If you’re experiencing unpleasant hot and cold spots room to room in your Mount Pleasant home, or if you’re replacing your HVAC system, now’s the right time to take a good look behind the scenes at your duct system. For better comfort and lower energy bills, an HVAC contractor will use these ductwork guidelines to design an HVAC system right the first time.
The ductwork system is a network tubes, outlets, grilles, boots, diffusers and other parts that bear the responsibility of providing a clear and unrestricted channel for airflow that circulates between the HVAC system and the living spaces. For a system with no moving parts, the ducts serve important functions for HVAC performance and energy efficiency. Here are the basic components:
- Return side – The blower or air handler pulls air from the living spaces in through the return grilles and ducts. Larger homes, homes with sprawling layouts and multi-level homes should have several return grilles to promote balanced airflow.
- Plenum – The plenum connects the furnace, heat pump and A/C to the main trunk. If your ducts sometimes make a loud “boom’ noise, it may be the expansion and contraction of this joint. An expansion joint can be installed to relieve the tension.
- Supply side – Airflow is cooled or heated across the heat exchanger and is sent back to the living spaces via the supply ducts, an outlet and a diffuser. Supply side ducts are often trunk and branch, consisting of runouts from the main trunk, or a radial configuration, which are like spokes on a wheel with the plenum as the hub.
- Sealing tools – Duct connections, outlets, grilles and joints should be sealed with mastic and metal tape.
An HVAC professional is an important partner for inspecting, repairing and designing the ductwork system. If you’re undertaking a cooling and heating system upgrade, the ducts need to be inspected for correct sizing and configuration, in addition to ensuring there are no leaks, damage or holes. A visual inspection reveals issues with joint connections, inadequate insulation, fallen ducts, significant leaks and the general design of the system. A more sophisticated blower door test is used to locate leaks that are more difficult to see and feel, and can be appropriately sealed.
For new or retrofitted ducts, your HVAC pro should offer a few different diagrams how the new system may look and fit inside the home. There may be suggestions to locate long runs and runouts inside the living spaces, such as in raised floors, sealed chase and drop ceiling.
HVAC Guidelines: Manuals J, S, D
Professional ductwork guidelines and best practices for load calculations and HVAC system selection have been in use for decades, as published by the Air Conditioning Contractor of America (ACCA).
The process for designing an efficient and durable duct system is as follows:
- Perform a load calculation of the home using Manual J.
- Select the extra equipment for the ductwork, such as zoned temperature control.
- Size and select the new or replacement heating and cooling system using Manual S.
- Size and layout the duct design using Manual D.
Ductwork Guidelines: Sizing, Location, Sealing
Designing an efficient duct system is as simple as one, two, three for a certified and experienced contractor. Correct sizing, sensible and efficient location and impermeable sealing are the ingredients to maximum home comfort and lower energy bills.
- Sizing – Ducts must be sized correctly so that airflow from the heat pump, furnace or A/C isn’t under too much or too little static pressure. Runouts must be sized correctly to match rooms of various sizes and heat gain/loss of such rooms.
- Location – Ducts are best located inside the conditioned spaces rather than in unconditioned attics, crawl spaces or basements. Even when ducts are well sealed and insulated, there’s some degree of heat loss through the thin duct walls. If ducts are inside the living spaces, any heat energy transfer through duct walls is contained to the living space, rather than heating and cooling an attic, for instance.
- Sealing – Mastic is an important sealing component that dries in a malleable state, sealing tiny holes and cracks and easing tension at joints. Metal tape must be wrapped around all joints and connections.
If you would like more details about these ductwork guidelines or for other home comfort concerns, please contact Wood Air Conditioning, Inc.
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