APT DC Blog

  • Thursday, June 15, 2017 9:23 PM | Anonymous member (Administrator)

    At the 2017 APT DC Symposium this May, over 90 preservation professionals from a variety of backgrounds gathered to hear from experts working to increase energy efficiency in historic structures. The day’s presentations covered energy codes, energy models, increasing the efficiency of historic materials, and regional case studies. The day opened with a presentation from Historic Environment Scotland, demonstrating that the desire for efficiency in our historic resources is global!


    Our top ten takeaways from the Symposium are:

    1. International standards like the IgCC set a minimum baseline for energy codes, but codes can vary widely by local jurisdiction. Using an integrated design process and working with local code officials will ensure you are following the right directives for your structure and locality.

    2. Energy standards like LEED, ENERGY STAR, and others provide guidance in achieving a high level of energy efficiency for your structure.

    3. Achieving energy savings with historic preservation projects is well within reach, even though improvements to the envelope often aren’t feasible. Using energy models will help you determine improvements that provide the biggest savings for the lowest impact.

    4. There are many types of energy models available on the market. Using the right model at the right time will help you predict or assess energy savings before, during, and after a project.

    5. Think carefully about which components in your building are most appropriate for upgrades or modifications:

    • Floors (adding insulation, radiant heating)
    • Windows (adding draft strips, secondary glazing, insulating air gaps, solar screening, using shutters - interior or exterior)
    • Roof (adding insulation on the interior, adding ventilation, painting the exterior, greening)
    • Doors & openings (adding aerogel to frames or similar draft strips, adding vestibules)
    • Walls (adding or removing insulation, moisture barriers)
    • Mechanical upgrades (plug loads, LED lighting, sensors & their locations, relocating diffusers, increasing plant capacity with larger chillers/cooling towers, changing from constant air volume (CAV) air handling units (AHUs) to single-zone Variable Air Volume (VAV) systems)

    6. Energy modeling can show the order-of-magnitude effect of different upgrades to a Modernist curtain wall-clad building’s systems to help owners decide in which upgrades they would like to invest in (mechanical, lighting, enclosure, etc.).

    7. Mass masonry walls are prone to deterioration if insulated improperly. It’s important to use tools like hygrothermal analysis to determine the brick’s properties and select the right type of insulating material.

    8. New technologies like interior window retrofits will allow for greater insulation of historic sites without compromising original glazing materials or character.

    9. Before inserting new materials into an existing system, make sure to investigate how your building and its materials are designed to perform, and consider how modifying an existing system will affect the structure. Investigate the real cause of problems first - maintenance issues, leaks, improper flashing, failure of finishes, etc.

    10. There are many reasons to pursue energy efficiency in a historic preservation project: cost savings, occupant comfort, material preservation, and of course, environmental impact. Local programs like Sustainable DC recognize that historic resources are often most at risk for the effects of climate change. We all have a part to play in ensuring the worst consequences don’t come to reality!

    We’re so thankful to all our presenters for sharing their work with our audience! If you are interested in learning more, PDFs of their presentations have been made available on the APT DC Symposium web page. Thanks also to the sponsors who made the event possible: Encore Sustainable Design; The Weidt Group; Conservation Solutions, Inc; Quinn Evans Architects; EHT Traceries; Consigli Construction; and our host, the Fred W. Smith Library for the Study of George Washington at Mount Vernon.



  • Wednesday, April 26, 2017 8:55 PM | Anonymous member (Administrator)

    Welcome to Preservation Pointers, APT DC’s new blog series! Here, we will post about events, tours, and lectures hosted by APT DC. The blog will summarize the important points from those events which we feel are the most useful to preservation professionals.

    Preservation Pointers #1: Takeaways from APT DC’s April Tour of Cathedral Stone

    Cathedral Stone, Inc., manufacturer of specialty cleaning products, paint strippers, and repair mortars for masonry, hosted a tour and hands-on learning experience for APT DC on Saturday, April 22, 2017 at their manufacturing facility. The following topics were discussed.


    Masonry Cleaners

    There are several different categories of cleaning products available to preservation professionals for use on masonry. It is important to understand the proper uses and application for each, and to always test cleaners prior to full application. Some of the most common types of cleaners on the market are:

    • Biological Cleaners: Used to remove algae, lichen, and other forms of biological growth.
    • Detergent Cleaners: Typically mild, non-acidic, and safe for use on all masonry surfaces including calcareous and polished stone
    • Acidic cleaners: Containing varying concentrations of acidic cleaning agents. Acidic cleaners generally should not be used on calcareous or polished stones and should be used with caution.
    • Waterless Latex Cleaners: Cleaner applied in gel form that cures and can be stripped as a solid. This type of cleaner is ideal for interior surfaces where large amounts of rinsing water is not possible.

    Paint Strippers

    As the preservation industry moves away from solvent-based paint strippers due to health and environmental concerns, more water-based products are becoming available. Water-based paint strippers have the following advantages:

    • Non-flammable
    • Low VOC
    • Biodegradable
    • Applicators require no or little protective gear
    • Neutralization with only water or denatured alcohol
    • No need to cover, non-hazardous
    • No HAPs or TAPs (Toxic/hazardous air pollutants)
    • No BTEX chemicals
    • Non-carcinogenic

    Repair Mortars

    Failures in masonry restoration often result from patching materials that are stronger than the stone substrate. It is critical that patching materials have a lower compressive strength the substrate itself. Porous stone substrates also need to be able to breathe. Patching materials that have low water vapor permeability entrap moisture within the stone, leading to failure. Polymers, which are often used as an adhesive agent to form a strong bond with the substrate, can eventually lead to failure by trapping water and salts. They also tend to discolor over time because they are not UV stable.

    When selecting a patching mortar, it is critical to select a material that is colored with UV stable pigments that will not fade out. It is also important to recognize the effect of the amount of mixing water on the color of the cured mortar. When evaluating mortar samples for color, they should always be applied on a proper substrate. The practice of creating mortar samples in coffee cups, common among some masonry contractors, doesn’t give a true representation of color because water is not allowed to evaporate through the Styrofoam or plastic. Instead, samples should be placed on a porous substrate, ideally the same substrate where mortar will be applied.



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