Cooling Options

To Cut Energy Costs, Look for Low-tech Cooling First

Fans and natural cooling

Ceiling fans and breezes make rooms seem cooler by creating a mild wind-chill effect even if temperatures aren’t actually lowered. Whole-house fans that flush hot air out of the house at night and replace it with cool nighttime air can keep a house comfortable through much of the following day. Fans are much less expensive to run than conventional air conditioning.

Air conditioning

Ducted, whole-house systems are common in areas of high heat and high humidity, such as the southeastern U.S. Central air conditioners are rated by the seasonal energy efficiency ratioSeasonal Energy Efficiency Ratio (SEER) is the total cooling output (in BTU) of an air conditioner or heat pump during its normal annual usage period divided by its total energy input (in Watt-hours) during the same period. The units of SEER are Btu/W·h. SEER measures how efficiently a residential central cooling system operates over an entire cooling season. The relationship between SEER and EER depends on location, because equipment performance varies with climate factors like air temperature and humidity. (SEER(SEER) The efficiency of central air conditioners is rated by the Seasonal Energy Efficiency Ratio. The higher the SEER rating of a unit, the more energy efficient it is. The SEER rating is Btu of cooling output during a typical hot season divided by the total electric energy in watt-hours to run the unit. For residential air conditioners, the federal minimum is 13 SEER. For an Energy Star unit, 14 SEER. Manufacturers sell 18-20 SEER units, but they are expensive. ), which is the cooling output in BtuBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. divided by the power input in watt-hours over the course of a normal cooling season.

DIVE DEEPER

OTHER CONSIDERATIONS

Retrofitting for AC

In houses with forced-air heating systems, adding air conditioning is relatively simple because the ductwork is already installed. Where no ducts are in place, installing central air conditioning is more complicated.

GREEN POINTS

LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. -H Cooling approach potentially affects up to 4 points in EA1 (Energy & Atmosphere) or EA6.

NGBSNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. Under Ch. 5 — Lot Design and Ch. 7 — Energy Efficiency: up to 18 pts. for natural cooling options (505, 704 & 703); up to 24 pts. for cooling efficiency of central air conditioning system (703.4.5).

ABOUT COOLING

Consider living without air conditioning

For thousands of years, people have lived in hot climates without air conditioning. Because air conditioners use lots of energy, green builders should consider other cooling options before concluding that a house requires air conditioning.

According to the U.S. Department of Energy, two-thirds of U.S. homes have air conditioning systems, which collectively consume 5% of all electricity generated in the country and cost homeowners about $11 billion a year. In parts of the country where high temperatures, high humidity or both are a fact of life, air conditioning is considered a necessity.

There are, however, a number of ways to lower indoor air temperatures short of installing large, energy-intensive air conditioning systems. Among suggestions from the American Council for an Energy-Efficient Economy:

Insulate and tighten. Well-insulated houses don’t need as much mechanical air conditioning as poorly insulated houses. Meeting or exceeding insulation levels recommended by the Department of Energy is a good first step. That’s easiest to do in new construction but still feasible as a retrofit, especially when it comes to attic insulation.

Choose low-solar-gain glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill.. Windows with low solar heat gainIncrease in the amount of heat in a space, including heat transferred from outside (in the form of solar radiation) and heat generated within by people, lights, mechanical systems, and other sources. See heat loss. coefficients will help lower indoor temperatures and significantly reduce cooling loads.

Replace inefficient appliances and products. Replacing old refrigerators with energy-efficient models, exchanging incandescent light bulbs with fluorescents and unplugging electronic equipment when not in use to reduce phantom energy loads all contribute to a cooler interior.

Use cool exterior finishes. Light colored roofing and siding can reduce cooling demands by as much as 15%.

Keep it shady. Planting deciduous trees and shrubs near south- and west-facing walls can help block intense summer sun. Window shades and horizontal trellises are an option where outdoor plantings are not practical or ineffective.

Update existing cooling equipment. If the house already has an air conditioning system, consider replacing it with more efficient (14 SEER(SEER) The efficiency of central air conditioners is rated by the Seasonal Energy Efficiency Ratio. The higher the SEER rating of a unit, the more energy efficient it is. The SEER rating is Btu of cooling output during a typical hot season divided by the total electric energy in watt-hours to run the unit. For residential air conditioners, the federal minimum is 13 SEER. For an Energy Star unit, 14 SEER. Manufacturers sell 18-20 SEER units, but they are expensive. of higher) equipment. Energy efficiencies have improved sharply since the 1970s. The Department of Energy estimates that moving to high-efficiency equipment, along with other steps, can reduce energy consumption by between 20% and 50%.

All of these steps can reduce or eliminate the need for an expensive AC system. At worst, they should allow the installation of a smaller system than would otherwise be required, lowering long-term operating and maintenance costs.

FURTHER RESOURCES

BuildingScience.com:
Conditioning Air in the Humid South—Creating Comfort and Controlling Cost

"Hot Climate Design" by Martin Holladay

Tags:
3.
Wed, 07/20/2011 - 17:03

Passiv Haus - one reaction in Europe: ACTIVE HOUSE
by John Gant

The issues of Passiv Haus to reduce daylighting and natural ventilation, perhaps excessively, for ever-increased air-tightness has led to a thoughtful response by others - see this new movement: http://www.activehouse.info/ "ACTIVE HOUSE" seems to be a very sensible evolution.


2.
Fri, 07/16/2010 - 16:46

Response to Larsen
by Martin Holladay, GBA Advisor

Larsen,
The GBA Encyclopedia has an extensive section discussing evaporative coolers:
http://www.greenbuildingadvisor.com/green-basics/fans-and-natural-coolin...


1.
Fri, 07/16/2010 - 16:10

Swamp coolers
by Larsen

Evaporative cooling is a good option for dry areas.


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