Timber Framers Guild Forums General General Forum Questions vapor barrier placement withn a built-up enclosure

Vapor retarder (or vapor diffusion retarder) is the same thing as a vapor barrier. Vapor barrier is probably more commonly used (that is what it used to be called) but vapor retarder is more accurate. Vapor barrier is misleading because it implies it stops all vapor transfer when in fact it does not. It does allow some vapor to pass through to some degree (you can't completely stop it).