NECB 2011: A Cost Perspective

The Province of Alberta will adopt the National Energy Code of Canada for Buildings (NECB-2011) on November 01, 2015, making the code the driver of building design and construction. Compliance will be achieved through three paths: the Prescriptive Path; the Trade-off Path; and, the Performance Path. The code sets high energy efficiency targets, a move that is great for sustainability. Besides, code enforcement and energy modelling career opportunities will increase.

The NECB-2011 focuses on energy. It does not address any potential increases in direct and collateral costs. This is understandable because factors that determine costs are complex and unpredictable and differ by compliance path, building design, and geographic region. Energy savings need to be incorporated into total project costs to form a clear picture of their true value and inform investment decisions.

The Prescriptive Path establishes the minimum requirements for primary building components: thermal transmittances of opaque envelope and fenestration; fenestration-to-wall area ratio; equipment energy efficiencies; and, lighting power densities. The requirements of the NECB for most, if not all, geographic regions are more stringent than in previous building codes. Direct cost increases will come from thicker or higher-quality insulation, better fenestration, more efficient HVAC equipment, and better lighting fixtures. Collateral cost increases will stem mainly from the building envelope. Insulation requirements will influence above-grade and below-grade wall thicknesses and the quantity of framing material. The design of load-bearing components may depart from convention, with increases or, unlikely, decreases in cost.

The second path offers two compliance options: the Simple and the Detailed Trade-off procedures. In both options, the limitations stated in the code render some buildings ineligible. The two options allow for component-by-component variations from the prescriptive requirements if it can be shown that the energy consumed by each component is less or equal to the prescriptive case. For eligible buildings, it may still be difficult to apply the trade-off paths due to lack of data that are needed to perform analyses that inform definitive investment decisions at the early stages of a project. Where the trade-off paths are applicable, it will pay to perform a cost analysis to justify any departures from the prescriptive case.

The Performance Path is the most flexible one and allows the use of different iterations of the building components to demonstrate a whole building energy consumption that must be less than, or equal to, the energy that would be consumed by a reference building designed and constructed to the prescriptive requirements. Whole-building computer energy simulation is mandatory in this case. This approach can be used to optimize both energy consumption and total costs. Cost increases due to the envelope can be minimized by finding the onset of diminishing returns, beyond which point it does not pay to increase the insulation levels because subsequent additions yield progressively insignificant energy savings. In “deep” buildings in a Prairie climate, this phenomenon may occur well below the code’s prescribed resistance-value (R-value) for the opaque envelope. The onset of diminishing returns depends on a facility’s energy profile, which is unique to each design and the climate. A “deep” building is defined here as one whose envelope has relatively little influence on the energy profile, like commercial and institutional buildings with low skin-to-floor area ratios, but with large internal heat load densities. Once the onset of diminishing returns for the envelope is identified, the focus for energy improvements shifts to mechanical and electrical systems.

Thousands, even millions, of dollars may be saved over the life of a facility if the Performance Path is combined with Value Engineering/Analysis or Life Cycle Cost Analysis to provide insight into, and optimize, the total project costs. Most green technologies are new and relatively expensive, making a detailed cost analysis essential where they are involved and, especially, when utility costs are low. In such situations, a simple payback period, based only on the initial capital costs and the projected energy savings, will not suffice. When all is said and done, a serving of green technology is more palatable if it is accompanied by a favorable discounted return-on-investment. Building developers, design-built contractors, and other investors will need the services of both energy modellers and construction cost consultants.

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