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Museums, Galleries, Archives, and Libraries

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Environmental Control in Museums, Galleries, Archives, and Libraries

Maintaining a stable environment is one of the most critical aspects of preserving heritage collections in museums, galleries, archives, and libraries. Environmental factors—primarily temperature, relative humidity (RH), air quality, and light—directly influence the longevity and integrity of artifacts. Proper management of these parameters ensures that collections are protected from physical, chemical, and biological deterioration while balancing operational and energy costs.

Evolution of Environmental Management in Heritage Spaces

Historically, strict temperature and RH control were considered essential for all artifacts. Museums often aimed for constant RH and temperature levels throughout the year. However, contemporary research, guided by standards such as the ASHRAE Handbook for Museums, Galleries, Archives, and Libraries, has shown that:

  • Not all artifacts require extremely tight control.
  • Some fluctuation within a controlled range is acceptable and often unavoidable.
  • Excessively rigid control can be costly, environmentally unsustainable, and unnecessary for less sensitive items.
Modern HVAC strategies now focus on mitigating harmful fluctuations rather than maintaining a rigid set point.
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The Interdependence of Temperature and Relative Humidity

Temperature and RH are closely linked:

  • Cooling air increases its relative humidity.
  • Heating air decreases its relative humidity.

This interdependence means that controlling one parameter often affects the other. Poorly managed conditions can cause three primary types of damage:

  • Biological Damage – growth of mold, bacteria, and other microorganisms.
  • Chemical Damage – oxidation of inks, pigments, dyes, and paper degradation.
  • Mechanical Damage – cracking, warping, flaking, and delamination of artifacts.

Set Points: Definition and Significance

A set point is the target temperature or RH that an HVAC system aims to maintain. Set points can be interpreted in two ways:

  • Short-term setting: The thermostat or humidistat level over hours or days.Heating air decreases its relative humidity.
  • Annual average: A long-term average, which may adjust seasonally for energy efficiency.
    • Typical museum set points: 50% RH and 15–25°C.
    • Factors influencing set points: Artifact sensitivity, building performance, HVAC capabilities, and climate variations.
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Fluctuations and Class of Control

While maintaining a stable set point is important, the real threat to artifacts comes from fluctuations in temperature and RH rather than the nominal values themselves.
  • Class of Control: Defines the acceptable range of fluctuations over time.
  • Goal: Minimize rapid or large swings that can cause stress to materials.
  • Example: Wood, paper, and textiles are highly sensitive to RH changes, whereas stone or metal objects tolerate broader ranges.

Temperature and RH Guidelines

Research indicates that:

  • Lowering temperature within a physically safe RH range significantly increases chemical stability. Even a small reduction can drastically slow degradation.
  • Adjusting RH alone has a smaller impact on chemical stability.
  • Cold storage for highly sensitive or unstable artifacts can provide substantial preservation benefits.

Physically safe RH range: Ensures minimal irreversible physical damage such as emulsion cracking or flaking in photographs, paper, and other gelatin-based materials. 

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Efficiency, Reliability, and Energy Management

Investing in HVAC systems for heritage spaces is not solely about temperature and RH control. Other critical considerations include:

  • Energy efficiency: Minimizes operational costs while maintaining precise environmental control.Heating air decreases its relative humidity.
  • Reliability: Prevents downtime that could jeopardize collections.
  • Compliance with standards: Ensures safety and quality by following:
  • SMACNA (Sheet Metal & Air Conditioning Contractors’ National Association)
  • ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers)
  • ISHRAE (Indian Society of Heating, Refrigerating and Air-Conditioning Engineers)
  • NBC (National Building Code of India)

Types of HVAC Systems for Heritage Collections

WCSIPL offers solutions tailored to the specific needs of museums and archives:

  • Air-cooled chiller plant with AHU: Efficient for moderate climate control needs.
  • Water-cooled chiller plant with AHU: Suitable for large facilities and high-density collections.
  • Direct expansion plant with AHU: Offers precise control for critical environments.

Each system is designed to:

  • Maintain stable temperature and RH within the required class of control.
  • Reduce energy consumption.
  • Ensure minimal risk of environmental damage to sensitive artifacts.
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Key Recommendations for
Museum Environmental Control

Conduct a risk assessment to identify sensitive materials and prioritize areas.

Set appropriate set points considering artifact requirements, building characteristics, and HVAC capacity.

Focus on controlling fluctuations, not just achieving absolute temperature or RH values.

Implement energy-efficient, reliable systems to reduce costs without compromising preservation.

Follow national and international standards for HVAC design and operation.

Benefits of Professional HVAC Solutions for Museums

  • Preservation of valuable artifacts and collections.
  • Minimized risk of biological, chemical, and mechanical damage.
  • Improved energy efficiency and operational savings.
  • Long-term reliability and reduced maintenance downtime.
  • Custom solutions aligned with collection requirements and building constraints.
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Frequently Asked Question
Need more help? We’re here to answer any questions you may have.
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Why is temperature and humidity control important for museums and archives?
Incorrect temperature or relative humidity can cause biological, chemical, and mechanical damage to artifacts. Controlling these parameters ensures the long-term preservation of valuable collections.
Most museums maintain an RH of around 50% and temperature between 15–25°C, but the exact set points depend on the type of artifacts, building design, and local climate.
Controlling fluctuations in temperature and RH is more important than hitting exact set points. Rapid or large swings in conditions are the main threat to sensitive artifacts.
Systems include air-cooled chiller plants, water-cooled chiller plants, direct expansion units, and AHUs, all designed to provide stable conditions, energy efficiency, and minimal environmental risk.
By using advanced controls, energy recovery systems, and reliable equipment, modern HVAC solutions maintain optimal environmental conditions while minimizing energy consumption and operational costs.
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