GARCIA • GALUSKA • DESOUSA Consulting Engineers Inc.

Cohasset Town Hall Cohasset, MA J#732 006 00.00 L#57295/Page 1/March 6, 2018

HVAC SYSTEMS

NARRATIVE REPORT

The following is the HVAC system narrative, which defines the scope of work and capacities of the HVAC system as well as the Basis of Design.

While there are several different HVAC system options that are suitable for the proposed Renovation and Addition Option, the proposed HVAC system described below represents highly energy efficient, moderate first cost HVAC system options that provide a high level of and that has demonstrated to have a low overall life cycle cost in comparison to other system options and are compatible with the existing building’s architectural and structural features. As part of the project’s future design development, we recommend that a building energy model and life cycle cost analysis of a minimum of three HVAC system options should be performed.

1. CODES

All work installed under Section 230000 shall comply with the all town, state, county, and federal codes, laws, statutes, and authorities having jurisdiction.

2. DESIGN INTENT

The work of Section 230000 is shown on the drawings and specifications. All work is new and consists of furnishing all materials, equipment, labor, transportation, facilities, and all operations and adjustments required for the complete and operating installation of the Heating, Ventilating and work and all items incidental thereto, including commissioning and testing.

Mechanical systems shall function to deliver the performance levels to maintain space comfort within specifications set forth by ASHRAE Standard 55-2010 (note: Central AHU humidification system is not in the project scope, humidification control shall be accomplished through use of the energy recovery), ventilation requirements within ASHRAE 62.1-2010, energy efficiency within ASHRAE 90.1-2010 and IECC 2012. Data center temperature and levels shall be designed within ASHRAE TC9.9-2008 recommended range (64.4 deg F to 80.4 deg F with a humidity level less than 60% RH) and Town record vaults shall be designed to maintain temperature and humidity conditions per the Owner’s Design Criteria and/or Massachusetts Archives Performance Guidelines for Safes and Vaults.

3. BASIS OF DESIGN: (MASS CODE)

Massachusetts Code values are listed herein based on local weather data values as determined from ASHRAE 2011 Handbook weather data.

Outside: Winter 7°F, Summer 88°F DB 73°F WB

Inside: 70°F +/- 2 (adj.) deg F for heating and 75°F +/-2 (adj.) deg F(55% RH) for cooling. Unoccupied temperature setback will be provided to maintain 60 °F DB during heating season and 80°F DB during cooling season.

Outside air is provided in accordance with ASHRAE Standard 62.1-2013 and IBC Mechanical Code (IMC 2015) requirements as a minimum. All occupied areas will be designed to maintain a level less than 850 PPM carbon dioxide.

TEL 508-998-5700 FAX 508-998-0883 email: [email protected]

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4. SYSTEM DESCRIPTION

HVAC ASHRAE Baseline: w/ Hot Water/DX/Energy Recovery Air Handling Units, Full , VAV with Hot Water Reheat Coil System (ASHRAE/IECC Code Baseline System) The Existing Town Hall and Addition Renovation will be served by (2) two 250 MBH code- efficient . Each boiler will have a variable speed in-line pump feeding an insulated hot water supply and return piping system. The piping from the hot water system will be distributed to central station air handling units. Each AHU must have a full sized outside air connected to a large for the code required economizer cycle with a second similar duct and louver for relief air. Each of the AHUs shall have a dedicated split system condensing unit for cooling. Each AHU will provide heating, ventilation, and cooling through a mixed air distribution ductwork system connected to (VAV) terminal boxes with hot water reheat coils and induvial temperature controls will be provided for each space. Supply and return air ductwork will run to each room or zone to provide code required ventilation as well as space heating and cooling.

