This document, presented by Alkis Triantafyllopoulos (ASHRAE HVAC Trainer) on December 8, 2021, focuses on Variable Air Volume (VAV) systems, Demand Control Ventilation (DCV), and Chilled Beams. It encompasses the types, functionality, installation considerations, and advantages of VAV dampers within ventilation systems.

1. VAV Systems Overview An introduction to various VAV unit types is provided, including:

• Single Duct (cooling only or with reheat)
• Dual Duct terminal
• Induction VAV terminal
• Parallel Flow Fan Powered VAV terminal
• Series Flow Fan Powered VAV terminal

2. Types of VAV Damper Operation A distinction is drawn between:

• Pressure-Independent VAV: A terminal unit equipped with an airflow measurement controller, adjustable for maximum and minimum airflow setpoints.
• Pressure-Dependent VAV: Lacks air measurement and maintenance capabilities, with actual airflow being a function of static pressure and damper blade position.

3. VAV Damper Definition A VAV damper is defined as an electro-mechanical air supply regulation damper for air ducts, incorporating a differential pressure (Δp) sensor. These dampers are manufactured in both circular and rectangular configurations.

4. Measurement Station (ΔP Sensor) The Δp sensor is utilized to measure total and static pressure immediately upstream of the damper blade. The differential pressure value (Δp) enables the calculation of airflow in m³/h, following the formula   , where  is volumetric flow, c is a geometry-dependent constant, Δp is differential pressure, and ρ is medium density. An electric motor for the VAV damper processes the differential pressure information to convert it into airflow, dynamically adjusting the blade position. This motor incorporates a PID controller to facilitate smooth airflow regulation.

5. Air Damper Classification Air dampers are classified as:

• Circular
• Single-blade (rectangular dimension)
• Multi-blade (rectangular dimension) The position of the blade(s) directly determines the volumetric airflow.

6. VAV Damper Characteristics

• Air leakage class: Typically C on the body and 3 on the blade, in accordance with PN-EN 1751.
• Low speed operation: Operates at speeds up to 0.45 m/s, yielding low noise levels suitable for sensitive environments such as hospitals, operating rooms, and theaters.
• Pressure range: Operates within a pressure range of 30-1000 Pa.
• Corrosive environments: Rectangular dampers are designed to operate with "dirty" return air and "light corrosive gases" (ISO 12944 max. class C3).
• Regulator tightness: Exhibits a C2 tightness class (casing C, blade 2) in accordance with EN1751.

7. Application Examples

• Constant Air Volume (CAV): A VAV damper can function as a CAV system by configuring minimum (Vmin) and maximum (Vmax) airflow setpoints. For instance, in an occupied space detected by a motion sensor, Vmax is requested; otherwise, Vmin is maintained. A VAV damper on the return side acts as a slave to the supply damper, ensuring balanced airflow to prevent over- or under-pressure conditions.
• Variable Air Volume (VAV) in a space: An illustrative example of variable air supply in a given space is also included.

8. Installation of VAV Dampers Correct installation, adhering to manufacturer guidelines and maintaining necessary distances from duct corners and bends, is critical for optimal VAV system operation. Deviations from these guidelines can induce turbulent airflow at the measurement station, resulting in inaccurate airflow readings and compromised control.

9. Advantages of VAV Dampers over Simple Motorized Volume Dampers While simple motorized dampers may offer similar two-position operation, VAV dampers provide distinct advantages:

• Continuous feedback: VAV dampers offer real-time feedback on actual airflow, a capability absent in simple dampers.
• Energy efficiency: Prevents excessive energy consumption when not required.
• Reduced noise: Contributes to lower operational noise levels.
• Controlled environment: Ensures precise air conditioning and ventilation, thereby avoiding uncontrolled environmental conditions.

10. ASHRAE Ventilation Rate Procedure—Multiple-Zone System ASHRAE standards for multiple-zone systems are briefly discussed, including the calculation of uncorrected outdoor air intake (Vou​) and the occupant diversity ratio (D).

11. Advanced Measurement Solutions Advanced solutions for airflow measurement are introduced, encompassing:

• Measurement of temperature/speed in addition to airflow.
• Ultrasonic sensors (probe-less internal design) offering high accuracy, minimal pressure loss, ease of cleaning, reduced maintenance, and lower noise output.
• Capability for local data display, Bluetooth-enabled setup/commissioning/monitoring, and integration with BMS/Modbus systems.

Key Sections and Compliance Pathways: The standard is under continuous maintenance by a Standing Standard Project Committee to ensure regular updates. Compliance with various sections is mandatory for data center projects:

