@Opus 17 wrote:They would only qualify if they are "a system designed primarily and specifically to reduce heat gain or loss". And if they are such a system (I have doubts) then it doesn't matter if they are interior or exterior.
The OP said these are "plantain shutters", which are pretty similar to blinds. Both are often considered to be primarily to reduce heat gain (at least by the manufacturers; owners usually view the primary purpose as privacy).
But your previous comment made an excellent point about the Energy Conservation Code; I have no idea if it deals with shutters/blinds or not.
