I am working with an insulation company who has already applied 2" of closed cell foam over the deck of a roof deck that has been remediated for mold twice. It was thought by spraying the foam, there would be no chance of the mold coming back. This is a million dollar home in the Chicagoland area and homeowner is trying to sell the home but a private home inspector says the foam will shorten the life of the roof and he has scared off perspective buyers with his talk. I have told the insulator, that I am not going to say anything that I am not sure of or have some documentation.
I agree the home owner should have solved the source of the mold before doing anything to the home first. Unfortunately, we are beyond that point. I am told that the ventilation has now been taken care of and I plan to check the ventilation out this coming week. If anyone has anything to add to the conversation or thoughts to help the homeowner sell his home and have the buyer feel comfortable with the purchase, please let me know. I have been doing this for 9 years and never had a case like this and want to make sure not to say anything that will get my tail in the ringer.
Way to much information is missing to even say something definitive but I can say that yes it can shorten the life of the roof... by about two weeks (shingles) http://thehtrc.com/2011/what-is-a-hot-roof
As for mold, the iso or is it exothermic reaction should have killed the mold on the sheathing while covering it completely should be enough to encapsulate it - was this done under the roof sheathing or over it
For the roof shingle issue that is an unfortunate issue with many home inspectors that have been given improper information. Shingle color actually has a greater effect than non-ventilation. There will be some shingle degradation but it will be very minimal.
Here is a great article on non-vented roofs.
Here is the link to the study referenced in the article-
As you probably know mold will grow if conditions are right, it just requires organic matter for food, moisture, warmth, and oxygen. So if those conditions are corrected you should be okay.
You say that 2" of closed cell foam is applied OVER the roof deck. Where exactly was the foam applied? Is this a flat/low slope roof? If its to the underside of the roof deck? You mention ventilation. How about the ceiling plain...was that air sealed? 2" of closed cell foam is about an R13 depending of which brand of foam was used. R13 alone applied to a roof deck is not enough to stop condensation.