HVAC Calculation Engine
ASHRAE-based · CLTD Method · SI/Imperial Hybrid
--No user
Room 1
ENGINE READY
ASHRAE 2023
Define room geometry, occupancy, and load inputs. All calculations derive from this module. Defaults follow ASHRAE 62.1 and ECBC guidelines.
Room Geometry
MOD-01A
Internal clear dimension
Floor to ceiling
Create one entry per window area and orientation
Each exposed wall may face a different orientation
Defaults to plan area unless you override it
Used if floor / ground exposure is the active load path
1 window · 6.00 m² · SE
2 walls · 54.00 m² gross
WINDOW SCHEDULE
AREA + ORIENTATION
EXTERNAL WALL SCHEDULE
AREA + ORIENTATION
Solar & System Design Inputs
MOD-01A+
Use project peak cooling design day
Hourly SHGF design point
Optional project grouping tag
Clear glazing default
Internal shade / office profile
Used in roof conduction load
Design Basis & Cleanroom Target
MOD-01A++
Selects whether outdoor-air ventilation, ACH, cleanliness, clinical, lab, or process criteria control compliance.
Comfort mode treats ACH as advisory unless this is set to mandatory.
Used only when Design Basis = ISO cleanroom.
Operational mode applies the stronger airflow template.
Affects leakage and make-up air assumptions in cleanroom mode.
Certification still requires particle counts, HEPA integrity, and pressure qualification.
Comfort / general HVAC mode is active. Switch to ISO cleanroom when you want class-based airflow and cleanroom design concepts.
Occupancy & Internal Loads
MOD-01B
Seated, light work assumed
ASHRAE 62.1 minimum: 10–15
ECBC office: 10–15 W/m²
Computers, monitors etc.
Design Conditions — ASHRAE Climatic Data
MOD-01C · ASHRAE HOF 2021
Select a city to auto-fill ASHRAE data
ASHRAE OUTDOOR DESIGN CONDITIONS (0.4% Summer / Cooling)
Summer design dry bulb
Coincident wet bulb
Derived from WBT+DBT
Used in CLTD correction
For SHGF correction
For atmospheric pressure
Winter design condition
0.4% dehumid wet bulb
ASHRAE 55: 23–26°C
Typically 10–15%
ECBC: ≤0.44 W/m²K
Cooling load calculated using CLTD (Cooling Load Temperature Difference) method per ASHRAE Fundamentals. Each heat gain component tabulated separately.
SENSIBLE HEAT
—W
LATENT HEAT
—W
TOTAL LOAD
—W
ROOM AREA
—m²
Heat Gain Breakdown — CLTD Method
ASHRAE HOF Ch.18
| COMPONENT | FORMULA / BASIS | AREA / QTY | FACTOR | SENSIBLE (W) | LATENT (W) |
|---|---|---|---|---|---|
| Run calculations to populate table | |||||
Sensible Heat Ratio (SHR) = Sensible Load / Total Cooling Load. Guides coil selection, dehumidification requirement, and AHU bypass factor.
SHR Analysis
MOD-03
Run calculations first.
SHR Interpretation Guide
REFERENCE
| SHR RANGE | INTERPRETATION | SYSTEM IMPLICATION | TYPICAL APPLICATION |
|---|---|---|---|
| 0.95 – 1.00 | Mainly sensible load | Standard DX, low dehumidification | Dry climates, server rooms |
| 0.85 – 0.95 | Low latent content | Standard AHU, no special treatment | Offices, classrooms |
| 0.70 – 0.85 | Moderate latent | Dehumidification coil needed | Retail, restaurants |
| 0.55 – 0.70 | High latent load | Low bypass factor coil, deep cooling | Kitchens, gyms, labs |
| < 0.55 | Dominant latent | Dedicated dehumidification system | Pools, tropical climates |
1 TR (Ton of Refrigeration) = 3517 W = 12,000 BTU/hr. The platform now keeps separate TR_design, TR_final, and TR_catalog values so airflow constraints do not overwrite the cooling load.
TR DESIGN
—
TR FINAL
—TR
TR CATALOG
—TR
W/m² INTENSITY
—W/m²
Tonnage Selection Logic
MOD-04
Standard AC Sizes (TR)
REFERENCE
Supply airflow is physics-based and constrained by the highest of thermal airflow, ventilation airflow, and ACH minimum. CFM/TR can be lower on high ΔT systems.
