Load calculation (Manual J)
Room by room heat gain and loss from R-values, window U-factors, orientation, infiltration and duct location. It's the base for everything else, and it keeps equipment from being oversized.
Starting at $185HVAC design engineering · Dallas-Fort Worth
Every comfortable room starts with a calculation.
Manual J, D and S designs modeled in Wrightsoft and ready for permit. We're a family-run engineering practice that checks every room, so nobody has to guess the tonnage.
- ACCA aligned
- Wrightsoft® modeling
- Bilingual EN / ES
- Family owned in DFW
- Online across the US
35+years of combined engineering experience
$185starting price for a Manual J
1revision included on every package
4steps from your plans to a permit-ready PDF
Who we work with
Pick what fits your work.
HVAC contractors
Stop paying a designer for slow weeks
Send plans when you have a job. You get Manual J, D and S back and pay per project, with 12% off once you send 5 a month.
For contractors Home buildersDesigns that get through plan review
A load calc and duct design for each plan you build, 1 revision included, and 40% off each extra lot with the same plan.
For builders ArchitectsMechanical design that fits your set
We size the system from your drawings and send back clean load, equipment and duct documents for the permit set.
For architectsProperty owners and remodelers send plans too. Same process, same prices.
What we design
Six services. One set of numbers.
Every project runs on the same model, from the load calculation to the bill of materials. Each step feeds the next, so what gets installed matches what was engineered.
Duct design (Manual D)
Trunk and branch sizes, friction rate and equivalent length calculated for the CFM each room needs. Fewer hot and cold rooms, less noise at the registers.
In the J, D & S package, $395Equipment selection (Manual S)
Manufacturer performance data checked against your Manual J loads at real operating conditions, not just the rated capacity on the label.
With Manual J, $210Commercial loads (Manual N)
Retail, office and industrial spaces, with lighting and equipment gains, occupancy and ASHRAE ventilation in the model.
Starting at $450Bill of materials
For HVAC contractors: every fitting, elbow and length of duct, pulled from the same engineering data that sized the system. Built with our own AG3 Estimating Platform and added to the HVAC Design Package.
$95 per engineering hour · included for partnersPrice calculator
See your price in 20 seconds.
Pick the service, the size of the house and the number of systems. Manual J starts at $185, Manual J & S at $210 and the full J, D & S package at $395, up to 2,000 sq ft. 1 revision included.
Are you an HVAC contractor?
Stop paying for downtime.
An in-house designer costs a salary every week, whether you land five jobs that month or none. Add payroll taxes, software licenses and training time. With AG3 you pay only when you have a project to send.
Slow month, you pay for zero projects. Busy season with five jobs stacked up, we take them without you hiring anyone.
- Pay per project, not per payroll cycle
- No hiring, training, benefits or software licenses
- 1 revision included on every project
- ACCA aligned Manual J, D and S, done the same way every time
- You talk to the mechanical engineer on your project, not a call center
In-house designer
- Fixed salary every week
- Dead weeks between projects
- You hire and train
AG3 partner
- Pay only per project
- No dead weeks
- We handle the engineering
5+projects a month,
every month
every month
12%off every
project
project
What you get
Five documents. One system.
01 · MJ
Manual J design
Room by room loads from your exact plans, so the equipment isn't oversized.
View a sample
02 · MS
Manual S design
Equipment matched to manufacturer performance data for your climate and loads.
Ask about it
03 · MD
Manual D design
A balanced duct layout sized for static pressure and airflow, room by room.
View a sample
04 · BOM · HVAC contractors
Bill of materials
For HVAC contractors: every component, down to the fitting, so the installed system matches the engineering.
How we build it
05 · PDF
Permit-ready documents
Reports laid out the way plan reviewers expect, to cut the back and forth with the building department.
Get yoursAG3 Estimating Platform
Your materials list comes from the design.
Most design firms hand off a PDF and stop there. You're left to work out materials and quantities from the plans, usually in a spreadsheet.
We built our own platform for that. It reads the finished Wrightsoft design and builds the bill of materials in the same pass. No re-typing numbers from a report and no separate takeoff.
Send us your supplier price list and we'll price that exact list against what you actually pay, not a national average.
The bill of materials is for HVAC contractors. It's added to the HVAC Design Package at $95 per engineering hour, and it's included for partners. For HVAC contractors
- Reads Wrightsoft® directly, no manual re-entry
- Itemized to the fitting, no "add 10% for waste" guess
- Material and labor costs from your own supplier prices
- Built and maintained in house by AG3
How we work
From plans to permit in four steps.
- 01
Send your plans
Upload the floor plan and whatever specs you have. We'll ask for anything missing.
- 02
Get your estimate
We review the plans and send a fixed price with a delivery date before any work starts.
- 03
We model it
The house goes into Wrightsoft room by room to size every duct and unit.
- 04
Check and deliver
We check the design against ACCA, ANSI and ASHRAE methods and send the permit-ready PDF.
Samples
See what lands in your inbox.
A sample report with the client details removed. Yours follows the same format. More on samples
HVAC Design Package sample
One house, start to finish.
Manual J loads, Manual S equipment selection, the Manual D duct layout and the ENERGY STAR design report for a two-story home with two systems.
16 pages · PDF · 1.4 MB
How we run a Manual J load calculation
How we model your duct layout in Wrightsoft®
Who's behind it
A family engineering practice.
Mechanical engineer
Rafael
17+ years in HVAC, ventilation and fire protection. Runs every project through Manual J, S and D against ENERGY STAR and ASHRAE standards.
Structural engineer
Andreina
Master's in Structural and Earthquake Engineering and 18+ years finding risk and checking code compliance. Speaks English, French and Spanish.
AG3 started at our kitchen table before it ever reached a jobsite. Today it's 35+ years of combined engineering experience, still run by the two of us.
As parents, we know a house is where a family will live for years. We design every project, residential or commercial, with that in mind.
Family first
The values we run our home with, we run the business with.
Precision
Every number comes from a calculation, not a rule of thumb.
Bilingual
We work with you in English or Spanish.
Responsibility
We treat your project like our own house.
Good to know
Common questions.
What is a Manual J, and why does it matter?
Manual J is the ACCA method for calculating a home's heating and cooling load, room by room. Without it, equipment gets sized by rule of thumb. Too big and it short cycles and leaves the house humid; too small and it can't keep up on the hottest days.
Do I need Manual D and Manual S too?
Manual S matches the equipment to your Manual J loads, and Manual D sizes the ducts to deliver that air. They work together: a good unit on undersized ducts still performs poorly.
What do you need from me to get started?
The property address and floor plans, plus window and insulation specs if you have them. We'll ask for anything missing before we start.
What if my project needs changes?
Every package includes 1 revision on the same plans, like fixing a plan reviewer's comment. If the plans change, the redesign is quoted at $95 per engineering hour.
Ready when you are
Let's size it right the first time.
Send your plans today and get an estimate back.