The importance of duct design and how it affects your heating and cooling system

In many homes, heating and cooling is provided by a furnace and air conditioning unit situated in the basement or other convenient location and distributed through ducting. If ducting systems are poorly configured, they can waste a significant percentage of your energy. Some experts say poor ductwork can be attributable to losses as high as 40 percent.  As such, proper duct sizing and design is very important to ensure home comfort.

Capacity of Ducting

Duct sizing is the most important factor to be considered as the circulation fan blows air to every room at low pressure through the ducts from your indoor blower of your furnace or air handler.

If your ducts are too small, the reduced air flow will be unacceptably low making it difficult to maintain equipment performance and comfortable temperatures in your home.

This same scenerio could occur if you enlarged your home or upgraded your heating system and did not make the necessary corresponding alterations to the original ducting design.

Air Distribution

The next important aspect you need to consider is how to make sure each room gets sufficient air. The duct sizing, shape, number of bends, take-off length and overall layout all affect the flow of air.

This is not a simple exercise and in order to get it right your ducting should be designed by a professional.


Ducts are often placed out of the way in attic, wall voids or crawl spaces that are not well-insulated or not insulated at all. These ducts should be properly insulated to avoid heat loss in winter and, conversely, heat gain in summer.


Air will always take the path of least resistence and where there are restrictions, air will be diverted elsewhere, resulting in unbalanced airflow distribution. When flexible ducting is specified, care must be taken during installation to ensure that it is properly supported without kinks and is kept at allowed lengths to keep the airflow in check.

If you live in the Kansas City area, Overland Park Heating & Cooling, Inc. will ensure that your duct sizing, design and installation are carried out to your complete satisfaction. We have a fully equipped shop to fabricate ducting to suit your home. Contact us today.

Our goal is to help educate our customers in Overland Park, Kansas about energy and home comfort issues (specific to HVAC systems). 

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