SUPPLY AIR CFM
—
FRESH AIR CFM
—
RECIRCULATION CFM
—
AIR CHANGES/HR (ACH)
—
Airflow Calculation Summary
MOD-05
Duct sizing using CFM = Area × Velocity. Standard velocity: Main duct 500–900 FPM (2.5–4.5 m/s), Branch 300–600 FPM (1.5–3 m/s). Equal friction method.
Duct Sizing Results
MOD-06
Run calculations first.
Rectangular & Circular Duct Comparison
DETAILED
| DUCT SEGMENT | CFM | VELOCITY (FPM) | RECT SIZE (in) | CIRC DIA (in) | AREA (ft²) |
|---|---|---|---|---|---|
| Run calculations to populate | |||||
Velocity Guide
ASHRAE HVAC SYSTEMS
| DUCT TYPE | APPLICATION | FPM | m/s | NOTE |
|---|---|---|---|---|
| Main Supply | High velocity | 800–1500 | 4–7.5 | VAV, large systems |
| Main Supply | Low velocity | 500–800 | 2.5–4 | Standard comfort systems |
| Branch Supply | Typical office | 400–600 | 2–3 | Residential, quiet spaces |
| Return Air | Low velocity | 300–500 | 1.5–2.5 | Always lower than supply |
| Flex Duct | Last leg | 200–400 | 1–2 | Keep length < 3m |
External Static Pressure = sum of all duct friction losses + fitting losses + equipment pressure drops. Determines fan selection. Similar to Hazen-Williams hydraulic tables.
DUCT FRICTION LOSS
—Pa
FITTING LOSSES
—Pa
EQUIPMENT LOSSES
—Pa
TOTAL ESP
—Pa
ESP Calculation Table (Hydraulic Analogy)
MOD-07
Run calculations first.
Equipment selection uses catalog-style AHU ranges and fan curve bands. Airflow, ESP, and motor power are matched to a practical equipment shortlist rather than a generic fan-only rule.
DESIGN AIRFLOW
—
DESIGN ESP
—Pa
SUGGESTED AHU
—
FAN TYPE
—
MOTOR kW
—kW
AHU & Fan Selection
MOD-08
Diffuser quantity based on 150–200 CFM per diffuser. Return air sized at 80–90% of supply. Uniform distribution with return on opposite wall or ceiling.
SUPPLY DIFFUSERS
—
RETURN GRILLES
—
CFM / DIFFUSER
—
RETURN AREA (m²)
—
Diffuser Layout Logic
MOD-09
Psychrometric analysis computes dew point, wet bulb temperature, humidity ratio, enthalpy, and specific volume. Used for ADP (Apparatus Dew Point) and coil selection.
Outdoor Conditions
Indoor Conditions
Coil Selection
ADP & Bypass Factor Analysis
MOD-10B
Complete engineering calculation report. Ready for PDF export or inclusion in MEP documentation package. All intermediate results included per ASHRAE standard practice.
Run calculations to generate report.
Software architecture following layered design pattern: Models → Services → Calculation Engine → UI Layer. Modular, reusable, and ready for integration into full MEP platform.
Layered Architecture
UI Layer
React / Angular / Vue · REST or direct service call
InputFormComponent
ResultsDashboard
DuctSizingPanel
ReportExporter
PsychrometricChart
FanCurveVisualizer
Calculation Engine
Pure functions · No side effects · Unit-testable
CoolingLoadEngine
SHRCalculator
TonnageSelector
AirflowCalculator
DuctSizingEngine
ESPCalculator
FanSelector
DiffuserLayout
PsychrometricEngine
CoilSelector
Service Layer
Business logic · Validation · Orchestration
HVACDesignService
ProjectService
InputValidationService
ReportGeneratorService
ClimateDataService
StandardsReferenceService
Model Layer
Data structures · TypeScript interfaces · Serializable
RoomInputModel
OccupancyModel
CoolingLoadResult
DuctSegment
ESPTableRow
FanSpec
PsychrometricState
ProjectConfig
Core Data Structures
// TypeScript interfaces — MEP HVAC Engine v2
interface RoomInputModel {
geometry: { length: number; width: number; height: number };
occupancy: { count: number; activity: OccupantActivity; freshAirCFM: number };
loads: { lightingWm2: number; equipmentWm2: number };
envelope: { windowArea: number; orientation: Orientation; wallExposure: number; uValue: number };
design: { outdoorDBT: number; outdoorRH: number; indoorDBT: number; indoorRH: number; safetyFactor: number };
}
interface CoolingLoadResult {
peopleLoad: { sensible: number; latent: number };
lightingLoad: { sensible: number };
equipmentLoad: { sensible: number };
windowLoad: { sensible: number };
wallLoad: { sensible: number };
roofLoad: { sensible: number };
