The energy efficiency of a heating and Air conditioning ductwork system is considerably reduced when the duct system is broken. Every ounce of conditioned air should travel directly from the furnace to the living area. In some circumstances, the cost of repairing torn or broken ducts outweighs the cost of the repair materials.
The different types of HVAC ducts
The aim of all duct systems is the same. Local building codes, on the other hand, frequently determine the type of material utilized, as well as its installation method and position.
(Before we go any further, make sure you’re wearing the proper personal protective equipment, such as a dust mask, eye protection, and gloves.)
- A rectangular trunk line or plenum is the starting point for galvanized sheet metal systems. The system then connects the individual floor penetrations with branch lines constructed of circular sheet metal or smaller rectangular ducts. Sheet metal ducts are held together by S-shaped clips and cleats, also known as s-locks and drives; round sheet metal ducts are held together by screws. Sheet metal duct is sealed using foil-backed duct tape or sheet metal suitable mastic by installers. To avoid condensation while using air conditioning, some applications, such as attics or enclosed systems, require insulation.
- Fiberglass duct board: Compressed fiberglass boards with a foil outer covering are used in this type of duct. Each joint is held together with foil-backed duct tape, mesh, and duct sealing compound. Ridged fiberglass sheets come in thicknesses of one, 1.5, or two inches.
- Flex duct: This low-cost, easy-to-install duct has three layers: an inner layer that is held together by a spiral wire rib, a fiberglass middle layer that provides thermal protection, and an outer layer that serves as a vapor barrier. A technician slides the inner liner over a sheet metal collar when installing a flex duct. He next seals the inside liner with code-approved duct tape and secures it with a duct strap, which is a huge zip tie or worm-gear clamp. Flex ducts every four feet are commonly recommended by installers. This prevents connections from pulling away from the collar and causing sags.
- Spider systems make use of a centralized plenum that feeds several branch lines. The majority of branch lines are connected to a boot that supplies air to an interior area. When the system requires more than one plenum, each extra plenum is fed by a big branch line.
The ductwork in sheet metal
Galvanized sheet metal ducts are used in many residences in northern regions. These ducts are located between the floor joists. The heat that radiates from these ducts aids in the warming of the flooring. The sealant occasionally loses its grip, allowing warm air to escape.
- Loosen the hanging straps or brackets on both sides of the repair area to expose the leaky seam. Reduce the duct’s height to inspect the leaking junction. In most cases, more sealant is all that is required; nevertheless, big gaps should be totally exposed and inspected. If the big gap was caused by a missing or poorly placed S-lock, disassemble the joint and reconnect it properly.
- Repair the S-lock by slicing the old mastic off the joint’s surround using a utility knife, if necessary. Take out any screws that are holding the S-lock in place. Straighten the tabs on both drives’ ends and pull them out of the joint. Disconnect the joint. Tension normally prevents total separation. Remove the old S-lock from the connection. With a screwdriver, open the S-lock and slip it back into place. Each duct end’s flat metal should slide into the S-lock gap formed by the screwdriver. With a hammer, install the drives.
- Seal the duct joint by smearing a 1/8-inch thick layer of code-approved duct mastic over the joint with a paintbrush. Mastic made exclusively for galvanized sheet metal ducts is available from manufacturers.
Fiberglass Duct Board is a type of duct board made of fiberglass
Aside from an occasional internal cleaning, fiberglass duct board heating and air-conditioning duct systems rarely require maintenance or repair. High-powered vacuums are used by professional duct cleaners to remove dust from the duct’s inside surface. While this sort of duct can endure some damage, extended moisture exposure contaminates and degrades the fiberglass. Although damp areas of duct boards often dry without trouble, experts frequently recommend removing saturated duct board sections owing to mold concerns.
- Drain the duct: The fiberglass coating acts like a sponge, absorbing water and preventing drainage. Place a bucket under the duct and use a screwdriver to make a small hole in the foil outer liner. Keep the bucket underneath the duct until it no longer drips.
- Remove the damaged area as follows: Cut out the moist region using a non-serrated knife blade forced through the duct. In and out motions should be used. A serrated knife’s notches grasp the foil backing’s reinforcement threads, which are visible on the outside of the duct as triangle-shaped lines.
- Make a patch to replace it: Measure the opening using a tape measure and transfer the measurements to a fresh sheet of duct board, or use the old part as a template. Using a non-serrated knife, cut the duct board.
- To apply the patch, follow these steps: Insert the patch into the hole and press it down until the foil backing is flush with the surface of the existing duct. Apply a piece of foil-backed duct tape to the seam, ensuring that the tape’s middle is centered over the seam. Using a squeegee, apply pressure to the tape. A piece of mesh can be used to cover the tape. Using a paintbrush as an applicator, apply a 1/8-inch thick layer of duct mastic to the mesh.
