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Make sure the drapes block IR. There are instances of even local police forces flooding the front of a house with IR light, and viewing the activities inside with IR viewers -- all of this through closed drapes.

What sort of materials DO block IR ? Lycra ? Wool ? Cotton ?

And how do we test drapes without buying them first ?

My guess would be that something like aluminum foil would do just fine I remember seeing some ads for some space age drapes that block all IR as to prevent your room forom overheating from sunlight in the summer and from your room leaking heat to the outside in the winter... looked a lot like aluminum foil to me... any idea on whether this stuff can still be found today?