All posts by Stacy Sanders

Lighting a space is not as simple as you may think…

          What Goes Into Good Lighting Design?

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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 Space

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

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

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.

Summary

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.

Commissioning Lighting Controls

LED-Light

Lighting controls are becoming more and more complex. Long gone are the days of simple on/off wall switches being the only source of control. Typical control methods now required by energy codes and/or building certification programs (e.g. LEED) include:
  • Occupancy/vacancy sensors
  • Daylight-responsive photosensors
  • Dimming
  • Time switches
  • Whole building programmable systems

To function properly, all of these types of controls must be correctly installed, calibrated, and, in some cases, programmed.

According to the Lighting Controls Association, more than 30% of new buildings have problems with their lighting systems. Many of these issues, they suggest, could be resolved prior to building occupancy through the commission process. We’re all familiar with commissioning – a quality assurance program to ensure that building systems operate as the owner intended. Commissioning of HVAC and associated controls is often the first thing that comes to mind, but the process can be applied to lighting and other systems also.

The latest editions of the International Energy Conservation Code (2015) and LEED (v4) both require lighting systems commissioning. LEED does not have specific requirements, but refers the reader to ASHRAE Guideline 0 – The Commissioning Process. The IECC, which applies to most projects, is more specific and requires verification of the following:

Occupancy (vacancy) sensors

  • Placement and aiming
  • Operation

Time-switch controls

  • Programming
  • Override operation

Daylight responsive photo sensors

  • Location
  • Calibration
  • Operation

Lighting controls are becoming increasingly complicated, mainly due to energy code requirements. With the increased complexity comes more potential for errors during installation. Commissioning can identify controls that may not operate properly so that corrections can be made before a building is occupied.

 

ENERGY CONSERVATION

OCCUPANT BEHAVIOR: KNOWLEDGE AND CONTROL

Reducing building energy consumption involves three main areas: equipment selection, building design, and occupant behavior. Equipment selection deals with choosing energy-efficient products, such as HVAC systems and lighting. Building design includes incorporating architectural features, materials, and construction techniques intended to lower energy use. These may include window placement and type, building orientation, and roof assemblies. Becoming more and more recognized as an important aspect of energy conservation is occupant behavior. Even a well-designed building with high-efficiency equipment will not operate as efficiently as possible if occupants waste energy.

There are two parts of the occupant behavior component: knowledge and control. They need to be aware of:

  • What they can do to contribute
  • How their contribution can help
  • The result of their conservation efforts

 

Additionally, occupants need to know where to locate the following in their area and how they apply to energy savings:

  • Heating/cooling controls
  • Lighting controls
  • Additional plug loads (appliances, office equipment, computers, etc.)

 

A recent study by Carnegie Mellon University sought to determine the effects of knowledge and control on energy usage in an office setting (although the same principle would apply in others, such as schools). In other words, would giving occupants information regarding their consumption and control over it cause them to conserve. Study results indicated that sharing energy use data and giving control caused occupants to conserve. For the study offices were equipped with Plugwise products[1] – receptacles that can provide real-time usage data and instantaneous control wirelessly via a smartphone application. An in-depth discussion of this product is beyond the scope of this paper. Information can be disseminated via other low cost or no cost methods.

[1] www.plugwise.com

These methods can be used to provide general information about energy usage and energy conservation:

  • Newsletter
  • Staff meetings
  • Posters/signage
  • Social media

The amount of control occupants have can vary from building to building. Lighting control can range from an on/off switch for all lights to bi-level switching to dimming, and even more complex schemes. In older buildings occupants may have great control over room temperature settings, while in new or renovated facilities, it is likely limited to a narrow bandwidth. In any case, occupants need to be educated in selecting lighting and temperature settings that will provide the appropriate room environment while saving energy. The more levels of control that are offered, the more occupants can match their environment to the tasks performed and conserve energy at the same time. In addition to a general environment of energy conservation, more deliberate efforts may be needed at times. On days when there is a power emergency or 4CP alert[2], for example, occupants might be asked to reduce their individual usage. This could be accomplished by turning off unnecessary lights, changing thermostat settings, or turning off unused plug loads. In order to do this, they need to know how all of the controls in their classroom, office, etc. operate. The request to implement immediate energy conservation can be made by email, instant messaging, or audio announcements, for example. Energy conservation requires a multi-faceted approach, including building design, equipment selection, and occupant behavior. Giving occupants information on how and when to conserve, the ability to do it, and data and feedback on how well they are doing all encourage energy savings.

[2] Some retail electric providers notify customers of a potential 4CP event. By curtailing load during this time period, users can lower TDSP charges for transmission and distribution for the next year.