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Insulated structural concrete block walls
One of the main advantages of a single-wythe masonry wall is achieving a highly durable finished wall inside and out, without the addition of interior or exterior claddings. However, with requirements by the 2011 NECB for many areas in Canada, it may be difficult to achieve an acceptable level of energy performance with traditional single-wythe CMU construction.

Even with the addition of SPF in vacant unit cores, traditional single-wythe concrete block walls produce a maximum RSI of approximately 1.14 (R-6.5) using the traditional 200-mm (8-in.) block unit. Nevertheless, numerous solutions have been developed for the addition of insulation within the concrete block unit to create an insulated structural concrete block.

Insulated concrete blocks have been on the market for several years. Theses concrete masonry products (Figure 8) integrate either EPS or XPS rigid insulation into the webs. The installation of the insulation occurs at the time of
the wall construction; it can achieve RSI values of up to 1.41 (R-8) with a 300-mm (12-in.) unit.

The alternative is a concrete masonry product with three face shells (Figure 9). It has the insulation inserted during the manufacturing process and achieves an RSI value of 2.64 (R-15) with a 300-mm-width, three-face-shell unit. The grooved insulation also provides for drainage.

An alternative to the insulated concrete masonry unit is the insulated concrete masonry form (ICMF). This type of masonry unit is typically manufactured using XPS insulation and replaces the EPS insulation in an insulated concrete form (ICF) with concrete masonry unit shell faces. However, unlike ICF, these concrete masonry units are still laid like a traditional concrete block wall and then filled with concrete (Figure 10). Thus, the system is essentially a fully grouted concrete wall, but without the web interference. These concrete masonry products have units that are typically 310 mm (12 ¹/4-in.) thick, with 50 mm (2 in.) of XPS insulation embedded into the unit at the time of manufacture.

The advantage of this system is the exterior and interior walls are finished with durable architectural finishes in a single step. The system achieves an average insulation rating of RSI 4.93 (R-28). A 25-mm (1-in.) gap for capillary break and drainage between the exterior shell and the embedded XPS insulation mimics a cavity wall system and significantly reduces the likelihood of water ingress through the mortar joints that can occur in single-wythe concrete masonry walls. Integral water repellant on the interior wythe also helps mitigate water ingress.

The face shells of the 310-mm thick units are tied together with plastic webs that double as horizontal reinforcement cradles and ties for vertical bars like ICF units. These plastic webs/handles/rebar cradles create a much lighter block than if concrete webs were used. These CMUs, which are approximately the same width as a traditional 300-mm (12-in.) units, weigh about the same as a standard 200-mm (8-in.) concrete block.

Conclusion
Canadian masons and product manufacturers are adapting to meet modern construction requirements. In the majority of Canadian locations, wall-to-glazing ratios of approximately 25 per cent permit an achievable R-value for most traditional full-bed masonry rainscreen veneers by using the tradeoff compliance path of the 2011 NECB. For single-wythe masonry walls, the low glazing ratios (typically less than 10 per cent) found on warehouse, big-box commercial, and school gym walls may be achievable with the trade-off compliance path; they are definitely achievable with full-building modelling or the use of insulated concrete masonry units. Insulated concrete masonry units in the form of insulated concrete blocks or ICMFs can achieve RSI values of between 1.41 and 4.93 (R-8 and R-28), ensuring there are masonry products that can meet the high R-value demands of the country’s national energy code.

Mark D. Hagel, PhD, P.Eng., is the executive director of the Alberta Masonry Council. He holds bachelor’s degrees in actuarial science/applied mathematics and civil engineering, and a doctorate in civil engineering. Hagel was previously employed as a technical services engineer for the Canadian Concrete Masonry Producers Association (CCMPA) and as a building envelope engineer and structural engineer with a Calgary consulting firm. He can be reached via e-mail at markhagel@albertamasonrycouncil.ca.