Museums are often housed in monumental buildings, most of which were not built for this purpose. For preservation of artifacts
in a museum, the indoor climate is often restricted to a very narrow interval for temperature, but most of all for relative humidity.
This restricted indoor climate originally dates from the 1970s. Unfortunately, restricted museum climates do not fit well into old
buildings. The indoor surface conditions near cold walls under winter conditions lead to mold growth and other deterioration
of the wall surfaces. Moreover, the museum conditions of artifacts near cold walls are not in line with museum recommendations.
To show the building physical effects of a restricted indoor museum climate on old buildings, case studies were carried out
in several Dutch museums. Buildings and their HVAC systems were analyzed in a methodical way. For at least one year, temperature
and relative humidity were recorded in different rooms and at different external wall surfaces of the museums. Additionally,
outdoor climate, CO2 concentration, ventilation, and infiltration measurements were performed.

The results of this measurement campaign reveal that there were a large number of indoor climate conditions that did not
satisfy the originally formulated restricted climate. There was a large contrast between target indoor museum climate and
measured resultant indoor climate in rooms and near external walls.

The target indoor climate in museums that are housed in monumental buildings should be reconsidered. A multidisciplinary
network of people involved with indoor climate in museums (conservators; museum, monumental building, and HVAC consultants;
and building physicists) has been set up to formulate new guidelines for the indoor climate in Dutch museums. The current
ASHRAE guidelines are introduced as an assessment tool for measured climates; results are used to determine the usability of
ASHRAE in the Dutch situation and to optimize indoor climate and system performance.