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A 5,000- 6,000 Btu/hr air conditioner drawing about 500 watts can be installed in one window of a designated cool room (it is important that the installation is insulated and well-sealed
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A battery storage system can provide reliable back-up power during a grid power outage
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A cool roof utilizes materials with high solar reflectance and thermal emittance to reflect solar energy and reduce heat gain to the home
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A cool room should have low enough heat gains to be easily cooled by a small single-zone cooling system such as a mini-split or a window air-conditioner as shown here
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A ground source heat pump with an open-loop piping system using vertical injection and recharge
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A ground-source heat pump has the same components as a standard air-to-air heat pump except that the liquid-to-refrigerant heat exchanger coil is located inside rather than outside
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A ground-source heat pump with a closed-loop horizontal “Slinky™ “piping arrangement
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A mini-split air-conditioning system can be a highly effective low-energy approach to provide cooling to one designated zone in the house
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A modern single-inlet direct evaporative cooler draws outside air through an 8- to 12-inch media filter
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A properly sized cold climate heat pump can meet 100% of a home’s heating load in nearly any location in the United States
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A reversible window fan can operate via thermostatic or remote control and can selectively exhaust air or bring in outdoor air
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A screened-in porch will protect windows from rain, provide shade, and allow more airflow through windows than window screens would
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A shallow, open floor plan allows free flow of cross ventilation through the house
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A variety of battery-powered fans can be used for a cool room without electric power; most charge off a USB charger so they can be solar charged
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Air seal a heat pump or air conditioner air handler cabinet at all seams, holes, and junctions
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Air speeds generated by a typical ceiling fan are in the ideal range for providing occupant cooling without causing disruption
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Airflow can be directed across thermal mass in the ceiling, floor, or elsewhere inside the home through various window and louver configurations
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An innovative U-shaped heat pump offers SEER 15 efficiency and operation with smart phones
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Building Science Corporation used convection to help cool this structural insulated panel (SIP) cottage in Georgia.
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Ceiling fans can be used to aid a night flush strategy by helping to cool down wall and floor surfaces more thoroughly at night, and by providing comfort ventilation during the day
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Comfort ventilation focuses on airflow over occupants; in this example of wind-driven cross ventilation, the air is directed through the main occupied areas of the bedroom
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Concept behind an evaporative cooler – warm air is cooled as the air passes through a wet medium and gives up some of its heat to evaporate the water
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Cool towers like this one at the Zion National Park Visitor Center can provide cooling to a building without any energy consumption
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Cooling air temperatures that can be achieved by a direct evaporative cooler at various outdoor conditions
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Create a cool room to shelter from extreme heat by selecting a room in the basement or on the north or shaded side of the house, air sealing and insulating, providing low-wattage and battery-operated cooling, and reducing interior heat loads.
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Deep overhangs and porches provide midday shade for most of the windows on this home in Albuquerque, NM.
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Dense hedges can encourage cross ventilation (left image) or not (right image) depending on how they are placed relative to windows
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Double fan window units can have multiple operational modes; most often outdoor air will be brought in at night when outdoor conditions are cooler
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Ducted whole-house fans should be installed with the duct curved and the fan suspended from rafters to reduce noise and vibration transmission to the living area.
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Ductless indoor units like this one are controlled individually by handheld remote controllers.
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Ductwork located in a vented attic is subject to high attic temperatures and significant heat gain through the walls of the ducts
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Earth tubes buried in the ground can provide pre-cooling of ventilation air or primary cooling if designed deep and long enough
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ENERGY STAR-rated ceiling fans and openable windows oriented to prevailing summer breezes help provide low-cost cooling.
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Evaporative Cooler Sizing in ACH based on wet-bulb temperatures at 1% summer design conditions
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Evaporative coolers use a fan to draw outside air through a wetted pad which cools and humidifies it
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Evaporative cooling is most appropriate in areas where the summer design mean coincident wet bulb temperature is less than 70°F, shown in purple here and labeled as region “A”
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Even when wind is blowing parallel to a wall, an open casement window can create a zone of higher pressure near the window opening, driving airflow into the house
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Example expanded performance table from a 1.5-ton air conditioner
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Example of an earth-sheltered home in hot climate Tempe, AZ uses the cooling properties of the ground to decrease cooling costs
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Having both low and high ventilation openings is necessary to promote airflow from the stack effect
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If a cool room is directly under an attic or roof, having lighter colored roofing (home on left) will reduce heat gain to the space as compared to darker roofing (home on right) because the temperature of the roof will be lower (see thermal image)
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In a typical old style multi-inlet evaporative cooler, the blower fan draws outside air in through multiple media filters and blows it into the home
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In heating mode, split system heat pumps absorb heat from the outside air and “pump” that heat to the indoor air handler unit, which releases it to the inside air.
