Understanding Full Frame High R-Value

R-Value is a measure of thermal resistance used in the building industry. A high-R-value window has a greater resistance to heat flow and a higher insulating value than one with a low R-value. R-value is the inverse of the U-factor (R = 1/U) and is expressed in units of hr-sq ft-°F/Btu.

Full Frame R-Values

At Serious Energy we always report the full frame R-value of our windows and not just the center of glass performance. SeriousWindows framing systems are engineered to maintain a constant temperature and insulation across the entire full frame.

The thermal image below shows the cross section of a standard dual-pane low-e aluminum framed window and the cross section of SeriousWindows’s fiberglass frame with two panes of glass and one layer of suspended film. The colors depicted show the amount of thermal energy (Btu/h-ft2) passing through the frame. Purple means virtually no thermal energy is transferring through. The more green, red, orange and yellow means the more thermal energy that is passing through with red representing the most energy being transferred. The white areas in the image at left indicate the highest level of heat transfer - this is like a highway for heat to leave the home.

The thermal image clearly shows that in well made multi-paned, low-e windows, the main source of thermal energy transfer is through the framing system. Knowing the full frame R-value of a window is critical in ensuring that you are getting a high quality, energy efficient window.

SeriousWindows framing system provides a full frame R-Value, preventing unwanted heat or cold from passing though the framing system

Modeled via THERM 6.1 Simulation software, Lawrence Berkeley National Labs

Five Factors That Affect Full Frame R-value of a Window

• The type of glazing material (e.g., glass, suspended film, treated glass)
• The number of air chambers created by multiple layers of suspended film or glass panes
• What type of gas, if any, is used to fill the air space(s)
• The thermal resistance of the frame and spacer materials
• The "tightness" of the window – how much air leaks through

Most windows on the market today can achieve a relatively high center-of-glass performance number, but if they are poorly manufactured, they can leak air or have a frame made of material that is not an effective insulator that can increase condensation and create a draft.

Example Comfort and Energy Efficiency Benefit of Full-Frame High R-value SeriousWindows

SeriousWindows were used in a new construction project in upstate Oregon. This home is built to Passive Design standards that requires super-insulating performance of windows and walls (high R-value and exceptional air infiltration performance for maximum air tightness). When construction on the house was completed, and before heating was turned on, the contractor wanted to see how well our windows could perform based on measuring the temperature across the full frame of the window compared to the temperature of the walls.

The following images show a thermal gauge taking a reading outside of the house in the evening with a temperature of 45 degrees, then a reading of the inside of and exterior facing wall with a temperature, and finally, SeriousWindows at the frame and at the corner. The temperature of our window was only 1.5 degrees different from the wall temperature.

SeriousWindows glass and frame temperature is 69.5º F even though the outside temperature is 45º F. A warm interior glass and frame can reduce a home's energy use and create a comfortable home indoors, year-round.