02.27.09Dennis Roberts, President, Energy Efficiency Done Right

Article Viewed 880 Times
8 Comments

Daylighting could be one of North Americas most sought and seldom realized building goals. How could the well documented benefits of more natural light in schools and buildings be so desired yet so elusive? The answer is no mystery and can be resolved to the benefit of the students, building inhabitants, building owners, even the environment.

"Despite a long history of using daylighting as a design strategy, building owners, architects, engineers and lighting designers are only just beginning to understand how to use it effectively." according to a Building Operating Management article. "The biggest problem with daylighting design is we still take a traditional building approach to a daylighting project," says Eric Truelove, director of sustainable design and HVAC engineer for Renschler. In other words, the architect and owner design the building and then hand it off to the engineers, who hand it off to the contractors." "In a typical case, the architect's design offers plenty of glass for light, but that light brings with it too much heat, forcing the engineer to increase the cooling tonnage when the building is complete. It also becomes difficult to decrease lighting energy costs because when the building is complete, occupants demand blinds to cut down on glare. As a result, the blinds are drawn much of the day, requiring the use of electric lights. An owner who thought daylighting was going to save money finds out that the design not only costs more upfront but costs more to operate as well." So the end result is the no daylighting productivity benefits and ongoing added expenses with no end in sight.

This is a very expensive and counterproductive result. When you consider that buildings are responsible for about seventy per cent of the electricity used in America and that the daylighting unachieved scenario is multiplied by ten of thousands of times every year, the composite cost is no doubt in the tens of millions. Since America is a large net energy importer, these unnecessary costs are a drain on our economy. I would like to call attention to a simple but very effective way to reverse this expensive and unproductive trend. This step alone could provide the desired daylighting in new and existing buildings, while reducing cooling, heating, and lighting costs.

The challenge of daylighting is to have the natural light but control the glare and heat. Once again according to Director Eric Trulove, architects almost always want clear glass and specify glass with transmittance of 80 percent. "They often don't realize until you show them that glass with 40 percent transmittance looks clear too," he says.

"By selecting for certain optical properties, the building owner not only maintains a view out the window and brings daylight in, but increases energy efficiency as well. By going from a transmittance of 80 percent to 45 percent, Truelove says, the building's cooling load can be cut in half."

A simple solution that provides more of the desired daylighting and a decrease in the building's cooling load by one half! This is an approach that should be quickly utilized as there is no down side and a huge beneficial upside. Visible transmittance should be a consideration in building planning to the benefit of the building inhabitants, building owners, and energy efficiency goals.

This plan could be taken a step further by modifying the numerous building that failed to meet their daylighting goals. Most of these building fell short of the desires daylighting goals due to the installation of glass with a transmittance of eighty per cent or higher. By installing window insulators the light transmittance could be reduced to a range of twenty-two to twenty-six per cent. This would mean that only twenty-two to twenty-six per cent of the potential heat from sunlight would enter the building space. Window insulators would also reduce the heating load in those buildings due to the reduction of thermal heat lose.

The sheer amount of blinds and other window coverings on buildings are a testament to unachieved daylighting and energy efficiency in buildings and schools. There are many excuses for why we have known about the benefits for daylighting for so long but have done so poorly at achieving it. The costs of this failure are huge and ongoing. With the knowledge and resources we have now, there should be no more excuses.

We know you have something to say!

There is an immediate need for articles on the hot topics in the Power Industry! EnergyPulse, like no other publication, also provides a means for our readers to immediately interact with experts like you.

Contribute Today!

Please view our Author Guidelines and send submissions to the editor.

Reader's Comments

Date	Comment
Bob Amorosi 2.27.09	Dennis, Many understand the energy benefits of the state-of-the-art low transmittance window technology in your article. The problem historically is that reducing energy consumption or using it more efficiently wasn't on most consumers' minds as long as energy has been plentiful and cheap to heat and cool buildings. Obviously the energy situation is changing. The real reason you don't see droves of consumers now running out to replace their windows and upgrade their home's energy efficiency is COST to retrofit existing homes. And new home builders will continue to use the old high transmittance windows as long as they are less costly, unless a home purchaser orders the upgrade and is willing to pay a premium for it. Here in Canada our federal and provincial governments offer substantial incentives to all consumers to upgrade their homes' energy efficiency, including new windows. Incentives include sales tax exemptions, others are sizeable grants to subsidize purchases. But if the window manufacturing industry really wants to see their state-of-the-art products more widely used, they should start by lowering their costs relative to old window technologies. Bob Amorosi, M.Eng. Resident of Ontario Canada
Kimo Sutton 3.3.09	Hey there in Canada eh. How is that socialism doing? Got healthcare down yet? We would do better to buy more oil from you when your dollars is diving like lead. Lets look to more efficiency in the design and then look at technology to have more than a couple of floors of sunlight transmission in bigger buildings where it could really save energy. Lowering cost is a function of the market place not a choice, come on get a look at your super market and see what cost less in summer. Also we have less money to spend and that makes choices come down to a budget, you know that thing that puts a stop to buying high priced gas and vacations to Canada. We have big problems that do not include throwing money at them although the administration may think so. We love Canada as a neighbor and friend but not telling us how to be the biggest most productive country in the world. Just as you do not like us telling you how to run your colony.
Bob Amorosi 3.4.09	Kimo; so you don't like socialism eh? Just wait for it in Obama's economic stimulus money to start flowing in the US. A HUGE portion of it is for health care reform. After the reforms he wants are implemented, you won't recognize your private health care system down there anymore, so you had better get used to much more socialism if you know what's good for you. In the meantime don't get sick - it might cost you your house unless you have a matress full of money to burn.
Paul Stevens 3.4.09	Hey Kimo, let me get this free market thing right. First, you allow large banks and investment firms to ruin the worlds economy, pay the CEOs of those banks and investment firms millions of dollars to do it, then bail them out with 1.3 trillion dollars of taxpayers money, without giving the taxpayers a say in it. So by free market, you mean "free money" for CEOs and failed investment and banking firms and "free inflation" for taxpayers? Too bad Canadian live in a socialist country. I bet they'd want some of that. Oh, by the way, per capita dollars spent on healthcare in Canada is lower than in the US. Unfortuantely everyone has access without having to go $100 K in debt. Pity us.
Rudy Gadsden 3.4.09	Back to the subject at hand...While I understand the benefits of using lower remittance windows to reduce the heat load, what effect does the use of this type of window has on cooling loads during cooler periods? In other words, shouldn't letting the sun shine in during the cooler weather reduce heating costs as well?
Bob Amorosi 3.4.09	Rudy, Yes in answer to your last question. There is potentially benefits of heating of the window itself provided these windows absorb more sunlight. If however it reflects more incident sunlight, then there is no benefit to heating costs.
Dick Maclay 3.5.09	Dennis, what about windows with variable transmittance? Let in the sun when it is cold out and not when it is hot. I have heard that such things exist beyond the scale of my glasses, but know nothing really about them.
Dennis Roberts 3.11.09	To respond to several question regarding my article, the lower visible transmittance windows do reduce heat gain during cooler weather also, however, window insulators are reversible to provide enhance heat gain during cooler weather. In'Flector Window Insulators are designed to be a solar rejector in hot weather and a solar collector in cold weather. Bullding with our local climate in mind, as well as using natural resources to lower dependence on fossil fuels makes great sense today and into the future. Vairable transmittance glass is still not a viable energy efficiency option for most consumers but holds promise. Thank you for the thought put into your responses to the article. Dennis G. Roberts

Do you agree or disagree with this article? Send in your own article.

Add your comments:

Please log in to leave a comment!

back to top