In variable climates, the system may include a reversing valve that switches from heating in winter to cooling in summer. By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a facility to be heated and cooled by a single piece of equipment by the same means, and with the same hardware.

In some older homes, there was a grey Mylar flexible duct. After years of use, it started to decompose. A duct cleaning company can come out and find why your air is so dirty and why your building doesn’t heat or cool like it used to. This is a savings on your part. You could also be sucking in Hot, dirty attic air. However, sometimes when a duct cleaning company comes out to clean it, the old duct can be destroyed and have to be replaced. Someone with little experience can replace this ductwork but if it isn’t done right it can ruin a lot of things and cost a lot in repairs.

Ventilation is the process of changing or replacing air in any space to control temperature or remove any combination of moisture, odors, smoke, heat, dust, airborne bacteria, or carbon dioxide, and to replenish oxygen. Ventilation includes both the exchange of air with the outside as well as circulation of air within the building. It is one of the most important factors for maintaining acceptable indoor air quality in buildings. Methods for ventilating a building may be divided into mechanical/forced and natural types.[16]


One problem occurred on Monday.  When we called at 2:30 in the afternoon to check on status, we were told that "the tech is on the phone with the parts supplier now".  It seems more likely that they had forgotten about us and our call woke them up.  But even if true, why the heck did they wait until 2:30 to order the part?  Maybe if they had ordered it in the morning they could have had it the same day.  So I'm taking off one star for that.
Ok what you said is true but in most cases ducts are in a duct flex format, and knowing that the dust in people's flex duct is just surface dust, any real debris that are in the duct itself will result in very little to no air flow which will keep your unit from performing properly, but if it is true allergy reasons then replacing your duct system is better for overall better air quality, plus if you do pay attention to the warranty on flexible duct is that it only has a 10 year warranty and typically only lasts for 20 years so do your research before having a duct cleaning, and to add one more thing if your duct work is completely metal and you can't see visible insulation then your duct on the inside has insulation inside of it, if you replace that with duct work that is clean metal on the inside and wrapped with insulation on the outside then it will further reduce the air bourne fiberglass and dust.
Free cooling systems can have very high efficiencies, and are sometimes combined with seasonal thermal energy storage so that the cold of winter can be used for summer air conditioning. Common storage mediums are deep aquifers or a natural underground rock mass accessed via a cluster of small-diameter, heat-exchanger-equipped boreholes. Some systems with small storages are hybrids, using free cooling early in the cooling season, and later employing a heat pump to chill the circulation coming from the storage. The heat pump is added-in because the storage acts as a heat sink when the system is in cooling (as opposed to charging) mode, causing the temperature to gradually increase during the cooling season.

Installation: Replacement is quite easy, especially when an old refrigerant line set can be used. If the set is worn, it’s much better to pay the extra $400-$600 to replace it rather than risking it leaking later. When your AC loses refrigerant, you lose your cool air and the compressor is at risk of failing. A new installation means installing a coil in your furnace or air handler, running the line set between it and the coil in the condensing unit and adding refrigerant, if needed. Most ACs come pre-charged for 20-30 feet of line. If the line set is longer, a small amount of refrigerant is added.
HRV/ERV Ventilators: These whole-house ventilators exchange air. They are ideal for homes with what is called a “tight envelope,” homes where house wrap has been applied and airgaps in the attic, around windows, doors and outlets have been sealed. Air in these homes becomes stale and polluted, so exchanging the air is important to IAQ. Heat recovery ventilators (HRV) are designed for cold climates. Energy recovery ventilators (ERV) are best for warm climates.  Your cost for an installed HRV or ERV will range from about $2,000 to more than $5,000 based on its capacity and features.
You've probably noticed many appliances boasting an Energy Star Certification. What this means is that manufacturer voluntarily built the product to help reduce greenhouse gases and meet non-regulatory guidelines offered by the Environmental Protection Agency. To earn an Energy Star rating, a product or system must be tested by a third party that has been recognized by the EPA for meeting their testing qualifications.
Here in Frisco, TX…just had a tech come out to clean vents. I used a 30 bucks groupon for “complete vent cleaning”. He told me I have 3 AC units and groupon covers only 1. I told him to do the unit upstairs where the kids sleep. He decided on his own to do the downstairs unit. I yelled at him why he is not doing the unit I told him to do! He said they are all connected. I will clean two for you for the price of one… Oh really?
I had my ducts somewhat cleaned December 22, 2014. The hose of the machine the technitian used did not fit in some of my vents, therefore, he did not clean them. But I still paid $428.00 for the service. I will be calling the company on Monday, and kindly ask them to come back and clean the ducts they did not as they did not fullfill their part of the service.
I am 79 years old, bought a condo & spent a lot of money on it. this winter my first bill was 450.00. had my furnace checked out, which is on the roof. it was old rusted out & leeking oil. i talked to owner & had new unit installed. they came out to clean ducks & they were split & worn out. there is no crawl space because theres a unit above me. my real estate lady or this company will not help me fix this problem.
Engineers have pointed out some areas where efficiency of the existing hardware could be improved. For example, the fan blades used to move the air are usually stamped from sheet metal, an economical method of manufacture, but as a result they are not aerodynamically efficient. A well-designed blade could reduce electrical power required to move the air by a third.[28]
The Chartered Institution of Building Services Engineers is a body that covers the essential Service (systems architecture) that allow buildings to operate. It includes the electrotechnical, heating, ventilating, air conditioning, refrigeration and plumbing industries. To train as a building services engineer, the academic requirements are GCSEs (A-C) / Standard Grades (1-3) in Maths and Science, which are important in measurements, planning and theory. Employers will often want a degree in a branch of engineering, such as building environment engineering, electrical engineering or mechanical engineering. To become a full member of CIBSE, and so also to be registered by the Engineering Council UK as a chartered engineer, engineers must also attain an Honours Degree and a master's degree in a relevant engineering subject.
Multiple inventions within this time frame preceded the beginnings of first comfort air conditioning system, which was designed in 1902 by Alfred Wolff (Cooper, 2003) for the New York Stock Exchange, while Willis Carrier equipped the Sacketts-Wilhems Printing Company with the process AC unit the same year. Coyne College was the first school to offer HVAC training in 1899.[12]
In addition, the black dust was found in most of the heat registers. He could rub it off on his fingers but did nothing but spray compressed air on it which didn’t make it disappear since it wasn’t loose. Also, in the register in the basement he described the black dust as being oily. The reality of that situation is that I had the AC on until the morning of the service and minutes after he snaked the hoses in my back door it started raining. The basement register had condensation from the humidity all over it. It was not oily but wet. He asked for an old towel and wiped it out. Never saw anything so black – because I never had to clean soot. That is what I have in my ducts. Soot from years of the old coal furnace.
All of the products discussed above are registered solely for the purpose of sanitizing the smooth surfaces of unlined (bare) sheet metal ducts. No products are currently registered as biocides for use on fiber glass duct board or fiber glass lined ducts, so it is important to determine if sections of your system contain these materials before permitting the application of any biocide.

