UFC 3-410-01

28 July 2025

UNIFIED FACILITIES CRITERIA (UFC)

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

HEATING, VENTILATING, AND AIR

CONDITIONING SYSTEMS

This Page Intentionally Left Blank

UNIFIED FACILITIES CRITERIA (UFC)

HEATING, VENTILATING, AND AIR CONDITIONING SYSTEMS

Any copyrighted material included in this UFC is identified at its point of use.

Use of the copyrighted material apart from this UFC must have the permission of the copyright holder.

Indicate the Military Department Preparing Activity responsible for the document.

U.S. ARMY CORPS OF ENGINEERS

NAVAL FACILITIES ENGINEERING SYSTEMS COMMAND (Preparing Activity)

AIR FORCE CIVIL ENGINEER CENTER

Record of Changes (changes are indicated by \1\ ... /1/)

Change No. Date Location

This UFC supersedes UFC 3-410-01, dated 01 July 2013.

FOREWORD

The Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides planning, design, construction, sustainment, restoration, and modernization criteria, and applies to the Military Departments, the Defense Agencies, and the DoD Field Activities in accordance with USD (AT&L) Memorandum dated 29 May 2002. UFC will be used for all DoD projects and work for other customers where appropriate. All construction outside of the United States, its territories, and possessions is also governed by Status of Forces Agreements (SOFA), Host Nation Funded Construction Agreements (HNFA), and in some instances, Bilateral Infrastructure Agreements (BIA). Therefore, the acquisition team must ensure compliance with the most stringent of the UFC, the SOFA, the HNFA, and the BIA, as applicable.

UFC are living documents and will be periodically reviewed, updated, and made available to users as part of the Military Department’s responsibility for providing technical criteria for military construction. Headquarters, U.S. Army Corps of Engineers (HQUSACE), Naval Facilities Engineering Systems Command (NAVFAC), and Air Force Civil Engineer Center (AFCEC) are responsible for administration of the UFC system. Technical content of UFC is the responsibility of the cognizant DoD working group. Defense Agencies should contact the respective DoD Working Group for document interpretation and improvements. Recommended changes with supporting rationale may be sent to the respective DoD working group by submitting a Criteria Change Request (CCR) via the Internet site listed below.

UFC are effective upon issuance and are distributed only in electronic media from the following source:

• Whole Building Design Guide website https://www.wbdg.org/dod.

Refer to UFC 1-200-01, DoD Building Code, for implementation of new issuances on projects.

AUTHORIZED BY:

THOMAS P. SMITH, P.E., SES

Chief, Engineering and Construction U.S. Army Corps of Engineers

S. KEITH HAMILTON, P.E., SES

Chief Engineer and Assistant Commander Planning, Design and Construction Naval Facilities Engineering Systems Command

THOMAS P. BROWN, SES

Deputy Director of Civil Engineers DCS/Logistics, Engineering & Force Protection (HAF/A4C) HQ United States Air Force

MARK S. SINDER, SES

Deputy Assistant Secretary of Defense (Infrastructure Modernization and Resilience) Office of the Secretary of Defense http://www.wbdg.org/pdfs/ufc_implementation.pdf https://www.wbdg.org/dod i

TABLE OF CONTENTS

CHAPTER 1 INTRODUCTION

1-1 REISSUES AND CANCELS

1-2 PURPOSE AND SCOPE

1-3 APPLICABILITY

1-4 COMMENTARY

1-5 GENERAL BUILDING REQUIREMENTS

1-6 MECHANICAL CONSENSUS STANDARD

1-7 ENVIRONMENTAL SEVERITY AND HUMID LOCATIONS

1-8 CYBERSECURITY

1-9 UNIFIED FACILITIES SUPPLEMENT (UFS) 3-410-01

CHAPTER 2 GENERAL DESIGN REQUIREMENTS

2-1 HVAC SYSTEM SELECTION

2-2 DESIGN DOCUMENTATION REQUIREMENTS

2-3 [FOR NAVY PROJECTS ONLY] DEDICATED OUTDOOR AIR

SYSTEMS (DOAS)

