Retrofit 'Green' : The Building Envelope

"Not since the days of the oil crisis in the 1970's have Americans been so focused on energy consumption, especially weatherization. Just as the cost of heating and cooling has risen, so has the awareness of just how much energy seeps out of an average home every day. Central to this discussion is the role of older and historic buildings – and making them more energy efficient without jeopardizing their unique character."
- The National Trust for Historic Preservation

How do air and heat move through a building?

Building Envelope

When we talk about air seeping out of a building, we are primarily concerned with the building envelope, or the physical separator between the inside and the outside. The entire 'shell' of the buliding is considered, from the foundation to the walls to the roof and the framing and interior and exterior sheathing. In a building, all of these materials are joined together to form an effective envelope to protect occupants from the elements!

It is often the meeting of materials that affect heat loss. These joints are locations to inspect for possible air leaks. Simple and obvious improvements to these areas can make a huge difference in terms of air, or energy loss, and the tightness of the building envelope. Improvements to the building envelope are often the most simple, most effective and least expensive weatherization tactics. Thus, the first step in successful weatherization begins here - assessing the performance of the building envelope.

Energy Audit!

An energy audit, or home energy assessment, assesses how much energy a building consumes.

To save time, money & energy DO NOT replace windows, add insulation, buy a new HVAC system, or install new roofing, before understanding HOW your building envelope is performing!

Blower Door test

The blower door test requires sealing up your building to make it as air tight as possible. A high-powered fan is mounted to an exterior door frame and pulls the air out of the building, depressurzing the space. An air pressure gauge measures this difference in air pressure between the inside and outside. The difference in pressure causes the outside air to seek its way into the building through any cracks, drafts or unsealed openings. By showing where air is escaping from the building envelope, the blower door test provides obvious direction- Seal up your existing holes! Insulation, new windows or new systems cannot save any building energy if there are cracks and drafts allowing air to escape!

In terms of improvements on historic buildings, we must proceed with caution, making improvements without damaging historic fabric or integrity.
An energy audit is the best first step, as it measures current energy use and models potential improvements, without actually making any alterations.

"The CGC recognizes that buildings are a primary contributor to Charleston's greenhouse gas emissions for which it is working to establish and implement energy efficiency standards including retrofitting guidelines within an historic context."

– Charleston Green Committee

Energy Audit @ the Preservation Society!

Our building is currently involved in a study to illustrate the feasibility of improving energy efficiency, while maintaining historic integrity and fabric. Analysis of our existing building will assess the efficiency of the building envelope and systems. Analysis of two years of utility bills will also assess peak consumption.

This information will help generate a computer model to simulate our building, in the context of a warm, humid climate. Within this model, improvement strategies will be tested to assess their effectiveness and determine the most cost effective ways to make our historic building more efficient, reducing our energy consumption (and monthly utility bills)!

In Charleston, we are fortunate to have organizations engaged in developing standards for energy efficiency specifically for Historic Structures. The Sustainability Institute has brought together a committee to modify the Building Performance Institute (BPI) standards specifically for historic structures in a hot, humid climate. Such an initiative puts Charleston in a unique position to truly improve the energy consumption of historic buildings, lessening our reliance on non-renewables and embracing a path towards sustainability. Learn more!


Sustainability Institute & Local Energy Audits!