Detail of restored roof; Link to Parknet
<photo>operational historic boiler

Identify    Protect    Repair    Replace    Remove   Re-Create

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.

photo of significant ceiling light in a civic auditorium in Kansas City, MO

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.

Not Recommended
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 measures.

Preventing accelerated deterioration of mechanical systems by providing adequate ventilation of attics, crawlspaces, and cellars so that moisture problems are avoided.

photo of a successfully concealed fan in a vented enclosure

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.

Not Recommended
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 results.

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.

Not Recommended
Replacing a mechanical system from the restoration period or its functional parts when it could be upgraded and retained.


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.

photo of a sprinkler system that is unobtrusively placed behind a false cornice

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 equipment.

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.

Not Recommended
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.

photo showing the inappropriate placement of new meters on the front elevation of a historic building

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 restoration period.

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 Periods

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 future research.

Not Recommended
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 fixture.

drawing of a 19th century gas lighting fixture used as documentation for duplicating the fixture in a restoration project

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.

Not Recommended
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 insufficient documentation.



The Approach

Exterior Materials
Architectural Metals

Exterior Features
Entrances + Porches

Interior Features
Structural System Spaces/Features/Finishes
Mechanical Systems



Special Requirements
Energy Efficiency
Health + Safety

The Standards



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Historical Overview