Concord, NH

St. Paul's School


During winter seasons, St. Paul’s School struggled to maintain daily temperatures with overnight mechanical setbacks in their 1936 schoolhouse. Window air leakage leading to occupant thermal discomfort drove St. Paul’s to replace approximately 500 windows in the building. SGH conducted whole building air leakage testing and used site-specific weather data to validate energy models before and after window replacement. SGH self-funded this research and worked in collaboration with St. Paul’s and Honeywell International Inc.

SGH performed a whole-building energy analysis with qualitative and quantitative air leakage tests for the metal-framed, leaded-glass windows. We predicted replacing the windows would reduce heating requirements and increase occupant comfort during heating seasons.

In a collaborative effort with St. Paul’s and Honeywell, SGH conducted field testing and monitoring to gather performance data before and after window replacement. Our program included installing a rooftop weather station, using temperature/humidity loggers to record interior conditions, conducting whole building air leakage testing, and recording electrical consumption and heat use. We collected data every 10 min. and regularly downloaded it from a laptop at the school to SGH through a dedicated web portal.

During a window replacement mockup, SGH conducted a hands-on Earth Day workshop for students and faculty to help them understand more about window air leakage and thermal efficiency.

Based on our research, we determined using whole building air leakage and site-specific weather data significantly improved the accuracy of our energy models. With actual data, our results fell within 8% of actual energy usage while they were off by nearly 65% using conventional assumptions. By replacing the windows, St. Paul’s was able to remove supplemental space heaters and implement overnight mechanical setbacks without impacting daily temperatures or occupant comfort.

Project Summary



Completion Date
Repair & Rehabilitation
Building Enclosures | Performance & Code Consulting | Applied Science & Research
Specialized Capabilities
Building Science | Energy & Sustainability | Environmental Simulations

Key team members

Jason Der Ananian
Jason Der Ananian
Associate Principal