Areas We Serve
Load calculations across the country — organized by climate zone, because the calculation changes with the climate, not the city limit.
We provide residential Manual J, S, and D load calculations across the United States. Because an accurate load calculation depends on local design conditions — temperature, humidity, and whether a home is heating- or cooling-dominant — we organize our work by climate zone rather than by city. The physics of the calculation is what changes from one region to the next, and the climate is what drives the physics.
- Every calculation is done remotely from your plans, so your location is never a barrier.
- A load calculation in a hot-humid climate is a different problem than one in a cold-dry climate.
- We work across all U.S. climate zones, grouped into five design-meaningful regions.
- Our deepest concentration is the Southeast, the Gulf Coast, and Texas — including Houston, San Antonio, and Dallas.
Why we organize by climate, not by city
A load calculation in Tampa and a load calculation in Denver share a method and almost nothing else. Tampa is fighting humidity and a cooling load that runs most of the year; Denver is fighting a sub-zero design night and a heating load that dwarfs its cooling. Same procedure, opposite problems. The thing that determines how a Manual J actually comes out isn’t the city name — it’s the design temperature, the design humidity, and the balance between heating and cooling. Those are set by climate zone.
That’s also why we don’t publish a thin page for every town. A city name on a page doesn’t change the calculation. The climate does — so that’s how we’ve organized what we know.
The climate regions we work in
Hot-Humid →
The Gulf Coast, Florida, the Deep South, and coastal and south Texas — Houston, San Antonio, Tampa, Orlando, Charleston, Savannah. Here the moisture (latent) load is the whole game, and oversizing does the most damage of any climate. This is the region we know best.
Hot-Dry
The desert Southwest and West Texas — Phoenix, Las Vegas, El Paso. High sensible loads, very low humidity, and big day-to-night temperature swings. (Dedicated page in progress.)
Mixed
The mid-Atlantic, the mid-South, and the Pacific coast — where heating and cooling loads are roughly balanced and the system has to do both jobs well. (Dedicated page in progress.)
Cold
The Midwest, the Northeast, and the Mountain states — heating-dominant climates with low design temperatures where undersizing leaves a house cold on a design night. (Dedicated page in progress.)
Very Cold
The northern tier and high elevations — extreme heating loads and design conditions well below zero, where equipment and backup heat have to be sized with no margin for a guess. (Dedicated page in progress.)
How it works, wherever your project is
Every load calculation is done from your plans and delivered digitally, so it makes no difference whether your project is across town from a major city or hours from the nearest one. You send the drawings; we apply the correct design conditions for that location and return a clean, defensible Manual J load calculation — with Manual S equipment selection and Manual D duct design when you need them.
Where we work most
We work nationwide, but our deepest concentration is across the Southeast and the Gulf Coast, with Texas especially active lately — Houston, San Antonio, and Dallas have been some of our busiest markets in recent months. Over the years that footprint has reached as far as Texas, Utah, Ohio, and Virginia, all the way back to Florida. Most of that volume sits squarely in the hot-humid and mixed climates, which is where our experience runs deepest.
Frequently asked questions
Do you only work in certain states?
No. We provide residential load calculations nationwide. We organize our work by climate zone rather than by state because the climate, not the state line, is what changes the calculation.
Why organize by climate zone instead of by city?
Because a city name does not change a load calculation, but the climate does. Design temperature, humidity, and the heating-versus-cooling balance are set by climate zone, and those are what drive the result.
Do you need to visit the property?
No. Every calculation is done remotely from your plans, so your location is never a barrier.
Which climates do you have the most experience in?
Our deepest experience is in hot-humid and mixed climates across the Southeast, the Gulf Coast, and Texas, including Houston, San Antonio, and Dallas.
Get an accurate load calculation — anywhere in the country
Send us your plans and we’ll apply the right design conditions for your location. We work with builders, contractors, and homeowners nationwide.
See pricing & start your load calculation →Climate Zone Technical Requirements Table
| IECC Zone | Climate Type | Key Design Focus |
| Zone 1-2 | Hot-Humid | Latent Load: Focus on dehumidification and high-efficiency cooling. |
| Zone 3-4 | Mixed-Humid | Balanced Design: Dual-peak capacity for hot summers and snap freezes. |
| Zone 5-6 | Cold | Heating Dominant: High R-value insulation and air-source heat pump sizing. |
| Zone 7-8 | Subarctic | Extreme Heating: Specialized design for sustained sub-zero temperatures. |
Contact Load Calculations HVAC for your Manual J Service
Whether you are a builder, contractor, or homeowner, trust 30+ years HVAC field experience for reliable and professional Manual J load calculation services. Contact us at 678-953-7704 or get started with our load calculation service page.