Climate control in southern Africa

I am a paintings conservator temporarily (until October) working at
the National Museum of Art in Maputo, Mozambique and have been asked
to give advice about the introduction of air conditioning. I would
really appreciate help from anyone with experience of preventive
conservation in tropical/sub-tropical museums.

The museum houses a large collection of paintings, mostly oil on
canvas and dating from the late nineteenth century to the present
day, as well as a number of wooden sculptures and artefacts. The air
conditioning would be aimed at the reduction of relative humidity.
The main problems at the museum are related to frequent humidity
fluctuations and levels of relative humidity which are almost
constantly above 70% (reflecting the outside humidity).

However, I have a number of concerns about  dehumidification.
Firstly, the electricity supply is unreliable so that there would
certainly need to be a back-up generator. Secondly, if the air in
the museum were dehumidified I would worry that this would simply
result in more humidity being drawn through the walls from outside
(the building is concrete) resulting in no significant change in the
humidity within the museum but possible damage to the building
fabric. Finally, if the dehumidification were successful I would be
afraid that this could have a detrimental effect on the wooden
objects in the museum which have always been kept in a more humid
environment.

The conclusion I arrived at was that it would be best to try to find
a system which would keep the relative humidity steady at its
current average and to introduce ventilation to help prevent mould
growth. This would mean that if the system failed the resultant
sudden fluctuation in relative humidity could not be any larger than
the current fluctuations and in most cases would be smaller.
Hopefully, with the help of a generator, the effect would be to
prevent problems caused by humidity fluctuations while also reducing
the likelihood of mould growth despite high humidity levels.

I would be very grateful for any comments on my reasoning and also
for specific information about suppliers of reliable, low
maintenance conditioning systems who might be willing to work in
Maputo. If any conservators in southern Africa have had especially
good or bad experiences with individual products or companies I
would also be interested to hear about them.


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                  Conservation DistList Instance 17:62
                  Distributed: Friday, March 26, 2004
                       Message Id: cdl-17-62-012
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