2-3.1 DOAS Associated with Light-Duty Equipment

2-3.2 DOAS Associated with Medium-Duty Equipment

2-3.3 DOAS Associated with Light-Duty or Medium-Duty Equipment

2-3.4 Additional Requirements

2-4 [FOR AIR FORCE PROJECTS ONLY] DOAS

2-4.1 DOAS Requirements

2-4.2 General Ventilation Requirements

2-5 [FOR ARMY PROJECTS ONLY] DOAS

2-5.1 DOAS and Energy Optimization

2-5.2 DOAS and Zone Sensible Cooling Systems

2-5.3 DOAS and Intermittently Occupied Facilities

2-6.1 Load Calculations

2-6.2 Outdoor Design Conditions

2-6.3 Indoor Design Conditions

2-7 SPECIFIC FACILITY OR SPACE TYPE HVAC REQUIREMENTS

2-7.1 Facility Air Conditioning Eligibility ii

2-7.2 Natural or Mechanical Ventilation Requirements

2-7.3 Intermittent Occupancy

2-7.4 Vestibules

2-7.5 Closets, Storage, and Utility Rooms in Air-Conditioned Facilities

2-7.6 Data Processing Centers and Server Rooms

2-7.7 Laboratories

2-7.8 Aircraft Maintenance Shops

2-7.9 Aircraft Fire and Rescue and Fire Station

2-7.10 Laundries and Dry Cleaners

2-7.11 Commercial Kitchen Ventilation

2-7.12 Vehicle Maintenance Facility Ventilation

2-7.13 Mechanical Rooms

2-8 ECONOMIZER

2-9 VARIABLE SPEED DRIVES

2-9.1 Design

2-9.2 Balancing

2-10 HUMIDIFICATION

2-11 STEAM SYSTEMS

2-12 FAN COIL APPLICATIONS FOR VENTILATION AIR

2-13 GROUND-SOURCE HEAT PUMPS

2-13.1 Sizing

2-13.2 Regulatory Requirements

2-13.3 Borehole Grouting

2-13.4 Piping

2-13.5 Ground Loop Circulating Pumps

2-13.6 Make-up Water

2-13.7 Freeze Protection

2-13.8 Extended Range Equipment

2-14 VARIABLE AIR VOLUME (VAV) COOLING

2-14.1 VAV System Sizing

2-14.2 VAV Direct Expansion System

2-14.3 VAV System Controls iii

2-14.4 VAV System Duct Design

2-14.5 Fan-Powered VAV Terminal Noise

2-14.6 VAV Terminal Maintenance Accommodations

2-15 VARIABLE REFRIGERANT FLOW (VRF) SYSTEMS

2-15.1 VRF System Controls Requirements

2-15.2 VRF System Refrigerants

2-15.3 VRF System Competition

2-15.4 VRF System Piping

2-15.5 VRF System Life-Cycle Costs

2-16 REDUNDANT SYSTEMS

2-17 CORROSION

2-18 EXTERIOR EQUIPMENT

2-19 SOUND AND VIBRATION CONTROL

2-19.1 Sound and Vibration Design and Construction

2-19.2 Sound Testing

2-20 DUCTWORK AIR LEAKAGE TESTING (DALT)

2-21 HVAC SYSTEM TESTING, ADJUSTING, AND BALANCING (TAB)

2-21.1 Balancing Valves

2-21.2 Flow Balancing Valves

2-21.3 Flow Limiting Valves

2-21.4 Balancing Dampers

2-22 COMMISSIONING REQUIREMENTS

CHAPTER 3 IMC MODIFICATIONS

3-1 GENERAL SUBSTITUTIONS

3-2 IMC MODIFICATION PARAGRAPHS

3-2.1 IMC CHAPTER 1 SCOPE AND ADMINISTRATION [Deletion]

3-2.2 IMC CHAPTER 2 DEFINITIONS

3-2.3 IMC CHAPTER 3 GENERAL REGULATIONS

3-2.4 IMC CHAPTER 4 VENTILATION

3-2.5 IMC CHAPTER 5 EXHAUST SYSTEMS

3-2.6 IMC CHAPTER 6 DUCT SYSTEMS

3-2.7 IMC CHAPTER 8 CHIMNEYS & VENTS

iv

3-2.8 IMC CHAPTER 9 SPECIFIC APPLIANCES, FIREPLACES AND SOLID

FUEL-BURNING EQUIPMENT

3-2.9 IMC CHAPTER 10 BOILERS, WATER HEATERS AND PRESSURE

VESSELS

3-2.10 IMC CHAPTER 11 REFRIGERATION

3-2.11 IMC CHAPTER 12 HYDRONIC PIPING

3-2.12 IMC CHAPTER 13 FUEL OIL PIPING AND STORAGE

3-2.13 IMC CHAPTER 14 SOLAR THERMAL SYSTEMS

TABLES

Table 3-1 DDC Minimum Points List

CHAPTER 1 INTRODUCTION

1-1 REISSUES AND CANCELS.

This UFC reissues and cancels UFC 3-410-01, Heating, Ventilating, and Air Conditioning Systems, 01 July 2013, and all subsequent changes.

1-2 PURPOSE AND SCOPE.

This UFC provides requirements and guidance in the design of heating, ventilating, and air-conditioning (HVAC) systems, together with the criteria for selecting HVAC materials and equipment.

1-3 APPLICABILITY.

This UFC follows the same applicability as UFC 1-200-01, paragraph 1-3, with no exceptions.

Additions, alterations, renovations, or repairs, except for one-for-one equipment replacements, to a HVAC system must conform to that required for a new HVAC system without requiring the entire existing HVAC system to comply with all the requirements of this UFC. One-for-one equipment replacements must meet the product requirements in paragraph Energy Efficient Products and the equipment efficiency requirements in the currently adopted version of ASHRAE 90.1 or International Energy Conservation Code (IECC), whichever is applicable, referenced in paragraph Energy Standards in UFC 1- 200-02. Do not execute additions, alterations, or repairs that cause an existing HVAC system to become unsafe, hazardous, or overloaded or result in new maintenance or control deficiencies in the existing systems.

1-4 COMMENTARY.

Limited commentary has been added to the chapters. Commentary is designated by a [C] and the commentary narrative is shaded.

1-5 GENERAL BUILDING REQUIREMENTS.

Comply with UFC 1-200-01. UFC 1-200-01 provides applicability of model building codes and government unique criteria for typical design disciplines and building systems, as well as for accessibility, antiterrorism, physical security, cybersecurity, high performance and sustainability requirements, and safety. Use this UFC in addition to UFC 1-200-01 and the UFCs and government criteria referenced therein.

1-6 MECHANICAL CONSENSUS STANDARD

Use the International Mechanical Code (IMC), including all published errata, as the DoD code for Heating, Ventilating, and Air-Conditioning, except as modified by this UFC, other UFC, and FC. When interpreting the IMC, the advisory provisions must be considered mandatory. Interpret the word “should” and “shall” as “must.”

1-7 ENVIRONMENTAL SEVERITY AND HUMID LOCATIONS.

In corrosive and humid environments, provide design detailing, and use materials, systems, components, and coatings that are durable and minimize the need for preventative and corrective maintenance over the expected service life of the component or system. UFC 1-200-01, section titled “Corrosion Prone Locations” identifies corrosive environments and humid locations requiring special attention. UFC 1-200-01, section titled “Requirements for Corrosion Prone Locations” provides examples of necessary actions. To determine Environmental Severity Classifications (ESC) for specific project locations refer to UFC 1-200-01 Appendix titled “ESC for DoD Locations”.

1-8 CYBERSECURITY.

All facility-related control systems (including systems separate from a utility monitoring and control system) must be planned, designed, acquired, executed, and maintained in accordance with UFC 4-010-06, and as required by individual Service Implementation Policy.

