Lighting with Daylighting

Learning Objectives

Daylighting
Shading
Daylight Harvesting
Daylighting Resources

Daylighting Defined

Daylight is direct or diffused light from the sun. Daylighting is a term applied to building design that includes natural daylight as a light source including windows, clerestory windows, skylights, light tubes, and atriums.

Shading Systems

Direct sun is glaring and shading is part of a good daylighting scheme. As will all well designed buildings, thorough consideration or optimizing daylight needs to be included early in the design process. Maintenance of any moving parts needs to be included in the building design, solutions include:

Exterior light shelf - an eyebrow on the outside of the building is designed to bounce the light into the space and to block direct sun from entering the building.
Interior light shelf - a shelf or plane interrupting the full height of the window, a few feet below the ceiling designed to bounce light into the interior, farther than the light would go without the shelf. they can be adjustable and used to shade direct glare from the sun.
Blinds and Louvers can be fixed or adjustable, controlled manually or automatically, translucent or opaque.
Curtains or Drapes soften and filter the light and depending on density and color will darken the space.
Between glass shading, coatings, and frosts all require
Skylights are difficult to cover because of light leaks around the edges or if applied outside, they can blow off or dust will cause poorly maintained systems to freeze and no longer adjust.
All coverings have the potential to reflect heat and light inside and outside.

Daylighting - Whole Building Design Guide - Design Recommendations

Seasonal performance of shading, redirection devices. Illustration by RNL Design

Whole Building Design Guide (WBDG) by Gregg D. Ander, FAIA
Southern California Edison

"Implementing daylighting on a project goes beyond simply listing the components to be gathered and installed. Daylighting requires an integrated design approach to be successful, because it can involve decisions about the building form, siting, climate, building components (such as windows and skylights), lighting controls, and lighting design criteria.
This overview is intended to provide specific details for Federal agencies considering daylighting technologies as part of a new construction project or major renovation. " [1]

The goal of 'Whole Building' Design, a program of the National Institute of Building Sciences, is to create a successful high-performance building by applying an integrated design and team approach to the project during the planning and programming phases.
Updated by U.S. Department of Energy Federal Energy Management Program (FEMP) Updated: 09-15-2016
https://www.wbdg.org/resources/daylighting

Lighting Controls & Daylight Areas

The state of California Building Efficiency Standards Title 24 mandates specific lighting controls for commercial spaces. Buildings over certain sizes are required to include daylighting and separate controls for artificial lighting of areas within and adjacent to daylighting.

Reflectance

Visit Seniors and Low Vision page for more on reflectance.

CLTC releases new Daylight Harvesting Guide

New CLTC Publication on Daylight Harvesting for Commercial Buildings

The CLTC is excited to announce a new publication in our Lighting Best Practices series, the Daylight Harvesting for Commercial Buildings Guide! This publication provides guidance towards meeting and exceeding California's Building Energy Efficiency Standards for daylight harvesting.

Daylight design guidelines and associated Energy Standards are provided in an easy to read, side-by-side layout, organized into sections for each building-related discipline that impacts daylight performance from building siting, through architectural and interior design, to construction, commissioning and operation.

This publication was developed with support from Southern California Edison and the California Energy Commission. Support was also provided by the University of California, Davis [2]
Publication Date: 08/27/2018
Download the guide 90 page PDF

Glare - consider glare in your daylighting design

Glare is the effect of brightness or differences in brightness within the visual field sufficiently high to cause annoyance, discomfort or loss of visual performance.
Glare – Disability Glare
If task performance is affected, it is called disability glare
Glare – Discomfort Glare
Visual discomfort caused by excessive brightness is called discomfort glare.
Glare – Direct Glare
Glare resulting from very bright sources of light in the field of view. It usually is associated with bright light from luminaires and windows. A direct glare source may affect occupant’s performance by reducing the apparent contrast of objects in the field of view, especially those near the source of light.
Glare – Indirect Glare
Glare produced from a reflective surface.
Glare – Reflected Glare or Veiling Reflection
Glare resulting from bright reflections from polished, glossy, or illuminated objects and surfaces in the field of view. Veiling reflections reduce visual contrast and make it difficult to complete seeing tasks such as reading glossy magazines or looking through windows or at computer screens. Often windows or light fixtures will reflect off surfaces obscuring what is beneath, anticipate this visual obstacle by careful placement of lights, windows, and tasks. Remember with glare, 'the angle of incidence equals the angle of reflection' just like billiards.
Visual Comfort Probability (VCP)
A rating system for evaluating direct discomfort glare. This method is a subjective evaluation of visual comfort, when viewing from a specific location and in a specified direction, expressed as the percent of occupants of a space who will be bothered by direct glare. VCP allows for several factors: luminaire luminances at different angles of view, luminaire size, room size, luminaire mounting height, illuminance, and room surface reflectivity. VCP tables are often provided as part of photometric reports.