered masonry veneers a popular material option.

Further, full bed-depth or thin veneers can add to the thermal mass and R-values of homes and office buildings. During the winter months, it is common for homeowners to raise the thermostat when they first arrive, since many building materials do not retain heat well. Masonry’s ability to store heat can directly impact utility bills by offsetting the need to warm a home during peak demand periods by a couple of hours.

It is also important to consider the insulating value of materials alongside their thermal mass when assessing energy efficiency. Thermal mass absorbs energy slowly and stores it for longer periods of time, which reduces indoor temperature swings, and often leads to a reduction in the size of mechanical heating and cooling systems. The benefits of thermal mass are most accurately reflected when utilizing energy analysis programs that assess the building type, location, and temperature variations over a 24-hour period, 365 days a year. Thermal mass is also directly proportional to the weight and density of the material and is most effective when used on the interior side of the insulation in the building envelope. This includes using loadbearing concrete masonry as part of a wall system.

There is also now a requirement to address and minimize thermal bridging and its impact on overall thermal performance to get more accurate data than using the simple R-value of a wall system.

A panelized stone panel in terrazzo colour at the New Brighton Athletic Park in Calgary, Alta., features an integrated drainage channel acting as a rainscreen and keeping the wall dry. It eliminates the need for the substrate to be attached to z-bar or drainage mats, but still has the reduced thickness and esthetics of a thin stone veneer and can be applied directly over rigid insulation.
A panelized stone panel in terrazzo colour at the New Brighton Athletic Park in Calgary, Alta., features an integrated drainage channel acting as a rainscreen and keeping the wall dry. It eliminates the need for the substrate to be attached to z-bar or drainage mats, but still has the reduced thickness and esthetics of a thin stone veneer and can be applied directly over rigid insulation.

“The impact of thermal bridging must be accounted for, not only for the backup, but also in all the components that attach the cladding to the backup wall to meet the requirements of NECB 2017,” said Hagel. “This makes it difficult to have a blanket solution as each building has a different type and number of thermal bridges that previously could be ignored.”

Eliminating the two per cent thermal bridging relaxation permitted in NECB 2011, which previously excluded ties and shelf angles, will make it more difficult for highly conductive building materials, especially steel, to meet the new codes. The latest thermal bridging calculations require measurement of the following elements.

Clear field transmittance or the heat flow from the wall, floor, or roof assembly

This transmittance includes the effects of uniformly distributed thermal bridging components like block ties, structural framing (e.g. studs), and structural cladding attachments that would not be practical to account for on an individual basis. (The clear field transmittance is a heat flow per area, and is represented by a U-value denoted as the clear field [Uo].)

Linear transmittance or the additional heat flow caused by details that are linear

This includes the slab edges, corners, parapets, and all of the transitions between assemblies. (The linear transmittance is a heat flow per length, and is represented by psi [Ψ].)

Adhered veneers require less thermal bridging, and the material provides an inherent thermal mass advantage that directly affects cooling and heating cycles.
Adhered veneers require less thermal bridging, and the material provides an inherent thermal mass advantage that directly affects cooling and heating cycles.

Point transmittance or the heat flow caused by thermal bridges that occur only at single, infrequent locations

This includes building components such as structural beam penetrations and intersections between linear details. (The point transmittance is a single additional amount of heat, represented by chi [χ].)

Masonry’s ability to meet these requirements, the NECB 2017 code, and combine effectively with other building materials as well as its thermal qualities, have made it a highly competitive resource among the design-build community. Whether employed as a standalone material or in combination with wood- or steel-studded structures, the complete system approach to wall materials has not only grown in popularity, but also improved the cost-effectiveness, structural integrity, energy efficiency, and building strength, while achieving the desired look.

Sustainability and durability take centre stage

As the transition to NECB 2017 hits home, provinces are gearing up with building designs integrating sustainability and durability.

“Asset management plans incorporating the life-cycle costs of building components are becoming mandated, leaning toward durable materials,” said Hagel. “The intent is to codify sustainability as, according to Carl Elefante, ‘the greenest building is the one that is already built.’”

Moving to NECB 2017 requires the building envelope to increase thermal performance by 10 to 14 per cent, Hagel explained.

“Energy code targets will require more rigorous thermal analysis and insulation and cross-disciplinary co-ordination,” he said. “In addition to this, jurisdictions are moving quickly toward requirements for building materials and components that are not currently codified in the national or provincial building codes to have a Canadian Construction Materials Centre (CCMC) number or an engineer’s stamp.”

Subsequently, masonry is playing an important role in Leadership in Energy and Environmental Design (LEED) projects. Another great advantage for masonry materials is the ability of the Portland cement in these components to absorb carbon dioxide (CO2). In clay brick veneer installations, only mortar joints absorb CO2, while concrete block and concrete masonry veneers (including manufactured stone) absorb the gas. Both types of masonry reduce the carbon footprint of a building by offsetting the gas used to produce the products via CO2 absorption either at the time of manufacture of the products (as with carbon-cured concrete products) or naturally over time through weathering carbonation.

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