Design Engineer for EAp1 and CxA for EAc3

Yes, you can have two firms doing commissioning, and I have been on both sides of that situation. However, the firm doing the EAc3 must be reviewing and directing ALL commissioning activities, so often there is an increased cost because of some overlap, and sometimes that can be good...the overlap I mean. If you want to do this because you think it will save money...it is false economy. You pursue Enhanced Commissioning because it will improve outcomes, not to get a point or two. Typically hiring one firm to do all the commissioning scope will be the most cost effective, and simplest way to go. However, if you have a highly qualified design firm that has significant commissioning experience, or even a department, but you want that additional set of eyes and quality assurance that you find with Enhanced, then getting another highly qualified commissioning firm can add value to the overall process. Caution: make sure both firms check their egos at the door. The goal is not for one to "out commission" the other, but to provide service that is more than just the addition of two firms. In the cases where I was involved in these situations, the other firm was great, and the relationship was synergistic with both firms wanting the best for the owner and design team. Add in a motivated set of contractors and temperature controls, and incredible things can happen to ensure operation of high performance buildings.