6:01 pm ET June 29, 2011 Q: I am a landlord for my own income property. Five weeks ago my tenant let us know that the air conditioner stopped blowing. I called the repair guy out that same day got it fixed. A week later tenant calls says it stopped blowing cold air. Called the repair guy out that same day got more parts fixed (all parts had been replaced inside the A/C, lines refilled). A few days later tenant calls again says it stopped blowing cold air again. The A/C guy came out found a pin sized hole in line, fixed it got it working. Instructed our tenant not to run the A/C at 70/72 degrees all day instructing her that air conditioners are not meant to run for extremely long periods of time, we live in Phoenix, Arizona and it’s over 100 degrees now. Then almost every day or so after that, the tenant complained that it was freezing up on them every day at 9-10 a.m. Every day we would call the A/C guy out they would get it running, and the next day it would do it again. A/C guys are baffled saying they have replaced everything, they don’t know what is wrong.

They have even had a YORK technician out to look at it, and get figured it out. The tenant admits to running it at a low temp all day without turning it off when its 100+ outside. Could my tenant be misusing the A/C and making it need repairs? If so, what do I do? My tenant is also harrassing my A/C guy so much that he doesn’t want to talk to her.–NewbieInAZ2424, Phoenix, AZ A: I would suggest that you purchase a home warranty from American Home Shield and either you pay the $60 service fee that AHS charges or your tenant does. This way every time something is wrong you make it your tenants’ responsibilty to call for service. If you tenants’ lease is almost up – I wouldn’t rent to them again either. Leah LaymanLeah Layman is a Realtor® with Keller Williams Realty Augusta Partners in Augusta, GA. A: It sounds like you’ve done everything you can to address your tenant’s concerns and the problem. If she has admitted to running the air conditioning at low temperatures all day after you and your technician have explained the consequences there’s not much more you can do.

After that she certainly doesn’t have the right to harass you or the technician. Furthermore, your tenant may be responsible for repairing any uninhabitable conditions she caused. Maybe you should consider talking to a real estate attorney for the best advice.—Anne Elizabeth Oliver is a Realtor® with Roy Wheeler Realty Company in Charlottesville, VA.recommended window ac unit A: Too many repairs, I think the air conditioning needs to be scraped and replaced with a another new or factory reconditioned unit.best deals on hvac units George in TucsonGeorge Szkup is a Realtor®  in Tucson, AZ.how to install a marine ac unit Are you interested in having a qualified REALTOR answer your questions? Click through to Ask a REALTOR® now.

Are you a REALTOR who would like to answer consumer questions? Click through to become an Ask a REALTOR® participant.Last updated: April 25, 2016. Shut that door and keep the heat in—it's a familiar cry inin summertime, you're more likely to see people closing doors and windows to keep the heat out and save on the air-conditioning. How can you have an airtight, energy efficient home that's also healthy andHeat recovery ventilation (HRV) and energy recovery ventilation (ERV) offer a solution, bringing fresh air into your home without letting the heatLet's take a closer look at how they work! Photo: The inside of a typical heat recovery ventilation (HRV) system. You can see the blue and red air ducts on the left, the diamond-shaped heat exchanger in the middle, and the air blowers on the right. HRV systems are made by many different companies, including Broan, Fantech, Honeywell, Vaillant recovAIR, Renewaire, and Venmar. and US DOE/NREL (Department of Energy/National Renewable Energy Laboratory).

Modern homes are usually built to far higher technical standards than buildings constructed a few decades ago and are much more energy efficient, largely thanks to better heat insulation. One key area of improvement has been to make buildings more airtight so they hold onto the heat we put into them for longer. But there's a drawback: our homes need regular changes of air to keep them healthy. Baths and showers, doing the dishes, and even simple breathing produce astonishing amounts of water inside our homes: according to leading ventilation manufacturer Vaillant, a typical family will produce 10–15 liters (3–4 gallons) of moistureLet that problem go unchecked and you'll get problems like mold and mildew, dust mites and a greater risk of asthma. doors and windows is the obvious way to get rid of moisture and bring in fresh air, but if you do that in winter you might just as well flush your money down the toilet: all the heat you've expensively

