December 01, 2025

Notify when to open or close windows

Save energy by using outdoor air for heating or cooling instead of running HVAC. Get smart notifications when outdoor temperature is perfect for opening or closing windows.

Use cases

Energy Savings

Free Heating - Warm winter days when outside air warmer than heating setpoint
Free Cooling - Cool summer nights when outside air cooler than cooling setpoint
Energy Savings - Take advantage of nice weather instead of running HVAC

Comfort & Awareness

Optimal Ventilation - Know the best times to air out your home
Weather Awareness - Stay informed about ideal conditions

Products needed

Essential Equipment

Indoor Temperature Sensor

Can use smart thermostat's sensor or standalone temperature sensors

Outdoor Temperature Sensor

Popular brands: Ambient Weather, Ecowitt, Aqara outdoor sensor
Weather station integration (Weather Underground, OpenWeatherMap) OR physical outdoor sensor

Smart Home Platform

For notifications and logic: Home Assistant, SmartThings, Hubitat, etc.

Optional Enhancements

Contact Sensors

Track which windows are currently open/closed

Weather Forecast Integration

Predict upcoming conditions for better planning

Basic automation setup

IF outside temp > inside temp + 5°F (in heating season) THEN send notification "Open windows for free heating!"

For Heating Season (Winter)

Trigger: Outside temp rises above thermostat heating setpoint
Conditions: Windows currently closed • House in heating mode • Daytime hours (optional)
Action: Send notification "Outside is warmer than inside! Open windows to save energy."

For Cooling Season (Summer)

Trigger: Outside temp drops below thermostat cooling setpoint
Conditions: Windows currently closed • House in cooling mode • Evening/night time (optional)
Action: Send notification "Outside is cooler than inside! Open windows to save energy."

Platform-specific examples

Home Assistant

Trigger Outside temp rises above heating setpoint

Condition Windows closed, heating mode, daytime

Action Send notification with current temps

Option: Add temperature difference threshold (5°F min)

SmartThings

IF Outdoor temp sensor > thermostat setpoint

AND All windows are closed

THEN Send notification "Open windows for free heating"

Hubitat

Trigger Outdoor temp rises above indoor temp + 5°F

Condition Windows closed, heating season

Action Send notification "Open windows for free heating"

Setup: Use Rule Machine with temperature comparison

Apple HomeKit

Limitation Limited native temperature comparison

Workaround Use Home Assistant or similar hub for logic

Alexa

When Outdoor temperature changes

Condition Outdoor temp > Indoor temp by 5°

Action Send notification to phone

Google Home

Limitation Limited native support for complex temp comparisons

Workaround Use IFTTT or Home Assistant for logic

Advanced features

Notify to close windows

Alert when outdoor temperature is no longer favorable:

Create automation with these elements:

Trigger: Outside temperature drops 5°F below inside temperature
Condition: At least one window is open AND in heating season
Action: Send notification: “Getting cold outside ([temp]°F). Time to close windows and resume heating.”

Weather forecast integration

Predict optimal window times using forecast data:

Create automation triggered at 5 PM:

Check evening forecast temperature
If forecast shows cool evening (below 65°F) AND currently warm inside (above 72°F)
Send notification: “Forecast shows cool evening. Good night to open windows!”

Include estimated savings

Calculate potential savings:

Include message in notification: “Open windows now - save ~$0.50/hour vs running AC!”

Rain alert for open windows

Warn before rain if windows open:

Create automation with these elements:

Trigger: Weather forecast changes
Condition: Rain predicted in next period AND windows are open
Action: Send high-priority notification: “Rain expected soon - close windows!”

Troubleshooting

Issue: Too many notifications

Causes:

Temperature constantly fluctuating around threshold
Notifications sent every time temp changes
No cooldown period between notifications
Both heating and cooling alerts active simultaneously

Solutions: ✅ Add “for: 15 minutes” delay to trigger - ensure temperature stable ✅ Increase temperature difference threshold (5°F instead of 2°F) ✅ Send maximum one notification per 2-hour period ✅ Only notify during specific hours (morning, evening) ✅ Add actionable notification - dismiss or snooze for certain period ✅ Use notification cooldown automation

Cooldown example: Add condition: Only send notification if previous notification was sent more than 2 hours ago (check automation’s last triggered time)

Issue: Notifications not helpful

Causes:

Notification sent at inconvenient times (middle of night, at work)
Temperature difference too small to matter
Outdoor conditions not actually comfortable (humidity, wind)
Windows already open

Check:

✅ Add time restrictions: Only notify 7 AM-10 PM
✅ Only notify when home (presence detection)
✅ Check window sensors - don’t notify if windows already open
✅ Increase minimum temperature difference (5-8°F minimum)
✅ Include humidity in decision (high humidity makes cooling less effective)

Fix: Add multiple conditions:

Only notify during awake hours (7 AM - 10 PM)
Only when someone is home (check home mode)
Significant temp difference (5°F minimum)
Not too humid (outdoor humidity below 70%)

Issue: Outdoor temperature sensor inaccurate

Causes:

Weather integration using wrong location
Outdoor sensor in direct sunlight
Sensor too close to house (heat radiance)
Weather service data delayed or inaccurate

Solutions: ✅ Verify weather integration location (check lat/long coordinates) ✅ Use multiple weather sources and average them ✅ Mount physical sensor in shaded area, away from walls ✅ Compare multiple weather services (OpenWeatherMap, Weather Underground, local station) ✅ Add calibration offset if sensor consistently off ✅ Use nearest weather station data instead of forecast

Related automations: