Why caulk outside window?

[Rick]

If I caulk the inside why do I need to caulk the outside? Isn't the air sealed once I caulk all gaps on the inside?

[Joshua Putnam]

Does it ever rain where you live?

[tbasc]

Research the way walls are built. Pay close attention to flashing. Sealants are used to exclude water, including wind driven water. TB

[nicksanspam]

You don't, except to prevent rainwater leaks. The vapor barrier should be on the inside in a cold climate, to prevent condensation inside walls...

It's also easier to find and fix air leaks from the inside, on a cold day, using a large exhaust fan and cheap siliconized latex caulk that dries clear.

Nick

[Buck Turgidson]

If you caulk both sides, you'll have a dead air space, and dead air space increases insulating value.

[Matt]

In your case, you don't need to caulk inside or outside. The plastic sheeting over all the windows takes care of everything. And who cares if your trailer gets a little water in it anyway? It's probably the first time the floors have even come close to being washed.

[John Hines]

To keep water out of the walls. The caulk on the inside is for airflow, and looks.

[Martik]

I forgot to mention that the new windows I am installing are completely SEALED from any air/water leaks. I guess the caulking would be a BACKUP measure.

[John Hines]

One caulks the gap between the sealed window unit, and the wall it is installed in.

[Norminn]

Helps keep the heat in. Helps keep water and insects, like termites, out.