Ductwork How to Install A Duct Takeoff
HVAC systems use ducts to supply, recycle, and remove air from building interiors to ensure that the indoor air quality and thermal comfort remain in the acceptable realm. The primary materials of these ducts include galvanized steel, aluminum, fiberglass, plastic, fabric, and PVC. Design-wise, there is usually the main duct and many subsidiary branch ducts.
Now air flows fast through the main duct, but it cannot make sudden sharp turns. That leads to problems with ensuring smooth air flows through the subsidiary branch ducts. In turn, that can hamper the adequate supply of air to the building interior.
To overcome this issue, you can cut round, oval, or rectangular openings in the main duct and install duct takeoffs in these. They ease the transition of air from the main branch into the subsidiary branches, and the airflow can, thus, continue unimpeded. You can attach the takeoffs to the main duct with metal tabs or snap-in attachments and further seal the joints with adhesive foam gaskets to prevent air leakage.
Types of Duct Takeoffs
There are round takeoffs, directional takeoffs, and rectangular takeoffs. Let’s look at these ductwork takeoff:
These are the most commonly used and cost-effective of all the available duct takeoffs. They have tap-in side collars or elbows or tabs at one end and use these to connect from the main branch to the subsidiary branch. The opening in which they are fitted on the main branch is of the same size as the subsidiary branch duct into which they feed the air.
For increased airflow movement, you can install conical or square-to-round takeoffs. The openings with which these connect to the main branch duct are larger than the size of the subsidiary branch ducts into which they open. Due to this, air can change directions and easily enter the subsidiary branches.
By fitting rectangular takeoffs with larger fitting openings into commercial rectangular branch ducts, you can ensure that there are smoother airflow pathways. Rectangular takeoffs are also known as High-Efficiency Takeoffs (HETOs) and may come with a preinstalled balancing damper and a gasket flange to ensure that the fitting is well-sealed. Rectangular takeoffs also work well with rectangular to round fittings. However, they can be expensive as compared to other fitting options.
These takeoffs are fitted with protruding vanes that turn in the airstream and help move the air more quickly into the subsidiary branches. However, they work efficiently only for the first connected branch duct, and the airflow efficiency is not as good for the subsequent air ducts. That happens because, with staggered air ducts, the air has no way to straighten out after moving through the fitting.
Addressing Placement Issues with Duct Takeoffs
The most important issue with installing duct takeoffs is getting their placement on the main branch duct right. You must consider the entire duct system and plan the placements in a way to get maximum airflow through the ducts. It can be inconvenient to correct the airflow issue at a later stage, so it is best that you try and get the duct placements right to begin with.
Understanding how air flows through the ducts can help you with placement planning. When air changes its direction inside the ducts, it will move over a distance of at least two feet before it can regain its original flow. You can take advantage of this characteristic by marking the places where the air will change its direction and fitting the duct takeoffs at distances of two feet from these sections.
Using Duct Takeoff Software
The advent of estimating software has made life easier for ductwork estimators. Using the software, you can get clear views of ductwork layers, detect all the bends, and make exact measurements of the ducts, fittings, grilles, dampers, and other components. You can share the data with co-workers and clients and consult with them to make any necessary changes. You can also use the duct takeoff software to get a list of the materials you will need and their exact quantities. In this way, you will be able to get the duct takeoff installation work with accuracy and efficiency, and your business will consequently profit.