Mechanical System Design

Proper sizing and design of your home’s heating and cooling system is essential for the optimum performance and longevity. Sustainably Built provides complete mechanical sizing and design for new and existing homes according the ACCA design process. Because proper design helps ensure that your system will function properly, many code officials now require Manual J and Manual D prior to permit.

Manual J

The first step in any design is to calculate the design, or peak, loads of the home.  Using ACCA’s Manual J calculation method, we will determine the peak loads based on the proposed (or existing) construction of the home, including the insulation levels in the walls, ceilings and floors, the U-value of the windows, and the air leakage rate of the home.

Manual S

Once the loads have been calculated, we’ll select a system that’s properly sized to meet the home’s needs, to prevent the extra cost and lower performance of an oversized system.

Manual D

Proper duct sizing ensures that the right amount of air is delivered to the right places, eliminating problems like cold rooms or noisy ducts. We’ll work with the architect and the structural engineer to be sure that the duct design works within the aesthetic and structural requirements of the project.


For local projects, after the duct system is installed we will inspect and test the system (at rough, before drywall) to be sure that the system is installed and performing according to the design. Testing the system prior to drywall ensures that any mistakes can be corrected without costly rework.

Because Sustainably Built is a third-party designer, we’ll work for you, our customer, to ensure that your system is sized and designed to optimize its performance and energy efficiency, and ultimately, to provide you with the most comfortable home possible while using the least amount of energy.