I live in Toronto, Canada. I have a bonus room over a garage that gets pretty hot in the summer and cool in the winter (no hvac in thsi room either). It has R12 batts with an interior vapor barrier. The inside of the knee wall is unface, so my plan was to cover up the exposed batt side in the attic. I purchased Silverboard but I thought I was getting Silverboard XS. After installing everything, I realized I received the wrong product. If I don’t tape the seams, can I avoid creating a double vapor barrier? I didn’t really do a perfect air sealing job since it is a best effort retrofit. I’m wondering if I should scrap it all and just use something like a building wrap. It is only 1/2″ Silverboard.