Environmental Engineering Reference
In-Depth Information
steam or water pipes should be avoided. Object humidity may be destructive,
even if the ambient relative humidity is under control.
1. Sun gain: Libraries and museums usually have windows, sometimes
of stained glass and skylights—more are in trafic areas than in topic
stacks or storage areas. Care must be taken to minimise the effects of
the sun; shortwave (actinic) rays are particularly injurious. Heat gain
from skylights, often over artificially lighted frosted glass ceilings,
can be reduced by a separate forced ventilation system.
2. Transmission: In winter, effects on objects located close to outside
walls and possible condensation of moisture on the objects and the
surface of outside walls must be evaluated. In summer, possible radi-
ant effects from exposure should be considered.
3. People: Some areas may have concentrations as high as 1.0 m
2
per
person, although office space will have closer to 10 or 15 m
2
per
person, and topic stack areas up to 100 m
2
per person.
4. Lights: Careful analyses of the required lighting intensity should be
made in various rooms and in view of daylighting availability.
5. Stratification: In reading rooms, large entrance halls and large art gal-
leries with high natural or false ceilings, air temperature may stratify.
7.3.5.2 Design Concepts
All air ducted systems are preferred in library public areas, but careful
evaluation of relative humidity is essential. This is also true for museums
because exhibit items are generally irreplaceable. In museums, people loads
vary, depending on whether there is a new exhibit and on the time of day, the
weather and other factors. Thus, individually controlled zones are required
to maintain optimal environmental conditions. Attempts to establish a mod-
ular system for partitions have been only partially successful because of the
wide range of sizes of items in the exhibits. In art museums, particularly,
partitions may create local pockets with hot air supply or exhaust; transfer
grilles may be placed in the partitions to obtain some air flow movement.
Another problem is the location of room thermostats and humidistats.
7.3.5.3 Special Considerations
Many old manuscripts, topics and artefacts [11,26-31] have been damaged
or destroyed because they were not kept in a properly air-conditioned
environment. The need for better preservation of such valuable materials,
together with a rising popular interest in the use of libraries and museums,
requires that most of them, whether new or existing, be air-conditioned. Air-
conditioning problems for museums and libraries are generally similar but
differ in design concept and application. Figure 7.9 depicts an example of
artefact deterioration due to excessive humidity [26,32].
