Psychrometric Card for Home Assistant

A native, lightweight Lovelace card that renders a live Psychrometric Chart using real-time entity data.

This card visualizes the state of air in your home against the ASHRAE 55 Comfort Zone. It features unlimited custom state points, color customization, and an innovative Seasonal Weather Heatmap layer driven by EPW climate files.

Features

• Real-Time Visualization: Plot indoor, outdoor, and HVAC supply points dynamically.
• ASHRAE 55 Comfort Zone: Calculates the comfort polygon based on metabolic rate, clothing level, and air velocity (PMV model).
• Weather Heatmap: Import standard .epw (EnergyPlus Weather) files to render a historical frequency heatmap directly on the chart.
• Zero Dependencies: Built with native SVG and HTML Canvas. No heavy libraries like D3.js or Chart.js.
• Theme Aware: Automatically adapts to Home Assistant Light and Dark modes.
• Mobile Friendly: Responsive design that scales to fit any dashboard column.

Installation

Method 1: HACS (Recommended)

1. Go to HACS > Frontend.
2. Click the 3 dots in the top right corner and select Custom repositories.
3. Add https://github.com/corrgraphics/psychrometric-card as a Lovelace repository.
4. Click Explore & Download Repositories and search for "Psychrometric Card".
5. Click Download.

Method 2: Manual Installation

1. Download psychrometric-card.js from the Releases page.
2. Upload the file to your Home Assistant config/www/ directory.
3. Add the resource to your Dashboard configuration:
   • Settings > Dashboards > Three dots (top right) > Resources.
   • Add Resource: /local/psychrometric-card.js
   • Type: JavaScript Module.

Configuration

Basic Example

type: custom:psychrometric-card
title: "Home Climate"
altitude: 1000  # Elevation in feet
points:
  - name: "Living Room"
    temperature_entity: sensor.living_room_temperature
    humidity_entity: sensor.living_room_humidity
    color: "#10b981"
  - name: "Outside"
    temperature_entity: sensor.outdoor_temperature
    humidity_entity: sensor.outdoor_humidity
    color: "#3b82f6"

Advanced Example (Comfort & Weather)

type: custom:psychrometric-card
title: Home Climate
points:
  - name: Outside
    temperature_entity: sensor.home_temperature
    humidity_entity: sensor.home_relative_humidity
    color: "#3b82f6"
  - name: Upper Floor
    temperature_entity: sensor.thermostat_temperature
    humidity_entity: sensor.thermostat_humidity
    color: "#10b981"
  - name: Main Floor
    temperature_entity: sensor.esphome_temp
    humidity_entity: sensor.esphome_hum
    color: "#ffcc00"
clothing_level: 0.6
metabolic_rate: 1.25
air_velocity: 10
altitude: 5610
weather_file: /local/epw/local.epw
weather_window_days: 15
heatmap_colors:
  - rgba(158, 210, 196, 0)
  - rgba(158, 210, 196, .5)
  - rgba(218, 131, 30, .5)
chart_style:
  saturation_line: "#9ed2c4"
  wet_bulb_lines: "#10b981"
  grid_lines: rgba(255, 255, 255, 0.1)
  axis_lines: "#9ca3af"
  comfort_zone_fill: rgba(158, 210, 196, 0.2)
  comfort_zone_stroke: rgba(158, 210, 196, 0.6)
  label_background: rgba(0, 0, 0, 0.5)
enable_trails: true
trail_hours: 12
enthalpy_trend_hours: 24

