I think that the coding and permit industry is a joke!! They will not allow the homeowner to apply for the permit it has to be the licenced contractor. It would make since to allow the homeowner to apply for this. But it is all about money!! They really don't care if its up to code because if they did then they wouldnt care who applied and payeed for it, but they want the contractor to do it so if they do something wrong they can fine them instead of just pointing it out and allowing them to do it right.
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.
HVAC is an important part of residential structures such as single family homes, apartment buildings, hotels and senior living facilities, medium to large industrial and office buildings such as skyscrapers and hospitals, vehicles such as cars, trains, airplanes, ships and submarines, and in marine environments, where safe and healthy building conditions are regulated with respect to temperature and humidity, using fresh air from outdoors.
If you’re anything like most of our readers, you’ve spent hours online researching HVAC information in preparation for replacing your old heater or air conditioner. I’m the same way; it’s a big investment! You may want to consider saving yourself some time and money by getting an HVAC-Facts Report from this online HVAC installation cost calculator.  Take a look:
Although HVAC is executed in individual buildings or other enclosed spaces (like NORAD's underground headquarters), the equipment involved is in some cases an extension of a larger district heating (DH) or district cooling (DC) network, or a combined DHC network. In such cases, the operating and maintenance aspects are simplified and metering becomes necessary to bill for the energy that is consumed, and in some cases energy that is returned to the larger system. For example, at a given time one building may be utilizing chilled water for air conditioning and the warm water it returns may be used in another building for heating, or for the overall heating-portion of the DHC network (likely with energy added to boost the temperature).[4][5][6]
I took off stars for two reasons. Minus one star for issues trying to use the $50 for $25 voucher I purchased through Yelp. Although there was no minimum stipulated, the office wouldn't take it for the initial $59 diagnostic fee. If I used the 10% off First service that they offer, then they won't let me use the voucher on the actual repair bill.  I was stuck with paying the full $59 diagnostic fee.

In the case of heated water or steam, piping is used to transport the heat to the rooms. Most modern hot water boiler heating systems have a circulator, which is a pump, to move hot water through the distribution system (as opposed to older gravity-fed systems). The heat can be transferred to the surrounding air using radiators, hot water coils (hydro-air), or other heat exchangers. The radiators may be mounted on walls or installed within the floor to produce floor heat.
I’m a heating and air conditioning contractor. I’ve been in the trade for over 15 years. I’ve witnessed numerous duct cleaning projects and talked with many duct cleaners. Duct cleaning as it’s usually promoted is a fraud. Most duct cleaners claim to deliver cleaner air. They deliver exactly the opposite. The studies on duct cleaning prove it, including a May 1998 study sponsored by NADCA and the EPA! The stories are compelling, but they can come up with stories that “prove” anything they want. Internet searches are dominated by results from those who are paid to tell you that duct cleaning is worthwhile. Search a little more and you’ll find the truth.
Clean air delivery rate is the amount of clean air an air cleaner provides to a room or space. When determining CADR, the amount of airflow in a space is taken into account. For example, an air cleaner with a flow rate of 100 cfm (cubic feet per minute) and an efficiency of 50% has a CADR of 50 cfm. Along with CADR, filtration performance is very important when it comes to the air in our indoor environment. Filter performance depends on the size of the particle or fiber, the filter packing density and depth and also the air flow rate.[30]
If your non metal ductwork is that dirty you should just have it replaced AND sealed. Also most duct systems are not very well designed. Look for proper sizing and do not go cheap with one or two intakes (return grills) You need them through-out the house. Here in Austin the duct cleaners are carpet cleaners and chimney swifts. (this is who the duct cleaning equipment mfgs call on when the hvac people do not get on board. They DO clean other types of ductwork and we (the hvac guys) have to fix them. I am not aware of any of these non hvac guys cleaning and servicing the actual equipment. Here in Texas it is against the law for them to do so. Treat the entire house as a system, not just the ductwork and /or hvac equipment. Home performance really does work to increase comfort and air quality while reducing operating costs.
The AC contactor (relay) and start/run capacitor(s) (see illustration below) fail most often and are inexpensive. So it's a safe bet to buy and install those parts right away, especially if your air conditioning service unit is older than five years. The condenser fan motor can also fail, but it runs about $150 — hold off buying that unless you're sure that's the culprit.