• Building Envelope (Section 5): Requirements for the building envelope must comply with ANSI/ASHRAE/IES Standard 90.1, Section 5.
• Heating, Ventilating, and Air Conditioning (HVAC) (Section 6): Specifies requirements for HVAC systems serving data center spaces, while HVAC for other spaces adheres to ASHRAE 90.1. Compliance involves general provisions (6.1), mandatory provisions (6.4), Maximum Annualized Mechanical Load Component (Annualized MLC) (6.5), and submittal requirements (6.6).
  • Mandatory Provisions (6.4): Equipment efficiency information from manufacturers must be verified through specific channels, including compliance with EPAct 2005 for covered equipment, listing in certification programs (if available), independent laboratory tests for unlisted products, or manufacturer-furnished data if no program exists.
  • Maximum Annualized Mechanical Load Component (6.5): This component is calculated using Equation 6.5 and must not exceed the values specified in Table 6.5. The calculation considers total annual cooling energy, pump energy, heat rejection fan energy, and air-handler fan energy, each assessed at 25%, 50%, 75%, and 100% of the Data Center ITE Energy load. The quantity of operating HVAC units may vary based on ambient conditions or other design factors, and redundant equipment can be included if partially loaded efficiencies are used.
• Service Water Heating (Section 7): Requirements for service water heating systems must comply with ANSI/ASHRAE/IES Standard 90.1, Section 7.
• Power (Section 8): Specifies requirements for electrical systems delivering power to the data center's IT load and other described equipment. Electrical systems for other uses and spaces must comply with ASHRAE 90.1, Section 8. Compliance involves mandatory provisions (8.4), submittals (8.7), and one of two maximum design electrical loss component (ELC) options (8.5 or 8.6). Electrical distribution systems serving mechanical loads are limited to pathway losses not exceeding 2%. When multiple electrical paths exist, calculations must use the paths with the highest losses to demonstrate compliance.
• Lighting (Section 9): Lighting requirements must comply with ANSI/ASHRAE/IES Standard 90.1, Section 9.
• Other Equipment (Section 10): Other equipment must comply with ANSI/ASHRAE/IES Standard 90.1, Section 10.

Submittals and Documentation: Detailed submittals are required, including record drawings with equipment location and performance, duct/pipe configurations, and design flow rates. Operating and maintenance manuals must also be provided, containing equipment data, routine maintenance actions, service agency contact information, and a narrative of system operation with set points.

EU Regulation and TC 9.9: ASHRAE TC 9.9, focused on energy-efficient data centers, reviewed and provided input on a European Union (EU) Regulation for servers and data storage products. This Ecodesign Regulation was approved in September 2018, with parts taking effect on March 1, 2020, and final items on January 1, 2023. Key areas of focus include minimum power supply unit (PSU) efficiency, power factor requirements, manufacturer requirements for repair/reuse disassembly, and idle/active power efficiency for servers and components.

ASHRAE Ventilation Standards 62.1 and 62.2: ASHRAE Standard 62.1-2019 addresses "Ventilation for Acceptable Indoor Air Quality" for commercial and institutional buildings. ASHRAE Standard 62.2-2019 focuses on "Ventilation and Acceptable Indoor Air Quality in Residential Buildings". Both standards are under continuous maintenance by Standing Standard Project Committees, ensuring regular updates and revisions.

Indoor Air Quality and Outdoor Air: Acceptable indoor air quality is defined as air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority of the occupants express no dissatisfaction. Outdoor air quality is influenced by both regional factors (e.g., ozone, particulate matter, carbon monoxide, sulfur oxides, nitrogen dioxide, lead) and local sources (e.g., toilet/kitchen exhaust, smoking lounges, restaurants, printing shops, cooling towers, automobile traffic, parking garages, dumpsters, loading docks, helicopter pads, emergency generators, manufacturing plants, industrial facilities, and landfills).

Ventilation Rate Calculation: The breathing zone ventilation rate (Vbz​) is a critical parameter, calculated as the sum of the ventilation rate required for people-related sources (Vp​) and building/area-related sources (Va​). This relationship is expressed as Vbz​=Rp​⋅Pz​+Ra​⋅Az​, where Rp​ is the outdoor airflow rate per person, Pz​ is the zone population, Ra​ is the outdoor airflow rate per unit area, and Az​ is the zone floor area. Minimum ventilation rates for various occupancy categories are provided (e.g., university/college laboratories, food and beverage service areas). For example, a 100 m² house with 4 occupants would require approximately 144 m³/h of breathing zone ventilation.

Air Distribution Effectiveness (E_z) and System Ventilation Efficiency (E_vz): The Zone Air Distribution Effectiveness (

Ez​) accounts for how effectively supply air mixes within a space. For well-mixed air distribution systems, 

Ez​ can range from 0.7 to 1.0 depending on the supply and return air configurations. System Ventilation Efficiency (

Evz​) is considered for multi-zone recirculation systems. Final calculations for breathing zone ventilation often involve dividing the initial calculated value by 

Ez​ (e.g., 144 m³/h / 0.8 = 180 m³/h), with potential additional factors for certifications like LEED.

Airtightness and Infiltration: ASHRAE Standard 119 (1988) defines normalized leakage and specifies tightness levels based on energy conservation. ASHRAE Standard 136 (1993) utilizes pre-calculated weather factors and normalized leakage to estimate the impact of infiltration on indoor air quality, thereby determining its equivalent ventilation.

Exhaust Ventilation: Specific exhaust rates are critical for areas like kitchens, bathrooms, and WCs to ensure pollutant removal. Examples of residential exhaust rates include 180 m³/h for a residential kitchen and 90 m³/h for a bathroom/shower or WC/toilet.

Ventilation System Components: Centralized ventilation systems often incorporate heat/energy recovery units to improve efficiency. Air filters are essential components, with minimum requirements typically including ISO ePM1 55% (F7) or greater for supply air, and ISO ePM10 60% (M5) or greater for fresh air and return air. Cooling (water or DX) , heating (water or combi) , package units , and sound attenuators are also integrated into ventilation systems. Demand Control Ventilation (DCV) systems utilize presence, CO2, and humidity sensors to modulate airflow based on real-time needs. Both centralized and decentralized ventilation solutions are employed.

