Evaluating the value of window replacement or determining the type of window/glazing to be used can be difficult. Pella’s architects and engineers use a program called THERM and a custom-developed Envelope Analysis tool to model results. These tools can help ensure you are getting the best performance from your building envelope strategy.
THERM’s heat-transfer analysis allows you to evaluate a product’s energy efficiency based on local temperature patterns that may relate directly to problems with condensation and moisture damage. All three models below show similar color infrared lines in the existing wall; however, the window and glazing are different. Observation shows that the existing glazing will have condensation issues, since the temperature falls below the calculated dew point.Original Wall Description:
- Brick exterior and CMU wall construction
- Replacement of window
- Furring and drywall added to the interior
- Indoor air temperature: 72°F
- Outdoor air temperature: 0°F
- Interior relative humidity: 25%
- Calculated dew point: 34.25°F
Software: THERM 6.3, WINDOW 6.3
Codes/Standards: NFRC 100 — 2010 and ASHRAE 90.1
Project shown above: Fred and Sara Machetanz Elementary School, Mat Su Borough, AK, featuring Pella Impervia Fiberglass Single-Hung and Fixed Windows.