Every room has its own weather.

I live in a Climate climate, and it's Season .

Bedroom

…

…ppm

CO₂ · …

Cutaway drawing of a three-floor house: attic, bedroom, bathroom, nursery, living room, kitchen, stairs and basement.

Drag the sun through a day in this house

The whole house at …

How to read it Good in range Fair keep an eye Poor act now

Will your windows sweat tonight?

Two numbers decide it: how wet the air is inside, and how cold it is outside. Move the sliders and watch the glass.

Humidity inside55 %

Temperature outside30 °F

How this is worked out: the dew point with the Magnus formula, and the inside surface of the glass estimated for an ordinary double-glazed window, with the room at 68 °F. It is an estimate for a typical window, not a measurement of yours.

Maybe. The glass is close to the dew point.

A few more points of humidity, or a colder night, and the window starts to sweat.

Dew point 51 °F · window glass about 54 °F

Know the words

The scales a healthy house sits on, with the word we use for each step.

Humidity

EPA: aim for 30–50 %, and keep it below 60 % at all times.

too drybelow 30 %

good30–50 %

damp50–60 %

mold-proneabove 60 %

CO2

ASHRAE 62.1 uses 1,000 ppm as its ventilation guide. The 800 ppm line is a rule of thumb.

freshunder 800 ppm

stuffy800–1,000 ppm

staleover 1,000 ppm

Temperature

ASHRAE 55: the comfort range for most people indoors, rounded.

chillyunder 66 °F

comfortable66–76 °F

warmover 76 °F

Tonight, on every street

Behind every lit window, a different forecast.

A damp basement here. A stuffy bedroom there. An attic that bakes by four. Find your room, read its number, and fix what it tells you.

Find your room's forecast

Every room has its own weather.

Attic

Basement

Bedroom

Bathroom

Kitchen

Living room

Nursery

Will your windows sweat tonight?

Behind every lit window, a different forecast.