Get An Inside Look On Why Ductwork Design Matters

Though often overlooked in its importance to an HVAC system, your ductwork design matters. This is because ductwork is responsible for distributing conditioned air throughout your home.

Ductwork typically brings air from the A/C or furnace to its source and sends into your home through a supply duct. The air then naturally flows to different parts of your home where a return duct is located.

If the air pumping into the room is unable to circulate to the return duct, it gets stuck in the area surrounding the supply duct. It stays there while the air pressure continues to rise, and with no other option, the air seeps out of the house. This causes the HVAC system to continually work to generate more cold air.

Meanwhile, no air reaches the area around the return duct, so the air pressure drops. This causes air to seep in from the outside to balance it out. The temperature in this part of the house becomes noticeably different. In fact, this poor ductwork design creates two zones, and you don’t want your house to experience either.

Leaks or cracks in the ductwork can also impact how much you spend each month on utilities. Up to 20 percent of your conditioned air is lost before it ever reaches its destination. It leaks out of the ducts in places such as the attic or basement where it does no good.

To fix these issues, you will need to work with an HVAC contractor to upgrade your ductwork design.

Good Ductwork Design: Critical for Savings

Good ductwork design can help save money through increased efficiency, balanced air distribution, and proper air flow rates.

Efficient ductwork design is created to distribute air correctly through the home. Depending on the layout of your home, the general types of ductwork designs for maximum productivity are truck-and-branch style or spider systems. Professional technicians can help with various methods of eliminating energy loss in ductwork for maximum savings.

Incorrectly sized ducts or ductwork which does not allow the air to flow properly will possibly require a redesign to keep the home comfortable. Properly sealed and balanced ductwork will use less energy and reduce costs.

Keep in mind that a leaky ductwork system does not balance air distribution, and the system may be using too much heating or cooling in certain areas of the home, creating unnecessary expense for the homeowner. These leaks may cause you to adjust the thermostat to make the affected rooms comfortable, increasing the cost of running the HVAC system.

Of course, the best ductwork design can leak over time due to regular wear and tear. If you have solid ductwork but experience leaks, consider maintenance on your system.

If designed correctly, ductwork will include proper methods of supply and return for the air. This insures that the air flows through the system at the proper rate. Proper air flow rates will increase the productivity of the unit, decreasing costs to run the unit.

Aging Ductwork? How to Tell if You Need a New Design

Aging ductwork can compromise your system’s optimum performance, efficiency, and air quality. Look at the following factors when assessing your aging ductwork design.

  • When were the ducts installed? Often, residential ductwork from the original construction was designed inexpensively and without much thought for longevity. The seals, joints, and seams from the original equipment can deteriorate in less than 10 years.
  • Once you have evaluated the age of the ducts, visually inspect them in easily visible areas such as the attic or crawl space. Look for deteriorating duct tape used to seal the ductwork and any disconnected spans. Watch for an abundance of dust coming from the seams which can indicate air leaks, and take note of any rust or corrosion.
  • How is the airflow in rooms? Rooms that have a reduced volume of airflow may indicate duct segments that have been disconnected, damaged, or clogged with dust and debris. If you notice temperature variations, it could mean air leaks in the ductwork or deteriorating insulation causing thermal loss from the duct.
  • After collecting this information, schedule a duct blower test with an HVAC contractor. Contractors use a blower fan to pressurize ducts and a computer to calculate the amount of air leakage in relation to total airflow.

Three Elements of Efficient Ductwork Design

Heating and cooling the average home accounts for approximately half – and sometimes more – of consumed energy. But your home’s heating unit is only one side of the energy-usage equation. The other side is the duct system. Efficient ductwork design and installation are essential for maximizing energy savings and equipment performance. There are a few different elements to efficient design.


Ductwork components consist of ducts, air-supply registers, return grilles, insulation, and sealing tape or cement. For an efficient layout:

  • Use ducts for all air distribution – do not use building cavities such as walls or raised floors.
  • Install ductwork in the most direct and closest route from the air source to the living space.
  • If possible, do not install ducts in unconditioned spaces. You quickly lose heat energy with damaged, leaky ducts or if the insulation falls away over time.
  • Install return grilles on each level. For the most efficient results, install smaller air grilles in each room with registers to maximize air distribution and comfort.
  • Try jumper ducts and transfer grills to enhance air distribution.

Sealing and Insulation

  • Tightly seal all duct joints with mastic and fiberglass mesh and/or aluminum tape. You may wish to mechanically fasten joints as well.
  • Once you have sealed the ducts, install insulation for any ducts in unconditioned areas. You may want to insulate ducts in conditioned areas as well to maintain temperature for distant registers.
  • Mechanically fasten duct connections at the registers and grilles. It’s common for these connections to loosen or disconnect over time, so inspect them yearly or have a professional inspect them.

Air Distribution

Accurate air supply and return is critical for maintaining even air pressure throughout your home. Uneven air pressure can force air exchange between indoor and outdoor air, burdens your heating unit, and increases utility costs. Install volume dampers in the ducts to increase your control over air flow.

Ductwork Design Best Practices

Keep it tight

Design ducts so none of the runs have to travel too far to reach a room or area. If that happens, occupants of that room are likely to complain that it’s too cold in the winter and too warm in the summer.

Watch your routing

When possible, rout ducts through conditioned areas. If conditioned air is leaking, at least it will leak into an area that’s supposed to receive heated or cooled air. Conditioned air traveling through the ducts won’t lose heat energy to cold air outside (or by warm air diluting cool air inside the ductwork in the summer). When ductwork has to run through unconditioned areas, it should be well-sealed and insulated.

Ducts also shouldn’t be twisted to make tight turns or routed through wall cavities. Straight ductwork has the least resistance to airflow and will make it easy for your air handler to provide the airflow rates your heating and cooling devices need to operate efficiently.

Use appropriately sized ducts

Ducts that are too small will have a high resistance to airflow which may prevent your air handler from achieving sufficient airflow rates. Even if it does, the high air velocities in the ducts will be noisy. The air velocities in ducts that are too large will not be effective at distributing air throughout the rooms.

Use as few separate pieces of ductwork as possible

Every place where you connect pieces together is a potential spot for air leaks. This leakage wastes conditioned air and can allow external air into circulation.

It’s all about balance

Airflow should be closely balanced, with as much air delivered as gets routed back to the HVAC equipment. Otherwise the pressure differential will result in unwanted air loss or gain via air leaks in exterior walls.

You can accomplish this balance by ensuring the return flow has the same airflow capacity as the supply. You will also need to ensure every supply register has a route to a return register. To accomplish this, either include a return register in every room, or install wall and door grilles to supply a suitable route.

Don’t neglect your ductwork

If possible, each room with a supply register should have a return register as well. When this isn’t possible, there should be pass-through grilles and other design elements to allow airflow between rooms.

Tightly seal duct sections with mastic sealant and metal screws. Never use standard duct tape.

While these tips are a good start to planning ductwork, you will want to consult a professional to work out the details, like calculating exactly what size of ducts would be appropriate.

If you think you may not be getting the most out of your HVAC system, it’s time to let a professional give it a look. Contact Stack Heating, Cooling & Electric today to have your ductwork inspected by a reliable contractor.

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