A home’s ductwork is to the cooling and heating systems what piping is to a home’s plumbing system. While leaky and inefficient ducts do not create physical damage to home and property the same as do leaky water pipes, leaky and poorly designed ductwork creates problems with comfort and air quality, and certainly puts a drain on the wallet. Stay cool and comfortable this summer — and keep more money in your pocket — with this ductwork design guide.
Good Ductwork Design is Cool
Good ductwork design may not be exciting, but it sure is smart, cool and hot according to seasonal temps. Ducts are traditionally tucked away from sight in the attic, walls, basement and/or crawl space. So, ductwork doesn’t often receive much attention or its due respect.
Many folks don’t even realize the sophisticated engineering and system components behind these simple metal tubes, rigid ductboard and plastic-lined flex ducts. Following are the parts, components and tools of a ductwork system:
- Plenum: This component connects the main duct trunk to the A/C, furnace or heat pump.
- Supply ducts: Cooled, heated or ventilated airflow is channeled to the home through supply ducts.
- Supply outlets: Located on the ceiling, floor or wall, the air outlets are used to adjust airflow into a room.
- Return ducts: Return air from the living spaces is pulled through the return ducts to the A/C, furnace or heat pump.
- Return grilles: Air is pulled through the return grilles, and perhaps an air filter, into the return ducts.
- Metal tape, mastic sealant, joint collars and metal screws: Good ductwork design includes these parts for air-tight sealing of duct joints, seams and connections.
New or Redo – Sizing, Location, Sealing
In reality, good ductwork design is more than important for comfort and air quality; it is necessary to maximize home efficiency and the performance of the cooling and heating systems. The ducts must be sized correctly, installed in the most efficient locations (preferably inside the conditioned spaces) and ducts must be sealed up tight.
Anything less and you’ll be sweating in the hot Chantilly summer, even before you open the sky-high cooling bills. Whether you are installing new ductwork with a system upgrade or new home construction, or you are revamping your existing ductwork, here’s what good ductwork design entails:
- Sizing: Water pipes, again, are a good analogy for air ducts in regards to sizing. Given a constant supply for volume of water through the piping, the size of piping affects water pressure at the outlet. In terms of HVAC ductwork and airflow, smooth and balanced air pressure is vital for comfort and energy efficiency. Static pressure inside the air ducts — air pressure and volumetric capacity — affect electricity consumption in blower operation. For good ductwork design, the supply and return ducts are sized appropriately to the volume of air the blower moves to provide smooth airflow to the living spaces in the most efficient manner possible. These calculations are tallied using Manual D and S (duct and system sizing) from the Air Conditioning Contractors of America.
- Location: Metal ducts easily conduct heat energy through the thin walls. When ductwork is installed outside the insulation barrier (e.g. attic and crawl space), lost heat energy is lost cooling and heating dollars. Duct installation best practices regard the conditioned spaces in the home as the ideal location for air ducts. Drop ceilings, raised floors and sealed chases are good places for air ducts. If ductwork must be installed in unconditioned spaces due to space constraints, the ducts should be wrapped or covered with insulation.
- Sealing: Leaky ducts lose airflow which you have paid to cool and heat. Smart duct design involves steadfast duct sealing with metal screws, mastic sealant, metal tape and joint collars for the appropriate seam and application. Mastic sealant is a gooey paste that seals the tiniest cracks and holes in metal-to-metal duct seams. You may wish to mechanically fasten connections, such as boots and elbows, with metal screws, in addition to mastic and metal tape. All duct connections, seams and joints should be wrapped with metal tape.
Finally, your HVAC professional should inspect the ductwork upon completion for leaks using a blower door test. Only after the ducts are confirmed air-tight should insulation, if needed, be installed.
If you are concerned about ductwork design for your northern Virginia home, undertaking new construction, cooling and heating systems upgrade, or you just have unanswered HVAC questions, please contact Griffith Energy Services. for friendly service and the right answers.
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