We have done this for last 3 years to conserve heat/cooling in side our TT. I would caution anyone doing this in the hot summer months to not use the bubble wrap on windows exposed to the direct sun. If you do, pay close attention to make sure the plastic is not turning brown, and baking on to the glass. However, in the winter time it works great, and still allows for sun light to enter for lighting purposes. Yes, if needed you can use two layers.