In 2019, during the first big heatwave in Paris, I remember how exhausting it already was. In 2026, after three more heatwaves, I saw how much harder it gets for people without air conditioning. Cooling down at home is not obvious, and every window decision feels urgent when you are tired and hot.

That is why I built Ventilate: a calm guide for heatwave days, when to open, when to close, and where to put a fan so it actually helps.

Heat is still hitting Europe hard, and I keep meeting people who open windows at the wrong hour or miss the short evening cool-down. Small habits make a real difference.

What Ventilate does today:

• Per-window advice based on your home layout and local weather
• Next action times, so you know what matters now
• A heat toolkit with practical guides, plus widgets and reminders
• Everything stays on your device. No account required.

Android is live on the Play Store. iOS is coming very soon.

The app is in active development, and I am building it as part of RevenueCat’s Shipaton hackathon. I would genuinely love your feedback, especially if you live in a hot European city without AC.

Question for you: what part of summer heat at home feels the most confusing today, timing your windows, fan placement, or something else?

Thank you for being here early. I will be in the comments all day.

— Bathilde