Hello, I am managing a project and the contractor notified me that a specified material (in this case, "ISO" roofing insulation) is "unavailable". I expect a "Substitution for Cause" request to be forwarded. However, instead of offering a change order that reduces the contract sum, I am being told this will cost me another $100,000 or more. Is that valid, or should the contractor be responsible for the additional costs? In other words, who "eats" this extra cost - the contractor or the owner? Thanks, Kelsey Granville