Over the years, the historic preservation of buildings has evolved from a small gesture to a nationwide endeavor to understand the national heritage, legacy, and values they bestow onto their communities. In addition to its creation in 1968 at the federal level with the National Historic Preservation Program, all 50 states have established State Historic Preservation Offices (SHPOs) at the local level to represent their communities and cultures. Along with cultural preservation, the increased importance of reusing existing structures and reducing carbon footprint can be the reason when identifying a building for historic renovation. The embodied carbon of an existing building is estimated to account for 50-75 percent when compared to that of new construction. The following article outlines best practices when considering a project for historic renovation.
Get a historic consultant involved EARLY
First, it is important to get a Historic Consultant, or someone familiar with the process of historic preservation, involved with the project early. A historian’s knowledge of existing databases, the process for nominating a property, and knowing what information is important to include can save a project time and money and protect it from potential pitfalls that can happen along the way.
Do your due diligence
Though it may seem obvious, it is important to determine how old the building is. If the building is not fifty years old, then it does not qualify as “historic”. Established in 1948 by the National Park Service, the aptly named “fifty-year rule” sets a benchmark for determining historic significance and minimizes the potential for controversy about this determination. Secondly, check to see if the building has been listed on the historic registry. Authorized in 1966, the National Register of Historic Places is the official database of projects ranging from buildings, structures, and district sites, to objects located throughout the United States. In addition to this registry, many State Historic Preservation Offices (SHPOs) have their own database that may contain further information on a project. It’s important to check these databases for vetting a building’s viability to receive tax credits. Most projects listed on the National Register of Historic Places have received some form of funding or incentives, but there are one-off buildings that never received such funding and are seeking to rehabilitate a portion of the building that may qualify for tax credit incentives. Assuming the building meets the “fifty-year rule”, a building must also convey its significance through its physical features, otherwise known as integrity. The seven aspects of integrity (location, design, setting, materials, workmanship, feeling, and association) are all used in determining a building’s why, where and when of significance.
Establish your approach
Congratulations – you’ve determined your prospective building indeed possesses historic integrity and you understand the importance of preserving it. The next steps will establish how to approach the treatment of a historic building. Like the medical profession, historic preservation standards encourage their own Hippocratic Oath of first and foremost – do no harm. A hierarchy of approaches has been established within the Secretary of the Interior’s Standards, intended to promote responsible preservation practices by presenting methods of least intervention to most intervention:
Preservation – incorporating necessary measures to maintain the existing building’s integrity and state of being, usually established through ongoing maintenance. New interventions do not apply to this treatment.
Rehabilitation – the act of altering or adding to a historic property to establish a similar or changed use to a building, while maintaining the historic characteristics of the building.
Restoration – reinstating a building to a particular time period of significance by removing elements from other periods and reconstructing missing defining features from the designated restoration period of significance.
Reconstruction – the re-creation of missing buildings or portions thereof by replication through new construction and materials for interpretation.
While all of these methods can be used on a project in varying capacities, rehabilitation is the most commonly used method by developers as more often than not, a different use is being considered for the space. It is important to vet this use against the historic characteristics of the building to determine if the prospective building is a viable candidate for the new use. In addition to these methods, the National Park Service has provided a series of preservation briefs to help assist in methods for specific building components that may be part of the project.
Be careful what you touch
An instinctive approach to an old leaky building might involve improving the insulative values of the envelope components. In some cases, this might spell disaster for the building you’re trying to preserve! It is important to be cautious and understand that well-intentioned new upgrades could have adverse effects on an old building. For example, an uninsulated masonry building, while not thermally efficient, has the great ability to dry out any moisture penetrating the walls or trapped within the brick or clay tile cavities. Assuming the building masonry is a character-defining feature and is unable to insulate the outside of the building, the next best intention would be to insulate the interior. While we have improved the amount of thermal energy transfer between the indoor and outdoor environments, we have taken away the ability for the exterior masonry to dry from the interior. This can cause moisture to be trapped within the masonry walls undergoing freeze-thaw cycles, further damaging the exterior masonry wall. Joseph Lstiburek, Ph. D., P. Eng., of the Building Science Corporation has published an article on the importance of addressing water infiltration before considering insulating mass walls from the interiors, especially in regions like Iowa.
Get a historic consultant involved OFTEN
Finally, in addition to getting a historic consultant involved early, it is important to keep them involved throughout the project. During design, vetting certain interventions with the existing structure can shed light on how the approach could be perceived by SHPO and whether changes should be made prior to submitting appropriate documentation for approval. A city’s code enforcement has the potential to be at odds with requirements for historic preservation. It’s important to understand which changes to a building are necessary from a life safety, or accessibility standpoint and how they might impact their implementation to maintain historic integrity. Should the project need to complete a value engineering exercise to reduce costs to maintain the project’s budget, it's important to understand how potential changes in scope could affect what is being submitted (or already submitted) to SHPO for a project’s scope to understand potential ramifications.