Feature spec
Goal: Send a clear invoice after finishing a job.
- Add a client, line items, a due date, and payment instructions.
- Preview the total before exporting a PDF.
- Keep an editable draft if export fails.
App Overview
ASHRAE HVAC Duct Sizer
The ASHRAE HVAC Duct Sizer application allows you to quickly size one HVAC duct run or a range of duct sizes using the constant friction method
$5.99 · In-app purchases
PRICE
$5.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
N/A
No ratings yet
Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.
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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included16 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
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Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Screen plan
Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.
States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.
Differentiate and validate
Hypothesis: Contractors need faster repeat invoices more than more templates.
First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.
The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.
Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.
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Free quick prompt For a smaller starting point
Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for ASHRAE HVAC Duct Sizer: map the core Business workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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Opportunities
AI-GENERATED OPPORTUNITY HYPOTHESES
These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.
Hypothesis 1
Include detailed user guides and tooltips.
Assumption to check: Limited user guidance for complex calculations.
Validate with people who use this workflow before building.
Hypothesis 2
Add offline access for calculations.
Assumption to check: No offline functionality.
Validate with people who use this workflow before building.
Hypothesis 3
Enhance sharing features for results.
Assumption to check: Poor sharing options.
Validate with people who use this workflow before building.
Hypothesis 4
Simplify subscription model.
Assumption to check: Subscription fatigue from too many pricing tiers.
Validate with people who use this workflow before building.
App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
App Store description
The ASHRAE HVAC Duct Sizer application allows you to quickly size one HVAC duct run or a range of duct sizes using the constant friction method. Think of this application as a digital version of the classic Trane Ductulator. In the "Size by Airflow" mode, you can specify the total airflow in CFM (or L/s), the aspect ratio and one of either the velocity of air or the friction loss per 100 feet (30 meters). The results include both the exact and rounded height and width (or diameter) dimensions and the calculated velocity and friction loss. In the "Size by Dimensions" mode, you can analyze an existing duct system. There are options to input the existing duct dimensions and one of either the airflow or velocity values to derive the calculated duct friction loss. In the "Range of Duct Sizes" mode, you can specify minimum and maximum friction loss and airflow values to display a range of duct sizes that fall in between the friction loss bounds. You can specify additional parameters such as the duct shape (rectangular, round, or oval), the air temperature and the air pressure. You can also choose to display values in either English (IP) or Metric (SI) units. This application uses slider controls that allow you to quickly increment or decrement the input values and immediately observe the calculated results. This app now works on your iPhone and iPad and adjusts its screen size accordingly. Finally, you can email all of the inputs and results from all 3 input modes to perform further analysis using your desktop computer. The email includes HTML text and a .CSV attachment that can be imported into any popular spreadsheet. The ASHRAE HVAC Duct Sizer application was designed by Carmel Software Corporation for ASHRAE.
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Screenshots
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Build scope
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Define the first version
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Set boundaries
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Check the hard parts
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
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BUILD KIT DIFFICULTY
Starter
From the Build Kit assessment.
A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.
