How to Calculate the Possible Energy Savings of Commercial Skylights
By Jeff Brain | July 27, 2015
Commercial skylights offer many benefits, including greater employee productivity, increased customer returns, and a more satisfied workforce. However, most facility managers are more interested in dollars and cents when it comes to making lighting decisions. Installing commercial skylights will reduce the amount of energy your building consumes, in terms of both electric lighting and HVAC costs. This reduction in energy use translates into immediate and long-term cost savings for you.
If you want to estimate the possible energy savings before you make the decision to invest in commercial skylights, there are a few factors you must consider.
Calculating Energy Savings of Commercial Skylights
Some of the elements that go into calculating the potential energy savings of commercial skylights include:
Artificial lighting usage
First, determine how much energy the building currently consumes with artificial, electric lighting. You can do this by evaluating existing energy bills and taking a percentage based on the most current information in the Buildings Energy Data Book. For example, in 2010, lighting accounted for approximately 20% of the energy consumption in commercial buildings and 10% in residential buildings. For office buildings, the number can be closer to 40%.
Another way to determine current energy consumption from lighting is to multiply the number of existing fixtures by their input wattage to determine how many kilowatts you can save by turning them off for a certain number of hours during the day.
Depending on the type of commercial skylight you select, you can reduce lighting energy costs between 50% and 80%. This calculation will depend on the approximate building area that can be lit with skylights, the hours of operation, and the number of hours that the skylight will light the building.
Electric lighting contributes to the total heat load of a building, so the more lights you use, the more energy you will consume with HVAC use. To calculate potential HVAC energy savings, you will need to know how many light fixtures there are in the building, what type they are, how much heat they generate, and how long they are in use each day.
Commercial skylights may also require more air conditioning use to keep the indoor temperature consistent. Skylights that do not provide thermal protection will allow heat to enter or escape, increasing energy consumption from HVAC use. Commercial skylights with a lightwell or light tube will prevent both heat gain and heat loss. Lightwells and light tubes act as dual-pane windows, which insulate the interior against the external temperature and reduces HVAC costs.
The type of commercial skylights you select will also influence how these calculations are made. Each skylight product has a unique design that makes it more or less efficient. Traditional skylights, for example, are flat and do not bring light in when the sun is low on the horizon, so you will only be able to turn off electric lighting for a few hours of the day. With solar-tracking skylights, however, the sunlight will go indoors from sunrise to sunset. They generate ten or more hours of natural light per day, allowing you to keep electric lights off for most or all of the workday.
The good news is that you do not have to calculate all of these savings yourself. Ciralight is here to help you estimate just how much energy you can save with SunTracker commercial skylights. We will work closely with you to calculate energy savings, estimate a timeline for the return on your investment, and even approximate the potential financial returns on the health and productivity benefits of natural lighting.