Manual D Duct Design & Duct Modifications in Broomfield, CO
Your furnace or AC can only perform as well as its ductwork lets it. We measure airflow and static pressure, then use Manual D to size and redesign your ducts so every room gets the air it needs.
- Added and resized return air
- New or larger supply runs
- Trunk line resizing and redesign
- Duct sealing and balancing dampers
- Ductwork for additions and basements
Duct design that matches airflow to each room
Manual D is the ACCA standard for residential duct design. It starts with each room's airflow from the Manual J, then sizes every supply and return so the blower can deliver that air within its available pressure.
It accounts for duct material, length, fittings, filters and coils, all the things that add resistance. We use it for new systems and to design modifications to the ductwork you already have.
- Airflow for each room
- Supply and return duct sizes
- Trunk and branch layout
- Pressure budget for the blower
- Register and grille sizing
Your ducts may be holding your system back
Most homes in Broomfield and the north metro were built with ductwork sized by rule of thumb. Add a finished basement, a bigger AC or a new high-efficiency furnace, and the ducts often can't keep up.
The result is rooms that never feel right, a system that sounds like it's working hard, and energy you pay for that never reaches the room.
- Rooms much hotter or colder than the rest of the house
- Weak airflow at some registers
- Whistling returns or loud air noise
- System runs constantly in July or January
- Dust, stuffiness or uneven humidity
- A new system that never fixed the comfort problem
Duct modifications that fix airflow at the source
Every change is based on measurements and sized with Manual D, not guesswork. We recommend these on installs and when we find airflow problems on maintenance visits.
Add or resize returns
Upstairs and closed-off rooms often lack return air. Adding returns lets conditioned air actually flow into them.
Resize supply runs
Undersized or crushed runs starve rooms of air. We replace them with runs sized to the room's load.
Trunk redesign
An undersized main trunk restricts the whole system. We redesign it to lower static pressure and restore airflow.
Seal and balance
We seal leaky joints and set balancing dampers so each room gets its share of air.
Measured before, measured after
Test
Static pressure, airflow at registers and room temperatures to see what the system is really doing.
Design
A room-by-room Manual J load and a Manual D duct design for the changes.
Modify
Returns, supply runs and trunks built and sealed to the design.
Verify
We test again and show you the before-and-after readings.
More on HVAC design
Duct design questions
What is Manual D?
Manual D is the ACCA standard for residential duct design. It sizes supply and return ducts so each room gets the airflow its Manual J load requires, within the pressure the blower can provide.
How do I know if my ductwork is the problem?
Common signs are rooms that are much hotter or colder than the rest of the house, weak airflow at some registers, whistling or loud returns, a system that runs constantly, and high static pressure readings. We measure static pressure and airflow to confirm it before recommending changes.
What is static pressure and why does it matter?
Static pressure is the resistance your blower works against to move air through the filter, coil and ducts. When it's too high, airflow drops, the blower works harder and gets louder, and heating and cooling capacity falls.
Do I need all new ductwork?
Usually not. Many homes need targeted changes: an added return upstairs, a resized trunk, a few new or larger supply runs, and sealing. We fix what's actually limiting airflow.
Is flex duct bad?
Not when it's sized, supported and installed correctly. Problems come from undersized, kinked, crushed or overly long flex runs, which add a lot of resistance. Manual D accounts for the duct type and length.
Should duct work be done when I replace my system?
It's the ideal time. New equipment can only perform as well as the ducts let it, and modifications are easier while the system is apart.
Fix the airflow, fix the comfort
Request an evaluation and we'll measure your ductwork and show you what it's doing.