<h2><p>Air-Conditioning</p></h2>		
		<p><a href="#anchor01">Cooling Basics</a></p>
<p><a href="#anchor02">Reducing Loads</a></p>
<p><a href="#anchor03">Maintenance And Upgrades</a></p>
<p><a href="#anchor04">New Air-Conditioning Systems</a></p>
			<h1>Cooling Basics</h1>		
		Heat flows from a higher temperature to a lower one. In winter, houses lose heat; in summer, they gain it. Just as heating bills benefit by reductions in heat loss, cooling loads—and bills—benefit by reductions in heat gain. Most summer heat gain comes from three places: solar radiation, internal gains, and air leakage in the building and ducts.		
			<p>Where does the heat come from?</p>		
		In the winter, the largest energy loads in most homes come from conductive heat loss through walls, ceilings, and windows. Air leakage in the building enclosure and ducts are a close second. Radiation effects are minimal. In hot weather the tables are turned. Conduction plays a minor role; the source of most air-conditioning loads is solar radiation through windows and uninsulated roofs. The same solarheat gain that provides free heat in winter is a major driver of air-conditioning in summer. And it’s not just south-facing windows; in fact, east and west-facing glass contribute more to air conditioning per square foot than south-facing glass. Even conductive heat gains through a poorly insulated attic are largely driven by radiation, when the sun shining on the roof superheats the attic far above outdoor temperatures. 
Internal gain is the name for heat that is generated inside a building by lights, appliances, and people. It is significant and can exceed all other sources besides windows. Some things that we do indoors, such as cooking, dishwashing, showering, and bathing, are obvious sources of heat. Anything that uses electricity gives off heat: refrigerators, lighting, televisions, computer equipment, and their accessories. There are less-obvious sources too, such as standby loss from water heaters. In addition to solar and internal heat gains, duct leakage in a central air-conditioning system is also a large contributor to cooling energy use. Building-shell leakage is a smaller driver in hot climates, but it’s still important to seal leaks in humid climates to reduce the risk of hidden condensation in wall or floor cavities.
			<p>How air conditioners work</p>		
		Virtually all residential air-conditioning systems use a compressor-driven refrigerant vapor cycle to cool house air. The compressor cycle controls refrigerant temperatures in the condenser and evaporator coils, which absorb heat from indoor air at a low temperature, then reject it outdoors at a higher temperature. Air conditioners, heat pumps, and refrigerators all use the refrigerant vapor cycle to essentially push heat uphill, from a cooler place to a warmer place. An air conditioner pushes heat from the cool indoors to the hot outdoors, cooling the interior. In addition to sending indoor heat outdoors, an air conditioner must also reject the heat generated by the compressor and fan motors.
Another aspect of air conditioners is their ability to dehumidify, as well as cool, indoor air. This happens when water condenses on the cold fins of the evaporator coil as humid air passes across them. Dehumidification is an important component in maintaining healthy indoor air quality and comfort. Water that is evaporated in air contains quite a bit of heat energy, which must be accounted for in the system’s design. The energy required to remove excess humidity is called latent load, and it comes from moisture sources within the home and, in humid climates, outdoor air leaking indoors.
			<h1>Reducing Loads</h1>		
		With cooling, just as with heating, as the loads are reduced you spend less to stay comfortable. Think of the air conditioner as removing heat that builds up, rather than “cooling down” the house. The better you are at preventing heat from building up, the less heat your air conditioner must remove and the less time it will have to run—saving you money. There are two approaches to reducing cooling loads: reducing
your need for cooling and reducing heat gains in your house.
			<p>Reduce the need for cooling</p>		
		One surefire way to cut cooling costs is to use your air conditioner less. A house with more insulation, better windows, and less air leakage is comfortable with no air-conditioning for more of the summer. Setting the thermostat higher, particularly when the house is empty, reduces the system’s run time and saves energy. 
Fans can also help raise the temperature at which you feel comfortable. By installing an efficient ceiling fan and keeping the air moving in occupied rooms, most people can comfort- ably increase the temperature setting of their thermostat by 4°F to 6°F, saving 20 percent to 35 percent on their cooling bills. Fan flow
should point downward to maximize the feeling of air movement in the room. Oscillating and box fans can also provide portable comfort. When using any type of indoor fan, remember that it will keep people cool only while they are in the room. Turn off fans when you are not using them, because they generate heat.
