Archive for Industry News

Sweating Ducts in the Crawlspace

By · March 31, 2012 · Filed in Industry News · No Comments »

Why are your air ducts sweating in the crawlspace? Why is that a problem? When ducts start sweating, they create a vicious cycle.

If you can remember back to your Eighth Grade Science Class, you would know that warm air can hold more water than cold air. The point at which the cool air can hold no more water is called dew point. Condensation happens at dew point. Click here for more information than you want to know about how the psychrometric chart can be used to determine when ducts will sweat.

Here is a much easier to use calculator to determine when dew point is reached and condensation is produced. Here is the problem: when your AC is working properly, it is blowing about 20°F cooler air through your supply air ducts than what it is sucking in through the return filter. So, if you have your thermostat set at 72°, then the temperature of the air going through your air ducts is about 52°. The insulation on your ductwork is a maximum of an inch and a half to two inches, with and R value of 4.2 to 6. When it gets wet from condensation it looses even more R-value. The bottom line is, the temperature of the air in the duct is close to the temperature of the duct insulation surface. So use the dew point calculator to find out what conditions it takes to create condensation on your ductwork, understanding very little insulation from the ductwork is effective. In Nashville in the summer we will frequently experience temperatures of 80° and relative humidity of 80Rh, which produces a dewpoint of 74°. It would take a duct insulation value of at least R12 to prohibit condensation on the ducts, not possible without a custom, cost prohibitive space blanket insulation. The best way to prevent duct sweating is to lower the dewpoint by lowering the humidity.

How do you lower the relative humidity in the crawlspace? The less expensive way is to install a Crawlspace Conditioner. It draws in drier air across a passive dehumidifier to exhaust the moist air. It sometimes takes some experimenting to dial in the right cycle of cfm and air exchanges, along with the economy or Extreme vapor barrier to get the desired crawlspace environmental performance.

A more reliable way is to close the crawlspace, instal a dehumidifier and possibly fans for a larger area and create a semi-interior room in your crawlspace. If you were to create a conditioned crawlspace by Crawlspace Makeovers, the most extreme conditions your crawlspace would experience would be a temp of 70° and and Rh of 60%, which would create a dewpoint of 55°… no sweating ducts!

Dead mouse in the air ducts

By · April 28, 2010 · Filed in Industry News · No Comments »

What should you do if you smell something dead in your air ducts? Many times you are right, some animal has died in your ducts. The first thing to do is to find it. The best way to do that is with a boroscope or robot. Once it is found, it must be removed. Then what?

Most rodents I know have poor hygiene habits. Plus, when they die they tend to loose body fluids and fall apart (that was gross). So what do you do about all the gross stuff in your ducts? There are different opinions, and unfortunately, little research to prove the effectiveness of sanitizing ductwork. Yes, there are sanitizers which are registered with the EPA for use on the hard surface interior of the ducts. Yes, many duct cleaners provide, and even promote fogging the ductwork after cleaning. It is neither encouraged, nor discouraged by the EPA and the National Air Duct Cleaners Association (NADCA), an association which trains and promotes air duct cleaning industry standards. It makes everything smell clean, but,

  • does it sanitize the interior of the ductwork? No proof.
  • Is it a waste of money? Who knows?
  • Should you replace the duct where the animal was found? That is our recommendation.
  • Should you replace the duct everywhere the rodent went? That is a tough question requiring a longer answer.

As we discussed earlier, everywhere they go most rodents deposit urine, feces, and any food remains they have eaten. Duct cleaning tools are designed to remove dust and debris, not bacteria. If it could be wiped clean, then it would be okay. Just like cleaning your hands, spraying disinfectant on them has been proven to be much less effective than washing them with soap and rinsing with water. And fogging a disinfectant in the ducts may not work. So, ideally, all the ductwork where the rodent had been presumed to be would be replaced. Will it cause health problems if you don’t replace it all? It’s hard to say, but, to be sure…

Ultimately, it comes down to your budget and health standards. In a commercial building, you wouldn’t want to take chances. In your home, it’s your decision.

In any deodorization project, the first rule of thumb is to remove the source. Then clean and deodorize as necessary. HVAClean can help you with both.

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Dirty sock odor in air ducts

By · April 28, 2010 · Filed in Industry News · No Comments »

Do you have the smell of dirty socks when your air conditioner comes on? Your HVAC unit may be experiencing Dirty Sock Syndrome (clever name, huh?). The bad smell is coming from your air conditioner condensation drain pan.

In English, a condensation drain pan is where the condensate made on the evaporator coil drains before is travels out the condensation line. Okay, let me try again. When your air conditioner is on, the air goes through a coil, thin slices of aluminum, that are made colder by the freon (that is why you set your AC thermostat to “auto” so it can cycle on and off and not grow mold). As the air travels through the coils, it gets colder, plus it loses moisture because of dew point. The moisture it loses is collected on the evaporator coil (get it? The evaporator coil evaporates moisture from the air as it passes through). The water made from condensation runs down the coil into the pan and then out the condensation line (usually a one inch PVC line that has water running out the other end when the air conditioner is running).

