Daylighting The most brilliant reason to cut a hole in your roof. What is Daylighting? Daylighting is the controlled admission of natural sunlight into a building via diffused skylights or windows. Done correctly, it can save energy and money by reducing the need for electric lighting during daylight hours without causing heating or cooling problems. Table of Contents 1 Daylighting is More Than Skylights 4 How Much Daylighting is Enough? U-Factors, Solar Heat Gain Coefficient and R-Values 6 Hailstone Damage 8 Advanced Prismatic Daylighting 10 Curb Mounted Prismatic Skylight 12 Smoke & Heat Vent Skylights 13 Roof Curb Systems 14 Roof Curb Components 16 Energy-Efficient LED Lighting 17 Lighting Controls 18 Xeleum Lighting Products 19 SkyCalc™ 20 Daylighting Building Model – Case Study BC LEED® Certification Daylighting is More Than Just Skylights. Daylighting integrates energy-efficient lighting and a daylight-responsive lighting-control system. 1. Skylights 2. Energy-Efficient 1 LED Lighting 2 4 3 3. Lighting Controls 4. Windows Harness the Sun. Harvest the Savings. Electrical lighting Electric lighting accounts for 30 to 60 percent of the total accounts for electrical energy consumption in commercial buildings. For many institutional and commercial buildings, strategic 30-60% daylighting can reduce total energy costs by as much as one- of total electrical third. By generating waste heat, electric lighting adds to the energy consumption loads imposed on a building’s mechanical cooling equipment, Daylighting can all while producing greenhouse gases. reduce energy cost 33% Nucor Building Systems 1 No Matter the Environment, Daylighting Brightens the Outcome. Education daylight and views of the outside to higher levels of A study initiated by the Pacific Gas and Electric Company satisfaction and productivity. Businesses that utilize (PG&E) shows that students with the most daylighting productivity-focused energy-efficiency measures in their classrooms progressed 20 percent faster on math view them as a distinct competitive advantage. tests and 26 percent faster on reading tests in one year than Warehouses those without daylighting. The study found a uniformly Daylighting created a bright and airy work environment positive and statistically significant correlation between the for a 635,000-square-foot distribution center in presence of daylighting and better student test scores. Romeoville, Illinois with connected light loads of .535 Offices watt/square foot and 2 percent effective skylight-to- The study initiated by PG&E shows that the daylighting floor ratio (1 unit per 1,600 sq. ft.). The distribution features incorporated into a 15,000-square-foot office center averaged 3,094 daylighting hours per year. building reduced the need for electrical lighting during Retail normal operating hours, which in turn reduced the cooling The largest bill for retailers is lighting. A study initiated by requirements and allowed the building designers to PG&E shows daylighting dramatically increased sales in a downsize the heating, ventilating and air conditioning retail setting. One study shows a 40 percent increase in sales (HVAC) systems. Extensive monitoring of this building in daylit stores when compared to identical non-daylit stores. demonstrated that annual lighting energy (kWh) consumption was reduced by 32 percent. The study Properly daylit buildings can repay installation costs shows office workers performed 10 to 25 percent better quickly – often in fewer than five years. Daylighting can be on tests and recall when natural light was available. installed in buildings to replace electric lighting for 1/20th of the cost to install solar PV panels in order to generate This also improved employee morale and satisfaction an equivalent amount of electricity using the same sun with their work environment. Numerous studies link at the same high energy demand times of the day. Environmental Impact of Daylighting PG&E Case Study: Environmental Impact Daylight Harvesting on Walmart – 200,000+ sq. ft. Through Daylight Harvesting: One Distribution Center: • Connected light load – 1.2 watts/sq. ft. • 672,000 kWh annual reduction per store • 593,120 kWh annual reduction = 240 kW • 483 metric tons C02 reduction per store • 426 metric tons CO2 reduction • Average hours daylighting per year • Equal to electric use of 67 homes/year • Equal the electric use of 59 homes/year = 2,800 • Equal to emissions from 89 cars/year • Equal to emissions from 78 cars/year • Published average annual per-store savings = $100,000 • Equal to planting 110 acres of pine trees • Equal to planting 97 acres of pine trees • Bottom-line impact of 2,500 stores = $250 million per year 2 Nucor Building Systems Daylighting has been shown to increase productivity and grades while reducing absenteeism. Nucor Building Systems 3 How Much Daylighting Is Enough? Many factors are used to determine how much daylighting is needed to maximize your energy savings. U-Factors, SHGC and R-Values SHGC is the fraction of solar