freshAirLoad: { sensible: number; latent: number };
totalSensible: number;
totalLatent: number;
totalLoad: number;
shr: number;
}
interface DuctSegment {
id: string;
cfm: number;
velocity: number; // FPM
rectWidth: number; // inches
rectHeight: number; // inches
circDiameter: number; // inches
frictionPaPer100ft: number;
length: number; // ft
}
interface ESPTableRow {
component: string;
description: string;
quantity: number;
unitLoss: number; // Pa
totalLoss: number; // Pa
category: 'duct' | 'fitting' | 'equipment';
}
Calculation Engine Pattern
// Pure function pattern for CoolingLoadEngine
// Each module is a pure function — testable, composable
class CoolingLoadEngine {
static calculatePeopleLoad(occupants: number, activity: OccupantActivity) {
const loads = OCCUPANT_LOAD_TABLE[activity];
// ASHRAE Table 1, Chapter 18
return { sensible: occupants * loads.sensibleW, latent: occupants * loads.latentW };
}
static calculateWindowLoad(area: number, orient: Orientation, shgf: number) {
const sc = 0.87; // Shading Coefficient (clear glass default)
const clf = 0.55; // Cooling Load Factor (office, internal shade)
return area * SHGF_TABLE[orient] * sc * clf;
}
static calculateWallLoad(area: number, uValue: number, cltd: number) {
return uValue * area * cltd; // Q = U × A × CLTD
}
static run(input: RoomInputModel): CoolingLoadResult {
const people = this.calculatePeopleLoad(input.occupancy.count, input.occupancy.activity);
const lighting = input.geometry.length * input.geometry.width * input.loads.lightingWm2 * 0.9;
const equipment = input.geometry.length * input.geometry.width * input.loads.equipmentWm2 * 1.0;
// ... assemble all components, return result
}
}
True dynamic SHGF: solar position computed from latitude, day-of-year, and hour angle. SHGF plotted hourly (8 AM–6 PM) per orientation. Glass orientation and incidence angle correction applied.
DESIGN HOUR SHGF
—W/m²
PEAK HOUR (8–17)
—
SOLAR ALTITUDE
—°
SOLAR AZIMUTH
—°
Hourly SHGF vs Time — Dynamic Solar Model
MOD-11 · ASHRAE HOF 2021 Ch.14
Solar Position Data — All Orientations
HOURLY BREAKDOWN
| HOUR | ALTITUDE (°) | AZIMUTH (°) | N | NE | E | SE | S | SW | W | NW |
|---|---|---|---|---|---|---|---|---|---|---|
| Run calculations first | ||||||||||
Simplified psychrometric chart: DBT on X-axis, humidity ratio W on Y-axis. Points: OA (outdoor), RA (return air), MA (mixed air), SA (supply air), ADP (apparatus dew point). Process lines and SHR line shown.
Psychrometric Process Chart — Air Conditioning Cycle
MOD-12 · ASHRAE HOF 2021 Ch.1
State Point Data
ALL POINTS
Multi-room project management. Each room runs the full calculation engine independently. Results aggregated at building level with diversity factor. AHU grouping available.
Project Storage
LOCAL
Total Project TR
—
Diversity Factor TR
—
Total CFM
—
Total Rooms
—
Diversity Factor
ASHRAE
Typically 75–90% for mixed-use buildings (ASHRAE)
AHU Group Summary
GROUPING
Run room calculations to generate AHU groups.
Room Results Summary
ALL ROOMS
| ROOM | AREA (m²) | RSH (W) | RLH (W) | RTH (W) | W/m² | TR_design | TR_final | CFM_final | SHR |
|---|---|---|---|---|---|---|---|---|---|
| Add rooms to begin | |||||||||
Bill of Quantities and cost estimation. Rates are editable. Costs aggregate the current multi-room project and AHU grouping. All costs are shown in ₹.
Equipment Cost
—₹
Ducting Cost
—₹
Diffuser Cost
—₹
Grand Total
—₹
Rate Schedule (Editable)
MOD-14A · INDIA MARKET 2024
Split: ~₹12K | Cassette: ~₹18K | AHU: ~₹25K
Supply+Return incl. insulation
4-way ceiling, powder-coated Al
19mm PE foam on supply duct
Chilled water piping (CW system)
Erection, testing & commissioning
Bill of Quantities
MOD-14B
| ITEM | DESCRIPTION | QTY | UNIT | RATE (₹) | AMOUNT (₹) |
|---|---|---|---|---|---|
| Run calculations first | |||||
ASHRAE-style annual energy simulation using the bin method, part-load equipment modeling, and separate process-air energy. The active room is simulated first, then rolled up at project level for a quick planning view.