HVAC Baseline System Summary: • Requires a dedicated with access to the exterior for large for indoor AHU’s serving the Existing Town Hall • Requires a mechanical room for boilers, , pumps, air separator and glycol feed tank(s). • Two (2) Condensing units (1@20 Ton and 1@25 ton) will be located outside at grade. • liquid and refrigerant suction piping based on manufacturer’s recommendations from Condensing units to AHU’s • Two (2) 250 MBH code-efficient boilers • Heating Hot water pumps (primary/standby with VFD’s), piping, associated insulation, valving, and accessories. • Central station air handling units systems consisting of: o One (1) Roof mounted packaged DX (direct expansion)/hot water air handling/energy recovery/economizer unit at 9,000 CFM to serve the Addition Renovation building office areas o One (1) Roof mounted packaged DX (direct expansion)/hot water air handling/energy recovery/economizer unit at 3,500 CFM to serve the Main meeting room of the Addition Renovation building o One (1) Indoor split DX (direct expansion)/hot water air handling/energy recovery/economizer unit at 4,000 CFM to serve the Existing Town Hall building office areas o One (1) Indoor split DX (direct expansion)/hot water/energy recovery/economizer air handling unit at 5,000 CFM to serve the Auditorium of the Existing Town Hall building o Associated supply, return/exhaust ductwork, insulation, dampers, and air distribution devices. • Louvers for indoor AHU’s and EF’s • VAV boxes with hot water reheat coils will zone each room or group of rooms based on exposure and usage • Requires about 18”* of ceiling plenum space for ductwork and other mechanical equipment.

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HVAC Option #1: Boiler/ w/ Hot//Energy Recovery Air Handling Units, Full Economizer, 4-Pipe Induction/ Coil Unit System The Existing Town Hall and Addition Renovation will be served by two (2) 500 MBH condensing boilers and a single 40 ton chiller. Each boiler will have a variable speed in-line pump feeding an insulated hot water supply and return piping system. The chiller will have a variable speed in-line pump feeding an insulated chilled water supply and return piping system. The piping from both the chilled water system and hot water system will be distributed to central station air handling units. Each AHU must have a full sized outside air duct connected to a large louver for the code required economizer cycle with a second similar duct and louver for relief air. Throughout the New Addition Renovation, Induction Units with hot/chilled water coils and ducted supply ventilation air will be used to zone individual rooms and groups of rooms to provide better temperature control. Throughout the Existing Town Hall, Fan Coil Units with a dual temperature water coil will be used to zone individual rooms and groups of rooms to provide better temperature control. Supply and return air ductwork will run to each room or zone to provide code required ventilation. Return air ductwork will run from each room or zone back to the four air handling units.

HVAC Option#1 System Summary: • Requires a dedicated mechanical room with access to the exterior for large louvers for indoor AHU’s serving the Existing Town Hall • Requires a mechanical room for boilers, expansion tanks, pumps, buffer tanks, air separators and glycol feed tank(s). • A single 40 ton chiller will be located outside at grade • Cooling System Chilled water pumps (primary/standby with VFD’s), piping, associated insulation, valving, and accessories. • Two (2) 500 MBH condensing boilers • Heating Hot water pumps (primary/standby with VFD’s), piping, associated insulation, valving, and accessories. • Central station air handling units consisting of: o One (1) Roof mounted packaged DX (direct expansion)/hot water air handling/energy recovery/economizer unit at 2,800 CFM to serve the Addition Renovation building office areas o One (1) Roof mounted packaged DX (direct expansion)/hot water air handling/energy recovery/economizer unit at 1,500 CFM to serve the Main meeting room of the Addition Renovation building o One (1) Indoor split DX (direct expansion)/hot water air handling/energy recovery/economizer unit at 1,500 CFM to serve the Existing Town Hall building office areas o One (1) Indoor split DX (direct expansion)/hot water/energy recovery/economizer air handling unit at 3,500 CFM to serve the Auditorium of the Existing Town Hall building o Associated supply, return/exhaust ductwork, insulation, dampers, and air distribution devices. • Louvers for indoor AHU’s and EF’s • Induction Units will zone each office/room or group of rooms based on exposure and usage • Induction Unit system requires about 24” of ceiling plenum space for ductwork and other mechanical equipment • Fan coils will zone each room or group of rooms based on exposure and usage • Requires about 18”* of ceiling plenum space for ductwork and other mechanical equipment. *This assumes fan coil units shall be wall mounted or floor mounted console style units. Horizontal ceiling suspended fan coil units would require approx. 24 in. ceiling cavity space.

