Our expertise · Building Performance & Engineering
Manual D Duct Design
Connect the airflow plan to a duct system that can actually deliver it.
A load calculation and an equipment selection tell you how much air each room needs. They say nothing about whether the ducts can deliver it. Every foot of run, every fitting, every tight pass through the framing and every undersized return adds resistance, and a layout that looks fine on the plan can leave the farthest rooms short of air once it is built. Manual D sizes the ducts and lays out the system against the equipment's real blower performance and the space that is actually available. Green Summit prepares residential duct-design calculations and layouts as part of a defined building-systems scope, connecting airflow requirements, equipment performance and available space with the duct system the project team will install.
- Licensed engineering firm
- RESNET Rating Provider No. 1998-221
- Founded 2014
- Engineered substantiation, not estimates
Who this is for
Developers, builders and design teams, housing authorities, Tribal housing programs and HERS Raters who need a documented duct design behind the airflow their homes are supposed to deliver.
What we do
- Review the inputs. Room airflow needs, the selected equipment and its blower data, duct routing, fittings, available space and return-air paths establish the basis of the analysis, and we flag what is missing before we design.
- Calculate and coordinate. We prepare the duct sizing, the layout assumptions and the pressure-loss calculations, and identify the inconsistencies that need a design-team decision.
- Control the revisions. When a material building or equipment change affects the result, we update the analysis and reissue it, so the design on file describes the system being installed.
Our process
- Define the dwelling, the system and the output required. We settle which equipment the ducts will serve and what the deliverable has to support.
- Review the inputs and complete the project-specific calculation. We size every run, fitting and return path against the blower the equipment actually has.
- Resolve questions, issue the deliverable and identify any field-verification needs. The design goes to the installer, the inspector and, where the project requires it, the duct-leakage tester.
Benefits
- Documented assumptions instead of informal sizing rules.
- A clearer connection between the building design, the equipment and the airflow it needs.
- Information the team can use for permitting, contractor coordination and related certification work.
Why Green Summit
Green Summit is a consulting partner delivering end-to-end compliance solutions in building performance, specialty tax incentives and advisory services. Founded in 2014, we are a licensed engineering firm and RESNET Rating Provider No. 1998-221, and our modeling and field-verification experience keeps the duct design connected to what will actually be installed. We see the installed ducts in the field, and that experience shows in how we draw them.
The local jurisdiction determines the submittal requirements and any required professional seal, and we tell you at the outset what your jurisdiction expects. Where the project also carries an energy-code pathway or a certification, the same team keeps the duct design consistent with the load calculation, the equipment selection and the field verification.
Frequently asked questions
What is Manual D duct design?
Manual D is the ACCA procedure for sizing and laying out residential duct systems so that each room receives the airflow the load calculation calls for. It works from the equipment's blower performance and the pressure loss of every run and fitting, within the space available for the ducts and the paths available for return air. The output is a documented design the installer can build to and the inspector can check against.
Does duct sizing replace duct-leakage testing?
No. Design determines the proposed airflow and pressure relationships; leakage testing evaluates the installed duct system. A project may need both, and they answer different questions.
Can we reuse an existing duct layout?
Only after we assess it against the required airflows, the equipment's performance and the physical constraints. A drawing alone does not establish the condition or performance of existing ducts, so we never accept one as proof that the system will work.
Which records should we provide?
Room airflow needs, the selected equipment and its blower data, duct routing, fittings, available space and return-air paths. We flag missing information and settle any assumptions with you before issuing the final analysis.
Can you coordinate this with the other Manual calculations?
Yes. Manual J establishes the loads, Manual S supports equipment selection and Manual D supports duct design. We scope them together so the inputs and decisions stay consistent, and a change in one flows through to the others.
Does the calculation guarantee comfort or code approval?
No. Installation, balancing, controls, how the home is actually used and the authority's review all matter. The calculation documents a defined design analysis, and we never present it as a promise about every aspect of installed performance.
Let's design a duct system that delivers the airflow.
Tell us the dwelling, where it is, the equipment you have selected or are considering, and the stage the project is in.
Related solutions
- MEP, HVAC & Hot-Water Coordination
- Residential Energy-Code Compliance
- Energy Modeling
- Manual J Load Calculations
- Building Systems Commissioning & Functional Verification
Program and technical references
ACCA: Manual D
Program information reviewed September 22, 2026. Current applicability, qualifications and program terms are confirmed for each engagement.
Or call 321-273-2200 · inquiry@greensummit.com