References: ASHRAE Standards 90.1-2019, 55-2017, 189.1-2020, and 211-2018 are among those available for reference

Impact of High Humidity: Elevated humidity levels are shown to have detrimental effects. High humidity significantly accelerates mold growth, with studies indicating increased growth rates above 60% relative humidity. Furthermore, high humidity induces corrosion in materials. Corrosion rates increase steadily on damp surfaces as water molecules begin to behave as an electrolyte, and while impeded on wet surfaces due to thickness, they become limited by oxygen diffusion when fully immersed. Moisture also influences the resistance values of various materials, including PVC, cellulose-acetate, nylon, and presspan, generally reducing resistance as relative humidity increases. Hygroscopic materials such as wood, leather, cotton, and paper absorb moisture from the air, increasing their moisture content with rising relative humidity. Maintaining optimal relative humidity ranges (typically 30-50%) is crucial for protecting materials like steel, non-ferrous metals, gold-plated contacts, wire insulation, and rubber/elastomers from corrosion, mold, mildew, and fungus. In cold room applications, warm moist air infiltration leads to fog, frost on evaporator coils, and ice accumulation, significantly impairing system performance.

Dehumidification Techniques: Two primary dehumidification techniques are explored: Cooling Cycle-Refrigerant and Sorption.

• Sorption Technology: This method utilizes a desiccant wheel composed of a corrugated fiberglass structure impregnated with a desiccant material such as silica gel or lithium-chloride. The process involves passing warm, humid air through the desiccant wheel, which adsorbs moisture, followed by a regeneration process where heated air desorbs the moisture from the desiccant. Psychrometric charts illustrate the reduction in moisture content achieved through this process.
• Cooling Cycle with Refrigerant: This technique involves passing warm humid air over a cold evaporator coil, causing the air to cool and condense excess moisture, resulting in cool saturated air. This air is then reheated by a condenser to produce warm, dry air. The process is depicted on psychrometric charts, showing a decrease in moisture content and dry-bulb temperature, followed by a rise in dry-bulb temperature after reheating. Refrigerant-based systems, however, are limited in their ability to work effectively at very low dewpoint air or produce air with very low relative humidity.

Conclusion: Effective dehumidification is essential for maintaining product quality, preventing material degradation, ensuring the functionality of electronic components, and achieving comfortable and healthy indoor environments across a wide spectrum of industrial, commercial, and residential applications. The choice between sorption and refrigerant-based technologies depends on the specific humidity control requirements and operational conditions.

Purpose and Scope of ASHRAE Standard 90.1: The standard's purpose is to set minimum energy efficiency requirements for building design, construction, and operation and maintenance plans. It also defines the criteria for compliance. The standard's structure includes sections on building envelope, HVAC, service water heating, power, lighting, and other equipment, along with appendices detailing methodologies for performance rating, climate data, and thermal bridging.

ASHRAE 90.1 and LEED v4 for BD+C: ASHRAE standards are integral to several LEED categories. For "Energy & Atmosphere," ASHRAE Guideline 0 & 1.1 are relevant for commissioning (up to 6 points), and ASHRAE Standard 90.1 is critical for minimum and optimized energy performance (up to 18 points). In the "Indoor Environmental Quality" category, ASHRAE Standard 62.1 applies to minimum and enhanced indoor air quality performance (up to 2 points), and ASHRAE Standard 55 is used for thermal comfort (1 point).

Mandatory Requirements for LEED Prerequisite (ASHRAE 90.1-2010/2016): Compliance with all mandatory requirements of ASHRAE 90.1 (specifically Sections 5.4, 6.4, 7.4, 8.4, 9.4, and 10.4) is a prerequisite for LEED certification. These include:

• Building Envelope (Section 5.4): Requirements for insulation R-value, fenestration (e.g., CE marking), continuous air barriers, and air leakage. Climate data, such as for Athens (3B) and Elliniko (3A), are considered.
• HVAC (Section 6.4): Minimum equipment efficiencies (based on Ecodesign regulations), zone thermostatic control with dead bands and automatic shutdown, ventilation system controls (e.g., shutoff dampers, garage ventilation based on contaminant levels), and automatic control for auxiliary heat, freeze protection, humidification, and dehumidification to prevent concurrent operation.
  • Demand Control Ventilation (DCV): Mandatory in high-occupancy areas (>50m² and >40 people/100m²) served by systems with air-side economizers, automatic modulating outdoor air dampers, or design outdoor airflow greater than 1400 L/s.
  • Variable-Air-Volume (VAV) Controls: Required for AHUs and FCUs with fan motors >4kW and direct expansion units with cooling capacity >32kW.
  • Direct Digital Controls (DDC): Mandatory for specific applications like air handling systems, and chilled/hot-water plants.
  • Economizer Fault Detection Diagnosis (FDD): Required for air-cooled direct expansion units with an economizer.
  • Insulation: Air duct insulation must comply with ASHRAE 90.1, and pipe insulation with EN ISO 12241.
• Service Water Heating (Section 7.4): Requirements for equipment efficiency, insulation, controls for temperature and circulating pumps, and specific controls for pools.
• Power (Section 8.4): Specifications for voltage drop and automatic receptacle control in certain office types.
• Lighting (Section 9.4): Controls for automatic shutoff, space control, parking garage lighting, and automatic daylight controls.
• Other Equipment (Section 10.4): Standards for electric motors (IE3 rating), service water pressure booster systems (variable pump speed, no operation at no flow), and elevator/escalator requirements. Whole-building energy monitoring capabilities are also required.

Energy Cost Budget Method and Simulation: The Energy Cost Budget Method (Section 12 and Appendix G) provides a performance rating pathway for compliance. This method compares the proposed design's annual energy cost against a budget building design, allowing for an energy savings score. Simulation models require hourly variations (occupancy, lighting, HVAC operation), thermal mass effects, and part-load performance curves for mechanical equipment, among other details.

