HUMIDIFICATION & DEHUMIDIFICATION


Protecting what cannot be replaced: the case for humidification


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Archives, museums, and heritage buildings all carry the same responsibility: protecting collections and historic interiors that cannot be replaced. Temperature control and energy efficiency tend to dominate building services conversations, but humidity control, particularly humidification, remains one of the most important and least visible contributors to long-term preservation. Stephen Finkel, DriSteem regional sales manager explains


ndoor environments today are shaped not just by outdoor weather but also by modern heating, ventilation, and energy-efficiency strategies. In many cases, these systems unintentionally dry the air. The result is slow, cumulative stress on historic materials that can place collections outside recommended conservation ranges. Understanding how humidity behaves indoors, and how controlled humidification stabilises sensitive environments, is essential for engineers and building managers responsible for long term stewardship, and risk management.


Climate variability and indoor moisture


No climate is static. From cold continental winters to temperate maritime regions and mechanically ventilated urban buildings, seasonal moisture swings affect buildings everywhere.


Outdoor weather does not automatically translate to indoor humidity. When air is heated, it becomes drier unless moisture is added. Heating increases the air’s capacity to carry moisture, lowering relative humidity even though no water has been removed. This happens in cold, mild, and even seemingly humid climates. For cultural institutions, this matters because collections and historic finishes respond to indoor conditions, not outdoor averages. Repeated swings or extended periods of dry air place stress on moisture sensitive materials regardless of location. While acceptable humidity ranges vary by collection type and standards, conservation professionals broadly agree on one principle: stability matters most.


Why is dry air so damaging?


Many artefacts and historic building elements absorb and release moisture in response to their surroundings. Wood, paper, parchment, textiles, leather, and layered painted surfaces all expand and contract as humidity rises or falls. As relative humidity falls, these materials release moisture and shrink. When it rises again, they absorb moisture and expand. Repeated cycles of shrinkage and expansion lead to cumulative and often irreversible damage, including:


• Cracking and warping of wooden objects and furnishings


• Delamination of veneers, finishes, and composite materials


• Paper becoming brittle and prone to tearing


• Flaking paint and loss of surface adhesion


This damage does not require extreme conditions. Long periods of moderately low relative humidity, repeated year after year, can be just as harmful as short exposure to very dry air. From a preservation and compliance standpoint, maintaining minimum humidity levels is just as important as preventing excessive moisture.


Heating and ventilation: well intended, but incomplete


Most heritage buildings rely on mechanical heating to provide comfort, control condensation, and allow year round use. Many also incorporate modern ventilation strategies to improve air quality and reduce energy use. While beneficial, these systems often prioritise temperature and airflow without fully accounting for moisture balance. Heated, mechanically moved air accelerates moisture loss unless humidification is deliberately included. The result is an environment that


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may feel acceptable to occupants but quietly undermines the stability that collections, lenders, and insurers expect. Effective environmental control depends on managing both temperature and humidity. Addressing one while ignoring the other creates gaps that often only become visible after damage has occurred or insurance conditions are challenged.


Reframing humidification as a protective measure


In conservation settings, humidification has sometimes been approached with caution. Concerns around condensation, mould growth, and potential impacts on historic materials, finishes, and building fabric are understandable, especially in older structures. In practice, it is uncontrolled moisture that


creates risk, not humidification itself. When properly designed and controlled, modern systems introduce very small amounts of moisture, only when needed, to restore balance rather than create excess.


The goal is not high humidity, but stability. That typically means maintaining sensible minimum relative humidity levels during dry periods and avoiding unnecessary fluctuation throughout the year. Applied with accuracy and restraint, humidification becomes a protective measure that meets recognised standards and insurance requirements.


Modern humidification for historic buildings


Advances in humidification technology have made it far more compatible with heritage environments. Systems can now be integrated discreetly, with minimal visual impact and little structural intervention. Successful approaches typically include accurate sensing and control, short moisture- absorption distances, careful distribution that respects architectural features, and compatibility with existing air-handling systems. For engineers working in conservation contexts, humidification no longer needs to be intrusive. When executed well, it operates quietly in the background, supporting preservation objectives, compliance expectations, and asset protection without drawing attention to itself.


The UK climate: a clear example


While humidity related risks affect heritage buildings globally, the UK illustrates how even moderate climates can pose serious challenges.


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Although outdoor relative humidity is often high, indoor conditions tell a different story. During the heating season, outdoor air is


brought inside and warmed, becoming drier unless moisture is added. As a result, indoor air in museums, archives, and historic buildings can drop to levels that stress sensitive materials, even when conditions outside appear damp. Extended winter operation and reduced ventilation can intensify this effect, making November through March a critical risk period for many sites. This pattern is not unique to the UK, but it highlights how reliance on outdoor climate assumptions can mask indoor conditions that fall outside conservation guidance and risk management thresholds.


Collaboration between conservation and building services


Effective humidity control relies on collaboration. Conservation specialists understand material sensitivity, acceptable ranges, and external obligations, while engineers understand air movement, controls, and building behaviour. When these disciplines work together early, humidification strategies can be tailored to collection needs while respecting building constraints. The result is realistic targets, clear operating limits, seasonally appropriate strategies, and fewer reactive interventions. From an engineering perspective, heritage buildings benefit most from simple, robust solutions that deliver stability over decades, rather than complexity for its own sake.


Protecting what cannot be replaced


Archives, museums, and heritage buildings exist to carry history forward while safeguarding assets entrusted to their care. While building systems will evolve, the collections they protect must endure. Humidity control remains one of the most effective and least visible tools available to support this mission. When approached with restraint, accuracy, and respect for historic structures, modern humidification quietly safeguards collections, supports recognised standards, and helps meet insurance expectations.


For engineers and facility teams, recognising


the role of humidification is not about adding complexity. It is about completing the environmental picture and basing preservation strategies on balance, stability, and long term thinking.


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