If the water gets stuck in the condensation pan, it starts to “sour” and smell like, well, dirty socks.

So how do you fix it? It depends on why the water is stuck in the pan.

  • If the air conditioner unit is not installed properly, the drain could be at the high side of the pan, so the water would always be in the pan. Put some kind of shim under the air conditioner unit so that water drains freely to the opening in the pan.
  • If the condensation line gets clogged due to insects, mud, slime build up, etc, water cannot drain out of the pan. What most people do is take some kind of air line and blow it out, from the unit side (don’t blow it from the outside back into the unit).
  • If the pan is dirty, it is probably because your coils are dirty. Use an approved coil cleaner to clean the coil, making sure to clean the condensation pan and blow out the condensation line.

After fixing the problem, the smell should go away, and not return until one of the problems returns.

If you need any help with an inspection or solving any of these problems, call HVAClean at 615-371-5355.

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Bad smell in air ducts

By · April 25, 2010 · Filed in Industry News · No Comments »

What should you do if you have a bad smell coming from the air ducts? One interesting fact is, in spite of all the advances in science, the only smell detector is your nose. However, instruments can measure volatile organic compounds (VOC)s, which may be in order if an initial investigation still leaves questions. There are many potential sources of bad smells coming from the air ducts:

  • Odors drawn in from the a musty crawlspace or attic
  • Skunk spray or dead animals in the HVAC unit or ducts
  • Plumbing vents tied into HVAC
  • Dirty sock syndrome

Damp, musty crawlspaces can impact the living space and duct work, especially if the ducts are not air tight, and they usually are not. When the return duct is leaky, it can suck air from the crawlspace when the air is being pulled to the unit. When the supply ducts are leaky, they can actually suck air in through the venturi effect. A qualified inspection will determine if your duct system can be repaired or needs to be replaced.

Sometimes a dead animal smell in the ducts is, well, a dead animal. Dead animals leave behind nasty contamination and need to be handled accordingly. Similarly, a skunk can spray the AC unit or ducts. The smell can be very obnoxious and if not treated by trained professionals, can linger for a very long time affecting the whole house and all the contents.

While pretty unusual, and certainly not in accordance with building codes, sometimes the plumbing vent can be tied into the condensation line from the HVAC unit. The tale-tale sign is a sewer gas smell in the ducts when the unit comes on. The unit actually sucks sewer gas through the condensation line into the duct system. The fix is to disconnect the two and reroute the condensation line.

The dirty sock syndrome is when there is a strong smell of dirty socks when the AC unit is running. Clever name, huh. The cause is usually from standing water in the evaporator coil pan. This happens when the condensation line is clogged, when the pan is not tilted enough toward the drain end or when there is too much debris in the pan to let it drain properly.

As you can see, a bad odor in the ducts doesn’t always mean cleaning the ducts will solve the problem. Should you have your air ducts cleaned? Probably, but make sure you have addressed any other issues that may need to get fixed.

Call 615-371-5355 to schedule an inspection to identify the cause and get a price for the solution to the bad odor.

Mold growing around the AC register

By · April 25, 2010 · Filed in Industry News · No Comments »

What should you do if you find mold growing around the AC register? What does it mean? How did it get there? Are you going to die? Well, yes, you will probably die eventually, but not from this :)

How did it get there? First, you must understand that mold is secondary water damage, which means, there must be moisture or humidity present. So where did the moisture come from? The same place that makes water form on the outside of a cold glass of water, condensation. If you remember in science class, dew point is when the moisture in the air reaches 100% relative humidity. Cold air cannot hold as much moisture as warm air, so when warm, humid air comes in contact with something cold, it reaches dew point and makes condensation, or water.

The air coming out of the air conditioning vents is about 20 degrees colder than the inside air, so if the air inside is too humid, condensation will form on the metal ducts at the opening and at the register. So what can make the air inside too humid? Setting your thermostat to “on” instead of “auto”, turning the thermostat up too high in the summer in a vacant house or seldom used upstairs, turning the thermostat down too low in the summer, having leaky air ducts which pull humidity from the attic or crawlspace, or a malfunctioning AC unit.

So what should you do if mold is growing around the register? Fix the cause, from the above paragraph, then wipe it off. Don’t you need some kind of special mildewcide to kill fungus, like bleach, or a strong fungicide? It won’t hurt anything, but if you take away the moisture from condensation, mold cannot grow. You may have to remove the register to wipe inside the entrance to the vent, and you may have to paint some of the drywall with a stain killer to fix the stains around the vent cover. Be sure to wear protective clothing and a protective mask or respirator, and don’t try this if you have allergies or health risks.

Should you clean the air ducts? Probably, because most air ducts need cleaning, especially if they have never been cleaned. But not necessarily because of the mold growing around the register. How can you really know if you need air duct cleaning?