Annual Energy
—
Cooling Energy
—
Fan + Process Energy
—
Annual Energy Cost
—
Simulation Status
ENERGY-01
Run calculations to generate annual energy simulation.
Energy Cost Inputs
ENERGY-02
Used for annual energy-cost reporting only.
Room load, conditioned airflow, process airflow, and fan duty are pulled from the active calculation result.
Active Room Annual Summary
ENERGY-03
No energy result available for this room yet.
Project Roll-Up
ENERGY-04
Project energy roll-up will appear after room simulations complete.
Simulation Inputs
ENERGY-05
Energy inputs are built automatically from the active room result.
Warnings & Recommendations
ENERGY-06
No active warnings.
Bin Energy Graph
ENERGY-07
Annual energy graph will appear after simulation.
Comparison Hook
ENERGY-08
Future-ready hook: compare alternate process-air or fan strategies through the same energy engine.
Dedicated AI design studio for alternate HVAC concepts. It compares cost-effective, balanced, and efficiency-first schemes from the active room result. In ISO cleanroom mode it also carries the selected cleanroom class into the comparison logic.
DESIGN BASIS
—
CURRENT LIVE SYSTEM
—
BEST CAPEX OPTION
—
BEST EFFICIENCY OPTION
—
AI Studio Status
AI-01
Run calculations to generate alternative design concepts.
Design Summary
AI-02
Alternative-design summary will appear after calculation.
Standards Basis
AI-03
The current comfort or ISO cleanroom basis will appear here after calculation.
Alternative Concepts
AI-04
Run calculations to generate alternative concepts.
Option Comparison
AI-05
Alternative comparison will appear after calculation.
ASHRAE Engine — Full Sized Design
AI-06
Generates a complete, deterministically sized HVAC design from your current room inputs using the ASHRAE Handbook of Fundamentals. The numbers below come from the engine, not the AI — AI is used only to narrate the result and to propose alternatives that are re-validated by the engine.
Idle.
Interactive 3D schematic driven by the active room result. Room size, AHU count, zoning, and duct sizes follow the live calculation output, but routing, air animation, and equipment geometry are visual only and must not be treated as a fabrication drawing, standard-compliant layout, or issued design model.
ROOM ENVELOPE
—
DEPLOYED AHUS
—
SUPPLY / RETURN
—
VISUAL ZONES
—
Drag the cube to orbit the model, or click a face for a clean orthographic view.
Owner dashboard shows only the top platform KPIs. Detailed user, activity, and pricing controls are separated into their own owner sections.
Companies & Active Licensing
OWNER-01
COMPANIES
—
ACTIVE LICENSES
—
Leads, Demo & Quote Requests
OWNER-02
TOTAL LEADS
—
DEMO REQUESTS
—
QUOTE REQUESTS
—
Owner Notes
OWNER-03
Run the backend server and sign in with the owner account to view owner KPIs.
Owner user management is separated from company-admin operations and shows platform users across companies.
COMPANY USERS
—
DAU
—
Owner User Management
OWNER-USERS
User records will appear here after owner login.
Daily active users and activity trend are reported separately from the owner dashboard KPIs.
DAU Table
OWNER-DAU-01
Daily active user analytics will appear here after owner login.
DAU Trend
OWNER-DAU-02
Activity trend graph will appear here after owner login.
Company pricing override is isolated from dashboard KPIs so owner pricing actions stay explicit and auditable.
Company Pricing Override
OWNER-PRICE-01
Choose a company and plan to override pricing for a specific account.
Pricing Override History
OWNER-PRICE-02
Active pricing overrides will appear here after owner login.
Company admin dashboard manages licensed users under one company. Admins can create, edit, and delete regular company users within the active license seat limit, while the owner panel remains separate.
LICENSED USERS
—
USER LIMIT
—
REMAINING SEATS
—
COMPANY PROJECTS
—
Licensed Company Users
ADMIN-01
Company user data will appear here after admin login.
Company Project Inventory
ADMIN-02
Company project details will appear here after admin login.
Generate Company User
ADMIN-03
Company admins can generate users only within the active license seat limit.
Company Admin Notes
ADMIN-04
Sign in with a company admin account to manage licensed users and company-wide project visibility.