Fonte (Source): Consulting – Specifying Engineer

Por (By): Michael Chow, PE, CEM, CxA, LEED AP BD+C, Metro CD Engineering, Columbus, Ohio

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Lighting designers must consider eight key factors when specifying lighting systems for nonresidential buildings. In addition to considering the type of lighting fixture (LED, fluorescent, etc.), they must also take into account daylighting, lighting controls, codes and standards, and other factors.

Learning objectives:

• Analyze eight key factors that must be considered when specifying lighting systems.
• Recall that codes, standards, siting, controls, and many other factors must be taken into account in each design.
• Create a lighting design that meets the owner’s needs and adheres to required code.

Designing lighting for a building may seem simple at first, but there are several items a lighting designer must consider. Where should someone new to lighting design start? The eight key factors in lighting design include:

1. The owner’s project requirements (OPR) that include project costs and schedule
2. The basis of design (BOD)
3. Codes and standards, including energy guidelines
4. Sustainability certifications (U.S. Green Building Council’s LEED, Energy Star, etc.)
5. Recommended lighting levels
6. Lifecycle costs
7. Safety and security
8. Maintenance and warranty.

Factor 1: OPR

The first step in a successful lighting design is to obtain the OPR. This is a document prepared by the owner of the building. This can also be the tenant if the space being designed is a tenant space that is rented. The OPR explains how the owner would like the space to be used and operated. The OPR should include:

• The goal for the design of the project
• How the building/space will be used
• The budget cost of the project (construction and soft costs)
• The schedule for construction completion
• Energy efficiency goals (e.g., Energy Star)
• Standards and codes including energy codes
• Sustainability goals
• Types of materials to be used
• Return on investment (ROI) and lifecycle costs requirements
• Safety and security requirements
• Training requirements
• Warranty requirements.

Most projects do not incorporate an OPR. This can lead to an owner receiving a building/tenant space after construction is completed that does not meet what the owner had envisioned. This can lead to costly redesigns, increased costs, and construction delays. An OPR that is provided prior to design is critical to the success of a project.

The majority of projects have an OPR only when the project is pursuing LEED certification. LEED’s Fundamental Commissioning prerequisite requires that an OPR be completed. The commissioning authority (CxA) is required to have the OPR so that the commissioning team can validate that what is being designed and built meets the owner’s vision through the OPR.

The OPR is essential to a successful project, yet few projects use this important document. In fact, some LEED projects develop the OPR after the design has already started. In many of these cases, the energy consultant or CxA is contracted and brought onto the team after the design has already started.

The CxA’s role is to represent the owner. Many times the CxA’s contract lies with the architectural and/or engineering firm, and occasionally with the contractor. Regardless of with whom the contract lies, the CxA needs to ensure that the design does not begin until the OPR is completed.

Here is a sample preliminary OPR’s lighting goals for the lighting system for a commercial office building:

• Lighting design including energy efficiency and controls shall conform to ASHRAE Standard 90.1-2010.
• Maximize daylighting to all employees. Use daylighting controls and light switches for all private offices.
• Use LED lighting.
• Meet or exceed the recommended lighting levels in the Illuminating Engineering Society (IES) Lighting Handbook based upon people 25 to 65 yr old.
• Use 3,500 K color temperature for all lighting.
• Minimum of 80 color rendering index (CRI) for all lamps and light sources.
• Provide night lighting at all entrance doors to the building.
• Project is targeting LEED-NC v3 Silver certification at a minimum.

Factor 2: BOD

The BOD is a document developed by the architectural and engineering firms and before the schematic design phase. It is based on the OPR and describes the technical approach planned to meet the OPR. The BOD contains the design parameters to be used and identifies the parties involved. It lists who is responsible for each component of the design. For example, the BOD may state the lighting designer is responsible for the coordination and design of the lighting system.

LEED also requires the BOD as part of the Fundamental Commissioning prerequisite. This allows the CxA to determine how the design team plans to meet the OPR.The BOD should list applicable codes and standards if they are not found in the OPR. For example, an OPR may state, “provide an energy-efficient building.” The BOD may state the design intent is to exceed ASHRAE Standard 90.1-2013 by 10%. It also should describe how the design intent will be met. A BOD for the above example may state the design will use high-performance lighting such as LEDs with efficacies with daylighting controls and occupancy/vacancy sensors.

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