introduced into your home will blow away in the breeze. house solves this problem by being automatically well ventilated, but it's probably also freezing cold because it's useless at holdinga modern energy-efficient home solves the draft problem but may be stuffy and underventilated. So what to do? Let's look to nature, which solved this problem some time ago. bodies are a bit like our homes inasmuch as they need regular supplies of fresh air and have constant clouds of damp, "stuffy" air to get rid of. How do they do it? With an ingenious inventionAs a child, you might have learned that it's better to breathe through your nose than through your mouth because your nose warms and filters incoming air. What your nose actually does is called heat exchange: it lets cool incoming air flow very close to warm outgoing air so heat energy is transferred between the two instead ofAs a result, the air you breathe in is warmer and the air

you breathe out is cooler—and (among other things) that helps your body to retain heat energy. Photo: The basic principle of a heat exchanger: a hot, outgoing fluid (red) flows past a colder, incoming fluid (blue). Without them actually mixing together, the hot fluid gives up most of its heat to the cold fluid. HRVs are essentially noses on houses: they consist of two ventilation ducts running next to one another passing between the inside and the outside of a house. One carries cool, fresh air in; moist, stale air out. The clever bit is that the airstreams run through a device called a heat exchanger that allows the outgoing air to pass most of its heat to the incoming air without the two airstreams actually mixing together (read how this works in our article on heat exchangers). Usually there's a fan (blower) in each duct that can be turned up or down either manually or automatically depending on the temperature and humidity levels.

supply may also have a bypass fitted to it so that on summer days when it's cooler outside than in, cold outside air can be channeled straight into the home without meeting outgoing air (much like opening a Artworks: Left: How an HRV works (simplified): The hot, moist waste air from the home (passing down the yellow duct) gives up virtually all its heat as it passes through the heat exchanger on its way out of the building. The cold, dry incoming air (flowing through the brown duct) picks this heat up as it flows in. Ideally, no heat is lost. Since the incoming and outgoing air flow past in opposite directions, this approach is known as a counterflow. Artworks: Right: How an HRV works (in more detail): This is the layout of an actual HRV unit showing the two airflow paths and six isolated compartments in a bit more detail. Fresh air enters the building from outside at point 1 and is pumped into the room at point 2, inside the building, passing through the three compartments colored gray, and following the blue arrowed path.

On the way, it picks up heat from the diamond-shaped heat exchanger (red), pulled by the pink blower. Stale exhaust air exits from the room at point 3 and leaves the building at point 4, passing through the three blue compartments along the red arrowed path. It also passes through the heat exchanger, giving up heat, and is helped on its way by the second blower, colored cyan. From US Patent 5,632,334: Heat recovery ventilator with room air defrosting feature by Peter K. Grinbergs and Grant W. Miles. Nutech Energy Systems Inc., May 27, 1997, courtesy of US Patent and Trademark Office, with colors added for clarity. In small homes, an HRV might consist of a single unit on one wall that effectively ventilates the entire building over time as doors open and close between rooms. In larger homes and offices, there may be ventilation grids in each room feeding into ducts that run between the floors or ceilings of the the building to a single ventilator on the outside wall.

Not all HRVs work in exactly the same way. called energy recovery ventilation (ERV) works in a similar way but transfers some of the moisture from the outgoing airstream into the incoming air, so it keeps the humidity in your home at a constant level. That's important if you don't want your home too dry. As a general rule, ERV is a better option if you have air conditioning and live in a humid climate, because it will help to keep moisture outside, reducing the load on your air conditioner and saving on the air-con bills. HRV is often better if you don't have air conditioning, or live in a less humid climate, since it will help keep the humidity down by transferring excess indoor moisture outside. HRVs and ERVs have an obvious appeal: they give you a warm well ventilated home and stop you "emptying your wallet" into the atmosphere every time you open your windows. In winter, they can help save on yourin summer, they reduce the need for air conditioning.

By keeping excess moisture out of your home, they're better for your building, your furnishings, and your health and they help to keep the "climate" inside your home at a more constant level. they retain about two thirds to three quarters of the heat that would normally be lost from your home through ventilation (some manufacturers claim 85–95 percent), so they really do save energy. Photo: Large HRV systems use ducts like these running between floors and ceilings. Photo by Warren Gretz courtesy of US DOE/NREL (Department of Energy/National Renewable Energy Laboratory). On the downside, HRVs are expensive to install initially (several thousand dollars is typical) and they're not guaranteed to pay for themselves (typical annual savings might be a few hundred dollars). You'll see most benefit in extreme climates: where the difference between the outdoor and indoor temperatures is greatest in summer,In milder climates, the benefits are much reduced