1-9 UNIFIED FACILITIES SUPPLEMENT (UFS) 3-410-01.

UFS 3-410-01 contains information that are not requirements but include background information and best practices based on experience and lessons learned. UFS 3-410- 01 also includes design documentation requirements, weather data access instructions, and Army policy information regarding district and islanded energy plants.

https://www.wbdg.org/FFC/DOD/UFC/ufs_3_410_01_2025.pdf

CHAPTER 2 GENERAL DESIGN REQUIREMENTS

2-1 HVAC SYSTEM SELECTION.

Comply with UFC 1-200-02 which provides requirements that influence the selection and design of heating, cooling, and ventilation systems and major system components.

For Army projects, comply with Evaluation of District and Islanded/Decentralized Utility Options with Life-Cycle Cost Analysis Guidance in UFS 3-410-01 to determine which alternative is most life cycle cost effective.

2-2 DESIGN DOCUMENTATION REQUIREMENTS.

Comply with the design analysis and drawing requirements in the UFS 3-410-01.

2-3 [FOR NAVY PROJECTS ONLY] DEDICATED OUTDOOR AIR

SYSTEMS (DOAS).

These requirements apply to Navy projects only. Final determination of equipment’s dehumidification capabilities is subject to approval by the Navy based on submitted equipment selections, control sequences, and psychrometrics. A Dedicated Outdoor Air System (DOAS) is the only allowed method for providing dehumidification of ventilation air (outdoor air) when HVAC systems are either light-duty or medium-duty.

• Light-duty systems include equipment which have limited dehumidification capabilities and that are not capable of continuously dehumidifying ventilation air at all full or part-load conditions. These include such equipment as zone-level or residential-grade heat pumps, packaged terminal air conditioners, mini-split systems, and fan coil units (whether using direct-expansion or chilled water).

• Medium-duty systems include equipment (such as centralized or single-zone air handling units) that use direct-expansion cooling with cycling refrigeration circuit(s) not manufactured or controlled for continuous dehumidification.

Exception: A DOAS is not required when the sum of all ventilation air into the facility is less than 750 cfm (354 lps) or when the 1% occurrence humidity ratio (as documented in the official engineering weather data or EWD) is below the humidity ratio at the indoor design condition for comfort cooling.

2-3.1 DOAS Associated with Light-Duty Equipment.

DOAS’s associated with light-duty equipment must be selected, designed, and controlled as follows:

• Cooling coil must be selected to meet outdoor air sensible and latent loads plus space latent load.

• Cooling coil must be selected and controlled to maintain a continuous coil leaving air dewpoint temperature no greater than 55.0 °F for applications requiring space conditions of 78.0° F (25.6 °C) dry-bulb / 57.9° F (14.4 °C) dewpoint / 50-percent relative humidity.

• Cooling coil must be selected and controlled to maintain a continuous coil leaving air dewpoint temperature suitable for applications requiring space conditions more stringent than 78.0° F (25.6 °C) dry-bulb / 57.9° F (14.4 °C) dewpoint / 50-percent relative humidity.

• Reheat coil must be sized to achieve unit discharge air temperature equivalent to the facility design temperatures for comfort cooling and comfort heating. The reheat coil must be controlled to support maintaining required space thermal comfort conditions while not using excessive energy. The unit discharge air humidity must be less than 90-percent to help prevent ductwork microbial growth.

• DOAS must not be subject to intermediate season (no-heat / no-cool) shutdown.

• DOAS must distribute airflow directly to zones without passing through light-duty equipment.

• DOAS air inlets and outlets must deliver airflow quantities equal to or greater than 20 cfm (10 lps) through each device to allow for proper system balancing.

[C] The DOAS is required to handle space latent loads in addition to sensible and latent loads in the ventilation air. The coil leaving air condition should be lower than the maximum indicated when necessary to address space latent loads. The coil leaving air condition must be calculated for the specific application to meet this requirement. The leaving air dewpoint temperature can be controlled based on dry-bulb temperature (at full saturation) or based on calculated dewpoint as preferred by the stakeholder or as necessary to achieve energy efficiency requirements.

No particular control strategy is mandated to meet the conditions given in this paragraph. For example, the requirement for the reheat coil to keep unit discharge conditions below 90% relative humidity could be met by using a discharge air temperature that is at a fixed offset (example: as 3 °F) from the coil leaving air temperature (resulting in less than 90% relative humidity) or it could be achieved using relative humidity sensors. Alternatively, fan heat may be sufficient to keep relative humidity below 90%. The strategy will depend on the DOAS configuration, available sensors, owner preferences, and other factors

2-3.2 DOAS Associated with Medium-Duty Equipment.

DOAS’s associated with medium-duty equipment must be selected, designed, and controlled as follows:

• Cooling coil must be selected to meet outdoor air sensible and latent loads, but not space loads.

• Cooling coil must be selected and controlled to maintain a continuous coil leaving air temperature no greater than 58.0 °F for applications requiring space conditions of 78.0° F (25.6 °C) dry-bulb / 57.9° F (14.4 °C) dewpoint / 50-percent relative humidity.

• Cooling coil must be selected and controlled to maintain a continuous coil leaving air temperature suitable for applications requiring space conditions more stringent than 78.0° F (25.6 °C) dry-bulb / 57.9° F (14.4 °C) dewpoint / 50-percent relative humidity.

• Reheat coil must be designed and controlled to maintain unit discharge air temperature to keep supply duct relative humidity less than 90-percent to help prevent ductwork microbial growth.

• DOAS must distribute airflow directly into inlet of associated equipment and must not distribute airflow directly into zones.

2-3.3 DOAS Associated with Light-Duty or Medium-Duty Equipment.

DOAS’s associated with light-duty or medium-duty equipment, in addition to other requirements, must be selected, designed, and controlled as follows:

• DOAS must be provided with energy recovery devices, if required for compliance with ASHRAE Standard 90.1

• Energy recovery devices must be controlled to maximize energy recovery through all seasons and never increase energy use of the DOAS cooling or heating coils.

