Reflective light scoops, "sails" or other structures adjacent to skylights and in atriums that reduce glare, control solar heat gain, and provide diffuse daylight.
Light scoops are an innovative type of skylight that were designed to increase the capture of sunlight in the winter relative to summer. The scoops consist of tilted panels of south-facing high visible-light-transmittance glass that offer advantages over a conventional skylight as it provides less light in the summer and more in the winter. A properly designed light scoop should decrease both summer cooling and winter heating loads. A Design Guide includes a performance comparison of light scoops vs. other conventional skylights (showing charts of workplane illuminance, but not energy savings).
Fourteen light scoops were installed at the Welch Allyn corporate headquarters in Skaneateles, N.Y. An evaluation of the light scoops indicated good user acceptance, but the evaluation did not attempt to determine energy savings. Light scoops are appropriate in places such as lobbies, shopping malls, and airports where occupants briefly move through the space (Radetsky, 2013).
A LEED building (EPA Region 8 HQ in Colorado) uses suspended parabolic sails to reflect sunlight that enters an atrium downwards. Daylighting sails used in interior applications can diffuse light and eliminate glare. They can be used in conjunction with light scoops. Distributed light provides additional comfort, but may not result in additional energy savings over the daylight admitted through an atrium or skylight itself. Sails are more of an enabling technology for natural lighting rather than an efficiency measure. Sails are used in applications like museums where uniform lighting is desired and direct exposure to sunlight can lead to fading.
Status:
Baseline Description:
This technology is appropriate for portions of virtually all commercial building except for unconditioned spaces. However, this will be most appropriate for interior spaces served by skylights and lacking windows, such as atriums, corridors, lobbies, and shopping malls. The numbers for total commercial building space are taken from preliminary updated numbers from the 2013 update to the Commercial Building Stock Assessment (CBSA) using the estimates for 2014 (before the update was completed -- from early January, 2014) multiplied times the percentage of commercial space that is conditioned based on the 2009 CBSA, times our rough estimate of 1% of available floor space. The space under consideration is interior space (as the perimeter is already lit) on the upper floor where a skylight can be used to provide illumination.
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
NEEA, 01/01/2014. Total Pacific Northwest Building Stock Based on Preliminary Numbers from the 2013 Update to the CBSA Northwest Energy Efficiency Alliance
CADMUS, 12/21/2009. Northwest Commercial Building Stock Assessment (CBSA): Final Report Prepared by the CADMUS Group for the Northwest Energy Efficiency Alliance
Lenora Radetsky, 01/01/2013. Light Scoops: A Design Guide Lighting Research Center, Rensselaer
Technical Advisory Group: 2014 Commercial Building TAG (#9) TAG Ranking: 31 out of 44 Technologies (2014 Commercial TAG strategies ranked separately) Average TAG Rating: 2.33 out of 5 TAG Ranking Date: 03/17/2014 TAG Rating Commentary: Need more specifics to properly evaluate. Any design solutions that add to daylighting capabilities are potentially good; specifics matter. It’s also difficult to predict performance of these systems on an annual basis. There are competing option that might do a better job in some apps. This is a component of a larger system. Its performance really depends on the rest of the system. There are several companies that offer them as parts of their systems, but I am not familiar with how well they work in terms of effectiveness and reliability. I support the ones that are dynamic rather than static. Limited applicability to particular architecture types? Might be challenging to incentivize, but is an aesthetically-pleasing yet functional intervention to address a common daylighting problem, the need to appropriately redirect atrium skylight. Not enough information to evaluate.