Passive House Standards and Design Implications: Standards from organizations like PHI (Germany) and PHIUS (US) define stringent requirements for these buildings. Space heating demand is limited to 15 kWh per square meter annually or 10 W per square meter peak demand. In climates requiring active cooling, space cooling demand is comparably stringent, with an allowance for dehumidification. Renewable Primary Energy Demand (PER) for domestic applications (heating, hot water, electricity) must not exceed 60 kWh per square meter annually for Passive House Classic. Airtightness is a critical parameter, with a maximum of 0.6 air changes per hour at 50 Pascals pressure (ACH50). Thermal comfort must be maintained with no more than 10% of annual hours exceeding 25°C.

Challenges in HVAC System Design for Hyper-Efficient Buildings: Providing comfort conditioning (ASHRAE Standard 55) in buildings with high-performance envelopes and minimal internal heat gains introduces significant complexity to HVAC system design. Identified "malfunctions" include:

• Low Ventilation Rates: Typical ventilation rates of 0.3 ACH are substantially lower than those required by ASHRAE Standards 62.1 and 62.2, leading to issues with Indoor Air Quality (IAQ), humidity control, and part-load operation.
• Dominance of Latent Loads: While advanced insulation and glazing reduce sensible loads, internal latent loads (from occupants, showers, kitchens) and ventilation-related latent loads can be considerably higher, leading to a very low Sensible Heat Ratio (SHR). This often results in unacceptably high indoor humidity. For instance, a 92.9m² apartment with three occupants might require total ventilation air of 35.3 L/s per ASHRAE 62.1, but additional extraction for bathrooms and kitchens can sum up to 47.2 L/s (0.7 ACH) or even 50.5 L/s per ASHRAE 62.2, significantly exceeding typical Passive House ventilation rates.
• Energy Recovery Ventilation (ERV) and Humidity: While ERVs are crucial for heat and moisture recovery (up to 80% humidity recovery) , in some cases, excessive humidity recovery can lead to undesirably high indoor relative humidity, even with the benefit of recovering latent heat.
• Terminal Sizing and Location: The inherently low heating/cooling loads and low user equipment power density in hyper-efficient buildings mean that conventional indoor units are often oversized, leading to cycling and diminished dehumidification capabilities at minimum part loads. Achieving uniform distribution of ventilation air and maintaining consistent conditions can be challenging with low conditioning airflow per unit area, making distribution system design critical.

Proposed Solutions and Best Practices: To address these complexities, the following are suggested:

• Ventilation System Compliance: Configure ventilation systems to comply with the relevant version of ASHRAE Standard 62.1.
• Thermal Comfort Adherence: Follow ASHRAE Thermal Comfort Standard 55, specifically addressing dehumidification requirements.
• Certified Energy Recovery Ventilators: Utilize certified energy recovery ventilators (HRV/ERV).
• Optimized Energy Recovery Control: Implement control strategies for energy recovery devices that maximize both energy efficiency and indoor comfort. A potential solution in moderate outdoor air conditions could be to bypass energy recovery for free cooling, as the energy penalty for disabling recovery may be minimal due to the building's low balance point temperature.
• Zoning Consistent with Terminal Sizes: Design space zoning to align with available terminal sizes to prevent issues with oversized units and maintain adequate dehumidification.
• Balanced Ventilation: Ensure continuous exhaust for kitchens and bathrooms, with make-up air provided as needed.

Conclusion: While hyper-efficient buildings offer significant energy savings, their unique load profiles necessitate a nuanced approach to HVAC system design. Careful consideration of ventilation rates, humidity control, and appropriate system sizing is paramount to ensure both energy efficiency and occupant comfort.

Methods of Energy Recovery: Recuperative Systems Energy recovery methods are categorized into Recuperative and Regenerative. Recuperative systems facilitate direct heat transfer between air streams without mixing. Various types are detailed:

• Cross Flow Heat Exchangers: These units are less efficient (maximum 65-70% even with a very large exchange surface area) but are characterized by a compact size.
• Counter Flow Heat Exchangers: These achieve very high efficiency (up to 95%) but require very large dimensions.
• Double Plate Heat Exchangers: Offering an efficiency of approximately 75-80%, these units maintain a compact size.
• Three-stage Recuperators: These devices achieve efficiencies around 75-85% and vary from medium to large in size.
• Run Around Coils: With efficiencies between 50-65%, these are compact and suitable for "clean rooms".
• Heat Pipes: These feature low maintenance, compact design, and suitability for clean rooms. Their efficiency varies with orientation: a maximum of 50% for horizontal arrays and up to 75% for vertical arrays.
• Wrap Around Coils: These systems facilitate pre-cooling and reheating of air, are suitable for dehumidification, lead to lower ΔT at coils, provide passive (free) reheating, and enable equipment savings through downsizing.

Methods of Energy Recovery: Regenerative Systems Regenerative systems involve a moving medium for heat transfer between air streams.

• Rotary-Enthalpy Economizers: These are very compact but are characterized by high maintenance, high pressure drop, and the presence of moving parts. They achieve a thermal efficiency of 80% and a latent efficiency of 40-50%.
• Heat Accumulators: These boast low maintenance, large design, low pressure drop, and no moving parts. They offer high thermal efficiency (90-95%) and a latent efficiency of 65%.

Enthalpy Economizers / Bypass Damper: Elaboration on enthalpy economizers notes that cooling return air generally requires less mechanical cooling energy than cooling outdoor air. Determining the precise changeover condition is complex due to the dual function of cooling coils in both cooling and dehumidifying supply air. Various control strategies and their potential errors are covered, including fixed-dry bulb, differential-dry bulb, fixed enthalpy, differential enthalpy, combi, and combi-differential. The importance of sensor accuracy and calibration is also highlighted.