• DOAS must be designed and controlled to be in operation during all occupied periods.

• Ventilation air does not require humidification regardless of how it is provided into facility.

• System controls must monitor the DOAS cooling coil leaving air temperature and unit discharge air temperature regardless of which point is used for control.

• A visual alarm must be initiated upon detection of cooling coil leaving air temperature being equal to or greater than 5° F (3 °C) above setpoint temperature at the Operator workstation (OWS) or at DOAS for construction without an OWS.

2-3.4 Additional Requirements.

Additional requirements are as follows:

• Zone terminal heating / cooling equipment must have occupant control and may be subject to intermediate season heating / cooling curtailment as directed by installation or command policy.

2-4 [FOR AIR FORCE PROJECTS ONLY] DOAS.

A Dedicated Outdoor Air System (DOAS) is the only allowed method for providing dehumidification of ventilation air (outdoor air) when replacing an existing DOAS delivering any quantity of ventilation air or when the sum of all ventilation air into facility is greater than 750 cfm (354 lps) and the 1% occurrence humidity ratio is above the humidity ratio at the indoor design condition for comfort cooling. The requirement for DOAS applies only to ventilation of non-industrial, occupied spaces that are heated or cooled for comfort.

2-4.1 DOAS Requirements.

Systems must be selected, designed, and controlled as follows:

• Cooling coil must be selected to meet outdoor air sensible and latent loads plus space latent load.

• Cooling coil must be selected and controlled to maintain a continuous coil leaving air temperature no greater than 55.0 °F (12.8 °C).

• Reheat coil must be selected and controlled to maintain required space thermal comfort conditions while not using excessive energy. The unit discharge air temperature must be maintained to keep the ventilation air relative humidity less than 90-percent to help prevent ductwork microbial growth.

• DOAS must not be subject to intermediate season (no-heat / no-cool) shutdown.

• DOAS must distribute airflow directly to zones through an independent and dedicated duct system.

• DOAS air inlets and outlets must deliver airflow quantities equal to or greater than 20 cfm (10 lps) through each device to allow for proper system balancing.

• DOAS must be provided with energy recovery devices in accordance with ASHRAE Standard 90.1.

• DOAS must be designed and controlled to be in operation during all occupied periods.

• Ventilation air does not require humidification regardless of how it is provided into facility.

• System controls must monitor the DOAS cooling coil leaving air temperature and unit discharge air temperature regardless of which point is used for control.

• A visual alarm must be initiated upon detection of cooling coil leaving air temperature being equal to or greater than 5° F (3 °C) above setpoint temperature at the Operator workstation (OWS) or at DOAS for construction without an OWS.

2-4.2 General Ventilation Requirements.

If a DOAS is not required, ventilation air may be brought in through the primary HVAC system only if the system is configured to continuously supply ventilation air.

2-5 [FOR ARMY PROJECTS ONLY] DOAS.

When the 1% occurrence humidity ratio for the outdoor air is greater than the humidity ratio at the indoor design condition for comfort cooling, dehumidification of outdoor air is necessary. When dehumidification of outdoor air is necessary and the total ventilation air for the building is 1000 CFM (470 lps) or greater, the use of a Dedicated Outdoor Air System (DOAS) must be included as required in the following paragraphs.

When used, the DOAS must include the following:

• Cooling coil(s) must be selected to meet outdoor air sensible and latent loads.

• Include an alarm with the HVAC controls that indicates if the outdoor air damper failed to open during occupied period.

• Condensation in the space or zone due to DOAS supply air temperatures must be avoided.

• Provide energy recovery devices where life-cycle cost-effective or where required by ASHRAE Standard 90.1.

2-5.1 DOAS and Energy Optimization.

DOAS must be included in at least one of the alternatives in the energy optimization and life-cycle cost analysis required in UFC 1-200-02.

[C] The need to condition large volumes of humid air to design set points and the associated reheat can result in a DOAS being an effective and life cycle cost effective energy conservation measure, particularly when using refrigerant hot gas reheat.

Consider the following when completing life cycle cost analyses for HVAC system selection:

• The additional outdoor air required per ASHRAE Standard 62.1 for VAV air handling systems that condition ventilation air (multiple-zone recirculating systems).

• Fan coil unit maintenance considering the available capacity of maintenance staff.

• Cost savings from the energy savings of fan coil unit or VAV (recirculated air) cycling.

• The HVAC system application. (Example: fan coil units may not be practical for a large open-space layouts or appropriate for the mission).

• Any difference in air-side economizer ability or control and associated energy cost savings.

2-5.2 DOAS and Zone Sensible Cooling Systems.

Zone sensible cooling systems include equipment which have limited dehumidification capabilities and that are not capable of continuously dehumidifying ventilation air at all full and part-load conditions. Examples include fan coil units, chilled beams, or zone-level heat pumps.

Regardless of life-cycle cost, when zone sensible cooling systems are used, DOAS must be used to dehumidify all outdoor air for conditioned spaces. The DOAS must separate the ventilation function from the space air conditioning function. The DOAS cooling coil must be sized using the 1.0 % occurrence humidity ratio and the corresponding mean coincident dry-bulb (MCDB) for the outdoor air conditions. Coil capacity must meet peak conditions.

2-5.3 DOAS and Intermittently Occupied Facilities.

Coordinate with the real property owner to determine if a DOAS is necessary for buildings that will be unoccupied for extended periods of time to avoid mold growth or moisture damage.

2-6 HEATING AND COOLING LOAD CALCULATIONS.

Heating and cooling system design loads for the purpose of sizing systems, appliances and equipment must be determined in accordance with the following requirements.

Perform a psychrometric analysis documenting that the system meets design criteria.

The analysis must provide calculations of system cooling load, energy/mass transfer through conditioning equipment and fans, and a system schematic indicating state point dry-bulb and wet-bulb temperatures (or humidity ratios) of outdoor air, mixed air, supply air, and return airflow streams. The system must provide the capability to condition ventilation air and maintain space relative humidity over the full range of cooling load.

