Verde Laguna: Summer tips to save money and stay cool

EDITOR’S NOTE: This is the first of a two-part series. The first focuses on passive solar strategies and lighting tips and the second will be on natural ventilation and cooling tips.

By making simple choices and using common sense, you can be on your way toward saving money and staying cool. The first step in this process is to understand our climate. Because sun matters, few things are as important as understanding the orientation of the building. We are going to play with the sun to take advantage of nature to provide cooling and light.

We can maximize solar access to boost the effectiveness of daylighting strategies, reducing the need for artificial lights, but at the same time controlling heating to minimize cooling loads. We are going to open the windows for natural ventilation and cooling to provide comfortable conditions within buildings during hot periods. When carefully combined, daylighting and natural ventilation can greatly reduce cooling loads in buildings, and eliminate or minimize the need for mechanical cooling. The challenge is to ensure the building responds appropriately to these two very different goals.

Another important factor is what occurs inside the building. If the activity and equipment inside generates a significant amount of heat, the internal thermal loads are going to add to the ones from the sun. This also affects the rate at which buildings gain or lose heat. In many buildings the largest single component of the cooling loads is the energy needed to remove the heat generated by lighting. Therefore reducing electric lighting can reduce up to 40% of the energy used for mechanically cooling buildings.

Window design is the most important building envelope consideration for energy conservation. In Laguna, their design should maximize daylighting, views to the exterior and ventilation, while minimizing solar heat. Daylighting is not used simply to illuminate interiors, but to increase satisfaction. The choice of glazing is critical in ensuring good daylighting. A wide range of glazing is available offering both admissions of daylight and low heat gain. High performance glazing systems can significantly reduce solar heat gain while still admitting daylight. However, replacing windows or glazing is going to be expensive.

So, the first tip is to stop the direct rays of the sun before they reach any window. Exterior shading devices are more efficient than interior ones to significantly reduce solar heat gain and control glare. The crucial design issue is to achieve a balance between solar control and daylighting. Awnings and overhangs on south and southwest orientations are the most effective means of solar control because they prevent sunlight from striking the windows. Movable systems are adjustable according to the season, but are more prone to failure. Fixed overhangs are more dependable, but their design must account for daily and seasonal variation of the sun’s path. A properly sized overhang on southwest- oriented windows can reduce energy use by up to 6%, and a further 20% can be gained by combining overhangs with daylighting controls.

There are no simple rules of thumb for appropriately sizing overhangs. Each one should be evaluated depending on its relative cooling and heating needs. The effectiveness of fixed overhangs depends on the relative projection from the window plane and the distance above the opening. Extending the overhang beyond the sides of the windows to prevent solar gain from the side is always a good measure. The use of louvered shades to allow more daylight to enter, while shading from direct sunlight, is another good alternative.

Tightly spaced louvers near the window shade high summer sun, while loosely spaced louvers further away shade low winter sun. Vertical fins at right angles from the windows on east and west orientations are typically most effective. Color is also important. The shading system should be light-colored if diffuse daylight transmittance is desired, and dark-colored if maximum reductions in light and heat gain is desired.

Interior shading systems are less effective because they allow the sun to enter the building. However, a few no-cost cooling tips include keeping windows and doors shut and shades closed during the day, to keep the house cool and reduce air conditioning needs. Close drapes, blinds and shades to keep the sun’s rays out of the home, particularly for south facing windows. To maintain exterior views while shading, consider fine mesh roll screens that reduce illumination and glare while allowing views.

When the sun goes down, lighting will be needed. This is when new technologies play a role to light spaces without creating unwanted heat. Another tip and good investment for summer energy savings is to replace incandescent light bulbs with compact fluorescent bulbs, or CFLs, to save on lighting and cooling bills. Incandescent bulbs only convert 10% of the incoming energy to light, with 90% wasted as heat. They seem to be heaters that happen to give light. About a third of the electricity used in buildings in the U.S. is for lighting and thus offers a large area for improvement. Many technologies exist that can contribute to lowering your bills. CFLs use less than a third of the energy of incandescent and last 10 times longer, and light-emitting diodes (LEDs) create almost no unwanted heat inside the home. The interior of your building will stay cooler — and you will be saving energy and money — by not running an air conditioner as often. So you will save money and use less while saving the environment.

GUSTAVO GRAD is a Laguna Beach resident and certified sustainable building advisor. He can be reached at [email protected]