What role does HVAC&R play in preservation?

Senior Conservator at the Alexander Turnbull Library, Vesna Živković, shares how documentary heritage is kept from degradation

Buildings such as the National Library of New Zealand Te Puna Mātauranga o Aotearoa are time capsules, preserving documentary heritage such as manuscripts, books, paper documents, newspapers, maps, prints, drawings, audio and videos, and other items from previous decades and centuries. IRHACE even has historical information stored with the National Library including minute books, proceedings of IRHACE conferences and symposiums, as well as Journals dating back to 1933.

To keep these items from degradation, control of environmental factors is important. Air conditioning has been used to achieve this since the Second World War when The National Gallery in Britain stored paintings at 50 per cent relative humidity and 20ºC in a subway for safekeeping.

“In the National Library, we currently have more than 7,000 square meters of collection stores with different collections, varying from newspapers, photographic negatives, books and manuscripts, to audiovisual materials, and each of these stores has its own HVAC plant,” says Vesna Živković, Senior Conservator at the Alexander Turnbull Library, National Library of New Zealand.

“When it comes to library and archives materials, they are mostly paper-based objects inherently sensitive to incorrect levels of temperature and relative humidity. The rule is the lower the temperature, the longer the life expectancy of those items. For example, newspapers are printed on acidic paper and are not intended to last, so if you keep them in room conditions, they will yellow, become brittle and disintegrate.”

Research shows that dropping the temperature by five degrees can double the life of chemically unstable material such as this.

“Thus, cooler temperatures are preferred for collections with long-term value. The guidelines for extended-term storage conditions specify different temperature ranges for the storage of mixed media collections based on their sensitivity and chemical stability, including cold conditions between 0ºC and 8ºC, and cool conditions, set between 8ºC–16ºC. Both Archives New Zealand and the National Library have these conditions,” says Vesna. “The National Library was purpose-built in 1985, which is rare for cultural heritage buildings, and was the first government building in New Zealand to have air conditioning installed.”

Lowering relative humidity also contributes significantly to extending the life expectancy of documentary heritage, says Vesna.

Conditions for the preservation of material in the library include:

• A cold room at 2ºC with a freezer at -25ºC. “The freezer is intended for long-term preservation but mostly for treatment of pests and also for freezing the wet library material in case of flooding. This is an option when there is mass damage to material and you cannot treat it immediately,” says Vesna.

• A cold store at 2ºC at 30 per cent relative humidity, intended for photographic negatives including nitrate and acetate negatives. This climate is equally important for the preservation of unstable (colour) negatives and transparencies.

• Cool stores ranging from 13ºC, 40 per cent relative humidity to 18ºC, 45 per cent relative humidity.

Changes to the National Library’s storeroom conditions

Previously, the National Library aimed to achieve a flatline of both relative humidity and temperature – which it succeeded in – as this was considered imperative and optimum conditions for the preservation of objects in cultural heritage institutions.

“However, current research on material deterioration and discussions on environmental sustainability have prompted the question of whether these tight environmental controls and maintaining specific set points and narrow ranges are necessary.

Furthermore, in a library or archives facility where you have mass of hygroscopic materials, the impact of fluctuating relative humidity would be slow and minimal,” says Vesna.

“What we are looking at now is broadening the environmental parameters. Rather than having, for example, 13ºC plus or minus -2ºC and 40 per cent plus or minus -10 per cent relative humidity, we are looking into allowing seasonal variations and we are in the process of reviewing our requirements for conditions in collections stores based on our current body of knowledge.”

Vesna cites ASHRAE Chapter 24, intended for museums, galleries, libraries and archives, and its advice on options for allowing seasonal and gradual variations depending on climate and conditions in the building, as well as sensitivity of materials.

Mechanical system shutdown tests have also been completed, focusing on two stores with an intention to explore shutdowns as an energy-saving option to be implemented in the library without compromising the preservation of collections. One is highly insulated and tests showed it’s possible to shut down the HVAC system for up to 10 hours overnight without impact on the system or conditions in the store. Shutting the system down over the day has also been tested to see the benefits.

“Another test we conducted was in a storeroom with windows. This test confirmed the high level of air leakage and we are now looking at how we can manage that to enable both an increase in the store’s resilience and proceeding with mechanical system shutdowns,” says Vesna.

“While the National Library building has very well-maintained climate conditions for the collections, there are options to manage the HVAC systems more sustainably in terms of energy efficiency, decarbonisation and cost reduction.”

In 2021, the National Library established the Alexander Turnbull Library (ATL) Environmental Management Team (EMT) with the aim to make recommendations for energy savings and sustainable practices, while upholding the long-term preservation of collection materials. Utility bill analysis indicated that the energy used to condition ATL collection storage areas represented around 80 per cent of the total energy consumption for the National Library building.

The ATL EMT conducted a series of controlled mechanical system shutdowns to confirm the viability of shutdowns as an energy-saving strategy and to inform on the performance of the selected ATL collection stores in terms of conditions for preservation of collections and system operations. The results of the tests and subsequent discussions within the team confirmed that no significant changes in conditions that would present risks to collections, health and safety, or impact on system capability were observed during any of the plant shutdowns. It was also noted that there are further options for energy savings within the HVAC&R systems at the level of ventilation, fresh air intake and dehumidification as they are considered the biggest consumers of energy in the National Library building.

At the beginning of 2024, the National Library initiated an implementation of a series of sustainability initiatives through the Property Capital Forward Works Project (PCFWP). This includes planned mechanical systems shutdowns, building tuning, replacement of supply air fans and enabling the implementation of DCV (demand controlled ventilation).

Photographs courtesy of the National Library of New Zealand. Photographer Mark Beatty.

The IRHACE collection at the National Library includes records relating to the organisations from which current institute is formed, such as IRACE minutes (1933-83), IHVE minutes (1977-86), a members list from the 1950s-80s, collection copies of the periodical Thermonews, and more. Materials were donated by IRHACE in November 2011.