HEATING, VENTILATION AND AIR CONDITIONING (HVAC) SYSTEMS:

Design: Complete operation protocols and maintenance procedures shall be provided for all HVAC equipment.  Procedures shall be written to be easily understood and implemented by facilities managers and teachers.  Teacher operable controls shall be affixed with a permanent label listing control instructions.

Sizing: Heating systems shall be sized according to standard engineering practice, using an interior design temperature of 70̊F and the standard ASHRAE winter design temperature (WDT) for the building location, or as approved.  Cooling systems shall be sized according to standard engineering practice using ASHRAE Total Cooling Load calculation procedures (ASHRAE Fundamentals, Chapter 29).

Heat Pump Systems: Heat pumps shall have a minimum HSPF of 7.5 and air conditioning systems shall have a minimum SEER of 12.0

HVAC Controls:  HVAC setback shall occur whenever the classroom is not occupied (at night, weekends, summer vacations and holidays).  The ventilation system shall be controlled by an occupancy sensor in conjunction with an on-off switch that can be accessed by occupants.  The occupancy sensor will shut off the system off 15 minutes after occupancy.  The heating and air conditioning system will be controlled by a 24/7/365 programmable thermostat with a minimum set back of 50 degrees for heating during unoccupied periods.  Thermostats are required to ensure correct operation for at least three days in the event of power outages.

Air conditioning:  If both air conditioning and electric heat are required, a heat pump shall be used as the primary heating/cooling system.

Economizer:  If air conditioning is not provided, economizer cooling is required

Ventilation Rates:  Minimum ventilation airflows shall meet the requirements of ASHRAE Standard 62-1989 and state codes: 15 cfm per person.

Heat Recovery Ventilation: Heat recovery ventilation is recommended.

Ventilation Duct Insulation:  All ventilation exhaust ducts shall be insulated to at least R-4.

Outside Air Source: The outside-air source shall be located at least ten feet from exhaust vents to minimize drawing outdoor pollutants and excessive outdoor noise.

HVAC Ducts: To minimize noise and to provide conditioned air evenly to all occupants, ventilation and air conditioning shall be provided through a series of ducts.

Ductwork for HVAC systems shall be installed to comply with the equipment manufacturer's static pressure specifications.

Ductwork shall be sealed using approved sealant as appropriate.  Metal ducts shall be sealed with approved mastic.

Duct board shall be sealed with mastic or UL181 pressure sensitive tape applied per UL listing.

Moisture Vapor Transfer: A vapor retarder of not more than 1.0 perm dry cup rating shall be installed in exterior walls, exterior ceilings and exterior floors. It shall be installed according to the manufacturer's specifications on the warm side (in winter) of all insulation.

Attic Ventilation: Adequate attic ventilation shall be maintained above all ceiling insulation by providing both high and low vents for roof rafter installed insulation, or gable end vents for insulation installed above a T-bar ceiling.

At least 1 square foot of net-free vent area shall be provided for every 300 ft² of ceiling area with 50 to 60 percent of the vent area located near the roof ridge and 40 to 50 percent located near the eaves. A minimum clearance of one inch shall be maintained between attic insulation and the roof sheathing when soffit vents are used.

Exception:  Attic venting is not required when Structural Insulated Panels (SIP) are used to create an un-vented "hot roof," or an unvented attic design is used. In the case of the use of SIPs, all panels shall be effectively sealed together.

General: The classroom shall be inspected on site to determine compliance with these specifications and manufacturer's instructions and/or local codes. An on-site set up guideline checklist shall be used to meet the following specifications.

Damage Repair: Damage occurring to factory-installed energy measures during transportation and setup shall be corrected. Any disturbance of insulation due to wiring or other on-site work shall be corrected.

Marriage Line: The ceiling marriage line shall be sealed using gasket and non-porous silicon caulking, foam or closed cell backer rod. 

Exception: The marriage line need not be sealed if the attic ventilation is provided through roof cap venting, using the rafter marriage line as the ventilation path.  In such a situation, however, there must be a vapor barrier installed between the T-bar ceiling and the attic insulation.

The floor and wall marriage lines shall be inspected to insure integrity during shipping, and replaced or repaired as necessary. 

Window and Door Frames: Window and door frames shall be installed and adjusted (if needed) according to the original equipment manufacturers instructions to minimize air leakage and water penetration.  Windows and doors shall be tested to ensure that they open and close easily and seal tightly, and confirm weather-stripping is correctly installed.

Other Penetrations: All penetrations in the building envelope, such as for piping, wiring, recessed fixtures in walls and ceilings, and exhaust-fan housings shall be sealed.

Ground Cover: A vapor retarder, consisting of 6-mil black polyethylene or approved linear low-density poly, shall cover the ground throughout the entire crawl space. All joints shall be lapped at least 8 inches.

Crawl Space Ventilation: Crawl space ventilation shall meet all applicable state or local codes.

HVAC System:

• If mechanical dampers are installed, they shall be opened to the 100% open position, or set to design specifications.

• A complete maintenance and operation manual shall be provided to the school facilities manager.  The manager shall use this manual and keep records of M&O for each unit.

Commissioning ensures the proper functioning of the classroom's mechanical systems and envelope.  Prior to the commissioning process, all parties should agree on the required tasks.  After the portable classroom is set up on site the commissioning shall include at least the following items:

• All mechanical equipment shall operate properly in accordance with the operation protocol provided by the HVAC manufacturer. The setback controls shall be set to ensure temperature setback and ventilation system shut down during nights, weekends, holidays and summer vacations. If provided, the 24/7/365 programmable thermostat shall be programmed for set back for nights, weekends, holidays and summer vacations.

• Outside fresh air supply flow measurements shall be taken to ensure that the correct mechanical ventilation rate is provided at the appropriate outside damper settings.  Exhaust air flow measurements shall be taken to ensure correct ventilation system flow rates are achieved if exhaust ventilation is employed as part of the ventilation system.

• Supply air-flow measurements shall be conducted to ensure the correct ventilation air-flow rates of 15 cfm per designed occupancy.

• If provided, exhaust fan air flow rates shall be tested. 

• During each classroom installation, the first representative classrooms shall be blower door and duct leakage tested to the values provided in the prescriptive path.  Additional testing is required until prescriptive path values are achieved.