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Ductwork design explained

One of the most critical elements of installing an HVAC system is determining the ductwork design necessary for your space, or whether ductwork is necessary at all.

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Ductwork design by Simon Blackley on FlickrOne of the most critical elements of installing heating and air conditioning systems is determining the ductwork design necessary for your space, or whether ductwork is necessary at all.

You will need to take several factors into consideration to ensure that your ductwork provides adequate airflow and circulation throughout the space. Choosing a contractor to assist you in the process is highly recommended to achieve the best and most efficient results for your home.

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Ductwork design and sizing

First, you should determine how to size air conditioning ducts. Three different methods are widely used in determining ductwork design and duct sizing.

    • The velocity method uses your desired air flow rate and air speed to calculate the ideal duct size.
    • The ducts for your HVAC system can also be designed via the constant pressure loss method. The constant pressure loss method often results in more materials being used, but the pressure loss calculations tend to be more accurate since this method is unique and specific to your building's individual duct system.
    • The static pressure recovery method provides intricate calculations that ensure consistent pressure levels at every inlet and vent within the system. While it may yield the best overall results, this system is complex enough that it is rarely worthwhile for use in residential AC or heating applications.

Whichever method you use, the end goal is to design a system that provides the right amount and speed of air flow and for the level of home cooling or heating required. This ultimately translates to greater heating and cooling efficiency and lower energy bills.

Ductless split systems

In some cases, however, ductwork is unavailable and the installation of ducts is impractical. Ductless split systems are intended to meet this need, allowing for greater flexibility without the need for ductwork design or installation.

According to the U.S. Department of Energy, up to 30 percent of heating and cooling costs can be attributed to duct losses in duct-based HVAC systems.

Ductless split systems virtually eliminate these losses, resulting in much more efficient heating and cooling.

A typical ductless split AC estimate may come in as much as 30 percent more than a traditional central air installation, with prices averaging from $1,500 to $2,000 per 12,000 BTU. In larger homes, this cost can add up quickly.

Some homeowners find the units themselves difficult to incorporate into their interior designs.


Finding qualified contractors who offer installation and warranty services can also be challenging. It is important to use contractors rather than attempting the installation or repairs yourself to ensure proper performance, temperature control and condensation drainage.

Regardless of the method you use to determine your ductwork design — or whether you avoid installing ductwork altogether — a reputable and experienced contractor can be a tremendous help during the design, installation and service of your HVAC system. Reply! can help you connect with a contractor for HVAC estimates and to install your system.

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Photo credit: Simon Blackley via Compfight CC.