A dehumidifier is an air-conditioner-like device that controls the humidity of a room or building. It is often employed in basements which have a higher relative humidity because of their lower temperature (and propensity for damp floors and walls). In food retailing establishments, large open chiller cabinets are highly effective at dehumidifying the internal air. Conversely, a humidifier increases the humidity of a building.


There is a lot of good, general information in the article. As with anything, the homeowner should do their due diligence in getting enough information to make an educated decision. Should duct-work be cleaned? YES! Does it need to be cleaned annually or even every second or third year? Not necessarily. It all depends on a bunch of variables. You're right that a well designed and balanced system will deliver the right amount of air flow, but sometimes conditions outside the home/business, make it a necessity to get the ducts cleaned. As for mold? NO filter is going to address a mold issue. If you have mold, you have a moisture issue that needs to be addressed. Also, in my 38 years of experience in the HVAC and sheet metal industries, washable filters are one of the reasons ducts need to be cleaned. They are no where near efficient in cleaning/filtering the air to the level that they should.
NADCA and EPA both have good points. Although, organizations are made to make money. Common sense and looking at NADCA and EPA pre-checklist. If you don't see it in the check list, you don't have to do it! But, if you do, look up Diamond certified co.s and the BBB. Beware of bait and switch scams, $60 vents and the like coupons which claim to help all for the measley sum of $79.00 bucks.
Be careful with HVAC change-outs.  Change-outs are only about 15-20% of the HVAC installation industry. Decrease HVAC installation cost by investing in new ductwork now if needed. Your ducts wear out too, and make sure that your ducts are in fantastic shape if you do this. Many contractors push this because it’s easy and cheap for them, with good pay-off. Do your research and replace them if you need to in order to avoid doing it later, as well as avoid potential health hazards from using old, broken ductwork.
As for the price I think my review was fair in stating what value we got for what I deemed to be a slightly higher price than others might charge.  I did not take any stars off for the price, and still am not, but I am taking another star off because of Alberto's comments, which are deceptive and not the same thing he told me in person.  Alberto, I suggest you stick with the high road in the future.

In the United States, HVAC engineers generally are members of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), EPA Universal CFC certified (for installation and service of CFC HVAC devices), or locally engineer certified such as a Special to Chief Boilers License issued by the state or, in some jurisdictions, the city. ASHRAE is an international technical society for all individuals and organizations interested in HVAC. The Society, organized into regions, chapters, and student branches, allows exchange of HVAC knowledge and experiences for the benefit of the field's practitioners and the public. ASHRAE provides many opportunities to participate in the development of new knowledge via, for example, research and its many technical committees. These committees typically meet twice per year at the ASHRAE Annual and Winter Meetings. A popular product show, the AHR Expo, is held in conjunction with each winter meeting. The Society has approximately 50,000 members and has headquarters in Atlanta, Georgia.

If you want to get some of the dust and debris out of your ventilation system, you can mix household cleaners like bleach with water, dip a cloth in the mix and then the wipe out the system. This will remove a layer of the spores, which could increase the quality of air a bit and help with the flow of air throughout the house until a pro can come out.
Here in Atlanta we get 6 to 10 $49 coupons in the mail weekly…I have always consider them a complete scam….just had my master bathroom& bedroom and guest bath completely remodeled down to the studs…Had my 3 returns nearest the area sealed to prevent sheet rock dust to spread…it worked and I personally cleaned all 7 returns when a 5 HP , new Rigid shop Vac($99 from HD)…took one hour and I found little evidence that “I need my ducts cleaned” Had quotes from $400 to $600…I use the best air filters for my air handler and change it every 2 to 3 months…..any dust is trapped in it and I believe the Air Duct folks are all cons….
You should be aware that although a substance may look like mold, a positive determination of whether it is mold or not can be made only by an expert and may require laboratory analysis for final confirmation. For about $50, some microbiology laboratories can tell you whether a sample sent to them on a clear strip of sticky household tape is mold or simply a substance that resembles it.
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