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In hot climate zones, shade building surface with vegetation for passive cooling.
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In hot, dry climates, passive cooling should focus on shading, night flush through cross ventilation and whole-house fans, potentially using high-mass construction
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In hot, humid climates, passive cooling should focus on shading, airflow through cross ventilation and ceiling fans, and low-mass construction
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Inducing airflow through the stack effect requires low inlets and high outlets such as a ridge hood or crown monitor
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Installing an ENERGY STAR ceiling fan is a low-energy way to improve comfort in a designated cool room
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Landscape trees and shrubs to funnel cooling breeze towards a home in hot climate zones.
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Landscaping and Bahama shutters can provide important shade for a designated cool room
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Light colors have been used on exterior walls and roofs to keep buildings cooler in hot climates for centuries, as shown by this traditional building in Morocco, built in the early 1800s
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Light-colored roofs and walls and deep overhangs for shade are some of the features used by builders in the hot-humid climate (Source: Alys Beach Construction).
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Locating windows on adjacent and opposite sides of the house will allow cross ventilation regardless of wind direction
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National HVAC Design Report - Cooling Equipment Selection (Version 3 / 3.1 (Rev. 09))
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Passive cooling techniques can reduce or eliminate the use of air conditioning and can be used for backup cooling during emergencies.
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Portable air conditioners offer flexibility with where they are located, but usually need to be installed near a window as they require one or two intake/exhaust ducts connected to the exterior
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Proper refrigerant charging is critical to maximizing performance for compression cooling systems
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Right - An energy recovery ventilation (ERV) brings fresh air into the home while exhausting stale air. Both ducts pass through a heat exchanger where heat from the warmer duct is transferred to the cooler duct.
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Right - This evaporative cooler is wall mounted to reduce leak effects and allow for ease of maintenance.
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Right – The outside unit of the mini-split heat pump system is installed on a concrete pad and away from shrubs.
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Right – This home uses a light-colored exterior wall to reduce solar heat gain
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Right – This home uses light tan stucco and white trim to reduce solar heat gain.
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Right – This metal roof is being coated with a cool (high SRI) coating to reduce solar heat gain
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Right (decent): For a relatively high-capacity ccASHP sized per Approach 3 or 4 to meet nearly 100% of the heating load, this heat pump’s modulating zone has a decent overlap with the home’s heating load line, reducing short-cycling.
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Right: Sized per Approach 1, this heat pump will have minimal short-cycling; since sized using Approach 1, it will require backup heat when temp is below 30°F but could still contribute significant heating down to heating design temp (-6°F) and lower
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Right: Sized per Approach 3 or 4, this heat pump’s modulating zone has a large overlap with the home’s heating load line, resulting in minimal short-cycling; the unit may require a small amount of backup heat during the very coldest hours of winter.
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Right: Sized per Approach 3, this heat pump’s modulating zone has a large overlap with the home’s heating load line; it will require backup heating but could still contribute significant heating for all hours of the heating season
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Right: This house plan orients broad building surfaces away from the west and east, trees are used to shade the west and east, and large overhangs shade windows on the south wall
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Roof-mounted solar panels shade the roof below them (left), significantly reducing the roof’s surface temperature (thermal image on the right - yellow region under the panels is cooler than the red and white region on the exposed portion of the roof)
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Shade trees planted on the east or west sides of a house are one of the most effective measures that can be taken to reduce heat gains
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Side by side comparisons of standard roofing colors (top row) and cool colors (bottom row) shows that solar reflectance (R) can be reduced significantly using special coatings with almost no change to the color
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Small, battery-powered evaporative coolers can be appropriate for personal cooling in arid climates (only)
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Some whole-house fans are equipped with an automatic drop-down cover to provide an air seal at the ceiling level when the fan is not in use
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Some whole-house fans use an automatic insulated cover achieve high R-values when the fan is not in use
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Sources of heat gain in a house include solar gains, infiltration, conduction through walls and roof, occupants, and internal equipment
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Sources of heat gain in a house include solar gains, infiltration, conduction through walls and roof, occupants, and internal equipment
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Tall annuals, like the sunflowers in this picture, can provide very effective shade in summer (left), provide a pleasant view from inside (right), and allow sun into the home in winter when the plants die back.
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The cool shingles on the right have been coated with a ceramic coating to reflect near-infrared radiation, resulting in a cooler roof as shown by these thermal images (red and yellow are hotter, green and blue are cooler).
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The ductless air handler of a ductless heat pump can be mounted above the ceiling so that only the register is visible
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The existing dark tile roof on this home (top photo) was covered with a light -colored coating on day 6 (middle photo), resulting in a significant reduction in attic temperature and cooling energy consumption (bottom)
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The high-efficiency mini-split heat pump provides cooling and heating; a drain pipe carries condensate away to a location that meets local code requirements.