Energy codes and lighting
Lighting designers have many resources when designing energy-efficient lighting in nonresidential buildings. Designers do not have to sacrifice quality or reduce lighting levels just to meet energy codes.
- Know the codes, standards, and guidelines that dictate energy-efficient lighting design
- Become familiar with COMcheck as a tool to design lighting within a nonresidential building
- Understand that there are trade-offs when different types of design methods are used to meet energy codes
According to the U.S. Department of Energy, lighting accounts for 20% of total commercial buildings' energy use. Energy codes were first developed in response to the energy crisis in the 1970s. Energy codes have led to the development of more efficient lighting.
The efficacy of a light source is measured in lumens per watt. The higher the number, the more energy-efficient the light source. For example, early versions of LED light sources were roughly 60 lumens/W. It is common now to see LED light sources with an efficacy greater than 90 lumens/W.
There are two major energy efficiency standards/codes in the United States. These energy codes encompass lighting and the amount of energy, typically measured in watts per square foot, for a building or area.
The first standard is ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings. The second code is the International Energy Conservation Code (IECC) developed by the International Code Council (ICC); all states have adopted some version of this.
Energy codes, such as ASHRAE Standard 90.1 and the IECC, are updated every 3 years. Typically, every update results in more stringent energy codes and lower lighting energy use as compared with the previous version.
ASHRAE Standard 90.1 along with the IECC have both been widely adopted as the benchmarks for energy efficiency in buildings. They have become the basis for building codes, and the standard for building design and construction throughout the United States. There are other energy codes such as California Title 24 and various other local energy codes.
Understanding codes in your area
How does a lighting designer know what codes and standards apply to the designer's project? A very useful resource can be found at the U.S. Department of Energy's www.energycodes.gov website, which lists the energy codes for each state. Local codes should also be checked by the lighting designer because local codes may supersede state codes in some states.
There is a section on the website titled "Status of State Energy Codes," with a drop-down menu allowing a lighting designer to select the state in which the project is located. Once a state is selected, the website will redirect the designer to the state-specific page that lists the commercial and residential energy codes. As an example, see Figure 1 for the listing for Ohio as of Aug. 1, 2016.
There also are pertinent links for energy codes related to each state. This includes ASHRAE 90.1, the IECC, and/or other energy codes. For example, the Current Code column in Figure 1 shows the 2009 IECC as the current energy code. It also states that ASHRAE 90.1-2007 is allowed as an energy code as a direct reference to the 2009 IECC. So for Ohio, both the 2009 IECC and ASHRAE 90.1-2007 are acceptable current energy codes.
It is important for a lighting designer to communicate with the rest of the design team when more than one energy code can be used. A consensus should be made among the design team members early in the design phase as to which energy code will be used. Most authorities having jurisdiction (AHJs) do not allow mixing of energy codes. For example, a lighting designer would not be allowed to show that the lighting design for a commercial building meets the 2009 IECC while the rest of the design team shows compliance with ASHRAE 90.1-2007.
Tools that help meet the codes
How does a lighting designer figure out how a commercial lighting design will meet the energy code? Determine what your project's requirement is by selecting the state, as described above, and view the state's "approved compliance tool." A lighting designer will need to know what form or tool is required to show that a project's lighting design complies with the state energy code. The compliance tool usually encompasses the design of the building's HVAC system, the building envelope, and the building's power in addition to the lighting design.
The most commonly used tool is COMcheck. In an example used with Figure 1, Ohio's energy code shows COMcheck as an approved compliance tool.
The COMcheck software product group allows the lighting designer to determine whether new commercial or high-rise residential buildings, additions, and alterations meet the requirements of the IECC and ASHRAE Standard 90.1, as well as several state-specific codes. COMcheck also simplifies compliance for building officials, plan checkers, and inspectors by allowing them to quickly determine if a building project meets the code.
Figure 2 shows which states can use COMcheck to show commercial buildings' energy code compliance. States that do not allow COMcheck will have a link to the accepted compliance tool/method once the state has been selected from the Status of State Energy Codes section of www.energycodes.gov.
COMcheck comes in many variations and can be downloaded onto a computer. There is also a Web-based version. The user interface is similar for both versions. Figures 3 and 4 show both versions' home screens.
The lighting designer should verify that the latest version of COMcheck is being used. This should be done before a project is started and again before it is ready to be submitted for code plan review. When connected to the Internet, the desktop version of COMcheck will automatically check for a newer version whenever it is first opened. The software also will provide a link to download the latest version.
Each project should have all the project details filled out even though it is listed as optional in COMcheck. This will help provide the plans examiner with details of the building location, the owner's contact, and the lighting designer. The designer/contractor section should list the name and contact information of the designer/engineer of record for the lighting design. This should match the name of the professional engineer's seal on the lighting plans.
Building area versus space-by-space method
COMcheck's "Interior Lighting Method and Areas" section is where the rubber meets the road. This is where the designer finds out if the lighting design meets the energy code. ASHRAE Standard 90.1 allows either a "building area method" or the "area category (space-by-space) method."
ASHRAE Standard 90.1's lighting section has a table that lists the lighting-power densities (LPD) using the building area method and also the space-by-space method. The building area method typically is easier to use than the space-by-space method. This is because the designer only needs to enter the entire square footage of the building or the area of an existing building being added or renovated to determine compliance.
Let's compare the building area method to the space-by-space method. ASHRAE Standard 90.1-2007 has a table that lists "office" for the building area method with an LPD of 1.0 W/sq ft. The same standard lists an "office-open plan" with an LPD of 1.1 W/sq ft. A lighting design may not comply with the building area method, but may comply with the space-by-space method due to the trade-offs allowed.
Figure 5 shows an example of a COMcheck's whole building area method concerning a 10,000-sq-ft office building with hypothetical LED lighting fixtures. This example shows the project is not in compliance with the building area method's LPD of 1.0 W/sq ft- which equates to 10,000 W. The example has a total proposed wattage of all the lighting fixtures at 10,104 W, which exceeds the allowable 10,000 W by 1%.
Figure 6 (see next page for example) shows the same building using COMcheck's space-by-space method. Each area within the building was entered along with the lighting fixture used in each area. Note that the office-open plan and the "office-enclosed" have similar LPDs of 1.1 W/sq ft, which is greater than the office LPD of 1.0 W/sq ft for the building area method. Even with the other supporting spaces listed (corridor, restroom, electrical/mechanical room), the total of these spaces has an allowable wattage of 10,850 W. This amount is 850 W greater than the allowable 10,000 W using the building area method.
Our office example shows that the space-by-space method allows more watts for compliance than the building area method. This allows our sample project to comply with the energy code selected (ASHRAE Standard 90.1-2007).
What does a designer select if a project's space is not listed in the ASHRAE Standard 90.1 space-by-space-method LPD table? ASHRAE Standard 90.1 states selection of a reasonable equivalent category shall be permitted. The designer should keep in mind that the AHJ (typically, the plans examiner) is the decision-maker when it comes to interpreting if the selected equivalent category will be allowed.