Configuration Options

Name	Type	Default	Description
points	list	Required	A list of point objects to plot (see below).
altitude	number	0	Elevation in feet above sea level (adjusts atmospheric pressure).
title	string	null	Optional header text for the card.
show_title	boolean	true	Show or hide the card header.
weather_file	string	null	Path to a .epw file (e.g., /local/weather.epw) for heatmap background.
weather_window_days	string	15	Number of trailing and leading days to render for seasonal weather data.
heatmap_colors	list	[Blue/Teal]	List of 3 colors for the weather frequency gradient (Low, Mid, High).
clothing_level	number	0.5	Insulation of clothing (clo).
metabolic_rate	number	1.1	Metabolic activity level (met).
air_velocity	number	20	Air speed in feet per minute (fpm).
chart_style	list	null	Chart look and feel configuration.
enable_trails	boolean	true	Enable historical "ghost" trails to Chart.
trail_hours	number	12	Number of historical hours to show.
enthalpy_trend_hours	number	24	Number hours to show on enthalpy trend chart. Set to Zero to dissable.
unit_system	string	imperial	Set to mertic to convert to SI units.

Point Object

Each item in the points list accepts:

Name	Type	Description
temperature_entity	string	Required. The entity ID for Dry Bulb temperature (°F).
humidity_entity	string	Required. The entity ID for Relative Humidity (%).
name	string	Label shown in the legend.
color	string	CSS color for the icon and legend dot.

Chart Style

Each item in the chart_style list accepts:

Name	Type	Description
saturation_line	string	Saturation line color
wet_bulb_lines	string	Wet Bulb Temperature line color
grid_lines	string	Background grid line color
axis_lines	string	Axis line color
comfort_zone_fill	string	ASHRAE 55 Confort Zone fill color
comfort_zone_stroke	string	ASHRAE 55 Confort Zone fill color
label_background	string	Point label background color and opacity

Weather Heatmap (.epw)

To visualize historical weather data:

1. Download an EPW file for your location (e.g., from Climate.OneBuilding.org).
2. Place the .epw file in your config/www/ folder.
3. Reference it in the config via /local/filename.epw.

The card parses this file and bins the hourly data into a frequency heatmap rendered behind the chart lines.

Credits

Developed by corrgraphics.

Math engine adapted from:

• ASHRAE Fundamentals (IP Units)
• CBE Thermal Comfort Tool (ISO 7730 PMV implementation)

License

MIT License

Additional Resources

Energy Plus Climate Files https://energyplus.net/weather-region/north_and_central_america_wmo_region_4/USA

Visual Color Gradiant Picker https://cssgradient.io/

Resource for determining ASHRAE 55 parameters for your space. https://comfort.cbe.berkeley.edu/

ASHRAE 55 Information

The ASHRAE 55 Standard is: Thermal Environmental Conditions for Human Occupancy.

The green box labeled “comfort zone” in the screenshots shown above is rendered based on inputs to your yaml config.

Air Velocity	The air moving around in your home. Do you have forced air hear or radiant heat. Fans, Poor Insulation, Etc.
.05 to .25 m/s	unnoticeably still
.3 to .5 m/s	pleasantly still
.55 to 1 m/s	pleasant but noticeable
1.05 to 1.5	slightly draughty
1.55 to 2	noticeably draughty

Clothing Level	When you are at home, what are you typically wearing?
0	Naked
.05	Underwear Only
.1 to .15	Shorts Only - No Shoes
.2 to .35	Shorts and T-Shirt - No Shoes
.4 to .55	Shorts and T-Shirt, Shoes
.6 to .75	Pants, Shirt, Shoes
.8 to 1.15	Pants, Shirt, Jacket, Shoes
1.2+	You are probably heading outside…

Metabolic Rate	The heat your body is producing
0	you are dead
.05 to .2	approaching death
.25 to .4	sleeping
.45 to .6	resting
.65 to .8	reclining and relaxed
.85 to .95	seated and relaxed
1 to 1.1	seated w/ sedentary activity
1.15 to 1.2	standing and relaxed
1.25 to 1.4	seated with light activity
1.45 to 1.6	standing with light activity
1.65 to 1.95	walking
2+	working out

You can input these or leave them @ default. Or you can create input sensors in home assistant to dynamically change this. (ie, sleeping @ night, motion or presence sensors to detect motion, seasonal clothing changes, etc.) Just add the sensor entity to the corresponding yaml config.