Energy Code Terms

“building thermal envelope”:

The basement walls, exterior walls, floor, roof, and any other building element that enclose “conditioned space”. This boundary also includes the boundary between conditioned space and any exempt or unconditioned space.

“conditioned space”:

An area or room within a building being heated or cooled, containing uninsulated ducts, or with a fixed opening directly into an adjacent conditioned space.

"energy certificate":

A permanent certificate posted on or in the electrical service entrance panel. the certificate shall be completed by the builder, listing all predominant R-values of installed insulation. In addition, U-factors for fenestration and HVAC energy efficiency equipment rating shall also be noted. ***Please note: Where there is more than one value for each component, the certificate shall list the value covering the largest area.


Skylights, roof windows, vertical windows (whether fixed or moveable); opaque doors; glazed doors; glass block; and combination opaque/glazed doors.

“R-value” (thermal resistance):

The inverse of the time rate of heat flow through a building thermal envelope element from one of its bounding surfaces to the other for a unit temperature difference between the two surfaces, under steady state conditions, per unit area.

“SHGC” (Solar Heat Gain Coefficient):

The technical definition for “SHGC” is the ratio of the solar heat gain entering the space through the fenestration assembly (window/glazed door/skylight) in comparison to the incident solar radiation. The term “solar heat gain” in the ratio includes directly transmitted solar heat and absorbed solar radiation which is then re-radiated, conducted or convected into the space. Another way to say it, is that “SHGC” measures how well a fenestration assembly blocks heat from the sunlight. “SHGC” is expressed as a number between 0 and 1. The lower the “SHGC”, the less solar heat the assembly transmits. The maximum “SHGC”, the energy code allows for new construction, is 0.40.

“U-factor” (thermal transmittance):

The coefficient of heat transmission (air to air) through a building envelope component or assembly, equal to the time rate of heat flow per unit area and unit temperature difference between the warm side and cold side air films.