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• Small boiler/pump room on ground floor • Mechanical rooms on ground floor.

HVAC Option #2: Boiler w/ Hot Water/DX/Energy Recovery Air Handling Units, Full Economizer, VRF System (Proposed Schematic Design System) The Existing Town Hall and Addition Renovation will be served by (2) two 250 MBH condensing boilers. Each boiler will have a variable speed in-line pump feeding an insulated hot water supply and return piping system. The piping from the hot water system will be distributed to central station air handling units. Each AHU must have a full sized outside air duct connected to a large louver for the code required economizer cycle with a second similar duct and louver for relief air. Each of the AHUs shall have a dedicated split system condensing unit for cooling. Variable refrigerant flow (VRF) ductless cooling units (DCUs) with refrigerant piping and condensate piping will run throughout the building and connect to an outdoor 30 ton VRF air cooled unit. Supply and return air ductwork will run to each room or zone to provide code required ventilation.

HVAC Option #2 System Summary: • Requires a dedicated mechanical room with access to the exterior for large louvers for indoor AHU’s serving the Existing Town Hall • Requires a mechanical room for boilers, expansion tank, pumps, air separator and glycol feed tank(s). • Two (2) Condensing units ([email protected] Ton and [email protected] tons) will be located outside at grade. • One (1) 30 ton (2 – 15 Ton Modules) condenser/VRF unit will be located outside at grade. • Refrigerant liquid and refrigerant suction piping based on manufacturer’s recommendations from VRF unit to DCUs • Two (2) 250 MBH condensing boilers • Heating Hot water pumps (primary/standby with VFD’s), piping, associated insulation, valving and accessories. • Central station air handling units consisting of: o One (1) Roof mounted packaged DX (direct expansion)/hot water air handling/energy recovery/economizer unit at 2,800 CFM to serve the Addition Renovation building office areas o One (1) Roof mounted packaged DX (direct expansion)/hot water air handling/energy recovery/economizer unit at 1,500 CFM to serve the Main meeting room of the Addition Renovation building o One (1) Indoor split DX (direct expansion)/hot water air handling/energy recovery/economizer unit at 1,500 CFM to serve the Existing Town Hall building office areas o One (1) Indoor split DX (direct expansion)/hot water/energy recovery/economizer air handling unit at 3,500 CFM to serve the Auditorium of the Existing Town Hall building o Associated supply, return/exhaust ductwork, insulation, dampers, and air distribution devices. • Louvers for indoor AHU’s and EF’s • DCU’s will zone each room or group of rooms based on exposure and usage • Requires about 18”* of ceiling plenum space for ductwork and other mechanical equipment. *This assumes VRF terminal units shall be wall mounted style units. Horizontal ceiling suspended VRF terminal units would require approx. 24 in. ceiling cavity space.

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HVAC Option #3: Geothermal System

• A high efficiency geothermal system could be paired with any of the three options listed above. • The geothermal system would eliminate the requirement for Chiller and Condensing equipment described in the option above, and central indoor heat pump equipment would be provided. • The geothermal system would require a well filed piping and pump distribution system to support the HVAC system cooling and heating plant requirements. • Geothermal systems could be Open Vertical Standing Colum Wall or Closed Loop design. Closed loops typically require a larger quantity of wells but the wells have a reduced depth and have smaller diameter piping. Open loop well quantity estimated @ sixteen (16) wells @ 500 ft deep each. Closed loop well quantity estimated at three (3) wells at depth of approx. 1300 ft deep each • Geothermal condensing water supply and return piping, pumps, valving and accessories are required.

Refer to Pros/Cons list for all HVAC design options.

Building Management System:

A new building energy management system (EMS) shall be installed for all HVAC system options. The EMS shall be an open protocol BACNet compatible building energy management system. The building EMS shall control building HVAC systems and shall store the information in a web- accessible database. The EMS will be capable to automatically distribute alarms and building information to support problem identification, maintenance and continued achievement of performance goals over the life of the systems. Typical components which the project shall require alarms, and monitoring include: would be Boilers, Air Handlers, , split system AC units, etc.

