It’s amazing the things you can’t see sometimes have the greatest impact on your annual energy savings and overall comfort. Most homeowners rarely think about their home’s ductwork, but the average builder or contractor has to put a tremendous level of thought into one of the most important aspects of any home’s climate control setup. Good ductwork design is an absolute must in order to reap the benefits from an energy-efficient heating and cooling system.
Why Good Ductwork Matters
The importance of good ductwork can’t be stated enough. A poorly designed duct systems is often the underlying cause of HVAC system problems in terms of air delivery, efficiency and overall comfort. For instance, improperly sealed joints allow conditioned air to leak through and create uncomfortable cold and hot spots in your home. Poor duct sizing and bad placement of return vents can cause pressure imbalances that lead to reduced airflow as well as increased wear and tear on heating and cooling system components.
Poor craftsmanship, design flaws or a combination of the two can easily cause an HVAC system’s overall efficiency to drop by up to 40 percent. It can also send an otherwise healthy HVAC system to an early grave due to increased wear and tear, since it has to work much harder to provide the optimal level of performance. In short, poor ductwork robs your home of the superior comfort you depend on throughout the year.
The Hallmarks of Good Ductwork
Good ductwork design starts during the planning stages of a renovation or new home build. It’s here that contractors carefully draft and refine an ideal duct system that meets the occupants’ expectations for superior home comfort and energy efficiency. At this point, builders and contractors should have a scale drawing on hand that highlights the length, sizes and location of all ductwork components, as well as airflow information and other important details.
But there’s more to good duct design than just planning. The ideal residential duct system should have the following qualities:
- All ducts should be located in conditioned spaces, otherwise they should be well-insulated. This helps the ducts retain conditioned air and avoid energy losses.
- All turns should be as gradual as possible to keep airflow at consistent speeds for proper air distribution.
- There should be enough supply and return vents in rooms to not only provide adequate levels of conditioned air, but also to maintain balanced air pressure.
Going by the Book
To help contractors and builders design climate control systems that offer optimal occupant satisfaction and energy efficiency, the Air Conditioning Contractors Association of America (ACCA) developed the Manual D, Manual J and Manual S procedures. These procedures are not just the key for designing an effective and efficient duct system for residential homes – they are also required by most building codes throughout the U.S.
- Manual J is the first step when it comes to designing and installing an energy efficient HVAC system. During this step, your contractor will conduct a series of load calculations in order to accurately calculate heat gain during warm weather and heat loss during cool weather. Your home’s geographic location, thermal properties and a variety of other variables are also factored in. Your contractor will perform whole-house (or block) load calculations as well as room-by-room calculations.
- Manual S is the next step in this process. Your contractor will help you choose the right HVAC system based on its overall performance and energy efficiency. System size, airflow and pressure are also included as determining factors.
- Manual D is the last step and it involves the actual layout of the duct system according to ACCA specifications, using the data gathered during Manual J and Manual S.
Best Practices for Contractors to Follow
- All metal ducts should be secured in place with the appropriate-sized sheet metal screws.
- Eliminate potential points for air leakage through the use of flexible mastic sealant on metal duct joints. Flex joints will benefit from the use of metal tape and compression straps.
- Duct joint gaps larger than 1/8 of an inch should be sealed with a combination of drywall or fiberglass mesh with mastic sealant.
- Always conduct a blower door test to find and take care of leaks and weak areas.
Contact the professionals at McDevitt Air to find out more about ductwork design and how it can best benefit your home. We proudly serve residential homeowners throughout the Savannah, Pooler and Bluffton areas.
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