What size furnace or AC do you actually need?
Most contractors size a replacement by matching the old unit or a rough square-footage rule of thumb. A real Manual J calculation replaces that guess with an actual number — and since we don’t sell systems, ours has no incentive attached to it either way.
A real, room-by-room calculation
Not a square-footage shortcut. Every room, accounted for.
Every room measured
Square footage and ceiling height for each room, not just a whole-house average.
Windows & orientation
Count, size, type, and which direction they face — a west-facing wall of glass loads very differently than a shaded north window.
Insulation & construction
Wall, attic, and floor insulation levels, and how the home was built.
Infiltration & doors
How much outside air the home is actually exchanging — a real factor, not an afterthought.
Heating & cooling loads, separately
Utah homes often need different sizing logic for winter and summer — both get calculated.
A written report
The final BTU numbers and equipment sizing, in a document you keep and can hand to any installer.
An unbiased number, before you commit to anything
- Getting replacement quotesHold every contractor's proposed system size to a real number instead of trusting whichever one sounds most confident.
- Conflicting quotesTwo companies gave you two different tonnages? We'll tell you which one is actually right.
- Suspect your current system is wrongShort-cycling, uneven rooms, or a system that never seems to catch up can trace back to bad sizing from the start.
Manual J Load Calculation
- Every room measured
- Windows, orientation & insulation factored in
- Separate heating & cooling loads
- Written report you keep
- No system sale attached
Want both? This pairs well with our Post-Install Inspection.
Manual J load calculation questions
What is a Manual J load calculation?
It’s the industry-standard method (from ACCA) for figuring out exactly how much heating and cooling a home actually needs, room by room — based on square footage, windows, insulation, ceiling height, and orientation. Most contractors size a system by matching the old unit or a rough square-footage rule of thumb. A Manual J replaces that guess with an actual number.
Why would I need this if I'm not replacing my system?
Three common reasons: you’re getting quotes for a replacement and want a real number to hold contractors to instead of trusting whatever they propose, you’ve gotten wildly different tonnage recommendations from different companies and want to know who’s right, or you suspect your current system was never sized correctly and want to know for sure.
Do you sell the equipment afterward?
No. We don’t sell or install new systems, so the number we hand you isn’t shaped by an incentive to justify a bigger, more expensive unit or win a sale. You can take the report to whichever installer you choose.
How is this different from what my HVAC contractor already does?
Most companies size a replacement by matching the old unit’s tonnage or using a rough square-footage rule of thumb — not a real room-by-room calculation. A proper Manual J accounts for your home’s actual windows, insulation, ceiling height, and orientation, which is often a meaningfully different number than the rule of thumb.
What do I get?
A written report with your home’s calculated heating and cooling loads (in BTUs) and the equipment sizing that matches — something concrete you can hand to any installer.
How much does a Manual J load calculation cost?
$240, flat and upfront. It can also be booked together with a Post-Install Inspection if you want both.
Get a real number, not a guess
Whether you're shopping for quotes or just want to know if your current system was ever sized right, we'll give you a straight answer — no sales pitch attached.