# Home Lighting Design For Aging Eyes. Part 2: the Math

PROLOGUE

Please note that this is the second part of a two-part series on Home Lighting Design For Aging Eyes – this is about The Math, the earlier submission is about The Basics. [Hang on mathphobes, this stuff boils down to one number times another number equals a third number – like 2×6=12, like  like that you can take to a lighting professional who can deliver the illuminance goods.]

RECAP

In Part 1, we were presented with a unique set of rules and restrictions for home lighting design for aging eyes to two purposes. First, to achieve home lighting design standards more suitable to aging eyes (which the literature allows begin to need extra light in their 40s). Second, to translate these new home lighting design standards into numerical targets of common metrics readily identifiable in the retail lighting marketplace.

Common home lighting metrics include lpW (lumens/Watt) which illuminance efficiency data have been around quite a while and CRI and CCT lighting quality data which were hard come-by up until the last few years, as fluorescent makers “warmed up” their bulbs, and, particularly, their compact fluorescent lamps, or CFLs.

EXAMPLE

Comment: OK, let’s try on an example.

A bedroom has an ambient fc target value of 40, i.e., 40 lm/ft squared. That’s a given. The bedroom we’re targeting in this example is, say, 200 ft squared in floor surface area. 40 lm/ft squared multiplied by 200 ft squared = 800 l, our lumen target.

This house designer is not immediately, if at all, interested in that with which the space gets lighted (noting that method will be specified in the plan set, but rarely materials), except that it be lighted evenly and, by specific instruction, avoid lighting flutter from ceiling fan blades interrupting cast light. He’s not interested in specific luminaires (handled broadly in notes attendant to a lighting design schedule) by type, size, or, usually, specific site. Immediately, home lighting designer interest is in determining lumens for given spaces.

Eventually, choosing among materials and methods is for the knowledge of lighting pros and interior decorators and the personal sense of clients, etc.

Comment: Again, it’s the lumen number for a space coming from the Rules in Part 1-The Basics that bridges the gap between your lighting interests and intentions and the folks who know a lot about lighting but not a lot about you. At its easiest, bring your lighting professional The Basics and The Math  and the plan set.

NIGHTLIGHTING SCHEDULE

These calculations end up in a home lighting design Nightlighting Schedule defining by-level and by-space fc target, actual square feet, lm target, and distinction of task or ambient. Some spaces are necessarily scheduled in more than one line when, for example, task illuminance target varies from, say, shower to vanity  both for different target levels and square footage. Comment: It’s labeled “Nightlighting” to oppose it to a “Daylighting” Schedule of natural illumination to interior spaces  separate subject. Nightlighting and Daylighting can interrelate  yet, another subject in residential lighting design.

NIGHTLIGHTING NOTES

A home lighting design Nightlighting Schedule can be presented with extensive notes, including:
1. selected types of luminaires indicated, in order to keep perspective broad;
2. certain materials preferred, e.g., brilliant reflectors to get the maximum illuminance out of CFL downlighting;
3. rules of artificial, or mechanical, illuminance design repeated as a fall-back reference;
4. methods emphasized, e.g., layering, dimmers, under-cabinet skirting, etc.;
5. materials array is recapped, e.g., pendant, sconce, cove, etc.;
6. lighting quality hurdles indicated; site-specific concerns identified, e.g., about lighting potentially high-hazard spaces, possibly troublesome glare, cold-weather fluorescent materials and methods, safety-switching, continuous service rating, etc.

ELECTRICAL & LIGHTING PLAN

The home lighting design Nightlighting Schedule and related notes get translated in the Electrical & Lighting Plan in plan view.

This is not about beating a dead horse with texted table, extensive notes, and now a floor plan expression of wiring including lighting. This is about taking the wiggle-room out of residential lighting design and installation in application.

First, let the home designer define the lighting plan overall. Let the interior designing be done by designers guiding clients, based on the lighting plan. Then let the installation, the construction begin based on the interior designing and lighting pro’s instructions.

This custom home designer writes on the electrical plan space-by-space. He prescribes: foot candles by site, e.g., vanity, overall bath; distinction of foot candles by site by, i.e., task and ambient; switching and circuitry; and notes that, aside from specified heights and spreads of sconce luminaire, all aspects of luminaire materials and methods are done by others.