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Good Ductwork Design Is Fundamental for a Comfortable Home

Published on: April 28, 2014
Inside hvac ductwork | AC Southeast®

Homes in the usually sunny Southeast are uniquely located to reap the benefits of good ductwork design for their forced-air heating and air conditioning systems. Combining cool but not frigid winters with the high, humid temperatures of summer, our Southeast U.S. homes need moderate heating and plenty of air conditioning.

Ductwork that efficiently moves heated and cooled air throughout your home will save you money, reduce fuel bills, conserve resources, and prolong the life of your furnace, heat pump and/or central air conditioner.

Ductwork Design Is Not an Afterthought

When you’re planning a new home or considering an addition, the time to incorporate intelligent, careful ductwork design is when the whole project is still on paper. A mechanical contractor should be part of the early design process, working hand in hand with your architect and general contractor to ensure the right sizing, layout and ductwork design of your home’s entire HVAC system.

Better Than Your ABCs

Three important letters should be part of the conversation you have with the mechanical contractor: J, S and D. These are the manuals, or software protocols, from the Air Conditioning Contractors of America (ACCA), a nonprofit industry group that sets the standard for HVAC contractors and equipment.

A good mechanical contractor uses Manual J to calculate the heating and cooling load of your designed home or addition. This guides the selection of HVAC equipment, both furnace and central air conditioner. Each room’s heating and cooling load is calculated (usually on a computerized spreadsheet program).

Next, the equipment is sized using Manual S. Correct sizing of heating and cooling equipment will save you money over the life of your home. Too large a furnace wastes energy and leads to short-cycling; too small a unit will struggle to keep up during extreme temperatures.

During equipment selection is a good time to consider the benefits and costs of desirable accessories, since choices here can affect airflow rates. The options include:

  • Whole-house humidifiers
  • Electronic air cleaners
  • Extended media furnace filters
  • UV lights to reduce microorganisms in the airflow

Manual D dictates the best ductwork design. Based on the specific models selected for heating and cooling using Manual S, the contractor lays out the duct runs, locates registers and vents, and chooses the size of ducts. Airflow in each room is carefully calculated so that small rooms are not overwhelmed when the furnace blows, and large rooms are adequately heated and cooled. Good ductwork design means lifelong comfort for you and your family.

Good Design Leads to Great Installation

Some contractors carefully size the main ducts and then less carefully plan the branches (ducts to each room) by simply installing 6-inch-diameter flexible ducts. While using one size duct for everything coming off the main duct saves the contractor money and time, this method works against the homeowner. The poor design will cause some rooms to get too little airflow and others to get too much, which causes problems throughout the system. A tiny half-bath in the front hall may be blasted by hot and cold air, tempting a homeowner to close the register. A master bedroom upstairs may never cool off, or may always feel uncomfortable. Poor design may also result in unbalanced airflow between return and supply ducts. Balancing the system becomes a nightmare during annual inspections and cleaning, and your furnace and air conditioner will not perform efficiently.

According to the Environmental Protection Agency and the Energy Star program, poorly designed or installed ducts can decrease energy efficiency by as much as 40 percent, leading to a drafty, uncomfortable home where the furnace overworks but can’t keep up with heating demands. The air conditioner will work harder, too, since it may be sucking warm air in from leaky ducts running through a hot attic. These problems cost you money year after year. Make sure your contractor correctly sizes branch ducts, locates registers and vents properly for balanced airflow, and seals every joint of every duct with mastic sealant (not ordinary duct tape, which loses its adhesion and falls off in a few years).

Benefits of Proper Ductwork Design

Investing in proper ductwork design while your home building or remodeling project is still in the paperwork stage will pay off over the life of your house:

  • Increased family comfort year-round
  • Furnace and central air conditioner work efficiently
  • Electricity, propane or natural gas use are minimized
  • Natural resources are preserved
  • Equipment lasts longer
  • Chances of breakdowns and repairs decrease

For more information about proper ductwork design for your Southeast U.S. home, contact us to find a contractor in your area. We are here to help you.