Project Snapshot: Ayer-Shirley High School | Thermal Composite – DOAS Units


Project Name: Ayer-Shirley High School
 Architect: Symmes Maini & McKee Associates
Mechanical Engineer: Symmes Maini & McKee Associates
Mechanical Contractor: E. Armanti & Sons, Inc.
Equipment: 4 Dedicated Outdoor Air Handling Units
Manufacturer: Annexair
Size: 3,500, 5,500, 10,000 and 12,000 CFM
DAC Sales Engineer: Pat Will

Project Overview:

The towns of Ayer and Shirley, on Massachusetts’ northern border, faced precipitous student enrollment declines as a result of the closure of the Fort Devens military base a decade ago. The towns came together to form a new district and share resources, and also to maintain a critical enrollment mass.  Whereas the original 1960 building once housed over 1,000 students, the new grade 9-12 population was planned for 460 students. The Massachusetts School Building Authority prescribed a combined middle and high school. SMMA convinced the communities to rethink the logic of this assumption by thoroughly analyzing the physical attributes of the building, and then stepping back and master-planning the District’s entire portfolio of schools.

Designing for Educational Success

Small, undersized spaces on eight distinct levels separated by narrow corridors and an underutilized open air courtyard with isolated community use spaces and tiny lobbies divided the student body and after-hours public uses making the building hard to navigate and supervise. The poor condition and environment led to over 100 students choosing alternative, out-of-district school options. SMMA aimed to maximize opportunity for pupil and adult interactions, incorporating corridor learning commons; teacher planning centers; small group rooms and larger flexible classrooms, with four teaching surfaces; and flexible, mobile furniture systems into our design. The building has remained occupied during construction, requiring careful shifting of spaces to allow for seamless, uninterrupted education.


HVAC Highlights:

  • DOAS Units
  • GAS Heat
  • Enthalpy Wheels
  • Thermo-composite panel system

The units on the Ayer Shirley High School project were supplied by Annexair and incorporated their Thermo-composite panel system.  The design looked for replacement units that would weigh the same as original and provide 30% more capacity.  Weight was a key design factor.  The Annexair units are 30% lighter than traditional steel units.  So we were able to satisfy the design criteria with a lighter unit.  Additionally the units come with a lifetime warranty against corrosion.    Best of all they are the same cost as traditional steel units.

Take a look at the specification for key features.

UNIT HOUSING SPECIFICATION (Thermo-composite) The unit housing shall be no-through metal with 2’’ Thermo-Composite and foam panel construction – interior and exterior.  No-through metal construction will be inherent to all the component construction in the assembly.  All panels and access doors shall be double wall construction with R14 foam insulation for every 2” of construction.  All foam insulation must be Greenguard certified®. Unit casing will have no exterior condensation at interior AHU temperatures down to 43F while unit exterior conditions are maintained at 95 F dry bulb / 85 F wet bulb.  The panels shall be tested in accordance with SMACNA and ASHRAE 111 to have a deflection of no more than L/1150 at 10’’ and withstand air pressures up to 8” w.c with less than 1% leakage.  Fire resistance of the panel will be in compliance with UL 94.

Thermo-Composite panels shall be provided for the entire unit construction, including but not limited to, walls, doors, floors, roof, interior partitions, and electrical compartment.  The frame shall consist of anodized extruded aluminum profiles which incorporates a thermally broken construction; welded together for reinforcement and insulated for superior thermal performance.  Base structure shall be fully welded and have integral lifting lugs which can be removed once the unit is installed.  All roof and side wall seams shall be positively sealed to prevent water and air leakage.  Panels will be non-load bearing type.

Access doors shall be provided to all major components to facilitate quick and easy access. Access doors will be made from the same material as the unit casing and shall incorporate thermal break construction.

Annexair - Composite Panel - Picture1Unit shall have the entire exterior finished with a PVDF coating designed for UV resistance. Paint shall pass ASTM B117 3000-hour salt fog resistance test and ASTM D4585 3000-hour moisture condensation resistance test. In addition, paint must meet AAMA 620-02 standard for color, chalking, gloss retention, and abrasion resistance. The air handler unit casing shall be provided with a lifetime warranty against corrosion resistance under normal use.

Related Thermo-composite Panel Blog Post:

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