The systems that lighting designers, HVAC engineers, electrical engineers, building-technology engineers, fire protection engineers, low-voltage electrical designers and integrators, and high-performance design engineers develop and specify are inherently interconnected. Designers can no longer design each of these systems separately. Truly integrated teams that reach across discipline silos to collaborate and innovate will meet the building owner’s needs.
This type of project design also goes beyond simply focusing on calculation programs. Calculation programs, such as COMcheck or other energy efficiency calculators, are only as good as the content that goes into the calculation or model. It is intellectual, thought-leadership-focused, innovative building designs that clients are looking for and that differentiate engineers from other commodity designers. Engineers must evaluate and apply results from modeling programs to help clients make informed decisions that will meet their project goals.
The integration of lighting and HVAC systems has moved beyond the simple considerations of adding capacity to HVAC systems to accommodate added heat from light fixtures. The study of integrating these two systems is much more than the simple study of wattage from light fixtures. With the advent of energy-efficient LED light sources and finite and automatic lighting controls, the study of systems integration requires whole building energy modeling with sophisticated software that can model the impact of lighting wattage, integrated sensors, daylighting strategies, and user control. This level of study is key to providing the type of integration of systems clients are demanding. Consulting engineers are primed to be able to provide clients with true integration of systems.
Heat from light fixtures
The lighting industry measures the efficacy of a light source by measuring the quantity of lumens that are emitted per watt that is used by the light source. This simple equation of lumens/watt is a means of determining the amount of light (lumens) provided by the amount of energy used by the light source (wattage). The types of light sources used in our industry in the past included incandescent sources that created more heat than light, providing approximately 10 to 20 lumens/W.
In the 1950s, fluorescent light sources were developed as a more efficient and longer-lasting light source, providing 60 to 80 lumens/Watt. Use became rampant and often led to over-illumination and to daylight being shut out of the interior of commercial spaces.
Over the past few years, LEDs have proved to be a robust, long-lasting, and highly energy-efficient light source, providing approximately 100 lumens/Watt. LED light sources also provide high color rendering and many color-temperature options. While the life of an LED system will depend on quality and type of LED, typical rated LED lamp life is 50,000 hours. This dramatic increase in the use of efficient light sources means that lighting designers no longer need to place as many lighting watts in built environments. As a result, watts per square foot have been substantially reduced while still providing usable light levels and high-quality lighting systems.
Advances in daylighting strategies also have helped reduce the amount of heat entering commercial spaces through vertical and horizontal glazing. This includes the glazing itself, which can be specified to have a low solar-heat-gain coefficient while having a high light-transmittance percentage, allowing more daylight to enter the space without substantial heat gain.
Shading devices also have advanced with new and improved materials that can be used combined with more robust modeling programs. In addition, automatic shading devices including glazing systems with shading integral to the system have been becoming more popular based on ease of use and reduction in initial costs.
Design teams comprising lighting designers and engineers working on high-performance buildings use programs such as AGi32, Rhino, and Diva to study daylighting strategies, from big-picture placement and orientation of buildings to detailed study of variations of glazing transmittances and shading devices. This is all performed to leverage and increase usable daylight in the space while keeping heat gain from daylight to a minimum.
After initial studies by lighting and high-performance design teams, HVAC engineers take the findings and use them to determine the impact on the HVAC system through whole-building modeling that includes energy use and loads for the entire building. These teams work closely to fine-tune the system through the design and documentation phases. When construction is complete, commissioning teams then move in to ensure the systems are working as designed.
LED light sources are low-voltage and run on dc power natively. To enable LED light sources to be used in the ac-dominated electrical world, LED light sources are equipped with a power supply or driver that transforms the ac power to dc power. Transforming at the light sources causes some loss of efficiency.
There are systems being developed that use dc power within buildings, which would increase the efficiency of the LED systems. This type of system is interesting to contractors because the cabling can be Cat 5 or Cat 6 cables, similar to a low-voltage information technology (IT) system. These dc systems could also be designed to transmit and receive HVAC system equipment information on the same plug-and-play network.
Additionally, power from solar power-generating systems run on dc power. Currently, solar systems are transformed to be able to run on ac systems. If the power generated by the solar-array system can be run on dc systems and backed up when the sun is not shining, the systems can be up to 20% more efficient.