THE CHALLENGE
The Barnstable High School Library was plagued by overheating and inability of the HVAC equipment to adequately heat and cool the space. Three Nesbitt HVAC rooftop units that serve the Barnstable High School Library had reached the end of their useful life, require extensive maintenance, and two of the three units can no longer provide air conditioning to the 2-story Library Reading Area. The School Department planned on replacing these units, plus another five Nesbitt units of the same age throughout the building in the next five years.
In addition, the north and south faces of the Library Reading Area are comprised of full-height, single-glazed aluminum frame storefront systems (without thermal breaks) and are contributing to the extreme heat gain in the Library. Without attention, this condition continued to produce high loads on the HVAC equipment.
CBI’S SOLUTION
CBI provided options for replacing the existing storefront systems or applying surface treatments / shading elements to improve the solar heat gain coefficient, and our Mechanical Engineer Consultant assessed the impact that the existing storefront (if it was not replaced) or the proposed shading options would have on the HVAC equipment. Cost estimates were generated for various options and the School Department, after weighing the higher initial costs (to replace the storefront) versus the long term energy savings and pay backs on smaller RTU’s, determined that the best decision would be to replace the curtain wall now. Electrochromic glass (or smart/dynamic glass) was chosen for the main curtain wall which automatically transitions tint throughout the day using a photo sensor mounted on the exterior on the building.
In addition, we discovered that the existing distribution system resulted in a ‘short circuit’ as the return air grille was located in the upper corner of the Reading Area space next to the ceiling supply diffusers. We proposed resolving this problem by providing new return air ductwork at the lower floor area.