Repairing air duct systems of other types
The seam around the air handler or furnace on many duct board systems has to be repaired or sealed. This usually happens when the installer didn’t remove all of the manufacturing oil and dirt off of the air handler’s surface, or he didn’t seal the plenum around the whole outside perimeter.
- Cutaway the old sealant, mesh, and tape with a knife to remove the old sealant, mesh, and tape. Wipe any debris or grease from the exposed connector using a rag.
- The duct board insulation must touch the furnace and must be replaced if it is missing or damaged. Condensation forms otherwise, providing a breeding environment for mold and mildew.
- Use foil-backed duct tape to seal the junction between the plenum and the furnace.
- Apply mesh: Use mesh to cover the duct tape. Use a paint stick to press the mesh onto the tape in tight spaces.
- Apply a 1/8-inch thick layer of duct mastic on the mesh with a paintbrush to seal the joint. To access hard-to-reach regions, attach a paint stick to the brush’s handle. Allow the mastic to solidify according to the manufacturer’s instructions, then switch on the air handler and check for drafts with your touch.
In other cases, such as when the air handler or furnace is located in a small closet, the installer is unable to seal portions of the duct’s outside surface due to a lack of space. The installer must open an access hole and seal the joint from the inside in these circumstances. Use caution to avoid dripping mastic onto the evaporator coil of the system.
Duct that bends
An exposed air-conditioning duct collar is occasionally discovered during a home inspection. When the outer liner and insulation are pushed away from the collar by pressure, this happens. The system’s energy efficiency is considerably reduced by the exposed collar.
- Fix the problem that’s creating the exposed collar: Next to the slipping connection, add a hanger strap to relieve any tension. Additional hanging straps should be placed throughout the duct run.
- Cut the duct strap with wire cutters or pliers to disconnect the loose lining. Removing the insulation from the connection is a good idea. Adjust the outer lining to cover the insulation completely.
- Apply mastic to the outer layer’s butt edge to adhere to the outer liner. Slide the connection together and crush the materials together until the mastic seals the connection, then use a duct strap to secure it in place. Mastic should be applied on the outside of the joint.
Torn flex is another prevalent type of air conditioning duct damage. When an installation drags a segment of flex duct across roof trusses and the outer liner catches on a nail or truss connector plate, tears in the outer liner are common. The installer usually notices the harm and fixes it. However, occasionally, damage escapes examination, and the problem becomes your responsibility after the warranty period has expired.
- Close the rip in the outside liner using a 6-inch strip of duct tape in the center. Duct tape each side of the rip, starting at the middle and working outward.
- Apply a piece of mesh across the length of the repair to seal it. Duct mastic should be used to cover the mesh. The mesh holds the mastic together while it dries, preventing cracks.
Flex duct replacement
In some cases, such as a crushed duct or animal damage, replacing a segment of flex duct makes more sense than repairing it. The original system’s duct collars and hangers are used in the new section. This is determined by the cost of materials and the location of the repair.
- Remove the broken flex by peeling away the old duct seal and cutting the duct strap when removing a flex connection. Remove the insulation from the connection, revealing the inner liner. Remove the duct tape and duct strap that is holding the liner in place. Slide the damaged duct off the collar with care. Step three can be skipped. Technicians use a knife to cut through the flex duct while removing a tiny part. The blade cuts through all three layers at the same time, following the wire rib of the inner liner around the circumference. After the knife has completed a full rotation, remove it and snip the wire rib with wire cutters.
- Fold the outer liner of the existing duct over the insulation and slip it between the insulation and the inner liner, leaving about 4 inches of the liner exposed. Wrap the connection with duct tape after inserting a splice collar into the end of the duct’s inner liner. A duct strap is used to secure the inner liner against the splice collar. Insert the collar into the duct until the rib of the collar is flush with the insulation roll.
- Calculate the replacement section’s length: Add two feet to the spacing between the collars of the existing ducts. For each bend, add an additional foot to the calculation.
- Trim the new flex to the desired length: Extend the new flex duct to its maximum length. Tuck the outer liner between the insulation and the inner liner after rolling it over the insulation. Cut with a knife from the end of the insulation roll to the proper location on the duct. The outer liner should be rolled over the insulation.
- Install new flex by sliding the inner liner over the splice collar, leaving about 1 inch exposed. Duct tape that is code-approved should be used to seal the connection. Use the proper tool to tighten a duct strap over the inner liner. Butt the outer liner and insulation of the new section against the existing ducts. Using a duct strap, secure it in place. Duct tape or code-approved mastic can be used to seal the joints.
See more useful articles at my website blog2success.net.