2-6.1 Load Calculations.

Heating and cooling system design loads must be determined in accordance with the calculation procedures described in the ASHRAE Standard 183 unless otherwise specified herein.

Provide no more than a 1.15 safety factor for heating equipment and distribution sizing to account for morning warm-up.

2-6.2 Outdoor Design Conditions.

Use engineering weather data from the 14th Weather Squadron website (https://climate.af.mil/) for outdoor design conditions for Navy and Air Force projects.

For Army projects, use ASHRAE Fundamentals Handbook or 14th Weather Squadron engineering weather data. Refer to the UFS 3-410-01 for access instructions.

2-6.2.1 Spaces Conditioned for Comfort Cooling.

Size equipment and all system components to maintain and control indoor design conditions at each of the following: (1) the 1.0% occurrence dry-bulb and the corresponding mean coincident wet-bulb (MCWB) temperature, and (2) the 1.0% occurrence humidity ratio and corresponding MCDB temperature.

2-6.2.2 Spaces Conditioned for Specialized Technical Requirements.

Size equipment and all system components to maintain and control indoor design conditions at each of the following: (1) the 0.4% occurrence dry-bulb temperature and the corresponding MCWB temperature, and (2) the 1.0% occurrence humidity ratio and corresponding MCDB.

2-6.2.3 Spaces Conditioned for Comfort Cooling Using Evaporative Equipment.

Size equipment and all system components to maintain and control indoor design conditions at the 1.0% occurrence wet-bulb temperature and corresponding MCDB.

2-6.2.4 Spaces Conditioned for Comfort Heating.

Size equipment and all system components to maintain and control indoor design conditions at the 99% occurrence dry-bulb temperature.

2-6.2.5 Open Cooling Towers and Wet, Closed-Circuit Cooling Towers.

For sizing open cooling towers and wet closed-circuit cooling towers, add 5 °F (3 °C) to the 1.0 percent outdoor wet-bulb temperature.

2-6.2.6 Condensers, Condensing units, and Dry, Closed-Circuit Cooling Towers.

For sizing condensers and condensing units, add 5°F (3°C) to the outdoor dry-bulb temperature design condition.

2-6.3 Indoor Design Conditions.

Indoor cooling and heating conditions are determined as follows unless specified in a facility type UFC or FC or as approved by the authority having jurisdiction (AHJ) and the real property owner. The design must take into account all heat gains including the latent heat gain in the space.

[C] Indoor design conditions given are for the purposes of equipment and system design and sizing to ensure adequate capacity. The conditions given are not intended to restrict operational control settings. As an example: setting the space temperature control setpoint to 75 F would not be a deviation from this UFC. Controls setpoints, occupant adjustments, and other control parameters, where not defined in UFC 3-410- 02 should be coordinated with the end user.

The conditions given are to limit the potential for excessive oversizing of equipment because outdoor air conditions exceed design conditions only 1% of the time resulting in partial loading of equipment for a significant portion of the year. This can be exacerbated by raising or lowering the design conditions. Oversizing can result in poor control of humidity, excessive equipment cycling, and result in a decrease in energy efficiency. For typical occupant activities, clothing levels, and space air distribution velocities (such as in administrative or educational spaces) and when operational controls (thermostats) are set appropriately, equipment sized at the indoor design conditions given will meet ASHRAE Standard 55 most of the time. Approval may be sought from the AHJ and real property owner when space usage may necessitate different indoor design conditions. Consideration for approval of different conditions should include assurance that the design has mitigated the issues associated with equipment oversizing and energy efficiency.

2-6.3.1 Spaces Conditioned for Comfort Cooling.

78.0° F (25.6 °C) dry-bulb / 57.9° F (14.4 °C) dewpoint / 50-percent relative humidity.

2-6.3.2 Spaces Conditioned for Comfort Cooling Using Evaporative Equipment.

Provide conditions meeting ASHRAE Standard 55.

2-6.3.3 Spaces Conditioned for Comfort Heating.

68°F (20°C) dry-bulb.

Provide humidification as needed to maintain indoor humidity above 30%. Space relative humidity is permitted to be lower than 30 percent for up to 40 occupied hours per year. Coordinate with the architect to design the building envelope to prevent condensation in the wall/roof systems during the time humidification is in operation.

Include in the design analysis a dew point analysis profile (ASHRAE Fundamentals) for winter design conditions, showing condensation boundaries. The dew point analysis must consider the effect of air movement into the walls for buildings under positive pressurization relative to the outdoors.

2-6.3.4 Spaces Conditioned for Heating - High to Moderate Physical Activity.

55°F (12.8°C) dry-bulb. Examples of these facilities include areas in maintenance shops where engines are rebuilt and aircraft shops where instrumentation is repaired, warehouses areas where there are forklift loading operations, and aircraft hangars with high bay areas and limited amounts of people.

2-6.3.5 Spaces Conditioned for Heating - Freeze Protection.

40°F (4.5°C) at the 99.6 percent dry-bulb outdoor design temperature.

2-6.3.6 Spaces Which are Naturally or Mechanically Ventilated Only for Comfort.

Provide conditions meeting ASHRAE Standard 55.

[C] If mechanical cooling is provided as a back-up, the indoor conditions prescribed for spaces conditioned for comfort cooling and heating apply to sizing of the equipment and systems.

2-6.3.7 Spaces Conditioned for Process Cooling and Heating.

Process cooling and heating indoor design conditions are determined by the respective process requirements.

2-7 SPECIFIC FACILITY OR SPACE TYPE HVAC REQUIREMENTS.

2-7.1 Facility Air Conditioning Eligibility.

Facilities are eligible for air conditioning where facilities of similar structure and function in the local private sector are equipped with air conditioning. Air conditioning for comfort cooling is not allowed for the following facilities unless approved by the AHJ and real property owner for Army and Air Force projects. Air conditioning for comfort cooling is not allowed for the following facilities unless required to meet ASHRAE Standard 55 for occupied spaces and work areas for Navy projects. Comfort conditioning is allowed in administrative areas of the following facilities.

