Daylight: Even Better

Going Green
Green is an idea to believe in, but with a meter, the proof is in the reading. At the meter, energy use is measured and the collective cost comes due for lighting, air conditioning, heating, ventilation fans, computers, printers, network servers, fax machines and copiers...as well as other appliances in employee kitchens such as coffee makers, refrigerators, and microwaves. It all adds up, and the cost is enough to make a green believer out of anyone.

For the average office building in this region of Southern California, energy use looks like this:

• Artificial Lighting… 38% +/-
• Cooling… 30% +/-
• Heating… 7% +/-
• Service Water Heating… 10% +/-
• Plug Loads/ Miscellaneous… 15% +/-

Engineers and environmental design professionals use a category to measure energy usage in fans, called HVAC--Heating/Ventilation/Air Conditioning. This is a simpler way to look at energy magnitudes per class of use:

• Artificial Lighting… 38%
• Heating Ventilation Air Conditioning Fans… 38%
• Service Water Heating/ Plug Loads/ Miscellaneous… 24%

(These measurements are only generally true for electricity consumption in commercial and office buildings in the climate zones of Southern California. Individual analysis of a building will yield numbers that are tweaked slightly.)

Seeing The Light
It is one thing to define these energy lions; it is another to tame them. Knowledge is key. Knowing the current Building Energy Efficiency Standards issued and mandated by the California Energy Commission, called Title 24 in the energy trade, is essential. So, too, is knowing ASHRAE Standard 90.1, because of the vital and valuable guidelines for Building Envelope (insulation in floors, walls, roofs, plus Effective Apertures for skylights, windows, and doors) and Mechanical (heating, ventilation fans, motors, air conditioning, service water heating) and Artificial Lighting (fixtures, both interior and exterior).

But these are puzzle pieces needing to be put together. Knowledge isn't enough; insight is needed, too. And the first insight to be observed is this: not all light is created equal.

Daylighting is the sum total of sunlight introduced into the interior of a building through view windows (side lighting), clerestories (top lighting), and skylights (specialty roof windows, “solatubes”, and mass-manufactured acrylic units in metal frames). Daylight, generally, is twice as efficient as conventional fluorescent lighting, and still beats even the latest and greatest in artificial lighting such as CFL, LED, HID metal halide, or halogen incandescent. This is because of a vital ratio: the rate of illumination related to heat generation. When daylight is used well (meaning that glare, changing sunlight intensities, and solar heat gain are all carefully managed), it produces light at the lowest cost for a unit of illumination because there is no mechanical heat gain. So, the need for electricity to power air conditioning and ventilation fans goes down. The big opportunity is to find ways to make it go down dramatically.

And those opportunities are literally there all day, right in the sky.  This of course has been true for a long, long time. For decades, Solar Design (sometimes called Environmental Design) has been of keen interest, due to the environmentalist and energy-efficiency movements. Richard G. Stein, from his classic Architecture and Energy, says:

"By concern for quality we will be able to substantially reduce quantity. Since a secondary consequence of excessive lighting is a need for additional air conditioning at the rate of about one kwh of air conditioning for every two kwh of lighting, it is doubly rewarding to tailor light use to demonstrable need."

This is still true today. Even if lightbulbs are changed from inefficient to efficient, there is still that ratio to heed. Even if the warmed air is recycled mechanically, there is still that ratio. The ratio… beware… heat is building, just so people can see!

There is a better way.

How much illumination is required to read a handwritten note written with a Number 2 pencil on “96 Bright” multipurpose paper? The answer: within a range of 25 to 50 footcandles. Technically defined, a footcandle (Fc) is a unit of measurement from a single light source of one candela one foot away, so that one lumen falls onto an area 1 foot square; in terms of experience though, a daytime sky with few clouds measures between 2,000 to 3,000 Fc. A couple having a picnic under a shade tree on that same day would experience ambient (synonym: encompassing) light between 50 to 75 Fc. For the interiors of buildings, a good rule of thumb is 10/15/30/50/100+. That is, 10 Fc for hallways, 15 Fc for lobbies, 30 Fc for ambient, 50 Fc at desktops, 100 Fc and above for special spaces with unique work tasks, like manufacturing and printing.

Depending on the building type, it is possible to light interiors from 8:00 AM to 5:00 PM entirely without the need for artificial lighting. With some office buildings the mix of natural-to-artificial can be 70%-to-30% or 80%-to-20%, for example. But whatever the mix may be, this is always so: if daylighting is increased, then artificial lighting and HVAC decreases. With daylighting, it is a certain if, then.

All Together Now
The sum total of a building’s features determines its measure of green. What and How matters. What is included? How does it fit together, part to part? Buildings without the right features are thrown into the imbalanced misfiring of poor performance that sets up a financial kill at the meter. So the choice remains: go green or get killed.  

Daylighting… ?

Artificial Lighting… ?

HVAC… ?

Composition is everything. So, daylighting? What is to be done about skylights, clerestory windows, and various view windows properly guarded from excessive sun? In this region of the west with plentiful sun, there are apps to be applied. The Daylit Building can be as powerful as a solar panel. The best practices result in buildings not only having solar apps but becoming solar apps themselves.

Questions Asked and Answered:
Q: How do you prevent sun from overheating the rooms on the south and west faces of the building? Also from damaging fabrics?
A: Typically, tinting, photochromic glass, or a re-design of rooflines including permanent metal sunshades is involved. Sometimes it is effective to plant deciduous species that will shade these exposures in the spring and summer months— so from, say, late March through until late August or early September.

Q: How does daylighting affect the size of a photovoltaic system?
A: It results in smaller electricity demand, therefore a smaller photovoltaic system.

Q: Where do I begin?
A: Your requirements are unique to your building’s current energy consumption and your green goals. Start by making a mental note of what you want to accomplish: “I want to cut demand in my building by ___ % .” From this simply stated goal and marker, a BOD can be determined. A BOD is an acronym for a document called a Basis of Design that organizes the way green is implemented according to the owner’s green goals.

Q: Who is responsible for the BOD?
A: We are, at Green Convergence. A team will be assembled tailored to your specific need. Every BOD is a one-of-a-kind set of specifications.