Tag: microclimate

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New Box Test Results

Submitted by John Bergman-McCool

The Peabody is preparing for exciting building improvements in our collections area that will begin in April of 2023. They will include new storage furniture and an HVAC system that will control temperature and humidity. In advance of the project, we initiated a few tests to see how the environment inside our collections boxes would respond to moving around our building.

In a previous test, we sought to understand how silica gel might help mitigate fluctuating temperature and relative humidity (RH). Environmental monitors were placed in two boxes containing collections; one with a sachet containing silica gel and one without. The values were compared against a monitor that was measuring the ambient temp and RH in our collections area. The initial results of those tests are summarized in a previous blog. The silica gel appeared to bring down RH inside the box. However, once the silica gel had fully adsorbed humidity, the boxes themselves also seemed to buffer against shifting RH levels.

Silica efficacy test in boxes that contain collections. ‘Silica’ and ‘Without Silica’ boxes don’t exhibit the wide ranging RH and show a small decrease in temperature compared to the basement environment they are stored in. As we later learned, the RH is influenced by the collections inside the boxes.

During the new test, monitors were placed inside two empty boxes. One box was located on the first floor and a second box was moved in and out of our HVAC controlled storage area on a weekly basis. The data from inside the box was compared to environmental monitors logging ambient temperature and RH in the test areas. The results were enlightening and clear within the first month. Unlike the boxes containing collections, the empty boxes very closely mirror the temperature and RH of the spaces in which they are placed.

Empty box test from first floor. Test Box temperature and RH compared against first-floor monitors F1-1, F1-2, F1-3. RH and temperature in test box closely mirrors conditions outside box.
Empty box test from the second floor. Test box moved into and out of HVAC controlled storage. Test unit temperature and RH compared against test units inside (F2-6) and outside (F2-4) HVAC storage. RH in test box closely mirrors conditions outside box.

The conclusion from our previous test that the boxes were buffering the collections within from environmental changes was incorrect. The box environment was buffered by the collections inside.

Organic collection items- including bone, wood, and botanical remains- can absorb and release moisture in the air. In our collection area the ratio of air to collection items is high. Collections may influence temperature and RH in the storage area, but it might be negligible.  Inside the boxes that ratio is reversed; they hold more collections for a relatively small amount of air, which results in a microclimate. The box microclimate is influenced by the ability of collections to absorb moisture.

We now know that boxes don’t offer magical RH buffering abilities, but the empty box test did show us that they accomplish some buffering.

Looking closely at the box test that moved in and out of our HVAC storage in April 2022 shows that while temperature very quickly falls in sync with the new environment, RH may take as long as 24 hours to sync with the new conditions.

Empty Box test on second floor from April 2022. Analysis completed for highlighted areas included in tables below. Temp and RH peaks analyzed while outside HVAC storage numbered.

In addition, the test box environment has fewer peaks and valleys for RH (local maximums and local minimums), lower maximum increases and decreases in RH and temperature, and lower average increases and decreases in RH and temperature. Strangely, the test box had more temperature fluctuations while in HVAC storage. Some of the findings are included in the tables below.

While it was surprising to learn that our collections boxes don’t flatten large swings in RH and temperature, it is comforting to know that they are mitigating some of the fluctuations- not to mention protecting from other agents of deterioration like dust and light.

Analysis of Box environment against the environment outside of storage in April 2022. Outside of the HVAC storage the conditions inside the box and outside the box were similar enough to compare local maximums and minimums. Some local max. and min. values were small and have been included in larger trends in increasing and decreasing values referred to as ‘peaks’ in the following table.
Analysis of Box environment against the environment inside HVAC storage from April 2022. The local maximums and minimums did not match up for a 1:1 comparison. Maximum and average values were compared.