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Subject: Ventilation in museum storage units

Ventilation in museum storage units

From: Ida Hovmand <iho<-at->
Date: Tuesday, January 6, 2009
The  museum where I work has a purpose-built storage unit which
houses a mixed collection, where space no longer suffices. A
part-mezzanine consisting of solid board flooring has already been
put in place along one side, and both ends of the building. The plan
is to extend this mezzanine to cover about 80% of the ground floor
area. We would like to be able to keep maintaining the climate
around 50% RH,  but are uncertain as to how and to what extent the
climate will be effected, if we put in solid flooring over such a
large area of the ground floor.

The building is 37 x 16 metres. In the south end of the building a
room  (64 square meters) has been partitioned off for cleaning and
packing of objects, before they are placed in the store.  Access to
this room from the outside is through a large roller gate. The same
type of gate gives access between the "reception room" and the
storage unit itself. The building is made from clapboard timber
which is isolated and the interior is clad with wooden boards.

The idea is that the boards act as a buffer. The climate in the
storage unit is controlled by a dehumidifier connected to a
ventilation system. The air is sucked out at floor level at the
Eastern side of the building, and the dehumidified air is pumped
into the building underneath the ridge of the roof along the length
of the building. The concern is whether covering up so large an area
with the mezzanine could hinder air circulation, thus creating an
"upstairs" and a "downstairs" climate. Or that discreet areas with
"their own climates" are created. However there are gaps (43 cm)
between the sides of the mezzanine and the walls of the building.
These gaps will be continued along the new mezzanine and all
together create a space of 22 square meters for the air to
circulate. Air will also be able to circulate between the two levels
by the entrance of the storage unit (Southern end of the building);
an opening with stairs and access for a fork lift corresponding to
approximately 20% of the ground floor area.

The use of industrial grating is considered to be incorporated in
the mezzanine floor to aid air flow, however, the museum cannot
afford to make the whole of the mezzanine floor out of industrial
grating. Would it make any considerable difference to the air
circulation, if industrial grating was placed underneath the metal
shelving units on the mezzanine along the centre of the building?
(All together 3 square meters of grating).  There is a gap of 50 cm
between the floor and the lowest shelf. Or would grating serve
better somewhere else, like in the Northern end of the build where
there is no larger opening? Any advice on the matter would be most
appreciated as well as references to literature on the subject.

Ida Hovmand
Faelleskonserveringen v/Langelands Museum
Ostergade 25
5900 Rudkobing
+45 63516312

                  Conservation DistList Instance 22:38
                Distributed: Saturday, January 10, 2009
                       Message Id: cdl-22-38-020
Received on Tuesday, 6 January, 2009

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