Identify, Retain and Preserve
Identifying, retaining, and preserving visible features
of early mechanical systems from the restoration period
such as radiators, vents, fans, grilles, plumbing fixtures,
switchplates, and lights.
The significant ceiling light in this civic
auditorium in Kansas City, Missouri, represents
the 1930 Moderne style. It would be important
to retain and preserve it in any restoration project.
Photo: HABS Collection, NPS.
Altering visible decorative features of mechanical systems
from the restoration period.
Failing to properly document mechanical systems and
their visible decorative features from the restoration
period which may result in their loss.
Protect and Maintain
Protecting and maintaining mechanical, plumbing,
and electrical systems and their features from the restoration
period through cyclical cleaning and other appropriate
Preventing accelerated deterioration of mechanical
systems by providing adequate ventilation of attics,
crawlspaces, and cellars so that moisture problems are
Installing a fan (successfully concealed here in a vented enclosure) for increased ventilation can be a successful
low-tech substitute for air conditioning. Photo:
Courtesy, Shelbourne Village.
Improving the energy efficiency of existing mechanical
systems to help reduce the need for elaborate new equipment.
Failing to provide adequate protection of materials
on a cyclical basis so that deterioration of mechanical
systems and their visible features results.
Enclosing mechanical systems in areas that are not
adequately ventilated so that deterioration of the systems
Installing unnecessary air conditioning or climate
control systems which can add excessive moisture to
the building. This additional moisture can either condense
inside, damaging interior surfaces, or pass through
interior walls to the exterior, potentially damaging
adjacent materials as it migrates.
Repairing mechanical systems from the restoration
period by augmenting or upgrading system parts, such
as installing new pipes and ducts; rewiring; or adding
new compressors or boilers.
Replacing a mechanical system from the restoration period
or its functional parts when it could be upgraded and
Replacing in kind--or with compatible substitute
material--those visible features of restoration period
mechanical systems that are either extensively deteriorated
or are prototypes such as ceiling fans, switchplates,
radiators, grilles, or plumbing fixtures. Installing
a new mechanical system, if required, in a way that
results in the least alteration possible to the building.
Hidden HVAC systems should be used for formal
spaces. Here, a sprinkler system is unobtrusively
placed behind a false cornice at the end of a
corridor. Photo: NPS files.
Providing adequate structural support for new mechanical
Installing the vertical runs of ducts, pipes, and
cables in closets, service rooms, and wall cavities.
Installing air conditioning units in such a manner
that features are not damaged or obscured and excessive
moisture is not generated that will accelerate deterioration
of historic materials.
Installing a visible replacement feature that does not
convey the same visual appearance.Installing a new mechanical
system so that structural or interior features from
the restoration period are altered.
These new meters for the building's power usage
have been inappropriately installed on a primary
elevation. Photo: NPS files.
Failing to consider the weight and design of new mechanical
equipment so that, as a result, historic structural
members or finished surfaces are weakened or cracked.
Installing vertical runs of ducts, pipes, and cables
in places where they will obscure features from the
Concealing mechanical equipment in walls or ceilings
in a manner that requires the removal of building material
from the restoration period.
Cutting through features such as masonry walls in order
to install air conditioning units.
The following Restoration
work is highlighted to indicate that it involves
the removal or alteration of existing historic
mechanical systems and features that would be
retained in Preservation and Rehabilitation treatments;
and the replacement of missing mechanical systems
and features from the restoration period using
all new materials.
Removing Existing Features from Other Historic
Removing or altering mechanical systems and
features from other historic periods such as a
later elevator or plumbing fixture.
Documenting materials and features dating
from other periods prior to their alteration or
removal. If possible, selected examples of these
features or materials should be stored to facilitate
Failing to remove a mechanical system or feature
from another period, thus confusing the depiction
of the building's significance.
Failing to document mechanical systems and features
from other historic periods that are removed from
the building so that a valuable portion of the
historic record is lost.
Re-creating Missing Features
from the Restoration Period
Re-creating a missing feature of the mechanical
system that existed during the restoration period
based on physical or documentary evidence; for
example, duplicating a heating vent or gaslight
This drawing of a 19th century gas lighting
fixture is being used as documentation to
duplicate the fixture
in a significant interior as part of a larger
restoration project. Drawing: NPS files.
Constructing a mechanical system or feature that
was part of the original design for the building
but was never actually built; or constructing
a feature which was thought to have existed during
the restoration period, but for which there is