Daylighting Always A Compromise

Daylighting is always a compromise. How much light do you need vs. how much solar heat gain can you accept.

When considering a daylighting system there are three main performance measures.

  1. Light Transmission
  2. U Factor
  3. SHGC

The more light transmission you require will result in more solar heat gain. Reducing light transmission to reduce solar heat gain is not always the best trade off. A daylighting model may be necessary to determine the appropriate light level.

CPI LogoIn our research and experience, the best product for currently on the market is UniQuad by CPI Daylighting. UniQuad has the best light transmission percentage to solar heat gain in the industry. Coupled with Skylight Specialists Inc, they can also provide assistance with daylight modeling and studies.

UniQuad vs. Non-Removable Skin Systems

Not all daylighting is created equal! Glass, fiberglass and other non-removable building envelopes can’t compete with the UniQuad system.

Daylighting Technology Visible Light Transmission NFRC-100 Center of Glass U-Value
Glass (Clear/Dbl Glazed, 90% Argon Filled) 79% 0.48
FRP (Crystal/Crystal w/batt insulation) 30% 0.29
UniQuad (Clear Matte/Clear Matte, Air Filled) 50% 0.23

The UniQuad system is the best of both worlds – it will give you up to 50% LT with a U-Value of 0.2

Chase Bank of Loveland

Chase Bank of Loveland Hero

A Pyramid Skylight Retrofit Will Provide Improved Daylighting

The Chase Bank building in Loveland, CO has four low-rise pyramid skylights. The bank has experienced problems with these skylights over the years. Gaskets failing, condensation problems, and popping noises were a just few of the constant problems.

The biggest complaint, however, was the quality of the light and the heat from the sun. The light the skylights were projecting into the building was the number one complaint over the years. The longer the acrylic panels were in place the worse the yellowing of the light and the unbearable heat gain, especially on the second floor.

Going up to the second floor was like being an ant under a magnifying glass in the summer.
The Contractor

We discussed with the contractor and building owner the combinations of colors we could use to gain the control they were looking for. It was decided to use a blue polycarbonate outer layer with an interior layer of Ice White Matte. The Ice White Matte allows the light to be dispersed evenly across and down from each skylight.

A Daylighting Comparison: Yellowed Fiberglass vs. Translucent Polycarbonate

Daylighting and Energy Usage

hm-brown-daylighting-energy-usage-6

A good daylighting system is the easiest and most cost-effective way to light a space and reduce energy usage. After all, the sun provides everyone with a lot of free light and energy every day, it makes sense to take advantage of it. However, placing just adding in skylights or windows without thought is a recipe for disaster; or really just some discomfort, but you get the idea.

An average grocery store might save about $16,000 per year in operating costs, or $0.32 per square foot with the use of an appropriately sized skylighting system.

 

Controlled Daylighting

hm-brown-daylighting-energy-usage-3To achieve reduced energy usage and save on operating costs the daylighting must be intentional and controlled. It is equally important to install and implement lighting controls. If the office worker or employee’s turn on the electric lights, there will be no savings.

Why are electric lights so expensive to run? About half of a light bulb’s energy consumption is released as heat, making them fairly inefficient. LED technologies are improving this percentage, but they still cost money.

Potential Energy Savings

A good daylighting solution will reduce overall energy usage of any building. For example, the potential savings for a few typical buildings in the Los Angeles area were calculated*. An average grocery store might save about $16,000 per year in operating costs, or $0.32 per square foot with the use of an appropriately sized skylighting system. A typical elementary school might save about $7,500 per year in operating costs, or $0.23 per square foot. An industrial processing and distribution center might save about $0.12 per square foot.

*Using 1998 energy costs, weather conditions from the San Bernardino Valley, and a few default assumptions.

Translucent Vs. Transparent Daylighting

transparent vs translucent daylighting

When Should You Use Transparent Daylighting and When Should You Use Translucent?

Proper daylighting design requires use of both translucent vs. transparent daylighting. Glass or other transparent glazings provide a view of the outside, making the room feel larger and bringing the outdoors in. However, glass also brings in solar heat and causes glare, making the space uncomfortable and difficult to work in.

Translucent Vs. Transparent Daylighting

Translucent Daylighting Is the Most Cost Effective

Utilizing translucent daylighting is the most efficient and effective way to provide natural daylighting. Translucent panels are far more effective at blocking heat, providing savings in energy usage. Translucent panels also scatter the light, eliminating glare and reducing the amount of both artificial light and amount of daylighting needed, reducing both operating costs and installation costs. Translucent panels are cheaper to manufacture and install than glass, providing the best cost to usage ratio.

CPI Daylighting’s translucent polycarbonate, like their UniQuad or QuadWall products, provide highly diffused light without glare or solar heat gain. Diffuse light is like light on a cloudy day; small shadows, no spotlighting, low heat and easy on the eyes.

Transparent Daylighting Provides a View

Glass on the other hand provides a view. However the tradeoff is that it also delivers glare and solar heat gain. Glass is also expensive, and to get similar U-values, the glass has to be coated, triple pane, and insulated with argon gases, all adding to the costs. The seals will eventually break down, the gases leak out, and performance drops, and either replacements are expensive and difficult, or impossible.

But, there are areas that a view is necessary. No one wants to work in a building without a window or view outside. So the key is to balance the translucent vs. transparent daylighting in the design.

Translucent Vs. Transparent Daylighting Usage

For general use, walls at eye height (6 feet – 8 feet) should have some transparent glazing, allowing for views outside. In almost all other cases translucent daylighting provides the best performance at the best price. It really depends upon the usage: gymnasiums work best with translucent daylighting, and office buildings do well with translucent daylighting, as glare and heat can drop productivity quickly.