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Building construction regulations exist to protect the public and provide a minimum acceptable level of building performance.All in the building industry, including contractors, need to pay attention to these regulations.They impact how new construction or additions or renovations to existing buildings are approached, the costs of the work, quality of the work, and the degree a building will continue to perform over the long term.

Just as some look at a glass as half empty or half full, those in the building industry consider building construction regulationsdifferently.  Thisincludesthe model codes and standards that make up the technical provisions of those regulations.Regardless of your point of view the,these regulationsdo help to establish a common and uniform foundation for building design and construction.This helps ensure the costs to perform a given project are comparable amongst contractors, and provides a basis to answer consumer questions about the work and associated costs.The 2012 International Energy Conservation Code (IECC) provides a basis for the energy efficiency provisions of building construction regulations.Aside from the things like wall insulation that consumers cannot see and directly appreciate,the IECC now provides for air leakage performance testing—something that measures the performance of the as built home and consumers can more readily understand – and a new opportunity for air-conditioning contractors.

Building construction regulations have been in effect for over 200 yearsin some localities.Over time, more states have adopted statewide building regulations.In addition, the scope of topics covered has grown beyond structural and fire to include energy efficiency.

Energy efficiency has been a part of the building regulatory process in the United States for almost 40 years, starting with ANSI/ASHRAE/IES Standard 90-75 and the 1977 Model Code for Energy Conservation.Both documents contained provisions covering the energy efficiency of mechanical systems and equipment. Today, provisions covering energy efficiency in residential building design and construction can be found in the IECC.

The recent publication of the 2012 IECC provides opportunities for air-conditioning contractors. This article highlights key differences between the 2009 and 2012 editions of the IECC related to residentialconstruction.[1] Familiarity with thesedifferences allows contractorsto better understand the code, be more likely to support its adoption, and be better equipped to identifyand take advantage of the opportunities provided by these recent changes to the IECC.

The 2012 IECC building thermal envelope (roof/ceilings, walls, floors, doors, skylights and windows) provisions will result in lower heating and cooling loads.These reductions in loads, which transfer to reductions in system size and equipment capacity, can be attributed to several changes to building construction requirements that vary by climate zone:[2]

  • increased insulation levels in opaque (non-light transmitting) portions of the building thermal envelope (e.g., higher R-values)[3]
  • increased performance of windows, doors, skylights and other fenestration products and assemblies (e.g.,reduced heat loss and heat gain through lower U-factors and solar heat gain coefficients)
  • installation of a continuous air barrier and enhanced building thermal envelope sealing methods with mandatory testing to determine the rate of air leakage (e.g., reductions from sevento as low as three air changes per hour)

For instance,changes in requirements in Climate Zone 4 (i.e., Virginia, Kentucky, Delaware, and portions of 20 other states) between the 2009 and 2012 IECC include:

  • minimum roof/ceiling insulation R-38 to R-49
  • minimum wood frame wall insulation R-13 to R-20 or R-13 plus R-5 continuous sheathing
  • minimum R-10 to R-13 insulation applied to mass walls
  • skylight U-factor from 0.60 to 0.55
  • fenestration solar heat gain coefficients from not regulated to a maximum of 0.40
  • maximum infiltration rate from seven to threeair changes per hour

In addition to changes to the building thermal envelope,provisions for duct systems have also been revised.Building cavities can no longer be used as ducts or plenums.The minimum insulation levels for ducts remain the same (R-8 attic and R-6 elsewhere), but the allowable air leakage rates for duct systems have been reduced.The post-construction rate has been reduced from 8 to 4 cfm/100 sf of floor area.  For rough-in testing, the limits have been reduced from 6 to 4 cfm/100 sf of floor area with the air handler installed and from 4 to 3 cfm/100 sf of floor area without the air handler installed.If the ducts are installed completely within the conditioned space, the ducts need not be leak tested, nor are they required to be insulated.

The air leakage rate requirement in the 2012 IECC (maximum five or threeair changes per hour depending on climate zone) necessitates whole-house mechanical ventilation according to the International Residential Code (R303.4). These differences in the building thermal envelope and the HVAC system are then applied when using ACCA Manuals J and S.  These manuals are adopted by reference in the IECC and International Residential Code and must be used as the basis for load calculations and equipment sizing.

Systems and equipment associated with new construction will likely be smaller as a result of the 2012 IECC’s requirements.Where 2.5 tons might have been the norm under the 2009 IECC, now 2 tons is likely to be sufficient, with similar reductions for larger equipment.

The calculation of building loads for equipment sizing are impacted by the air leakage rate of the home.This creates a significant new business opportunity: blower door testing of the home.The code requires a blower door test to determine the air leakage rate of the home.Who better to conduct the test at rough in, not only to validate code compliance, but also to determine the actual leakage rate and ensure proper system and equipment sizing? Having these test results will remove major uncertainties in determining building loads, allowing contractors to reduce the degree of oversizing commonly done to assure the equipment can maintain comfort at all times.  This will also allow the contractor to fine tune the equipment and system design and bid but alsofully communicate with the consumer as to the validity of the required Manual J and S calculations and provide them the actual test result.

In summary, the 2012 IECC provides for increased energy efficiency by reducing heating and cooling loads and requiring air leakage testing of the home.This creates opportunities for using ACCA Manuals J and S to focus on the resultant loads and necessarysystem and equipment capacity.The time to “sharpen the pencil” in doing those calculations and the need to do air leakage testing creates opportunities for the air-conditioning contractor.Some may look at those costs as adversely affecting the bottom line and wining the job. Others will look at them as investments that increase competitive advantage through better equipment sizing and opportunities for providing additional services to the builder and consumer.

[1] Residential construction includes one- and two-family dwellings, townhouses, and multifamily residential buildings not over three stories in height.

[2] The IECC separates the United States into eight climate zones based on winter and summer conditions.

[3] The building thermal envelope is comprised of those assemblies or portions of assemblies that separate interior conditioned space from the building exterior or from interior spaces that are not heated or cooled or are vented to the building exterior.

Posted In: Residential Buildings, Technical Tips

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