Manual J/S/D HVAC Design | 5 STAR ENERGY

Ask about our high-quality Manual J Load Calculations and Manual D Duct Design services for commercial and residential projects.

What are Manual J / S / D?

They are standards and a protocol developed by Air Conditioning Contractors of America (ACCA) for the proper design and installation of HVAC equipment and duct work.

We build a virtual building or house in a design program which includes all the windows and doors. Once the virtual home is built the wall, ceiling, window and door attributes (insulation values) are entered into the program. Finally the appliance load and human factor are entered. The end result is a heat load calculation for the premises. You need the heat and cooling load to properly size the heating and cooling equipment. Once the equipment is sized it is time to lay out the duct work and balance the airflow.

Advantages to using Manual J – Equipment Sizing

A properly sized system helps provide optimum performance and takes guessing or “rule of thumb” estimates out of the equation. This also reduces cost, because larger systems cost more than smaller systems to install and use more energy to operate.

The biggest advantage is increased comfort, especially in the summer, by cooling and dehumidifying air simultaneously. If a system is too large it may not run long enough and the air could be cool but retain its humidity. If this happens, condensation can form on the registers and inside the duct work possibly causing big problems like mold. Conversely if the system is too small the home won’t stay cool.

  • Manual J - Equipment Sizing

    A properly sized system helps provide optimum performance and takes guessing or “rule of thumb” estimates out of the equation. 

  • Manual S - System Selection

    System selection is an important step for the proper design of the HVAC equipment.

  • Manual D - Duct Design

    Duct design delivers the correct amount of air to each room as determined by the type, size and location of the room in the home.

Manual S – System Selection

System selection is the next step for the proper design of the HVAC equipment. Each manufacturer has their equipment tested under laboratory conditions. The results are printed in or specification guide or AHRI for each piece of equipment. Your HVAC contractor or HVAC designer may specify a manufacturer based on their relationship with the distributor, on price, previous installations, past performance, warranties or parts availability.

Manual D – Duct Design

Duct design delivers the correct amount of air to each room as determined by the type, size and location of the room in the home. A room with many South facing windows will need much more cooling that a room on the North side of the house with fewer windows. A kitchen will have a much higher heat load than the den. Having the right size ducting to each of those rooms is vitally important. Utilizing the correct supply and return ducting sizes also reduces the static pressure in the system. Which in turn reduces the amount of energy used by the blower to move the air through the system. Again more comfort and energy savings.