Ductwork Installation & Replacement

Ductwork installation and replacement means building new supply and return ducts, or replacing worn-out sections, so your heating and cooling system can deliver air to every room. JC & JC HVAC Mechanical Contractors installs ductwork in homes across the DC Metro area. Request a ductwork assessment to find out what your system needs.

Ducts are easy to forget because most of them are hidden behind drywall, under floors or up in the attic. When they fail, the symptoms look like equipment problems: weak airflow, rooms that never reach temperature, rising energy bills and a system that seems to run all the time. Replacing or rebuilding the ducts often fixes complaints that a new furnace or air conditioner never could.

When should ductwork be replaced?

Ductwork should be replaced when it is rusted, crushed, disconnected or badly leaking, when the layout was never sized for central air, or when new equipment needs more airflow than the existing ducts can carry.

Age alone is not the deciding factor. Well-built sheet metal ducts can last a very long time, while poorly supported flex duct in a hot attic can sag and kink much sooner. We look at the condition and the performance of the system together.

• Visible rust, holes or separated joints in metal ducts
• Flex duct that is crushed, torn, kinked or lying on the attic floor
• Old cloth tape that has dried out and let joints fall open
• Ducts sweating or dripping in a humid basement or crawlspace
• Rooms with no return path, or a single small return for the whole house
• Static pressure readings well above what the blower is rated for

Before we recommend replacement, we measure. Static pressure at the equipment, temperature readings at supply registers and a visual check of every accessible joint tell us whether the ducts are actually the bottleneck. That keeps you from paying for new ducts when the real issue is a clogged filter, a dirty coil or a blower set to the wrong speed.

What does a ductwork installation include?

A complete ductwork installation includes removing failed ducts, installing new trunks and branches sized to the design, adding or enlarging returns, sealing every joint, insulating ducts in unconditioned spaces, and balancing the system.

Supply and return ducts

We fabricate and install sheet metal trunks and branches, and use insulated flex only where it can be run straight, supported properly and kept short. Returns get as much attention as supplies, because a starved return can cause noise and high static pressure.

Sealing and insulation

Joints are sealed with mastic or approved foil tape rather than standard cloth duct tape. Ducts that pass through attics, crawlspaces or garages are insulated to reduce energy loss and to keep summer humidity from condensing on cold supply ducts.

Registers, grilles and dampers

We size and place registers so air reaches the room without drafts or whistling, and install balancing dampers on branches so airflow can be adjusted after the system is running. When the design calls for zoning, motorized zone dampers are installed at this stage.

Equipment connections and transitions

The first few feet of ductwork off the furnace or air handler carry all of the system's air, so poorly built plenums and transitions cause outsized problems. We build supply and return plenums sized for the equipment, use smooth transitions instead of abrupt boxes, and make sure the filter rack is large enough that it does not choke the return.

What materials do you use for new ductwork?

We use galvanized sheet metal for trunks, plenums and most branches, insulated flex duct only for short, straight, well-supported final connections, and mastic or approved foil tape to seal every joint.

Sheet metal holds its shape, resists crushing and gives the smoothest airflow, which is why it forms the backbone of the systems we install. Flex duct has its place for short connections to ceiling registers, but long, sagging runs of flex can cause weak airflow. In attics, crawlspaces and garages, ducts are wrapped with insulation and a vapor barrier so summer humidity does not condense on cold supply ducts and drip onto ceilings.

Repair, partial replacement or a full new system?

Duct work falls into one of three scopes: a targeted repair of a few failed sections, a partial replacement of one floor or branch line, or a full new duct system designed around new equipment.

A targeted repair fits when the main trunk is sound and the problem is local, such as one crushed branch or a disconnected boot. A partial replacement makes sense when one area of the home, often an attic or an addition, was built poorly while the rest works well. A full replacement is the right call when the ducts are failing throughout, or when the layout was never sized for the system it serves. We base the recommendation on measurements from your home, and our ductwork design service handles the sizing when a new layout is needed.

How long does ductwork installation take?

Time on site depends on the scope and on access, from a targeted repair or a single new branch, to replacing the ducts on one floor, to a full system replacement in a finished home. We tell you the expected timeline before work begins.

Access is the biggest variable. An open basement and a walkable attic make the work faster. Finished ceilings, tight soffits and closed wall cavities mean more careful routing and sometimes small, patchable openings. We walk you through how we will reach the ducts before work begins, so there are no surprises in finished spaces.

We work one area at a time, keep the heat or cooling running whenever we can, and close up each day's work so the house stays livable overnight. If the system has to be offline for part of a day, we tell you in advance and schedule it around the weather.

What to expect during your visit

Expect a full inspection of the existing ducts, airflow and static pressure readings, and an explanation of what will be replaced and why before any installation begins.

• Assessment: we inspect every accessible run and measure system performance.
• Scope: we explain what will be replaced and why.
• Permits: as the licensed contractor, we pull the permits the job requires and meet the inspector.
• Installation: new ducts, sealed joints and insulation where needed.
• Balance and test: we measure airflow and static pressure on the finished system and adjust dampers before we leave.

When the work is done, we walk you through what changed, go over the before-and-after airflow readings, and explain how to set any zone controls or balancing dampers. You will also know which filter to buy and how often to change it, since the right filter is part of keeping the new ducts performing. Our installations are backed by our 1-Year Workmanship Warranty.

Related services

A new duct system is also a good moment to look at indoor air quality. Sealed ducts pull less dust from attics and crawlspaces, and a properly sized filter rack makes it easier to use a higher-grade filter without choking airflow. If anyone in the home has allergies, mention it during the assessment so we can plan the return and filter setup around it.

New ducts and new equipment perform best when they are planned together, so this work can be paired with heating installation and replacement or AC installation and replacement. If your ducts are structurally fine but full of dust and debris, our separate air duct cleaning service is the better fit. Browse all of our ductwork services for the full picture.

We install ductwork in Silver Spring, MD, Bethesda, MD and Washington, DC.

JC & JC HVAC Mechanical Contractors is a family-owned, licensed contractor based in Silver Spring, MD, providing residential and commercial service with 24/7 emergency availability. Call (301) 509-2475 or schedule your ductwork assessment online. Financing is available, and you can ask about our VIP Comfort Club maintenance plan.