Before The Architect - Articles, Illumination Schedule a/k/a Daylighting Schedule

House design policy and common sense: let the daylight in. . . with qualifications – maybe not too much, not too little, depends on where, depends on how, how about when, depends what it’s shining on, etc. This is about a Daylighting Schedule.

House design code: IRC 303.1 presents effectively and round-about that, at least in a sleeping room, “aggregate glazing area" should be not less than 8% of that room's floor surface area. (CABO’s tougher, fewer exceptions.) [Please note that this presentation has no direct connection with emergency egress.]

House design practice: who knows; the author has had reaction from "exactly, right" to "not so important around here" to "what are you talking about" from building authorities having jurisdiction.

Before The Architect develops a Daylighting Schedule to address code and a whole lot more.

To start, the term aggregate glazing area – otherwise undefined – is interpreted to mean translucent surface – glass, clear plastic, etc. and not associated frame, sash, muntins, trim, and the like….what Marvin Windows and Doors defines as “Lite", Pella as “Visible Glass", Loewen as "Exposed Glass Area," etc. Note, please, that if some folks weren’t interested in these surface areas, the big players in windows wouldn’t work it out in print. Before The Architect is interested.

A Daylighting Schedule, or Illumination Schedule –

Defines the proportion of aggregate glazing area to interior surface area in each major space of a residence, including habitable rooms, halls, walk-in closets, utility spaces for workshop and laundry and such, garage(s), etc.

Compares actual aggregate glazing area to calculated code target for each major space and presents the difference either in square feet or, increasingly likely, in percent of target – the latter seems easier to usefully understand.

Comments selectively by suggestion, indication, and definition about daylighting aspects of importance as designers’ opinions warrant.

Provides an opportunity to identify persistently darkish spaces or parts of spaces sufficiently distant from a natural light source so as to be considered unlighted, or not penetrated, by a natural light source, e.g., a space considerably back from the daylight from a covered porch, an exceptionally deep interior space

Daylighting experts put definable limits on the extent of useful daylighting that can penetrate a space or spaces, e.g., including but not limited to Lighting Design Basics by Mark Karlen and James Benya, John Wiley & Sons, Inc., 2004, p.34 and Interior Lighting For Designers 4th Edition by Gary Gordon, John Wiley & Sons, Inc., 1957, p.53ff. While this aspect of daylighting analysis can be judgmental, consideration of related adjustment to natural illumination is, in the author’s opinion, well worth the effort as a pre-emptive design alert to convenience and safety

Presents several bases of analysis –

	Of itself for natural light, in the house’s compass orientation and, possibly, its adjustment. and in personal assessment of infiltration and adequacy in daylighted spaces
	Ventilation, particularly as an indicator in cross-venting of sleeping areas and longer occupied rooms plus sizing and siting both supplies and returns
	UV intrusion indicator of where it may be less welcome and its power may need to be diminished
	Natural heat-build indicator for HVAC professional attention and various design means to lessen
	Daylight glare definition especially in areas, such as stairways, where glare could threaten safety
	Qualification for code-compliance of aggregate glazing area to space surface area in sleeping areas, notably more problematic in such spaces within story-and-a-half structures
	Suggestive guide to artificial lighting throughout, particularly ambient lighting and lighting controls
	Definitive cross-check on window and door size and site in both elevation and plan view
	Excellent perspective on the consequences of exterior design on interior functionality, occasionally leading to design changes ranging from marginal to major
	Guide to increased layering in low-daylight spaces
	Guide to continuous service rating in no- and very low-daylight spaces
	Motivation in single-storied deep spaces with exterior covers to penetrate those covers with niches in the roof, sunscreen, skylight, clerestory, etc.
	Motivation in single-storied deep spaces with or without exterior covers to add clerestories and light wells by way of dormers and other fenestration design modifications
	Motivation, particularly in story-and-a-half designs, to necessarily add dormers, skylights, skylight tubes, clerestories, and other fenestration design modifications

Note please that latter-day fixing of major mistakes to attain convenient and safe sizing and siting of windows, exterior door composition, luminaires, and light-reflecting and -absorbing features can be a remediation expense and physical inconvenience bigtime.