• Motor vehicle storage garages

• Aircraft maintenance facilities & hangars

• Special areas requiring high ventilation rates (Examples: woodshops, paint booth) unless approved by the AHJ and real property owner

• Vehicle storage areas of crash and fire stations

• Boiler plants and rooms

• Greenhouses

• General Warehouses

2-7.2 Natural or Mechanical Ventilation Requirements.

In areas where mechanical or natural ventilation may be feasible, evaluate the use of these methods in lieu of other air conditioning methods to meet interior design conditions. Address ambient noise levels and the availability of prevailing winds in the evaluation. Include the effect of outdoor humidity levels when designing the mechanical ventilation systems.

[C] In mild climates, where it is determined that air-conditioning is not necessary to maintain acceptable thermal conditions, natural ventilation, mechanical ventilation without mechanical cooling, or a combination may be used. Do not rely solely on natural ventilation or mechanical ventilation-only where these systems cannot meet required indoor conditions due to climate conditions. In such cases, mechanical cooling or heating will be necessary.

2-7.3 Intermittent Occupancy.

Facilities may experience different types of intermittent occupancy including:

• Long periods, sometimes months, of no occupancy such as when building users deploy.

• Daily extended periods of no or low occupancy such as barracks, housing, or some administrative facilities.

• Irregular or infrequent occupancy such as in reserve centers, chapels, auditoriums, theaters, or housing.

Design the systems and controls to avoid or mitigate negative impacts to the building and equipment due to the anticipated occupancy pattern of facilities. Design for humidity control during unoccupied periods to avoid building damage and mold.

2-7.4 Vestibules.

Vestibules must be heated to 50°F (10°C) to melt tracked-in snow in locations where conditions warrant. Provide heat for freeze protection when a wet-pipe sprinkler head is located in the vestibule. Otherwise, vestibules must not be heated or air conditioned.

[C] Consider the use of air curtains to limit infiltration. Consider pressurizing vestibules, from a source such as a DOAS, to limit outdoor air infiltration (while avoiding condensation and mold). Cooling vestibule spaces can lead to mold due to humid air infiltration and cool surfaces.

2-7.5 Closets, Storage, and Utility Rooms in Air-Conditioned Facilities.

Closets and unoccupied storage and utility rooms must be ventilated by transfer air from adjacent conditioned spaces at an airflow rate of 0.06 cfm/sf (0.028 lps/sf). Provide space conditioning as necessary for stored materials.

2-7.6 Data Processing Centers and Server Rooms.

HVAC designs for data processing centers and server rooms must follow ASHRAE Thermal Guidelines for Data Processing Environments and DOE-FEMP “Best Practices Guide for Energy-Efficient Data Center Design” unless specific manufacturer’s guidance exceeds the criteria contained within.

2-7.7 Laboratories.

The design of HVAC systems must provide control over space temperature conditions including contaminants and fume control appropriate to the space function. Exhaust systems must be provided with fume hoods to remove toxic substances as near to the source of the fumes as practical. Hood and system design must follow the recommendations of the following manual from the American Conference of Government Industrial Hygienists (ACGIH): ACGIH Industrial Ventilation: A Manual of Recommended Practice for Design. Where laboratories are required to be under a negative pressure relative to other areas in the facility, coordinate with the architect to locate these spaces in the interior to prevent negative pressure induced infiltration of outdoor air into exterior wall cavities. Medical labs must meet the requirements of UFC 4-510-01.

2-7.8 Aircraft Maintenance Shops.

Provide air conditioning for those functional areas where required for quality control of equipment, material, and task. Localized or spot air conditioning is allowed at individual workstations.

2-7.9 Aircraft Fire and Rescue and Fire Station.

Provide fire apparatus vehicle exhaust removal systems in all new, rehabilitated, or self-help Aircraft Fire and Rescue Station and Fire Stations. Projects must prevent exposure of fire fighters and contamination of living and sleeping areas to exhaust emissions. As required by NFPA 1500, such systems must permit the operation of the apparatus with the apparatus doors closed. Refer to UFC 4-730-10.

2-7.10 Laundries and Dry Cleaners.

For commercial laundries or dry cleaners or dedicated laundry spaces in facilities such as fitness centers, barracks, officer quarters, or lodging facilities, mechanical ventilation must be the primary method of heat dissipation. Evaporative cooling may be provided where indoor conditions can be met. Spot air conditioning or general air conditioning must be provided to keep the temperature in the work areas from exceeding 85°F (29°C). Coil discharge temperatures used in spot cooling must be 50°F (10°C) dry-bulb maximum for maximum dehumidification. Provide a readily accessible clean-out in all dryer exhaust ducts. These requirements do not apply to small laundry areas within a facility such as in small residences or where there few cleaning machines present in a larger multi-use space.

[C] Refer to applicable Facilities Criteria (FC) for requirements in laundries in specific facility types; such requirements supersede UFC 3-410-01 laundry requirements.

2-7.11 Commercial Kitchen Ventilation.

Comply with UFC 3-600-01, NFPA 96, ASHRAE Standard 154, and IMC. In addition, comply with the following requirements:

• Localized air conditioning or general air conditioning must be provided to keep temperature in the work areas from exceeding 85°F (29°C) dry-bulb (Example: near cooking equipment) if the main portion of the facility is air conditioned and the criteria for exhaust ventilation are met.

• Kitchen work areas, such as the kitchen and dish and pot/pan washing areas, indoor air (ASHRAE Standard 62.1 Class 2 Air) must not be recirculated to HVAC systems that serve any spaces other than the kitchen areas.

• Do not use evaporative coolers for kitchens in humid areas.

• Furnish make-up air for the range hood exhaust, tempered to within 10°F (5.5°C) of space temperature.

• If additional make-up air is required for kitchen exhausts, provide push-pull kitchen hoods with built-in heated make-up air supply.

