What Goes Into Good Lighting Design?
Lighting a space is not as simple as just picking some fixtures and letting a contractor install them. Good design can be complex and challenging at times, even to experienced designers. A number of factors must be taken into account to achieve an installation that provides a quality environment – proper illumination levels without glare – and meets applicable standards. These include: the appropriate fixture type, budget constraints, applicable codes and standards, and architectural features of the space.
Let’s take a more in-depth look at some of the considerations that go into good lighting design.
The most important consideration when designing lighting is the characteristics of the space itself. Its size, shape, ceiling height, and architectural features all influence the types and locations of fixtures to be selected. Other factors related to the space include:
- Its proposed function(s)
- The activities that will be taking place
- The desired mood/atmosphere
Each of these variables has an influence on fixture selection and placement.
Fixture Technologies and Types
Lighting technologies have evolved greatly. At one time, incandescent lamps were the only available electric light source. Fluorescent tubes became commercially available around 1940. Over the next 60 years these were the lamps of choice, and many varieties were developed along with ballasts to operate them. Other lamp types, such as halogens and compact fluorescents were also created. For large spaces (e.g. warehouses and gyms), mercury vapor and, later on, metal halide were the lamps of choice. Designers had a large selection of lamp types available and had to choose the right one for their particular project.
The newest lighting technology is the LED. These have become the first choice for many lighting projects, with their energy efficiency and projected long life. Many designers now use LED lighting exclusively, although other sources (e.g. high-efficiency fluorescent) have not yet completely been eliminated from the marketplace. In the near future, as prices come down and acceptance increases, all new lighting will likely be LED.
The purpose of lighting is broadly divided into three categories:
- General illumination – provides overall, ambient lighting in a space
- Task lighting – provides additional light for performing specific tasks
- Accent lighting – creates visual interest
The type of fixture(s) – direct, indirect, troffer, recessed can, etc. – that can best achieve the purpose, while also meeting all of the other project parameters is the one that is selected.
Specifications are the part of the construction documents that describe the materials to be used on a project. They can be performance-based or prescriptive. Performance-based specifications list operational requirements that a product must meet. Prescriptive specifications give a detailed description of products to be used. Lighting specifications are generally prescriptive, listing preferred manufacturers and model numbers, or specific features that proposed fixtures must have (e.g. lens type, finishes, mounting type).
Specifications may be open, allowing submittals from multiple manufacturers, or proprietary, where products from only one manufacturer are accepted. Proprietary specifications stifle competitive bidding and tend to drive up prices. They are used only when it is known that only one manufacturer can supply a product that meets all requirements. The designer should choose the type of specification and write it to maximize the ability of getting the product that will best fill project requirements and at a reasonable price.
Budget constraints are often the biggest challenge that lighting designers face. Sometimes owners know – or think they know – what they want, but their preferences don’t fit within their budget. Designers must select fixtures that will achieve the desired results while staying within budget.
Sometimes a project will bid out of budget. When this occurs contractors and the owner look for ways to reduce construction costs, a process often called “value engineering” (VE). Alternative products are sought that will still adequately meet design intent. Lighting is often a first target of VE efforts. Therefore, designers must recommend less expensive fixtures that will still perform satisfactorily.
Codes and Standards
The International Energy Conservation Code (IECC) establishes minimum design and construction requirements for energy efficiency. This is one of the codes of most interest to lighting designers. They must develop lighting plans to meet the IECC’s lighting power allowances, often called lighting power density (lpd). For example, in the 2015 IECC, the lpd for schools and universities is 0.87 watts/ft2. For reference, in the 2009 and 2012 editions of the Code, this allowance was 1.20 watts/ft2. The lower power densities can make adequately lighting spaces a challenge. LED and very high-efficiency fluorescent fixtures make the job a bit easier.
The Illuminating Engineering Society (IES) publishes lighting design and illumination standards. Their publications are recognized as authoritative. Designers typically follow IES guidelines regarding recommended illumination levels and other parameters, as they are often considered the “bible” when it comes to lighting.
Controls are playing a larger role in the operation of lighting. While controls are a part of design, they don’t particularly affect the type of fixture selected; therefore, they haven’t been discussed here.
Choosing some fixtures simply because they look good does not necessarily result in quality illumination. Designers must select fixtures from those available for a given application that will best produce the desired results. In addition to the architectural features of the space to be lighted, codes and standards and the owner’s budget must be considered.