Condenser Heat Recovery and Adiabatic/Evaporative Cooling: Brief mention is made of condenser heat recovery, concluding with a section on adiabatic/evaporative cooling, noting that water used can be sourced from cooling coil condensation.

References: Several ASHRAE Standards are referenced, including 90.1, 189.1, 62.1, and 55.

Fundamental Aspects of Energy Audits: At its core, an energy audit seeks to determine the quantity and location of energy use, assess its effectiveness, and identify avenues for enhanced efficiency. The basic steps involve:

1. Collecting and analyzing historical energy use data.
2. Studying the building to gather data on operational characteristics and indoor environmental quality.
3. Identifying potential measures for energy and/or cost reduction, or indoor environmental quality improvement.
4. Performing engineering and economic analysis of proposed modifications.
5. Preparing a prioritized list of measures, grouped to capitalize on synergies and cost reductions.
6. Documenting the analysis process and results in a comprehensive report.

Energy Audit vs. Energy Labeling: A key distinction is drawn between energy audits and energy labeling. Energy labeling relies on predefined operational parameters, whereas an energy audit is based on real operational data. Energy labeling typically accounts for heating, cooling, DHW, and lighting in conditioned spaces, while an energy audit comprehensively assesses energy use across all systems, including exterior lighting, plug-loads, ventilation motors, and refrigeration.

ASHRAE Standard 211P: Standard for Commercial Building Energy Audit: ASHRAE Standard 211P, a Public Review Draft at the time of presentation (August 2016), provides a structured framework for commercial building energy audits. The standard's scope explicitly excludes single-family houses, multi-family structures of three stories or fewer, and manufactured homes.

Levels of Energy Audits:

The standard defines three distinct levels of energy audits:

• Level 1: Walk-Through Analysis: This preliminary assessment involves a site walk-through, familiarization with building construction and operation, identification of major energy-using systems, and interviews with occupants to understand usage and issues. It aims to identify low-cost/no-cost energy efficiency measures (EEMs) related to controls and operations, and potential capital-expensed EEMs with preliminary cost and savings estimates.
• Level 2: Energy Survey Analysis: Building upon Level 1 findings, this level includes a breakdown of annual total energy costs by component. It involves determining key operating parameters such as setpoints, schedules, and equipment efficiencies (considering part-load or seasonal performance). An end-use breakdown is conducted using calculated methods, building energy models, or sub-metered data. This level also involves listing and grouping EEMs (e.g., envelope improvements, lighting upgrades, HVAC replacements, solar systems) while accounting for interactions between measures. Savings calculations (energy and demand) utilize stipulated values, engineering calculations, or building energy models, with an emphasis on long-term average weather data. EEM costs are estimated comprehensively, and an economic analysis (e.g., Simple Payback, ROI) is performed. A quality assurance review evaluates feasibility and reasonableness of projections.
• Level 3: Detailed Analysis of Capital Intensive Modifications: This most comprehensive level builds on Level 2 findings, focusing on capital-intensive modifications. It requires annual building energy modeling (e.g., using software meeting ASHRAE Standard 140 requirements) calibrated against actual building energy use per ASHRAE Guideline 14. A Lifecycle Cost Analysis (LCCA) is conducted, considering all cash flows (initial investment, operational costs, energy savings, etc.).

Benchmarking: A preliminary energy use analysis (PEA) includes benchmarking, where the Energy Use Intensity (EUI, kWh/m²) and Energy Cost Index (ECI, €/m²) are calculated and compared to similar buildings over a minimum of 12 consecutive months.

Relevant ASHRAE Guidelines and Standards: The presentation references several other pertinent ASHRAE documents, including Standard 105 (Building Energy Performance), Standard 180 (HVAC System Maintenance), Standard 189.1 (High-Performance Green Buildings), Standard 62.1 (Ventilation), Standard 90.1 (Energy Standard for Buildings), Guideline 11 (HVAC Control Testing), and Guideline 22 (Chilled-Water Plant Monitoring).

ASHRAE Standard 62 Framework: ASHRAE Standard 62.1 applies to all buildings except low-rise residential structures, with no retroactive application and no recommended ventilation rates for smoking. Standard 62.2 specifically applies to low-rise residential buildings, where all air systems may be suited, and thermal comfort, based on Standard 55, should be considered. Compliance with Standard 62.1 is achieved when a building is designed, constructed, operated, and maintained to meet requirements outlined in Sections 4, 5, 6, 7, and 8, irrespective of occupant satisfaction.

Outdoor Air Quality Considerations: Outdoor air quality is influenced by both regional factors, such as ozone, particulate matter, carbon monoxide, sulfur oxides, nitrogen dioxide, and lead , and local sources, including exhaust from toilets, kitchens, smoking lounges, restaurants, print shops, cooling towers, automobile traffic, parking garages, dumpsters, loading docks, helicopter pads, emergency generators, manufacturing plants, industrial facilities, and landfills.

Systems & Equipment: Key system and equipment considerations include ventilation air distribution, designing for air balancing, and proper exhaust duct location. Ventilation system controls can be either constant volume or Variable Air Volume (VAV). Air ducts require resistance to mold growth and erosion, and proper location of outdoor air intakes is necessary for protection against rain, snow, and birds. Air Handling Units (AHUs) comprise fans, coils (heating, cooling, DX), humidifiers, water sprayers, mixing plenums, filters, drains, and casing.

