Building Energy Codes.Paths to compliance.
Today’s Building Energy Codes
Today’s building energy codes are developed by organizations such as the International Code Council (ICC), the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), American National Standards Institute (ANSI), the Illuminating Engineering Society (IES), the American Concrete Institute (ACI), the U.S. Department of Energy, the Green Building Council (GBC) and National Resources Canada / National Research Council Canada.
Model building codes with an emphasis on energy conservation include the International Energy Conservation Code (IECC), National Energy Code of Canada for Buildings (NECCB), Leadership in Energy and Environmental Design (LEED), Passive House, Net Zero and others.
Building energy codes have no legal status unless adopted by an authority, such as a state, having jurisdiction for that region. Local codes may be modified from those adopted by the larger jurisdiction (such as a state or province), but only if the modifications are more stringent than what the larger jurisdiction requires.
The ANSI/ASHRAE/IES Standard 90.1, the Energy Standard for Buildings, Except Low-Rise Residential Buildings, is considered the technical lead for energy standards in North America. It is updated every three years, with the overall goal of each version to “create a consensus standard that saves energy and is technically feasible and cost effective.” The latest version of these model codes became effective in 2016.
The ICC, another member-focused association that publishes the International Energy Conservation Code (IECC), released the latest version of its building energy code in 2015. It, too, updates its codes every three years but is on a different revision cycle than that of ASHRAE. Generally, energy codes become more stringent with every iteration.
While energy code publishers update their codes on a regular cycle, states and other jurisdictions are not bound to adopt the latest versions within any particular time frame. Some states may adopt the new regulations in full as soon as they are released. Others may defer for a year or longer, or adopt only some of the changes. However, most entities do adopt the latest recommendations eventually, so any changes are worth noting.
Continuous insulation of building envelopes
The latest versions of IECC and ASHRAE building energy codes have made important changes to conserve energy through the continuous insulation of building envelopes. Both organizations define this as:
“Insulating material that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior or exterior or is integral to any opaque surface of the building envelope.”
The latest ASHRAE 90.1 2016 requires all uninsulated assemblies to be separately modelled for energy efficiency. Uninsulated assemblies include projecting balconies, the perimeter edges of intermediate floor slabs, concrete floor beams over parking areas, and roof parapets.
Both model codes offer different paths for achieving compliance. The ASHRAE 2016 codes offer a new third option known as the Performance Rating Method. Included in Appendix G, this option was previous used only to rate “beyond code” performance buildings. Now it is recognized as another path to compliance.
The three paths to code compliance are as follows:
- Prescriptive Method – all building elements are constructed to the level of performance as defined in the code. The Prescriptive path requires continuous insulation, specific insulation performance requirements (R-values) for various building envelope components, depending on construction type and geographic region, and imposes strict limits on glass-to-opaque wall ratios, where the window surface cannot exceed 40% of the wall surface.
- Energy Cost Budget Method – a comparative modeling system in which two models of the same building are created and compared. The first model is the proposed building as designed. The second model is the budget building design. This is the identical building but constructed to the code’s minimum requirements. The utility and other costs are then calculated and compared, identifying areas where changes might need to be made.
- Performance Rating Method – the project team proves (by using compliance software modeling tools) that the building will perform at least as well as if it followed the prescriptive requirements, and that the proposed design with have an annual energy cost that is less than or equal to the standard reference design (prescriptive method).
In both the Energy Cost Budget Method and the Performance Rating Method, compliance may be achieved through trade-offs. If windows are shown to perform poorly, for example, the project team can add more insulation to the roof, or install solar panels as an off-set to the energy loss of the windows.
The choice of compliance method may also be determined by the building design. For developers of high-rise, multi-family structures where floor to ceiling windows are desirable, the limits imposed by the Prescriptive path would require the project team to choose another path.
Whereas in the past “uninsulated assemblies” could be ignored if these assemblies comprised less than 2.5% of the total envelope surface area, the latest ASHRAE 90.1 2016 code requires that such uninsulated assembles be specifically modelled.
With each iteration of the codes, guidelines become increasingly stringent concerning continuous insulation. Although some municipalities are more progressive in code adoption and enforcement than others, they are all moving in the direction of tighter regulations and proof of energy savings and performance.
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