Ceiling-mounted whole-house fans that exhaust into the attic are another popular method to reduce the need for cooling, but they must be used properly to be effective. Air leaks between the attic and house must be sealed, and the attic must be well vented to the exterior, to ensure that the fan exhaust goes outdoors rather than back into the house.
			<p>Duct insulation and sealing</p>		
		<p>Recessed “can” light fixtures installed in an insulated ceiling are often big air leaks. Most common styles are full of holes to vent the fixture so it doesn’t get too hot. Also, an older unit can’t have insulation above, or within 3 in. of any part of the fixture, so each one represents a big “hole” for both air and heat flow. If you have a lot of them, the result can be an energy disaster. The best approach is to replace them with airtight fixtures that are rated for insulation contact, or “IC.” The IC rating allows insulation to surround and cover the light fixture. Not all IC-rated fixtures are airtight (AT), but building codes in most states require airtight IC fixtures, so they are easy to find.</p>		
			<p>Other special situations
</p>		
		<p>Attic air-sealing is complicated by the fact that there are so many types of houses, but there are some fairly common situations. First, don’t miss hidden attic areas. Sometimes an addition, dormer, or ell may have a separate attic that you can’t see, because the new roof was built right over the first roof.<br>Suspended ceilings can hide tremendous leakage areas, particularly if they have attic spaces above. In older houses, such ceilings are often installed to hide deteriorating plaster. There may be large holes in the ceiling or high on the walls that are hidden by the dropped ceiling.</p><p>Sometimes a suspended ceiling hides open framing that is insulated with only faced fiberglass batts. This is a huge air leak: neither the insulation nor the suspended ceiling is an air barrier. It’s best to remove the suspended ceiling and install new drywall.</p><p>Another potential air-leakage disaster is a wooden tongue-and-groove ceiling. Whether the ceiling is flat or cathedral, if there is no air barrier behind the planks (which is typical), the hundreds of lineal feet of cracks in even a small room can add up to a big leak.</p><p>Occasionally, air leaks occur in places that are virtually impossible to reach. If your house has a lot of cathedral-ceiling areas, you may have many plumbing vents and wiring holes that lead from partition-wall cavities up into the roof. These provide a path for warm humid air to escape in winter and for hot attic air to leak into interior walls in summer. Unless you are planning to re-roof or to gut those partitions in a remodel, your most likely options involve dense-packed cellulose insulation or two-part foam.</p>		
			<h1>Basement/Crawlspace Air-Sealing</h1>		
		After the attic, the basement or crawlspace is the next most important area to seal for several reasons. Like the top of a home, the bottom typically has the largest air pressure pushing air in or out of the house, so sealing those leaks results in larger energy savings. Second, though often smaller than attic leaks, basement and crawlspace leaks tend to be larger than those in exterior walls. More important, in most climates, air leaks in from the bottom in cool or cold weather. This leaking air can carry radon gas, mold spores, gases from pesticide treatments, water vapor, and any other subsoil nasties that may become airborne. Sealing leaks at the lowest level of your home helps prevent these undesirable elements from entering your home. Finally, most pipe-freezing problems result from cold air leaking in around the sills, where the pipes are often located.		
			<p>Basement walls</p>		
		<p>Generally, consider it most effective to create a good air barrier between the basement and the outdoors by sealing the walls. This is typically true even if you intend to insulate the floor over the basement. There are four common leakage areas in basement walls: service penetrations, stepped-wall transitions, bulkhead doors, and the sill/band joist area.</p><p><b>Service penetrations</b> Every home has basic service penetrations, such as those for electricity, telephone, plumbing, fuel lines, and cable TV. Often, these penetrations are made in the band-joist area, also called the box sill or ribbon joist in conventionally framed houses (in older homes, this may be one large sill beam). Sometimes penetrations come through the foundation (especially plumbing drains, which are always below grade).</p><p><b>Stepped foundation</b> walls are often built on hillsides in cold climates. The vertical parts of the steps are often particularly leaky.</p><p><b>Bulkhead doors </b>Another common source of basement leakage is the bulkhead door. Bulkheads are designed to keep out rain but not to stop air. If your basement is unfinished, the best way to deal with this is to install a new exterior door at the foundation wall inside the bulkhead.</p><p><b>Sills and band joists</b> The tops of foundation walls are often far from flat. The gaps may be small, but spread around the perimeter of a home, they really add up. Even recently built homes that have a foam sill sealer between the sill and the concrete may leak a lot of cold air there.</p>		
			<p>Pro Tip</p>		
		If you want to use your basement as living space, you should plan to completely air-seal and insulate the exterior basement walls.		