Ventilation Rate Procedures: Three main procedures for determining ventilation rates are recognized:

• Ventilation Rate Procedure (VRP): Applicable to various space types, based on contaminant sources and emission rates to dilute and exhaust bioeffluents and other contaminants. It is suitable for LEED certification.
• Indoor Air Quality Procedure (IAQP): A performance-based procedure where rates are calculated based on contaminant source emission rates and desired indoor concentrations.
• Natural Ventilation Procedure (NVP): Utilizes ventilation through openings (e.g., windows) with manual occupant control and specifies minimum opening sizes.

The breathing zone ventilation rate (

Vbz​) is calculated as the sum of ventilation rates for people-related sources (Vp​) and building/area-related sources (Va​), expressed as Vbz​=Rp​⋅Pz​+Ra​⋅Az​. Here, 

Rp​ is the outdoor airflow rate per person, Pz​ is the zone population, Ra​ is the outdoor airflow rate per unit area, and Az​ is the zone floor area.

Ventilation Efficiency and Operations: Zone Air Distribution Effectiveness (

Ez​) and System Ventilation Efficiency (Evz​) are critical for accurate ventilation sizing. Construction and startup procedures involve application, air balancing, testing of drain pans and outdoor air dampers, and thorough system documentation. Ongoing operation and maintenance are guided by an operation-maintenance manual.

ASHRAE Standard 62.2 for Residential Buildings: Standard 62.2 applies to all residential spaces in single-family houses or multi-family buildings up to three stories , including living rooms, bedrooms, kitchens, bathrooms, hallways, closets, storerooms, laundries, garages, and basements. Required mechanical ventilation rates are calculated based on floor area and number of bedrooms , with exceptions for unconditioned buildings in warm climates or those heated/cooled for less than 876 hours per year. Infiltration rates are considered, with ASHRAE Standard 136 used for houses with higher measured infiltration.

Ventilation System Components and Efficiency: Combination ventilation systems often incorporate Heat Recovery Ventilators (HRVs) for sensible heat exchange or Energy Recovery Ventilators (ERVs) for both sensible and latent heat transfer. Minimum filtration efficiency of MERV 6 is specified. Sound ratings for acoustical insulation, in-duct sound power level, and airborne sound power level are important considerations. Psychrometric charts illustrate heating, humidification, cooling, and various heat recovery processes.

Air Handling Unit Specifications and Energy Efficiency: AHU casing characteristics include deflection, air leakage factor, thermal transmittance, and thermal bridging factor. Energy efficiency classification is based on Eurovent guidelines, considering thermal energy for heating (including Heat Recovery System efficiency and climate dependency) and electrical energy for fans. European Standard EN13053 governs the rating and performance of AHUs, components, and sections. Prerequisites for energy efficiency calculations include air density, design conditions, velocities based on filter section area, and heat recovery dry efficiency at balanced air volumes. AHUs are categorized into subgroups based on outdoor air usage and recirculation rates, with corresponding energy efficiency class signs.

Conclusion: Mechanical ventilation is essential for both high-rise and increasingly for low-rise buildings aiming for Net-Zero Energy Buildings (NZEB). A well-designed mechanical ventilation system enhances indoor comfort and can reduce equipment sizing. In regions like the Mediterranean, cooling loads from ventilation often exceed heating loads, necessitating high-performance sensible/latent heat recovery systems.

Current ASHRAE Standards & Decarbonization Efforts: Key ASHRAE standards relevant to ventilation, indoor air quality, and energy efficiency are highlighted. Additionally, reference is made to the ASHRAE Decarbonization Task Force and associated standards addressing greenhouse gas emissions, refrigerants, passive house design, net-zero/net-carbon evaluation, and carbon emissions. ASHRAE Technical Committees involved in air-to-air energy recovery, evaporative cooling, and dehumidification equipment are also identified.

Methods of Energy Recovery: Two primary methods of energy recovery are discussed: Recuperative and Regenerative.

• Recuperative Methods (Heat Exchangers): These involve direct heat transfer between air streams without mixing.
  • Cross Flow: These heat exchangers are less efficient (maximum 65-70% even with a large surface area) but have a compact size.
  • Counter Flow: Offering very high efficiency (up to 95%), these require very large dimensions.
  • Double Plate Heat Exchanger: Provides around 75-80% efficiency in a compact size.
  • Three-Stage Recuperators: These units achieve efficiencies of about 75-85% and range from medium to large sizes.
  • Run Around Coils: With efficiencies around 50-65%, these are compact and suitable for clean rooms.
  • Heat Pipes: Characterized by low maintenance, compact design, and suitability for clean rooms, they offer efficiencies up to 50% in horizontal arrays and up to 75% in vertical arrays.
  • Wrap Around Coils-Dehumidification: These systems involve pre-cooling and reheating air, are suitable for dehumidification, lead to lower ΔT at coils, provide passive (free) reheating, and enable equipment downsizing.
• Regenerative Methods: These involve heat transfer through a medium that moves between air streams.
  • Rotary-Enthalpy Economizers: While very compact , they require high maintenance, have high pressure drop, and contain moving parts. They offer 80% thermal efficiency and 40-50% latent efficiency.
  • Heat Accumulators: These boast low maintenance, low pressure drop, and no moving parts. They offer high thermal efficiency (90-95%) and 65% latent efficiency , though they are of a large design.

