True Green / Making Choices About Original Design Features

Passive Climate Management Features in Traditional Historic Buildings

Original design features such as operable double hung wood windows, porches, and operable shutters were recently restored at Shadows-on-the-Teche in New Iberia, LA.

Traditional historic buildings (built before 1945) were often built in ways that recognize the high degree of individual controllability that buildings that respond to their climate and region can have. Traditional and vernacular buildings, constructed before fossil fuels were in widespread use, required active participation of building occupants to manage and control their comfort, health and productivity. The ability to control your environment is enhanced by traditional design elements such as those discussed below. If you have any of these features and they’ve been closed up or sealed shut, reopen them!!

Operable Windows & Shutters: Not only do operable windows allow you to ventilate your building and get fresh air in, the ability to control your own environment positively impacts your frame of mind. Shutters, whether interior or exterior, are not just there to look pretty. They keep the hot sun out during the hot summer day and the cold air out on the cold winter night.

Awnings: Provide shade and insulation and minimize the need for air conditioning.

Courtyards with Natural Cross Ventilation: Tropical and humid environments have effectively been using courtyards for millennia to ventilate, heat and cool buildings.

High Ceilings with Transoms Above Doors: High celings help to move hot air upward (remember, hot air rises and cold air sinks…). Transoms above doors are there to help move the air and ventilate spaces. Ceiling fans are particularly useful in moving the air around and ventilating rooms.

Roofs & Porches with Wide Roof Overhangs: Porches are not just there so you can visit with your neighbors, they also protect the interior spaces from hot sun and cold air. Wide overhangs shield the interior spaces from hot sun.

What To Do About Our Modern Heritage Buildings?

The original curtain wall at Mies van der Rohe's Farnsworth House was installed with plate glass.

While many of our traditional buildings are inherently green, many of our modern heritage buildings (those built between 1950-1980) are inherently “un-green”. Almost 60% of our building stock was built in this period and these buildings were typically the most energy-inefficient ever built. These are the buildings that are the biggest contributors to climate change. If we want to manage climate change, we need to address these buildings. As we begin to acknowledge the significance of modern heritage and acquire sites from that era, we find ourselves confronting questions and developing solutions reqarding authenticity, building fabric and energy efficiency that in many cases are the exact opposite of how we approach our traditional buildings. At two of our modern National Trust historic sites Farnsworth House and Philip Johnson Glass House, many of these issues are informing every decision we make. We are entering new territory with these buildings.

Experimental Materials & Assemblies: Glass curtain walls, precast wall and ceiling systems, concrete structure and panels – all have one thing in common – they were experimental materials and assemblies. The excitement of designing and building something completely new often superseded the rigorous research needed to confirm the longevity of these materials. Now, decades later, they may be crumbling and impossible to restore. Should we be forced to replace them in kind when they never worked or can we step outside the boundaries of the Secretary of the Interior’s Standards, and redesign and reinstall replacements that will work better and last longer but might look different?

Sealing Buildings with Curtain Walls: In this same period we seemed to have lost our minds and decided fresh air was bad and that operable windows were old fashioned and unnecessary. So we started hermetically sealing our buildings, installing curtain walls and windows that couldn’t open. How do we remake these features so that they improve our energy use, controllability and comfort but do not endanger the historic integrity of the buildings?

A turkey flew through the original plate glass curtain wall at the Philip Johnson Glass House. If anyone had been sitting on the Mies lounge they might have been seriously injured.

Hazardous & Dangerous Materials: Hand in hand with experimental materials went materials that were dangerous and toxic. Floor tiles made with asbestos. Curtain walls out of plate glass. Sealants with asbestos and paint with lead. The list goes on. Should we be restoring dangerous materials? I think not. The classic problem is the use of plate glass. At both Glass House and Farnsworth House, plate glass was originally used because tempered glass wasn’t readily avalable. But once tempered glass became the norm, whenever a piece cracked, the original owners replaced the glass with the newer, better type. As stewards for the public, we can’t continue the use of plate glass and as a result we change any cracked glass with tempered glass. That has led to interesting discussions with more traditionally-minded preservationists.

Disposal Approach to Construction: It was all about excess during this era. Why build a building to last when we could just replace it when we tired of it? While most of our primary resources at our historic sites were built to last, that doesn’t mean we may not encounter other resources at current or future sites that just were not built to last.

We will be confronting these challenges more and more as our building stock ages. The National Trust’s newest program – the Modernism + Recent Past Program will come head to head with the Sustainability Program and both will inform our Historic Sites Initiative. Stay Tuned…..

(This blog posting is a section in my upcoming “Best Practices for the Care of Structures & Landscapes Manual”.)