			<p>Safety First</p>		
		<p>Although air-sealing a home can theoretically increase radon levels, it is unlikely. Sealing leaks and slowing the stack effect is more likely to reduce the amount of soil gas— including radon—that is pulled into the house from underground. The only way to tell whether you have dangerous radon levels is to test your home. Because of the potential health risks, it is a good idea to test for radon whether or not you do air-sealing. If elevated radon levels are confirmed by at least two tests, find a certified professional to install a mitigation system. See <u>www.epa.gov/radon</u> for more information.</p>		
							<figure>
										<img width="934" height="1120" src="/wp-content/uploads/2018/06/blower-door-test.jpg" alt="" srcset="/wp-content/uploads/2018/06/blower-door-test.jpg 934w, /wp-content/uploads/2018/06/blower-door-test-250x300.jpg 250w, /wp-content/uploads/2018/06/blower-door-test-768x921.jpg 768w, /wp-content/uploads/2018/06/blower-door-test-854x1024.jpg 854w" sizes="(max-width: 934px) 100vw, 934px" />											<figcaption>A blower door is used to measure how airtight a house is. It’s also useful in helping identify where the air leaks are.</figcaption>
										</figure>
			<p>Blower-door testing</p>		
		<p>Air-sealing is a job that requires much more labor than material, which often suggests a do-it-yourself approach. However, air-sealing does require attention to detail and (in many homes) a willingness to squeeze into difficult places. If these qualities don’t describe you, it may be worth hiring a building-performance professional. Experienced professionals use a blower door to help find air leaks and measure the tightness of the building. The fan blows air into (or out of) the house, measuring how well the building enclosure contains pressure. This can be very handy, especially in a house with complex air-leakage paths.</p>
<p>It’s also good to keep the big picture in mind: If you are planning on renovating or adding onto your house, you will have a unique opportunity to seal leaks while the building is opened up. It may not make sense to manually seal leaks now that you know you will deal with them more effectively at the next stage, especially leaks that are small or hard to reach. Of course, if the next stage is a few years off, it may still be well worth hitting the big leaks at a minimum. A building performance&nbsp;professional can help you set priorities and make a long-term plan.&nbsp;</p>		
			<p>Sealing the floor deck</p>		
		<p>Although it is typically more difficult than sealing foundation walls, sealing the floor deck between the basement and the first floor may make sense. If you want to use the basement as living space, it’s almost always better and easier to insulate and seal the exterior basement walls. But if the house sits on an unfinished basement or vented crawlspace, you may benefit from sealing the floor from below.</p>		
			<p>Crawlspaces</p>		
		Crawlspaces are nothing more than short basements, usually just deep enough for the footings to be below the frost line. Unlike basements, they often have exposed dirt floors. Building code requirements for vapor retarders are typically inadequate, even when they are followed properly. Crawlspaces can be pretty nasty places; they often have inadequate drainage. Building codes that require these spaces be vented to the outdoors may make matters worse. The best treatment for a crawlspace is to include it in the conditioned space by sealing and insulating the exterior walls, just like a basement.		
			<p>Slab-on-grade</p>		
		<p>If your home (or part of your home) has no basement or crawlspace, it is probably a concrete slab-on-grade. Those homes are somewhat simpler to seal because there are fewer connections among building materials at the foundation. Your primary job with slab-on-grade construction is to caulk or otherwise seal the exterior walls where the house framing meets the slab.</p>		
			<h1>Sidewall Air-Sealing</h1>		
		<p>Exterior walls are not typically the leakiest parts of a house. Leaks occur in walls where services enter the home, where the framing of the house makes transitions, around rough openings for windows, and through and around window sashes.</p>		
			<p>Service penetrations</p>		
		Sealing cable, wiring, plumbing, and telephone service penetrations is fairly easy. Such openings are usually accessible from the exterior and are often small because some effort is made to weatherproof them during installation.		
			<p>Transitions in exterior wall framing</p>		
		One common example of a wall transition is a cantilevered floor, typically an overhang of 1 ft. to 3 ft. that is common on raised ranches and Colonial-style homes. Often, the plywood soffit at the bottom of the overhang is not sealed tightly, and air can leak through these gaps, which are easy to caulk.		
			<h1>Weatherstripping Doors and Hatches</h1>		
		<p>Most modern doors and windows have good weatherstripping built in, but older ones usually don’t. In addition, many homes have at least one less-finished, or even makeshift, door or hatchway as part of the thermal boundary.</p>		
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