Miscellaneous HVAC Systems: 1. In-line or roof exhaust fans shall be provided to serve the areas of the building that require separate dedicated exhaust systems utilizing exhaust air fans, ductwork and associated controls, i.e. Janitors Closets, Utility Rooms, etc. 2. All exterior stairways, entrances, and vestibules will be provided with hot water cabinet unit heaters. 3. Ancillary spaces will be heated by fin tube radiation, radiant heating panels, and/or convectors. 4. All corridors will be ventilated by the HVAC system that serves the adjacent area in which the corridor is located. Ventilation will be provided to ensure sufficient outdoor ventilation and make-up air is provided to offset the building exhaust air to maintain proper building pressurization. 5. Unit heaters will be provided to serve Mechanical and Utility Room areas. 6. Ductless high efficiency split system AC units shall be provided for the IT Server and Elevator Machine Room.

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5. DEMOLITION

All existing building HVAC systems shall be demolished, removed from the site and disposed of in a legal manner by the Contractor. Demolition activities shall be performed in a Phased manner as direct by the Project Architect.

6. TESTING REQUIREMENTS

The mechanical contractor shall provide testing of the following systems with the Owner and Owner’s representative present: • Boiler plant system • Air handling unit systems including all rooftop units, indoor air handling systems and exhaust air systems • Terminal heating and cooling devices • Automatic temperature control and building energy management system

Testing reports shall be submitted to the engineer for review and approval before providing to the Owner.

7. OPERATION AND MAINTENANCE MANUALS AND OWNER TRAINING:

When the project is completed, the Mechanical Contractor shall provide operation and maintenance manuals to the Owner.

Operator training and users’ project documents are required for O&M staff to properly maintain the facility. These documents include the O&M Manual, As-built Drawings, and a Systems Manual (System Manual shall be developed by the CxA).

Outside service providers and qualified, licensed and trained town staff will provide preventative maintenance and necessary repairs. Maintenance supervision and some actions will be performed by town staff, and require detailed training on the HVAC systems. Training will include the education of multiple members of staff, as chosen by the owner, in the proper use of the monitoring system.

The project mechanical specifications will outline this requirement and will require the video recording of M/E/P systems training sessions.

Basic level of maintenance typically includes changing of filters and visual inspection of equipment. Advanced level of maintenance typically includes seasonal changing between heating and cooling systems, visual inspection of the equipment, checking refrigerant levels in the chiller, and cleaning the boiler etc. The above is a sample of typical maintenance items. The end user shall decide what will be done in house and what will be contacted out. The end user should also review all maintenance contracts to verify the bill of goods.

8. RECORD DRAWINGS AND CONTROL DOCUMENTS:

When the project is completed, an as-built set of drawings, showing all mechanical system requirements from contract and addendum items, will be provided to the Owner.

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9. COMMISSIONING

The project’s HVAC systems shall be fully commissioned in accordance with project Commissioning specifications.

10. ENERGY EFFICIENCY GOALS:

The project design shall meet and exceed the following minimum requirements: 1) LEED v4 - Minimum Efficiency Guidelines 2) MA 780CMR 8th Edition Ch.13 Energy Efficiency 1301.1.1 IECC 2015. 3) ASHRAE Standard 90.1-2013.

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COHASSETT TOWNHALL RENOVATION/ADDITION HVAC SYSTEM OPTION COMPARISON

BASELINE PROS CONS • Lower piping installed costs due to two-pipe • Larger Size Ductwork would require system as chilled water piping is not required Architectural soffits, and reduced ceiling • Moderate to high overall installed costs heights. • Chiller plant and distribution systems not • Moderate noise levels required • Terminal units located in occupied space • Very low maintenance; no condensate • Higher automatic temperature controls drains, fans, or filters at terminal units installed costs on a per unit basis due to • Condensing equipment is centralized to amount of control devices required rooftop units only • Reduced temperature control if several • Reduced automatic temperature controls rooms or offices are served by the same VAV installed costs resulting from reduced control unit VAV RTU/AHU components • Reduced indoor air quality as a result of SYSTEM W/ HW • Heating and cooling are simultaneously being a mixed-air system REHEAT COILS available resulting in improved year-round • Maintenance of equipment is in occupied heating and cooling area • Higher energy consumption due to increased fan energy • Higher energy consumption as summertime use of hot water system is required for hot water reheats of VAV boxes • Overall ductwork costs are greater due to the larger supply and return ductwork systems providing mixed-air rather than ventilation only