• Dishwashing area exhaust ducts must be as short as possible with direct runs to outside of building. Ductwork must be aluminum or stainless steel and have watertight joints and must have a drain line from the low point.

Approximately 25 percent of the exhaust air must be exhausted from the ceiling level.

• When heat in kitchens rejected by refrigeration equipment exceeds 36,000 Btuh (10,551 W), heat recovery systems must be used unless not life cycle cost effective.

• The design must not allow recirculation of more than 75 percent of air (excluding hood exhausts) in the kitchen at any time.

• Portable and fixed recirculating, ventless, ductless cooking equipment or hoods listed and labeled in accordance with UL 710B are permitted without a separate NFPA 96 compliant hood and duct system.

• Electrically interlocked supply and exhaust air fans must be designed for at least 2-speed operation. Commercial kitchen Type I or Type II hoods for systems over 1000 CFM (470 lps) must be provided with variable speed and demand control for exhaust air. Provide control interlocks for supply and exhaust fans to ensure that the HVAC system air balance is maintained, and that the proper direction of airflow is maintained during normal operations.

[C] HVAC systems serving only the kitchen area may recirculate air. Air is not allowed to return from a kitchen area back to a central HVAC system that serves other areas.

Paragraph 2-6.3 Indoor Design Conditions applies to kitchen areas; however, it is recognized that the temperature near cooking equipment may be higher than the rest of the space. As stated, air-conditioning must prevent any area of the kitchen from exceeding 85°F dry-bulb.

UL 710B cooking equipment is fully compliant with NFPA 96 and IMC Section 507 without separate hood and duct system when installed and operated in accordance with the listing and the manufacturer’s instructions.

2-7.12 Vehicle Maintenance Facility Ventilation.

Ensure compliance with the ventilation requirements in UFC 3-600-01 and adopted codes and standards.

Vehicle maintenance areas include all spaces in which any repair and maintenance activity for a vehicle occurs and through which vehicles travel.

2-7.12.1 Vehicle Exhaust Systems.

Provide vehicle exhaust removal systems, for source capture of emissions from individual vehicles running in place, in all facilities where vehicles generate exhaust fumes and pollutants. Systems must prevent exposure of building occupants to exhaust emissions.

• Do not use underfloor vehicle exhaust systems.

• Provide one exhaust hose for each vehicle repair area or station unless an additional one is required by using service. Coordinate with the using real property owner to locate flexible hoses such that total length of flexible hose does not exceed 25 feet (7.6 m). Hoses must not interfere with maintenance operations or obstruct equipment such as traveling bridge cranes. Include hand or blast gate damper on each exhaust hose inlet.

• Provide one vehicle exhaust fan for each vehicle repair station and size each fan for one repair station unless specified otherwise by the real property owner or by using service standards.

• Do not discharge vehicle exhaust through building exterior walls.

Discharge vehicle exhaust above building roof level. Vehicle exhaust must be treated as Class 4 air in accordance with ASHRAE Standard 62.1 in maintaining required clearances from ventilation intake locations.

• Do not use polyvinyl chloride for exhaust ducts.

• Vehicle exhaust can contain flammable vapors and must not be combined with any other exhaust systems. Vehicle exhaust fans must be non-sparking.

• All exhaust system components must be compatible with the vehicle exhaust temperatures and exhaust requirements. Design exhaust transport velocities in the range of 3000 fpm (15 m/s) to 4500 fpm (23 m/s).

• Unless otherwise allowed by the real property owner or using service standards, design vehicle repair station exhaust inlets for 1400 cfm (660 lps) and 900 ºF (480 ºC). For vehicles with higher exhaust rate requirements, two exhaust lines may be combined.

2-7.12.2 General Exhaust System.

• The vehicle maintenance area must be maintained at a negative pressure relative to adjacent spaces with lower ASHRAE Standard 62.1 air classification.

• General building exhaust duct openings in vehicle maintenance areas must be located within 12 inches (0.3 m) of the floor and have multiple inlets to cover all parts of the floor area to remove vapor accumulations.

• Provide two stages of area exhaust in vehicle maintenance areas:

standby and alarm stages. Provide a hand-off-automatic switch. In automatic position, the exhaust system must operate in standby and alarm stages as follows:

• Standby First Stage Exhaust must provide an exhaust rate of 0.75 cfm/ft2 (3.8 lps/m2) for the entire vehicle maintenance area when the building is occupied. This does not include exhaust provided by the vehicle exhaust systems.

• The Alarm Second Stage Exhaust must provide an exhaust rate of 1.50 cfm/ft2 (7.6 lps/m2) for the entire vehicle maintenance area when any carbon monoxide detector senses carbon monoxide levels exceeding 35 ppm or any nitrogen dioxide detector senses nitrogen dioxide levels exceeding 1 ppm in the breathing zone. This does not include exhaust provided by the vehicle exhaust system. Detectors must be listed in accordance with UL 2075 or equivalent and installed in accordance with their listing and manufacturers’ instructions and recommendations. The gas detection system must activate visual and audible alarms. One carbon monoxide and nitrogen dioxide sensor are required for every eight vehicle repair bays. Sensors must be centrally located within the area they protect. The exhaust system must automatically revert to Standby First Stage Exhaust after the space is purged and contaminant levels drop below Alarm Second Stage Exhaust carbon monoxide and nitrogen dioxide setpoints.

• In the hand position, the exhaust system must operate in the Alarm Second Stage Exhaust mode (for comfort ventilation) except that visual and audible alarms must not activate.

• A manual on/off controlled, explosion proof, dedicated exhaust fan must be provided for any pit, below-grade work area, or subfloor work area used for lubrication, inspection, and automotive maintenance work, and exhaust inlets in these locations must be located 6 inches above maintenance pit floors. An exhaust inlet connected to a non-sparking exhaust fan must be provided for welding areas.

[C] Refer to NFPA standards such as NFPA 30A or NFPA 70 which include requirements for specific hazard classifications.