radiation admitted through Windows, doors and skylights can gain and lose heat by a window, door or skylight — either transmitted directly means of direct conduction through the glazing, frame and/ and/or absorbed or subsequently released as heat or doors, the radiation of heat into a building (typically inside a building. The lower the SHGC, the less solar from the sun) and out of a building from room-temperature heat it transmits and the greater its shading capability. objects, including people, furniture, machinery and interior A product with a high SHGC rating is more effective at walls and also air leakage through and around them. collecting solar heat during the winter. A product with When windows and skylights are rated for energy efficiency, a low SHGC rating is more effective at reducing cooling the rate of non-solar heat that passes through is quantified loads in the summer by blocking heat gain from the sun. as the U-factor, as opposed to SHGC, which quantifies the rate of solar heat that passes through the windows. SHGC Impact of Ceiling Height and U-factor ratings are specific to windows and skylights and measure properties differently from insulation R-values. 30 R-values are used to quantify the insulating capabilities of building materials used elsewhere in a building, such as 20 insulation behind walls, under floors, in the roof, etc. These 10 different values are each designed to measure very specific properties. This measurement is helpful when examining Minimum No. of Skylights Minimum No. 0 the individual factors that can all be addressed in order 10 11 12 13 14 15 16 17 18 19 20 to improve the energy efficiency of an entire building. Ceiling Height Including Splay (FT) U-factor is the rate at which a window, door or skylight conducts non-solar heat flow. It is Ceiling height has a major impact on the economics of a toplighting usually expressed in units of BTU/hr-ft2-oF. solution because a higher ceiling enables fewer, larger skylights For windows, skylights and glass doors, a U-factor may refer to be used to achieve similar lighting levels. Effective toplighting requires that light from skylights be reasonably even across a space, to just the glass or glazing alone. NFRC U-factor ratings, as is required for light from electric fixtures. A higher ceiling allows however, represent the entire window or skylight performance, skylights to be spaced farther apart because the additional height including frame and spacer material. The lower the U-factor, provides more distance for the light to spread horizontally outward the more energy efficient the window, door or skylight will be. from each skylight. (U.S. Department of Energy) Daylighting Roof Area Percentage Per Building Use Most building codes will require between 2% and 5% of roof area to be used for daylighting. Dark spots are often created below 2 percent, and the cost benefit advantages decline above 5 percent where electric light savings peak. Although local codes or design requirements vary, there are rules of thumb for all building types. Warehouse Manufacturing School Office Retail Overall Logistics 2-3% 3-4% 4-5% 4-5% 5% 4 Nucor Building Systems Sunlight Transmittance The ability of glazing in a window, door or skylight to transmit sunlight into a building can be measured and rated according to three energy performance characteristics. Reflected light & heat Solar light & heat +/- Skylights Solar light & heat +/- Windows Solar light & heat Reflected light & heat +/- Doors SHGC & VLT Reflected light & heat Visible Light Transmission (VLT) Relative Cost Savings/Losses, 4% SFR VLT is a fraction of the visible spectrum of sunlight (380 to 0.30 Phoenix, AZ 720 nanometers) weighted by the sensitivity of the human 0.25 eye and is transmitted through the glazing of a window, $0.31 ($/Y/SFR) 0.20 door or skylight. A product with a higher VLT transmits more 0.15 Burlington, VT visible light. VLT is expressed as a number between 0 and 1. 0.10 $0.20 The VLT you need for a window, door or skylight should be 0.05 determined by your building’s daylighting requirements and/ 0.00 Energy Cost Savings Cost Savings Energy or whether you need to reduce interior glare in a space. -0.05 Light-to-Solar Gain (LSG) Lighting Heating Cooling LSG is the ratio between the SHGC and VLT. It provides a gauge of the relative efficiency of different glass or How are SHGC Ratings Determined? glazing types in transmitting daylight while blocking The procedure for testing window products and assigning heat gains. The higher the number, the more light SHGC ratings is performed by the National Fenestration transmitted without adding excessive amounts of heat. Rating Council (NFRC) and was started in 1993. The NFRC is a This energy performance rating isn’t always provided. nonprofit organization that administers the only independent Reduced Heat Gain rating and labeling system for the energy performance of Reduced lighting energy use ranks by far as the greatest windows, skylights, doors and attachment products.