How to Replace Air Ducts in the Attic

Most people rarely spend time in the attic so don’t think about the ductwork up there. Nonetheless, the design and condition of attic ducts can impact comfort, efficiency, and air quality throughout your home. A contractor should install, inspect, and replace them. But many homeowners we speak to want to know more about the process. Here’s a look at how to replace ducts in the attic, to help you better understand how it’s done.

Determine How To Locate the Air Ducts

If you have existing ductwork, you can replace those air ducts with new ones in the same locations. But older ductwork can be inefficient to begin with because of how it was located and installed. Removing it can be tricky, so you may want to hire a professional. But before you install new air ducts, weigh your options first.

When locating ductwork in an attic, you can:

  • Move the Building’s Thermal Boundary: If the thermal boundary is at the attic floor, move it to the roofline. You can do this with vented and unvented roof assemblies. Insulation options include fiberglass or mineral wool batts, closed-cell polyurethane foam, rigid foam, and combinations of insulating materials.
  • Bury Ducts in Insulation on the Attic Floor: Depending on the material, condensation may form in hot, humid climates. Polyethylene flex ducts buried in cellulose, loose-fill fiberglass, and other air-permeable insulation are particularly vulnerable. You can encapsulate ducts in a layer of closed-cell polyurethane foam to prevent contact between the duct’s outer layer and humid air.

Choose the Right Type of Ductwork

Ducts are available as hard ducts and flexible ducts. Hard ducts are often found in homes built before 1970. Then until the mid-2000s, flex ducts were common, while new homes may have one or the other. Each has its benefits and disadvantages. 

Hard ductwork is smoother on the inside, so allows better airflow, and insulation is applied on the outside to avoid contaminating the air. In addition, the hard shell is more resistant to puncture. Flexible ducts are cost-effective and well-suited for tight spaces. The tubing contains ribbed coils that help keep things airtight.

Choose Ducts That Are the Right Size

Duct sizing is an extremely important consideration. If ducts are undersized, high air pressure, uneven heating or cooling, or noise can occur. Airflow throughout your home can be restricted so you won’t get as much cool air from vents. You can avoid these problems by choosing properly sized ducts from the start, so there are no issues related to installation.

Don’t Forget Duct Support

Unbalanced ductwork can cause a wide range of problems in your HVAC system. If hard ducts aren’t properly anchored, they can shift and bend. Flex ducts will sag without support, causing kinks that reduce airflow and system performance. If you’re uncertain how to replace air ducts in an attic with the proper support, consult with an HVAC professional.

Tips for Running Air Ducts in the Attic

When you’re installing attic air ducts, you can avoid problems by following these expert tips:

  • Install the ducts low to the floor to protect the materials from rising heat.
  • Don’t place ductwork against the roof deck; heat transfer can cause damage.
  • Install a horizontal air handler, which keeps cold air colder and more quickly distributes air into ducts.
  • Seal all duct joints and angles with mastic material to retain more air.
  • Insulate ducts with materials that resist moisture buildup, which interferes with ductwork performance.
  • Design your ducts to move air faster so less heat is added to the airflow.
  • Install a radiant barrier or reflective roofing material to reduce attic heat buildup.

Black Hills Knows How to Replace Air Ducts in Attics

At Black Hills, we can replace air ducts and provide air duct cleaning services. Ductwork replacement isn’t a job just anyone can do. It requires professional tools and expertise. Our licensed technicians are trained in the latest materials, products, and installation methods so can get the job done right the first time. If you need to replace the air ducts in your attic, call the pros in Olympia at 888-338-1312.