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OPTION 1 PROS CONS • Superior thermal comfort conditions. • Higher first cost. • Superior thermal comfort control as individual • Moderate automatic temperature controls unit with associated controls will be provided cost. for each zone. • Condensate drain maintenance (for AC). • Low maintenance costs. Primary • Maintenance of equipment is in occupied ACTIVE maintenance done at air handling unit. area. / • Fewer systems for heating/cooling • Distribution ductwork system is required INDUCTION • Relatively quiet: No fans within space. resulting in additional architectural features UNITS (e.g. ceiling space, soffits, etc.). • Chilled water pumps and associated VFD’s required increase capital investment, maintenance, and operating costs.

• Superior thermal comfort conditions. • Moderate first cost. • Superior thermal comfort control as individual • High maintenance costs for quantity of units unit with associated controls will be provided and factory authorized service is required for for each zone. VRW system. • All new equipment results in increased • Higher noise levels than induction due to fan system life expectancy. motor located within occupied zone. • Does not require distribution ductwork • High automatic temperature controls cost. system. • Quarterly filter changes per unit. • Refrigerant is self-contained in outdoor • Condensate drain maintenance (for AC). FAN COIL equipment. • Maintenance of equipment is in occupied UNITS • Lower ceiling plenum height required than area. induction units. • Wall mounted do not provide direct ventilation to the space. Space humidity monitoring is critical to avoid condensation at the units (natural ventilation). • Chilled water pumps and associated VFD’s required increase capital investment, maintenance, and operating costs.

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OPTION 2 PROS CONS

• Superior thermal comfort conditions. • Moderate first cost. • Superior thermal comfort control as individual • High operating costs due to air conditioning, unit with associated controls will be provided ventilation fans, and electric heat (VRF for each zone. units). • All new equipment results in increased • High maintenance costs for quantity of units system life expectancy. and factory authorized service is required for • Distribution ductwork system only required VRF system. for ventilation. • Highest noise levels of 3 options due to • Lower ceiling plenum height required than and fan motor located within induction units. occupied zone. • High automatic temperature controls cost. • Quarterly filter changes per unit. VARIABLE • Condensate drain maintenance (for AC). REFRIGERANT • Maintenance of equipment is in occupied FLOW (VRF) AIR area. CONDITIONING • Wall mounted evaporators do not provide direct ventilation to the space. Space humidity monitoring is critical to avoid condensation at the evaporator units (particularly when used with natural ventilation). • Refrigerant piping is located inside building with potential of leaks. ASHRAE 15 provisions must be met. • Manufacturer provided equipment controls to integrate to the Building Management System (BMS).

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OPTION 3 PROS CONS • Geothermal systems could be designed to • Highest First Cost - Geothermal systems serve as the heating and cooling plants for have a higher first installed cost, Option 1,2 and/or 3 listed above. primarily due to well field drilling, • Geothermal systems have very high excavation and piping costs. operating efficiencies and lower operational • Geothermal systems require some additional costs. maintenance and system monitoring. • Geothermal system reduces carbon footprint Open loop type wells typically have of building. higher maintenance costs than closed • Extended system service life, due to lack of loop systems. GEOTHERMAL outdoor chiller/condensing equipment. • Potentially higher electricity costs due to SYSTEM • Greatly reduced outdoor sound levels from heating via electricity in winter. However, a HVAC equipment, due to elimination of large supplemental high efficiency hot water boiler chiller/condensing unit(s) plant can be integrated into the system design for redundancy and flexible fuel pricing. • Higher automatic temperature controls cost. • Refrigerant piping is located inside building with potential of leaks. ASHRAE 15 provisions must be met. • Requires sufficient site for wells