Successfully introducing modern mechanical systems (HVAC) into historic buildings may be the most challenging aspect of an historic rehabilitation program. When that building is also used as part of an interpretive museum, it is generally the most controversial. Mechanical engineers must design for both the building and the collection. Planning changes to the interior environment of an historic building requires professionals knowledgeable in multiple disciplines. Without a team approach and thorough analysis, there is bound to be disappointment in the final product. Architects, engineers, curators, conservators, building owners, manufacturer's representatives, contractors, and others should see and understand the building in its historical context before they recommend changes.