CALCULATORS / BUILDINGS, HVAC AND COMFORT

Surface condensation pressure screening calculator

Condensation screen using supplied saturation pressure at surface temperature.

hvac-condensation.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	vaporPressurekPa
	1.902
	1.5216

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

surface avoids condensation1.90 kPa× fails

BASELINE INPUTS

relativeHumidity0.6 airSaturation3.17 kPasurfaceSaturation1.7 kPa

CALCULATED

vaporPressure1.902 kPa

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Surface-condensation screening
# Scope: Condensation screen using supplied saturation pressure at surface temperature.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

relativeHumidity = 0.6
airSaturation = 3.17 kPa
surfaceSaturation = 1.7 kPa

vaporPressure := relativeHumidity*airSaturation [kPa]

check surface avoids condensation: vaporPressure <= surfaceSaturation

scenario alternative: relativeHumidity = 0.48

Calculated from your source · not saved

Baseline · Baseline

surface avoids condensation1.90 kPa × fails

alternative · alternative

surface avoids condensation1.52 kPa ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

vapor pressure: vaporPressure = relativeHumidity*airSaturation [kPa]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

relative humidity: 0.6
air saturation: 3.17 kPa
surface saturation: 1.7 kPa

Calculated

vapor pressure: 1.902 kPa

Assumptions and limits

Condensation screen using supplied saturation pressure at surface temperature.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Surface-condensation screening. Inputs: air state; surface temperature. Outputs: dew-point margin; condensation condition. Model scope: Simplified heat and moisture balances; site-specific assumptions. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: air state, surface temperature
Outputs: dew-point margin, condensation condition
Modes: calculate, compare, sweep
Drawing: Building heat-flow diagram

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS