As the NCMA celebrates its 100th birthday, there is a movement afoot to reimagine single wythe masonry and make it a more competitive “Wall System.” The term, wall system, is one of the buzz-words around construction today. Architects are looking for all-encompassing solutions to meet the structural and energy code requirements for their structures. On the masonry side, we have lagged behind in this field allowing wood, tilt-up and steel structures to take some of our market share. But masonry is a resilient product and so is the masonry industry. Companies across the U.S. and Canada have been hard at work developing high performance wall systems to compete and gain wall share back.
This article shows how combining two of these wall system innovations (Korfill High-R® and ProBlock®) makes concrete masonry competitive again. These two systems utilize specialty shapes, integral insulation and ESCS lightweight aggregate to create single wythe wall systems that far exceed the status quo. For example, ESCS lightweight ProBlock® at 105 pcf along with integrally colored Korfill High-R units were used on the new Gold Fish Swim School. The incorporation of these systems significantly increased the R-value of the wall system. The whole wall R-value as designed increased from an R-9.3* with a normal weight mix design to R-12.1* with the ESCS lightweight mix design.
In North Carolina as in most states, masonry achieves prescriptive compliance using the maximum U-value table shown below. The table gives the maximum U-value that the wall can have for a particular zone and wall assembly type. The U-value is converted to an R-value simply by dividing 1 by the U- value, so 1 divided by 0.104 would yield an R-value of R-9.61.
For Zone 4 and Zone 5, the code prescriptive minimum R-value for a mass wall assembly would be R-9.61 and R-11.11 respectively. While the prescriptive path may be the easiest and most direct path to compliance, not meeting this prescriptive minimum does not mean the wall system cannot be used. It does mean some additional design and analysis work along with tradeoffs in windows, insulation or other items will most likely be required to comply with one of the performance methods in the code.
In this case, the use of the ESCS lightweight mix design and Korfill High-R eliminates the need to do this additional design work and makes prescriptive code compliance more than achievable in all the North Carolina Zones and most of the United States as well.
So why is ESCS lightweight aggregate so important in these innovative designs? It comes down to thermal resistance, as heat energy travels the path of least resistance and these specialty units are designed to minimize thermal bridging. In concrete masonry, the webs act as thermal bridges or energy transfer superhighways. The thermal bridges allow heat energy to effectively bypass the insulation within the block and decrease the overall energy efficiency of the unit. Since there does have to be at least 6.5 in2/ft2 of web area according to the ASTM C90 requirements, we have to figure out how to deal with them and make their impact on overall R-value as low as possible.
As thermal resistance in the concrete masonry increases, the amount of heat energy that goes through the web decreases. The thermal resistance of concrete masonry goes up as the density of the block goes down. The thermal resistance of 85 pcf ESCS lightweight concrete masonry is 3 times that of 135 pcf normal weight concrete masonry. This means that the ESCS lightweight block itself is up to 3 times better at resisting heat transfer. The net result, the use of innovative shapes and ESCS lightweight aggregate can increase the R-value of insulated blocks themselves 250% and more. This saves the owner of the building energy dollars and makes code compliance easier for the designer. Teaming ESCS lightweight aggregates with the inventiveness of today’s block producers opens doors once thought impenetrable.
ESCS Lightweight Block is the Answer to Todays and Tomorrows Energy Code Compliance Questions!
*Information courtesy CBIS TEK 322.
*135 pcf normal weight cmu
*All units solid grouted with 140 pcf grout