Historical mechanical systems

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01.jpg (22894 bytes)Preservation experts from the National Park Service recommend the following steps in restoring any historic structure. First, identify the historically significant features. Second, protect the features that are historically significant. Third, repair damage to historically important features. Fourth, replace what cannot be repaired. Fifth, recreate missing features that were historically significant. These steps are based on guidelines developed by the Department of the Interior.

Mechanical Systems: An introduction

Mechanical, lighting and plumbing systems improved significantly with the coming of the Industrial Revolution.

The 19th century interest in hygiene, personal comfort, and the reduction of the spread of disease were met with the development of central heating, piped water, piped gas, and network of underground cast iron sewers.Vitreous tiles in kitchens, baths and hospitals could be cleaned easily and regularly.

The mass production of cast iron radiators, as pictured above, made central heating affordable to many; some radiators were elaborate and included special warming chambers for plates or linens. Ornamental grilles and registers provided decorative covers for functional heaters in public spaces.

By the turn of the 20th century, it was common to have all these modern amenities as an integral part of the building.

02.jpg (14524 bytes)The greatest impact of the 20th century on mechanical systems was the use of electricity for interior lighting, forced air ventilation, elevators for tall buildings, and electric heat.

At left, is electric lighting and a decorative ceiling in an early 20th century office building. The new age of technology brought an increasingly high level of design and decorative art to the functional elements of mechanical, electrical and plumbing systems.

The visible decorative features of historic mechanical systems such as grilles, lighting fixtures, and ornamental switch plates may contribute to the overall historic character of the building and should thus be retained and repaired, whenever possible.

Their identification needs to take place together with an evaluation of their physical condition early in project planning. On the other hand, the functioning parts of many older systems, such as compressors and their ductwork, and wiring and pipes may often need to be upgraded or entirely replaced in order to accommodate the new use and to meet code requirements.

Step 1: Identify, retain, preserve

03.jpg (16476 bytes)Identify, retain, and preserve visible features of early mechanical systems that are important in defining the overall historic character of the building.

This may include radiators, vents, fans, grilles, plumbing fixtures, switch plates and lights. At right, an ornate gas lighting fixture has been electrified.

Not recommended:

  • 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.

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Step 2: Protect and maintain historically significant features

04.jpg (21453 bytes)Protect and maintain mechanical, plumbing, and electrical systems and their features through cyclical cleaning and other appropriate measures.

This boiler has been kept in good operating condition through ongoing maintenance.

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

Improve the energy efficiency of existing mechanical systems to help reduce the need for elaborate new equipment. Consideration should be given to installing storm windows, insulating attic crawl space, or adding awnings, if appropriate

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.

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Step 3: Repair damaged historical features

04.jpg (16170 bytes)Repair mechanical systems by augmenting or upgrading system parts, such as installing new pipes and ducts; rewiring; or adding new compressors or boilers.

At right, these elevators have been rehabilitated in a late 1920s commercial office building.

Not recommended:

  • Replacing a mechanical system or its functional parts when it could be upgraded and retained.

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Step 4: Replace what cannot be repaired

Replace in kind--or with compatible substitute material--those visible features of mechanical systems that are either extensively deteriorated or are prototypes such as ceiling fans, switch plates, radiators, grilles, or plumbing fixtures.

Not recommended:

  • Installing a replacement feature that does not convey the same visual appearance.

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Step 5: Alternations/Additions for new use

The following work is highlighted to indicate that it represents the particularly complex technical or design aspects of rehabilitation projects and should only be considered after the preservation concerns listed above have been addressed.

Install 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 the historic building material.

Provide adequate structural support for new mechanical equipment.

Install the vertical runs of ducts, pipes, and cables in closets, service rooms, and wall cavities.

Install air conditioning units, if required by the new use, in such a manner that historic features are not damaged or obscured and excessive moisture is not generated that will accelerate deterioration of historic materials.

Install 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.

11.jpg (6517 bytes)Not recommended:

  • Installing a new mechanical system so that character-defining structural or interior features are radically changed, damaged, or destroyed.
  • At right, new electrical meters have been inappropriately installed at a primary elevation.
  • 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 character-defining features.
  • 12.jpg (5694 bytes)Concealing mechanical equipment in walls or ceilings in a manner that requires the removal of historic building material.
  • Installing a "dropped" acoustical ceiling to hide mechanical equipment when this destroys the proportions of character-defining interior spaces.
  • Cutting through features such as masonry walls in order to install air conditioning units.
  • At right, historic building material has been destroyed by through-the-wall air-conditioners.
  • Radically changing the appearance of the historic building or damaging or destroying windows by installing heating/air conditioning units in historic window frames.

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To see a list of all of the stories in this series, click here.

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