Enthalpy Economizers / Bypass Damper: The analysis also delves into enthalpy economizers, observing that cooling return air generally requires less mechanical cooling energy than cooling outdoor air. Determining the changeover condition is complex due to cooling coils simultaneously cooling and dehumidifying supply air. Different limits (enthalpy, dry-bulb) for economizer operation and potential errors in fixed-dry bulb, differential-dry bulb, fixed enthalpy, differential enthalpy, combi, and combi-differential control strategies are discussed. Sensor accuracy and calibration are demonstrated to be crucial for effective operation, as evidenced by humidity sensor studies.

Adiabatic/Evaporative Cooling: This sustainable technique is presented as an effective method for air cooling.

Purpose and Scope: ASHRAE Standard 170 is under continuous maintenance by a Standing Standard Project Committee, ensuring regular updates and revisions. Compliance involves adherence to established procedures for timely, documented, consensus action on requested changes. The standard covers both new buildings and alterations to existing structures, requiring detailed programs from owners/managers specifying expected services, equipment, and special needs for temperature, humidity, and pressure in each space.

Systems and Equipment Requirements:

• Air Handling Units (AHU): AHU casings must resist corrosion and prevent water intrusion, adhering to standards like VDI 6022.
• Outdoor Air Intakes: Minimum separation distances from potential outdoor contaminant sources (e.g., exhausts, plumbing vents, combustion appliance flues, parking areas, loading docks, cooling towers) are specified to ensure clean outdoor air intake.
• Air-Handling System Controls: Controls must maintain minimum outdoor airflow under all design conditions, including unoccupied and turndown modes. Minimum air changes per hour must be maintained, and all systems require field verification of outdoor air.
• Exhaust Discharge: All ductwork within the building under negative pressure must be exhausted to the outdoor environment.
• Filtration: Various Minimum Efficiency Reporting Value (MERV) ratings are specified for different areas: MERV-8, MERV-14, MERV-16, and HEPA filters.
• Energy Recovery: Generally, zero cross-contamination heat recovery is preferred. However, airborne infectious isolation areas must not incorporate energy recovery systems. If an air-leakage system is selected, its leakage must be less than 5%.

Space Ventilation Categories and Design Guidelines: Ventilation requirements are categorized for three main space types: Hospital Spaces, Outpatient Spaces, and Nursing Home Spaces. Extensive tables provide detailed requirements for each space regarding pressure relationships to adjacent areas, minimum outdoor air changes per hour (ACH), minimum total ACH, exhaust direction, air recirculation by room units, unoccupied turndown settings, minimum filter efficiencies, and design relative humidity and temperature ranges.

Key design guidelines include:

• Air movement must flow from clean to less-clean areas.
• Variable Air Volume (VAV) systems, if used for thermal comfort, must not compromise pressure balancing.
• Ventilation rates specified in tables address comfort, asepsis, and odor.
• Recirculation units, if used, must have minimum filtration and be designed for single-zone application.
• AHUs serving multiple spaces must comply with ASHRAE 62.1.
• Night setback (or unoccupied mode) can range from 13°C to 30°C without compromising pressure relationships.

Construction, System Startup, and Operation & Maintenance: Construction phases demand protection of materials, duct cleanliness, and conditions to avoid microbial growth. Duct openings must be covered when AHUs are off, pre-filters installed, and systems cleaned prior to occupancy. System startup requires testing, adjusting, balancing, equipment startup, drain pan tests, and thorough equipment documentation. Ongoing operation and maintenance procedures include regular testing of positive pressure in operating rooms, HEPA filter pressure tests, and ensuring non-stop 24/7 ventilation in operating and C-section rooms.

Additional Resources: ASHRAE also publishes "Advanced Energy Design Guides" for large hospitals (achieving 50% energy savings) and small hospitals/healthcare facilities (achieving 30% energy savings) towards Net Zero Energy Buildings. The 2023 ASHRAE HANDBOOK HVAC APPLICATIONS includes dedicated chapters on "Health and Care Facilities," "Laboratories," and "Clean Spaces".

ASHRAE Standards and Resources: Several ASHRAE standards are foundational to evaporative cooling, including ANSI/ASHRAE Std 133 for testing direct evaporative air coolers , ANSI/ASHRAE Std 143 for rating indirect evaporative coolers , and ANSI/ASHRAE Std 212 for determining energy performance and water-use efficiency of add-on evaporative precoolers for unitary air conditioning equipment. Further resources are available in the ASHRAE HANDBOOK, specifically Chapter 51 ("HVAC Applications: Evaporative Cooling") and Chapter 41 ("HVAC Systems and Equipment: Evaporative Air-Cooling Equipment"). ASHRAE Technical Committee 5.7 oversees Evaporative Cooling.

Operation of Adiabatic Cooling: Adiabatic cooling involves the cooling of primary air through interaction with water sprays in a heat exchanger, with secondary air acting as an exhaust pathway, as depicted in integrated Air Handling Units (AHUs). The efficiency factor of adiabatic cooling is determined by the saturation temperature of the return air. For example, with return air at 25°C and 50% relative humidity, the saturation temperature is 18°C. Outside air can be cooled from 32°C to 21.5°C with an efficiency factor of 75%.

Efficiency Enhancement and Psychrometrics: Efficiency can be increased through multi-stage systems, with capabilities ranging from over 90% effectiveness for 2-stage systems to "cheating" at 110% for 2+ stages. Psychrometric charts illustrate the process at varying efficiencies, typically showing improvements from 70-80% to 90-100%.

Applications: Evaporative cooling is suitable for various applications, including:

• Integrated Adiabatic Cooling in Air Handling Units (AHUs): This integrates the cooling process directly within the air handling system.
• Data Centers: These facilities benefit from the precise temperature and humidity control offered by evaporative cooling systems.
• Hybrid Chillers: Evaporative cooling can be integrated with traditional chillers to enhance efficiency and reduce energy consumption.

