Considering adding a 4 season sunroom to our house. This will be the most used room. We live N.W. of Chicago and experience very cold winters. Would this be a option for us? We don't want massive heating and air conditioning bills. Contractors tell us this (4 season sunroom) is what we want. With a maximum r rating of 4 for the glass we are skepical since the rooms are mostly glass. We plan on including a gas fireplace and air conditioner. Thanks