First thank you for taking the time to read my question. This is a long debated topic in which I have read endless articles about. Some people like the company Grace debates that having the IWS (Ice and Water Shield) on first is best because if the gutters build up with ice and lift up the drip edge the IWS would protect the wood. Others say that having the IWS over the drip edge would be better because it allows the water that found its way under the shingles to run over the drip edge and into the gutter.
Could you explain what you have found works best for placing the IWS over or under the drip edge for shingles that will get both snow and rain? Please explain your reasoning as to why it is best.
In addition, could i just use Feltex underlayment synthetic fully over my IWS just for added protection?
-Roof pitch 6/12, Architectural shingles