Water Management and Safety: Water must be recycled in these systems, with unused water gathered to minimize waste. While water treatment is not strictly necessary, its implementation allows for once-a-year maintenance alongside standard device servicing; without treatment, cleaning of scaling effects from adiabatic heat exchangers is required twice a year. Despite water consumption, evaporative cooling leads to water savings in the broader energy landscape: for every 1 liter of water consumed in adiabatic cooling, 2 liters are saved due to reduced electricity usage at power plants (where water is vaporized for cooling processes). The design of these systems is also considered risk-free for Legionella bacteria due to their closed space operation. Condensate water can also be saved.

Conclusions: Evaporative cooling represents a highly energy-efficient and ecologically friendly approach, leading to significantly reduced cooling loads.

ASHRAE Standard 62 Framework: ASHRAE Standard 62.1 applies to all buildings except low-rise residential structures, with no retroactive application and no recommended ventilation rates for smoking. Standard 62.2 specifically applies to low-rise residential buildings, where all air systems may be suited, and thermal comfort, based on Standard 55, should be considered. Compliance with Standard 62.1 is achieved when a building is designed, constructed, operated, and maintained to meet requirements outlined in Sections 4, 5, 6, 7, and 8, irrespective of occupant satisfaction.

Outdoor Air Quality Considerations: Outdoor air quality is influenced by both regional factors, such as ozone, particulate matter, carbon monoxide, sulfur oxides, nitrogen dioxide, and lead, and local sources, including exhaust from toilets, kitchens, smoking lounges, restaurants, print shops, cooling towers, automobile traffic, parking garages, dumpsters, loading docks, helicopter pads, emergency generators, manufacturing plants, industrial facilities, and landfills.

Systems & Equipment: Key system and equipment considerations include ventilation air distribution, designing for air balancing, and proper exhaust duct location. Ventilation system controls can be either constant volume or Variable Air Volume (VAV). Air ducts require resistance to mold growth and erosion, and proper location of outdoor air intakes is necessary for protection against rain, snow, and birds. Air Handling Units (AHUs) comprise fans, coils (heating, cooling, DX), humidifiers, water sprayers, mixing plenums, filters, drains, and casing.

Ventilation Rate Procedures: Three main procedures for determining ventilation rates are recognized:

• Ventilation Rate Procedure (VRP): Applicable to various space types, based on contaminant sources and emission rates to dilute and exhaust bioeffluents and other contaminants. It is suitable for LEED certification.
• Indoor Air Quality Procedure (IAQP): A performance-based procedure where rates are calculated based on contaminant source emission rates and desired indoor concentrations.
• Natural Ventilation Procedure (NVP): Utilizes ventilation through openings (e.g., windows) with manual occupant control and specifies minimum opening sizes.

The breathing zone ventilation rate (

Vbz​) is calculated as the sum of ventilation rates for people-related sources (Vp​) and building/area-related sources (Va​), expressed as Vbz​=Rp​⋅Pz​+Ra​⋅Az​. Here, 

Rp​ is the outdoor airflow rate per person, Pz​ is the zone population, Ra​ is the outdoor airflow rate per unit area, and Az​ is the zone floor area.

Ventilation Efficiency and Operations: Zone Air Distribution Effectiveness (

Ez​) and System Ventilation Efficiency (Evz​) are critical for accurate ventilation sizing. Construction and startup procedures involve application, air balancing, testing of drain pans and outdoor air dampers, and thorough system documentation. Ongoing operation and maintenance are guided by an operation-maintenance manual.

ASHRAE Standard 62.2 for Residential Buildings: Standard 62.2 applies to all residential spaces in single-family houses or multi-family buildings up to three stories, including living rooms, bedrooms, kitchens, bathrooms, hallways, closets, storerooms, laundries, garages, and basements. Required mechanical ventilation rates are calculated based on floor area and number of bedrooms, with exceptions for unconditioned buildings in warm climates or those heated/cooled for less than 876 hours per year. Infiltration rates are considered, with ASHRAE Standard 136 used for houses with higher measured infiltration.

Ventilation System Components and Efficiency: Combination ventilation systems often incorporate Heat Recovery Ventilators (HRVs) for sensible heat exchange or Energy Recovery Ventilators (ERVs) for both sensible and latent heat transfer. Minimum filtration efficiency of MERV 6 is specified. Sound ratings for acoustical insulation, in-duct sound power level, and airborne sound power level are important considerations. Psychrometric charts illustrate heating, humidification, cooling, and various heat recovery processes.

Air Handling Unit Specifications and Energy Efficiency: AHU casing characteristics include deflection, air leakage factor, thermal transmittance, and thermal bridging factor. Energy efficiency classification is based on Eurovent guidelines, considering thermal energy for heating (including Heat Recovery System efficiency and climate dependency) and electrical energy for fans. European Standard EN13053 governs the rating and performance of AHUs, components, and sections. Prerequisites for energy efficiency calculations include air density, design conditions, velocities based on filter section area, and heat recovery dry efficiency at balanced air volumes. AHUs are categorized into subgroups based on outdoor air usage and recirculation rates, with corresponding energy efficiency class signs.

Conclusion: Mechanical ventilation is essential for both high-rise and increasingly for low-rise buildings aiming for Net-Zero Energy Buildings (NZEB). A well-designed mechanical ventilation system enhances indoor comfort and can reduce equipment sizing. In regions like the Mediterranean, cooling loads from ventilation often exceed heating loads, necessitating high-performance sensible/latent heat recovery systems.