At the Green Knowledge Cafe in September Jane Thompson Webb, Collections Care Officer for Birmingham Museums Trust, joined us to discuss heating. Turning down thermostats is an approach many of the green museums are adopting to reduce energy consumption and bills. However, concerns have been raised regarding the impact this will have on our collections. Jane’s solution – heating for collections not people – ensures green and cost-effective collections care.
What impact does heating have on our collections?
Temperature and relative humidity (RH) are inversely related. The higher the temperature, the lower the relative humidity (and vice versa). Low RH (dry air) can make objects brittle causing cracks while high RH (damp air) encourages pests and mould growth. Big changes in RH can be achieved with only a small amount of heating.
What should we aim to achieve?
We are aiming to achieve a stable, constant environment within the band 40-65% RH. Ideally RH should not fluctuate by more than 10% within a 24 hour period. For objects, the cooler the temperature the better because a higher temperature speeds up the decay process. This band is generally suitable for most objects in a mixed material collection, although you may wish to create a microclimate for objects that are particularly vulnerable.
Where do we begin?
Begin by monitoring temperature and RH, ideally continuously as above. Don’t invest in any changes without knowing what is happening in your museum – guessing doesn’t work! Similarly monitoring will enable you to understand the impact of any changes you introduce. When you have downloaded your environmental monitoring data count the number of days RH stays within the band 40-65%. Draw on the graph and annotate with explanations of any anomalies.
The next step is to insulate your building and seal draughts. There is no point in investing in a new heating system if the heat will simply escape from a leaky roof or door!
How should we heat the museum?
To create a stable environment, heating should be low-level and constant. Get heating, but don’t heat to a human comfort level, only to pull RH down. Heating 24/7 saves money because the system is not struggling to heat a room from cold. Staff will be cold but encourage them to wear layers or consider providing fleeces.
Plug in oil-filled radiators are ideal to control RH. These can be stand alone so you don’t have to disrupt the building. Ideally control using a humidistat which adjusts the temperature to regulate RH. Remember to place on a tray to catch any oil drips.
How should we plan heating for a new building?
As before, begin by insulating. If you can super-insulate the building you can keep conditions constant all year round without too much heating. Avoid air-conditioning because it’s expensive to install, maintain, has a limited lifespan and is often ineffective. If you are considering under-floor heating take into account that it needs to be on constantly because it takes a long time to warm up. A heating system controlled by humidistats and with separate controls (so that staff, volunteers and visitors can’t adjust the heating!) is the way forward. Choose an efficient system to allow you to heat constantly at a low-level in winter. Ideally select heating that is fuelled by an energy efficient source.
Here’s a re-cap of Jane’s top tips for heating…
- Monitor environmental conditions for 12 months before you make any changes.
- Heat for objects. Involve visitors by explaining how you are looking after the collections and how they are helping.
- Buy fleeces for staff comfort or install individual heaters in offices.
- Don’t aspire to unachievable standards just keep RH stable and below 70%.
- Leave things alone if everything’s okay but keep monitoring and condition check objects.