Sensors are indicated to be centrally located to ensure that sensors are spread throughout the facility and not collocated. Ensure sensor mounting heights are indicated based on gas density and intent to protect occupants. Carbon monoxide detectors should generally be in the breathing zone. Nitrogen dioxide detectors should be close to the floor and within maintenance pits.

2-7.12.3 Make-up Air System.

Single or multiple make-up air units with variable speed fans must be interlocked to track and supply make-up air for vehicle maintenance area general exhaust system and for each additional vehicle exhaust fan as each one is energized and deenergized.

Make-up air units must provide 55 ºF (12.8 ºC) tempered make-up air when the building is occupied.

As each vehicle exhaust fan is energized, for up to 50% of the total number of vehicle exhaust fans, the control system must automatically control make-up air unit(s) to provide additional make-up air for each vehicle exhaust fan’s airflow. Motorized outdoor air dampers at intake louvers must automatically open as required to provide the additional makeup air required if more than 50% of the vehicle exhaust fans are running.

2-7.13 Mechanical Rooms.

2-7.13.1 Mechanical Room Ventilation.

Where necessary to maintain temperatures within required operating conditions for equipment, mechanical rooms must be ventilated using outdoor air intake louvers and a thermostatically controlled exhaust fan. Use a supply fan in lieu of an exhaust fan in rooms where atmospheric burners are located. Provide the fan with a two-speed motor, which is sized, at the high speed, to have adequate capacity to limit the room dry-bulb temperature to a maximum of 10°F (6°C) above the outdoor dry-bulb temperature when both equipment and ambient loads are at their maximum peaks. The high speed must be activated 10°F (6°C) below the maximum temperature at which the most sensitive item of equipment in the room can operate. The low speed must operate at 20°F (11°C) below that of the high speed.

Where a refrigerating system is housed within the mechanical room, the design of the room must comply with ASHRAE Standard 15.

2-7.13.2 Mechanical Room Air Conditioning.

With real property owner concurrence, air conditioning may be provided to prevent severe corrosion in areas with an Environmental Severity Classification (ESC) of C4 and C5 and in high humidity areas identified in ASHRAE Standard 90.1 as climate zones 0A, 1A, 2A, 3A, 3C, 4C and 5C. See UFC 1-200-01 for determination of ESC for project locations. In project locations as described above, seal the mechanical rooms from air leakage. Return air must not be taken from mechanical rooms by air handlers serving occupied spaces.

2-8 ECONOMIZER.

Use fixed dry-bulb temperature high-limit shutoff control for air-side economizers. The high-limit setpoint must be no higher than the setpoints described by ASHRAE Standard 90.1, Chapter 6 paragraph entitled “High-Limit Shutoff.”

Where air-side economizers are used, except in packaged units with integral economizer control, provide separate dampers for economizer operation and for ventilation air requirements.

[C] Consider the use of water-side economizers where cooling tower or other water is available for heat absorption and where conditions may make them more life cycle cost effective.

2-9 VARIABLE SPEED DRIVES.

2-9.1 Design

Design and construct systems to deliver maximum design flows with variable speed drives operating between 55 and 60 Hz, unless using motor and drives designed and rated for higher frequencies. Account for dirty filter loading and wet cooling coils in fan design and selection.

2-9.2 Balancing

Do not exceed maximum rated revolutions per minute and rated full load amperage during any mode of operation, including with loaded filters and wet cooling coils.

Minimize throttling losses during system balancing. Replace or adjust fan drive sheaves to achieve system balance for belt-driven fans. Variable speed drives are permitted to exceed 60 Hz only for motor and drive systems designed and rated for operation at higher frequencies. Variable speed drive must be capable of controlling to maximum and minimum flows with a drive operational range not less than 25 Hz. Pump impeller adjustment is required only when either the maximum or minimum flow cannot be maintained by the variable speed drive.

[C] This requirement is for equipment using Variable Speed Drives only.

Running motors at frequencies higher than 60 Hz is allowed only for those designed and rated for such in order to manage risks such as rotor imbalance, increased vibration, increased heat generation, and premature failure of motor windings (from voltage spikes, electrical noise, and harmonics).

2-10 HUMIDIFICATION.

Use of district steam is prohibited as a humidification method. Use of wetted pad type or water spray type humidifiers is prohibited since these have the potential to inject Legionnaire bacillus as well as other pathogenic organisms into the air stream.

2-11 STEAM SYSTEMS.

Single-pipe systems must not be used for comfort heating. For safety purposes, low-pressure steam 15 psig (100 kPa gage) and below must be used where terminal equipment is installed in occupied areas. High- or medium-pressure above 15 psig (100 kPa gage) steam unit heaters may be used for space heating in areas such as garages, warehouses, and hangars where the discharge outlets are a minimum of 13 feet (4 meters) above floor level.

2-12 FAN COIL APPLICATIONS FOR VENTILATION AIR.

Fan-coil units must not be used for conditioning ventilation loads.

2-13 GROUND-SOURCE HEAT PUMPS.

2-13.1 Sizing.

Refer to ASHRAE HVAC Applications Handbook, Chapter Geothermal Energy, for terminology applicable to this paragraph. This paragraph refers to the “building load loop” which is the water piping system that circulates water to the heat pump units (sometimes referred to as a “condenser loop”). In some systems, this is separated from the ground loop or ground water by a heat exchanger. In other systems, the building load loop and ground loop are the same piping system. The terms “ground loop” and “ground loop heat exchanger” (GLHX) are interchangeable. Design and size the ground loop to prevent the loss of capacity over time due to heating and cooling load imbalances.

2-13.1.1 Sizing Ground Coupled Heat Pumps (GCHP) Systems.

For projects which are considering GCHP, field test the ground heat transfer capacity at the proposed well field site prior to design. Follow the requirements of ASHRAE Geothermal Heating and Cooling: Design of Ground-Source Heat Pump Systems and ANSI/CSA C448. If any conflict occurs between the two standards, use the more stringent requirements.