HVAC / runnable MCP tool
Run the Manual J Residential Load Calculator (ACCA 8th Edition Form J1) in your AI assistant
Through the free Intry MCP server, Claude, ChatGPT, or Cursor runs this exact calculator and hands back a verdict and the cited source, not a guess. Tool name: manual_j_load.
What it runs: Compute a residential heating and cooling load component by component, following the ACCA Manual J 8th Edition Form J1 worksheets against the REAL ASHRAE Chapter 14 design conditions of a named weather station. ⚠ THIS TOOL RETURNS NO WHOLE-HOUSE TOTAL AND THAT IS DELIBERATE, NOT A FAILURE. A Manual J heating total needs an opaque panel tally (Worksheet D: the wall, ceiling, door and floor constructions) and four site declarations that Manual J section 4-11 prints a zero-condition for, and THIS TOOL COLLECTS NEITHER. The web calculator at /tools/hvac/manual-j-load-calculator collects both and does report a whole-house heating total; send a user there rather than adding these components up. ⚠ THIS TOOL RETURNS NO COOLING TOTAL EITHER, for the same reason: it collects none of the answers one needs. ⚠⚠ THAT IS A STATEMENT ABOUT THIS TOOL AND NOT ABOUT THE PRODUCT, and until 2026-08-09 it read "NO COOLING TOTAL EXISTS ON ANY SURFACE OF THIS PRODUCT", which was a claim one tool made about surfaces it cannot see and which the web calculator falsified the day it shipped one. On that surface: It reports a whole-house COOLING load as the PAIR Manual J section 5-12 sizes equipment from: the total sensible load (Form J1ae line 20) and the total latent load (line 21). Either is withheld when a printed term of it is unanswered or has no printed route in the abridged edition, and the specific term is named on the result rather than folded in. The AED excursion adjustment is NOT one of the blockers: Manual J Appendix 3 section A3-2 (printed folio 421) prints that for MJ8AE the excursion adjustment is always zero, and this description said it was until 2026-08-09. Summing the components that ARE computed would give a number that is always too small, in the direction that undersizes equipment. Do not add them up and present the sum as the load. ⚠ THIS TOOL TAKES NO ZIP CODE AND RETURNS NO DISTANCE: the weather station is NAMED, by `state` and `station`, exactly as the ASHRAE Handbook prints it. Call with `state` alone to be told which stations exist for it. When a state has a station the tool cannot supply, it says how many the printed book lists for it rather than substituting a station from elsewhere. This is not an ACCA-approved Manual J and does not replace a permit-grade load calculation.
Ask your assistant
The one rule that makes it reliable: name Intry in your question. That is what tells Claude to run the manual_j_load tool and answer with the real number, the verdict, and the citation. Leave Intry out and Claude may just guess from memory, which is exactly what you are trying to avoid. Type something like:
“Use Intry to run an ACCA Manual J load for a 2,000 sq ft, 3-bedroom house on the NEW CASTLE, Delaware design conditions.”
“Ask Intry how many ASHRAE design-condition weather stations are printed for Texas and how many it has transcribed.”
Inputs
| Field | Required | What it is |
|---|---|---|
| state | yes | US state, spelled out as the ASHRAE Handbook prints it (e.g. 'California'). Used with `station` to select the weather station. |
| station | optional | The weather station name exactly as the ASHRAE Handbook prints it (e.g. 'ALAMEDA'). Case-insensitive. If you do not know it, call with `state` only and read the coverage answer. |
| conditionedFloorAreaSqft | yes | Conditioned floor area in square feet, e.g. 2000. |
| ceilingHeightFt | optional | Average ceiling height in feet, e.g. 8. Area times height is the above-grade volume Worksheet E needs. |
| bedrooms | yes | Bedroom count, e.g. 3. Manual J Figure 3-1 sets occupants = bedrooms plus one; that is the printed rule. |
| stories | optional | Storey count, a Worksheet E input. Manual J Table 5A prints single-story and two-story air change values only; a taller dwelling is outside the printed table and is refused rather than approximated. |
| tightness | optional | Manual J Table 5A envelope tightness class. All five printed construction rows are accepted. |
| fireplaces | optional | Number of fireplaces, e.g. 0, a Worksheet E term. |
| applianceOptionBtuh | optional | Manual J prints exactly two appliance block loads and this tool will not accept a third. Call without it to be told which two. |
| windowRoughOpeningSqft | optional | Total window ROUGH OPENING area in square feet, e.g. 240, not glass area. Table 2A and Table 3A-1 both use the rough opening; glass area understates every window by its frame. Omit or pass 0 for no glass. |
| windowExposure | optional | Table 3A-1 prints five compass groupings, not eight and not a bearing. Map a bearing yourself; this tool will not bucket one for you. |
| windowPanes | optional | Manual J check list item 6 admits clear 1, 2 or 3 pane glass, which is exactly this enum, so the pane count alone cannot put a dwelling out of scope. What the glass is MADE of can, and that is windowGlassType. |
| windowGlassType | optional | ★ REQUIRED whenever windowRoughOpeningSqft is supplied, and deliberately NOT defaulted. Manual J check list item 6 admits CLEAR glass only, and Figure 3-5 scopes the abridged edition's Table 2A to '(clear glass)' and its Table 3A to '(3A-1; clear glass)'. So heat-absorbing, reflective and low-e glass each end the calculation with that printed reason rather than being priced off the clear-glass table. Defaulting this to 'clear' would answer a check list item on the caller's behalf. |
| windowSash | optional | Sash type. Table 2A prints different U-Values for each. |
| windowFrame | optional | One of Table 2A's four printed frame constructions. Refused rather than defaulted: on the widest row the four columns span 0.38 to 0.72. |
| windowInternalShade | optional | One of Table 3A-1's four printed internal shade states. |
Add Intry to Claude
One paste and Claude can run this tool and every other Intry calculator, right from your phone.
Add Intry to ClaudeOpens Claude with Intry already filled in.
- Claude opens with the Intry connector already filled in. Review it and click Add.
- (If a field is blank, paste the link below into the URL field.)
- In any chat, tap + then Connectors and switch Intry on. Then name Intry in your question (“use Intry to…”) so Claude runs the tool instead of guessing.
https://www.intrysys.com/api/mcpNo login, no API key, and it works on every Claude plan, right from your phone.
Using ChatGPT, Cursor, or a dev tool? See the developer setup on the main page. The endpoint is https://www.intrysys.com/api/mcp.
Every answer comes with the ACCA Manual J 8th Edition Form J1 worksheet procedure and the ASHRAE Chapter 14 design conditions it was computed from, so you can check it or show an inspector. The numbers come from the same calculator we run on intrysys.com, and we re-check every one automatically before anything goes live, so the number Claude hands you matches the code.