Use case
Manual J for retrofit jobs — no blueprint required.
Describe the building from your site visit — wall construction, window count, insulation level, square footage. BuildSolver runs the ACCA Manual J on those inputs and hands back a sized calculation with every row cited to the standard.
Example retrofit
2,400 sq.ft single-story ranch · Houston, TX 77002 · existing R-22 condensing unit, replacing with R-410A. No original drawings on file.
FOR ESTIMATION ONLY · ACCA MJ8 §6.4
Free · No signup · Daily limit applies
01 · The problem
Most retrofits never had blueprints to begin with.
- AutoHVAC requires a blueprint PDF upload. A 1990s ranch that’s changed hands three times rarely has one — and the homeowner is waiting on the quote, not on records requests.
- Excel takes 30 minutes per revision. By the time you have a number, the homeowner has called two other contractors.
- Cool Calc / Wrightsoft are built for the permit phase. You need a sales-phase number that’s defensible enough to win the job, not a stamped submittal.
02 · How it works
Three steps. About 90 seconds.
- Describe the job. Square footage, location, construction type, window count, insulation. The chat asks follow-up questions like an experienced engineer would.
- BuildSolver runs Manual J. Deterministic code executes ACCA Manual J 8th Edition §6 (sensible) + §8 (latent) with climate-zone defaults from IECC. Every assumption is logged.
- Get the result and a client PDF. Block load, sensible/latent split, recommended capacity. Pro and Team tiers add company branding to the PDF.
03 · Why BuildSolver fits retrofit
Built for site-visit inputs, not PDF uploads.
The Primary use case is a contractor with a phone, on a driveway, describing what they see — not a back-office team digitising drawings. BuildSolver does not require blueprints, brand-specific equipment data, or a desktop license. Open the chat, type the description, get a number with citations.
04 · BuildSolver vs AutoHVAC for retrofit
Two valid approaches, different jobs.
AutoHVAC analyzes blueprint PDFs — a great fit for new construction where stamped drawings already exist. For retrofit work without blueprints, the inputs simply aren’t there.
| Feature | BuildSolver | AutoHVAC |
|---|---|---|
| Inputs | Conversational description | Blueprint PDF upload |
| Retrofit-friendly | Yes — no PDFs required | Limited (PDF required) |
| Time to first number | ~90 seconds | Depends on blueprint processing |
| Output transparency | Every row cites ACCA section | Black-box result |
| Mobile workflow | Yes | PDF upload via mobile |
05 · FAQ
Common questions about retrofit sizing.
+What if I don't have the original blueprints?
That's the point. Most retrofits don't. Describe the building from your site visit — square footage, number of stories, wall construction, window count, insulation level — and BuildSolver runs the Manual J on those inputs. Blueprints help, but they are not required.
+Is this accurate enough for a client quote?
Yes for the sales phase. BuildSolver runs the same ACCA Manual J 8th Edition procedures used by permit-grade tools, with assumptions logged in the audit trail. Use it to win the bid; if your jurisdiction requires a stamped Manual J for the permit, use an ACCA-approved package like Wrightsoft or Cool Calc.
+How is this different from AutoHVAC?
AutoHVAC analyzes blueprint PDFs — a strong fit for new construction where stamped drawings already exist. BuildSolver takes a conversational description instead, which matches the reality of retrofit work: phone call from the field, no PDFs, just a contractor who needs a defensible number in 90 seconds.
+Can I use this for commercial retrofit?
BuildSolver is tuned for residential and light-commercial work. For larger commercial systems with multiple zones, ventilation per ASHRAE 62.1, or complex equipment selection, run the preliminary on BuildSolver and have a mechanical engineer review before installation.
+Does it work on mobile?
Yes. The chat is fully responsive and PDFs render the same on phone and desktop. The Primary use case is exactly this — running a Manual J on your phone, in a driveway, before the homeowner sees the quote.
Try it on a real retrofit.
Free tier covers 10 calculations per day. No signup required for the first three. The result PDF is generic on Free; Pro and Team tiers add your company header.
Calculate yours