Comfort: Enhanced Triple Pane Glass

Calculating Comfort

Comfort levels

Renewal by Andersen and Berkeley Lab modeled the comfort in a typical living space within a typical home using our windows with Enhanced Triple Pane glass, as well as typical clear air-filled dual pane double-hung vinyl windows to -13.6°F sub-zero winter day in Minnesota, with the thermostat set for an indoor temperature of 72°F. Renewal by Andersen windows with Enhanced Triple Pane glass improve the comfortable area of a room.


*Actual experience may vary based on variables of your home and other conditions. Modeled with Renewal by Andersen double-hung windows with Enhanced Triple Pane glass with krypton glass blend fill and default performance values of a typical clear air filled dual pane vinyl windows a in a room with 4’x5’ and 3’x5’ windows. Scale of -3 to 5, maximum combined radiant and downdraft Predicted Percentage of Dissatisfied (PPD) difference from threshold. Values greater than 0 are uncomfortable.


Windows are typically large vertical surfaces that allow direct solar radiation and have relatively low thermal performance compared to insulating walls. These characteristics result in three primary drivers of comfort with respect to windows; direct solar gains, radiant heat exchange between the window and occupant, and drafts due to induced convection on the room-side window surface. Direct solar gains can be associated with visual discomfort (glare) and thermal discomfort (overheating), while radiant heat exchange and drafts drive comfort with windows in cold climates.


Thermal comfort is subjective. For instance, if two people occupy the same space one may feel hot and the other cold, even though their environment is the same. For this reason, in 1967 Povl Ole Fanger developed a comfort model that predicts the typical fraction of people dissatisfied in any given environment. His research showed that with large samples of people there will always be some fraction that are uncomfortable. Current industry practice is to design heating and air conditioning systems so that no more than 10% of the occupants are dissatisfied.


The Fanger model bases discomfort due to air movement to thermal sensation at the neck. Since windows are typically large vertical surfaces, the downdrafts formed when warm room air meets a cold window surface are most often strongest lower to the ground, not at the neck. A more relevant model for draft discomfort based at the ankle level was therefore developed in 2016 by a team led by Shichao Liu. A threshold of 20% of occupants dissatisfied due to ankle draft is currently accepted as industry best practice.


The Liu and Fanger models can be utilized together by reporting the fraction of occupants that are dissatisfied based on whichever model is closest to its threshold value.

Supporting Information: