Guidelines For Rehabilitating Historic Buildings: Mechanical Systems
GUIDELINES FOR REHABILITATING HISTORIC BUILDINGS: MECHANICAL
U.S. Department of the Interior
National Park Service
Preservation Assistance Division
An illustrated booklet addressing the Secretary's Standards and the
guidelines is available from the U.S. Government Printing Office.
The title is "The Secretary of the Interior's Standards for
Rehabilitation & Illustrated Guidelines for Rehabilitating Historic
Buildings", ISBN 0-16-035979-1.
Each of the guidelines included in the booklet mentioned above have
been separated into individual entries for specific use in HBPP.
This entry represents one of many guidelines included in the
booklet and describes RECOMMENDED and NOT RECOMMENDED applications
of the Secretary of the Interior's Standards as they relate to
Mechanical Systems. For a list of the Secretary of the Interior's
Standards for Rehabilitation, see 01091-04-S; For general
information relating to the purpose, organization and content of
the individual guidelines, see 01091-05-S. Both of these entries
should be referenced along with the information contained in this
MECHANICAL SYSTEMS: Heating, Air Conditioning, Electrical, and
The visible features of historic heating, lighting, air
conditioning and plumbing systems may sometimes help define the
overall historic character of the building and should thus be
retained and repaired, whenever possible. The systems themselves
(the compressors, boilers, generators and their ductwork, wiring
and pipes) will generally either need to be upgraded, augmented, or
entirely replaced in order to accommodate the new use and to meet
code requirements. Less frequently, individual portions of a
system or an entire system are significant in the history of
building technology; therefore, the identification of character-defining features or historically
significant systems should take
place together with an evaluation of their physical condition early
in project planning.
IDENTIFYING, RETAINING AND PRESERVING
- Identifying, retaining, and preserving visible features
of early mechanical systems that are important in
defining the overall historic character of the building,
such as radiators, vents, fans, grilles, plumbing
fixtures, switchplates, and lights.
- Removing or radically changing features of mechanical
systems that are important in defining the overall
historic character of the building so that, as a result,
the character is diminished.
PROTECTING AND MAINTAINING
- Protecting and maintaining mechanical, plumbing, and
electrical systems and their features through cyclical
cleaning and other appropriate measures.
- Failing to provide adequate protection of materials on a
cyclical basis so that deterioration of mechanical
systems and their visible features results.
- Preventing accelerated deterioration of mechanical
systems by providing adequate ventilation of attics,
crawlspaces, and cellars so that moisture problems are
- Enclosing mechanical systems in areas that are not
adequately ventilated so that deterioration of the
- Repairing mechanical systems by augmenting or upgrading
system parts, such as installing new pipes and ducts;
requiring; or adding new compressors or boilers.
- Replacing a mechanical system or its functional parts
when it could be upgraded and retained.
- Replacing in kind -- or with compatible substitute
material -- those visible features of mechanical systems
that are either extensively deteriorated or are missing
when there are surviving prototypes such as ceiling fans,
switchplates, radiators, grilles, or plumbing fixtures.
- Installing a replacement feature that does not convey the
same visual appearance.
NOTE: THE FOLLOWING REPRESENTS PARTICULARLY COMPLEX TECHNICAL OR
DESIGN ASPECTS OF REHABILITATION PROJECTS AND SHOULD ONLY BE
CONSIDERED AFTER THE PRESERVATION CONCERNS LISTED ABOVE HAVE BEEN
ALTERATIONS/ADDITIONS FOR THE NEW USE
- Installing a completely new mechanical system if required
for the new use so that it causes the least alteration
possible to the building's floor plan, the exterior
elevations, and the least damage to historic building
- Installing a new mechanical system so that character-
defining structural or interior features are radically
changed, damaged, or destroyed.
- Installing the vertical runs of ducts, pipes, and cables
in closets, service rooms, and wall cavities.
- Installing vertical runs of ducts, pipes, and cables in
places where they will obscure character-defining
- Concealing mechanical equipment in walls or ceilings in
a manner that requires the removal of historic building
- Installing "dropped" acoustical ceilings to hide
mechanical equipment when this destroys the proportions
of character-defining interior spaces.
- Installing air conditioning units if required by the new
use in such a manner that the historic materials and
features are not damaged or obscured.
- Cutting through features such as masonry walls in order
to install air conditioning units.
- Installing heating/air conditioning units in the window
frames in such a manner that the sash and frames are
protected. Window installations should be considered
only when all other viable heating/cooling systems would
result in significant damage to historic materials.
- Radically changing the appearance of the historic
building or damaging or destroying windows by installing
heating/air conditioning units in historic window frames.
END OF SECTION