THE DUCT SYSTEM

The duct system is employed in air heating and air cooling your home may be an assortment of tubes that distribute the heated or cooled air to the varied rooms. This method will create an enormous distinction in each the price and therefore the effectiveness of heating and cooling the house. The duct system will have a vital result on the health of the occupants through the distribution of indoor pollution. Changes and repairs to a duct system must always be performed by a certified professional.

COMPONENTS OF THE DUCT SYSTEM

A duct system may be a branching network of spherical or rectangular tubes — usually made of flat solid, fiberglass board, or a versatile plastic and-wire composite — set inside the walls, floors, and ceilings. Usually, you'll be able to see solely the outlet that may be a register coated with grillwork. Figure one shows a standard style of duct system.

This method consists of provide ducts and come ducts. Heating or cooling instrumentality (furnace, cooling, or heat pump) contains a lover that forces heated or cooled air into provide ducts resulting in the rooms. The fan gets its air provide through come ducts, that within the best systems square measure put in each area of the house. To save lots of on installation prices, most homes have one or 2 come registers set in common areas like hallways. (Some homes haven't any come duct systems. Such style shortcuts usually end in lower potency and better heating and cooling bills.)

ENERGY LOSSES AND PRICES

Typical duct systems lose twenty-five to forty p.c of the heating or cooling energy place out by the central chamber, heat pump, or cooling. Homes with ducts during a protected space like a basement might lose somewhat but this, whereas other styles of systems (such as attic ducts in hot, wet climates) usually lose additional. Duct repairs might be the foremost vital energy improvement live you'll be able to do if your ducts square measure within the attic.

If just one [*fr1] the standard loss of uninsulated and unsealed ducts that square measure in attics or crawl areas were saved, it might quantity to $160 off the whole heating and cooling bill during a typical home. This savings is predicated on the national average use of gas and electricity for heating and cooling at a national average energy price of seventy cents per them, and eight cents per kilowatt-hour. With these savings, the price to seal and insulate the ducts would presumably be acquired when 3 years.
These estimates apply to retrofit associate degree existing home. For brand spanking, new construction additional of the ductwork would be accessible to the installer and therefore the potential savings would be greater; and with lower price to put in the sealer and insulate, the payback would be but one year. Duct systems lose energy in 2 ways: by the conductivity of warmth from the nice and cozy surface, and air outpouring through tiny cracks and seams.

For simplicity, we’ll remark heat air for heating; however constant data applies to cooling once the cooling is on. Conductivity a technique duct systems lose energy is for the nice and cozy air within the ducts to heat the duct walls, that successively heat the cold air outside the ducts. If the ducts square measure in associate degree attic or ventilated crawl area that's nearly as cold because the outdoors, this heat is totally lost. If the ducts square measure during a basement, a number of the warmth lost from the ducts is also recaptured by warming the basement ceiling enough to cut back the warmth lost from the house.

Duct repair

Installation and Repair of Duct Systems once creating duct repairs, the contractor should work with the materials at hand. Luckily, the state of the art in duct repair is advancing speedily. “Is it alright to use duct tape?” That’s one among in every one of the primary queries asked in a duct repair category. The solution is simple: “A duct repair ought to last as long because of the ducts themselves.” Consequently, that rules out most styles of adhesive tape that one will usually purchase for duct protection.

 The fabric-backed, rubber-based adhesive tape that may be bought at the neighborhood ironmongery shop will fail speedily once subjected to the conditions of temperature, humidity, and pressure usually encountered in ducts. Additionally advanced tapes, specifically designed for duct repair, square measure coming near the market, and quite presumably some might stand the check of your time. However, the present stance ought to be, “When doubtful, don’t use it.” So, what will we recommend?

this relies on the fabric from that the duct is built, however, the simplest general answer may be a special UL Listed (not simply UL Classified) adhesive paste known as mastic (preferably one that's specially developed for duct repair). UL Classified mastic tests in the main for issues regarding hearth, whereas UL Listed mastic tests for several things, of that the foremost vital for our functions is co-adhesion (holding ability and elasticity).

Sealing — the correct protection procedure for smaller leaks (less than 1/4 in. wide) is to use a bead of mastic alone. For larger gaps, initially apply a layer of mastic a minimum of three in. wide on the whole crack length. Then infix a layer of covering material mesh a minimum of a pair of in. wide within the mastic, so apply a final layer of mastic over the mesh. Correct technique is best learned from associate degree seasoned professional. The method isn't troublesome, although typically it's awkward. Once repairing the ducts, set up your job. Bear in mind that the tasks of protection and insulating the ducts square measure equally vital. A strategically job can embrace the subsequent steps:

• sketch the duct system

 • measure the basic integrity of the duct system

• seal the ducts

• insulate the ducts

• Correct zone pressure imbalance issues.

After doing an associate degree analysis of the duct system, it should be recommended to exchange one or a lot of duct sections. This is often very true in the following situations:

 • Components of the building are used as ducts in such a way to create protection to a fault troublesome or of questionable worth

• Replacement is a smaller amount expensive than repair. The choice to repair or replace can usually be powerfully influenced by economic science. For instance, flex duct is comparatively fast and low-cost to install; flat solid and duct board square measure a lot of concerned. Once replacements are created, the ducts may be sealed.

 Duct protection may be divided into 2 portions:

• repairing massive leaks found throughout the final scrutiny

• finding and repairing different leaks:

Large leaks square measure sometimes disconnected ducts. Typically the physical reconnections are comparatively easy. At different times, the disconnection is caused by failure of some part, which is able to get to get replace. Once the massive leak is repaired, the full outflow round the remaining cracks and areas within the joint may be treated as smaller leaks, at the side of any antecedently found holes that aren't disconnects.

After all proverbial leaks square measure sealed, it’s time to hunt out the less obvious ones. This is often important as a result of most systems have sections that aren't simple to visualize, and leaks may be simply unnoticed.

A small hand-held smoke generator may be a handy tool for this job. Introduce the smoke at the water facet of the duct-blower fan and watch to visualize wherever it exits. Be certain, of course, that the smoke used is of tolerably low toxicity which the home is well ventilated throughout and once the take a look at.

Insulating — insulating the ducts is that the second a part of the duct repair job. Duct board and versatile ducts square measure sometimes given effective R-values starting from R4 to R8.

Sheet-metal ducts are also insulated or uninsulated. In either case, extra insulation may be adscititious within the sort of duct wrap.

 Pressure Testing — as a result of pressure imbalances will have serious health and safety implications in some systems, it's imperative that technicians learn correct pressure-testing techniques. Zone pressurization testing has 2 distinct goals. The first, and most vital, is testing for worst-case depressurization of a space or zone containing combustion appliances. As a rule, such a region of the building shouldn't be allowed to decompress quite three Pascal relative to the surface.

The second goal is to seem for pressure variations between zones that may be separated by closing a door. Pressure variations of quite a pair of to three Pascal ought to be eased by providing associate degree adequate flowing path between the zones.

 Coaching — any duct retrofit business warrant the name would require its technicians to receive active coaching at a decent duct-repair faculty. Periodic change of technique is additionally extremely suggested. Except for the fundamental hand-sealing technique, practitioners ought to follow of latest technologies of automatic duct protection. One in all these ways makes use of aerosol sealants blown into the duct with a computer-controlled adjustable-speed fan.