MT. VERNON, IOWA (February 4, 2013) – At first glance, the more stringent requirements found in the current 2009 IECC and the further strengthened 2012 IECC raise concerns for design and construction professionals for how to adapt current practice to comply. Based largely on the precedents found in ASHRAE 90.1-2007, these new energy standards force the industry to the implementation of continuous insulation for nearly every building type in most domestic geographic locations with few exceptions. Although the immediate conclusion might be that the Tilt-Up industry suffers from this position due to the large volume of uninsulated, speculative Tilt-Up buildings, a more astute look at the codes reveals advantages for industry growth.
In order to base an understanding on benefits for growth of the industry, the user must first identify the key elements of the strengthened energy code requirements for building envelopes. These include:
• 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% of gross wall area as fenestration.
Solutions to these primary requirements of the 2009 and 2012 IECCs may appear complicated and detailed, however the industry will find that Tilt-Up building technologies offer a straight-forward approach indicative of the performance values.
Tilt-Up buildings inherently deliver mass for the building envelope. According to section C402.2.3, mass walls are those weighing not less than 35 psf. A standard Tilt-Up panel of seven inches of concrete weights more than twice that at 87.5 psf. As described in Table C502.2(1), where minimum R-value 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.
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 high-performance continuous insulation without compromised values due to thermal bridging. The sandwich panel, exterior 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 system, without compromising the continuous insulation envelope.
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 energy code as a rated air barrier in 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.
The final piece of the puzzle for changes in the energy code that affect the building envelope is the restriction to 30% or less fenestration area. Although there is an allowable increase to 40% when extensive parameters are met, this means that a much greater percentage of the built environment and building envelopes must be opaque for buildings built under the 2012 IECC. 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%. 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 performance the Tilt-Up industry has known for decades. Instead of seeking answers for why the energy code may be perceived to handcuff or eliminate the possibilities for Tilt-Up, the TCA is challenging the market to identify the opportunities. Knowledge of the energy code requirements and the challenges faced by traditional competitive building technologies will result in smarter solutions for designers and owners moving ahead.
TCA was founded in 1986 to improve the quality and acceptance of site-cast Tilt-Up construction, a construction method in which concrete wall panels are cast on-site and tilted into place. Tilt-Up construction is one of the fastest growing industries, combining the advantages of reasonable cost with low maintenance, durability, speed of construction and minimal capital investment. For more information about the TCA, visit www.tilt-up.org or contact TCA headquarters at 319-895-6911 or [email protected].
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