Concrete Products

MAR 2013

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

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GUEST EDITORIAL BY JAMES BATY II NEW ENERGY CODES MAGNIFY TILT-UP BUILDING SYSTEM ADVANTAGES Tilt-Up Concrete Association Technical Director Jim Baty II weighs impacts on building envelopes designed to standards from the International Code Council's International Energy Conservation Code (IECC) and ASHRAE (American Society of Heating, Refrigeration and Air-Conditioning Engineers). At first glance, the more stringent requirements found in the current 2009 IECC and the further strengthened 2012 version raise concerns for design and construction professionals for how to adapt current practice to comply. Based largely on the precedents found in ASHRAE 90.12007, these new energy standards force the industry to the implementation of continuous insulation for nearly every building type in most domestic geographic locations. Although the immediate conclusion might be that tilt-up concrete proponents suffer from this position due to their large volume of uninsulated, speculative building projects, a more astute look at the codes reveals advantages for industry growth. Consider the key elements of the strengthened energy code requirements: • Opaque thermal envelopes must deliver continuous insulation. • Thermal envelopes must be adjusted for thermal bridging when continuous insulation is compromised. • Building envelopes in climate zones 4-8 must deliver a continuous air barrier and demonstrate minimum air leakage. • Building envelopes cannot have more than 30 percent of gross wall area as fenestration. Solutions to these primary requirements of the 2009 and 2012 IECC versions may appear complicated and detailed, however the industry will find that tiltup building technologies offer a straightforward approach indicative of the wall systems' performance values. Mass. Tilt-up buildings inherently deliver mass for the building envelope. According to IECC section C402.2.3, mass walls are those weighing not less than 35 psf. A standard tilt-up panel of 7 in. of concrete weighs more than twice that at 87.5 psf. As described in Table C502.2(1), where minimum Rvalue requirements per climate zone are found, mass walls require the lowest insulation value, primarily due to the effective performance combination of mass with insulation to dampen the diurnal impact on the building mechanical systems. 6 | MARCH 2013 Insulation. Continuous insulation required virtually throughout Table C502.2(1) is prescribed as being maintained across the entire surface of the opaque wall area, those regions not considered fenestration. Therefore, integrating a continuous layer of insulation with a minimum value after the effects of thermal bridging is quite difficult in most assemblies. However, tilt-up wall systems provide three options for cost-effective and highperformance continuous insulation without compromised values due to thermal bridging. The sandwich panel, exterior energy code as a rated air barrier in IECC section C402.4.1.2.1. This is further enhanced in the construction assembly with the natural design of the vertical wall joint between panels consisting of polyurethane caulk both on the inside and outside—easily satisfying C402.4.2. Maximum fenestration. The final piece of the puzzle for changes in the energy code that affect the building envelope is the restriction to 30 percent or less fenestration area. Although there is an allowable increase to 40 percent when extensive parameters are Instead of seeking answers for why new energy codes linked to ASHRAE and IECC may be perceived to eliminate tilt-up wall system options, TCA is challenging the market to identify code-driven opportunities. and interior layers of concrete separated by a continuous insulation layer are historically the top method for achieving this design and code requirement. Tilt-up systems also exist for integrating an exterior- or interior-only layer of insulation during the casting process or for applying these continuous layers to the vertical wall panels once they are erected. A key element to satisfying the code requirement is also maintaining the continuity of insulation envelope from one system to the next, such as from a wall to a roof, without compromising the continuous insulation envelope. Air barriers. One of the most stringent advances of the latest energy codes is the air barrier requirements for the entire building envelope. This is due to the reality that insulation alone reaches a diminishing return or impact on the energy budget for a building if air changes due to infiltration are not stopped. The solid concrete of a tilt-up panel is one of the few prescribed materials qualified by the met, this means that a much greater percentage of the built environment and envelopes must be opaque for 2012 IECC-compliant buildings. Greater opaque area results in larger volume for the tilt-up industry and a higher value for the construction method. From the outset, ASHRAE 90.1 has set a goal of reducing the nation's energy consumption for buildings by 30 percent. Although this was not initially achieved in 2009, it was finalized with the 2012 IECC based on predicted performance behaviors for the built environment. These goals are easily embodied in the quality wall system performance the tilt-up industry has delivered for decades. Instead of seeking answers for why the energy code may be perceived to handcuff or eliminate the possibilities for tilt-up, TCA is challenging the market to identify the opportunities. Knowledge of the energy code requirements and challenges proponents of traditional competitive building technologies face will result in smarter solutions for designers and owners. WWW.CONCRETEPRODUCTS.COM

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