In order to obtain accurate modeling results it is important to enter all surfaces through which heat is transferred in and out of the building. Model Inspector runs the following verifications of the building envelope input:

- There is roof or ceiling adjacent to outdoors.
- There is floor adjacent to outdoors or ground.
- Total floor area is within 10% of the area of horizontal projection of roof/ceiling. The horizontal projection of the roof is calculated using roof tilt in degrees and the area of the roof surface in sq. ft.
- The area of all exterior surfaces in the project is not less than the surface area of a cube of the same volume as the building. The building volume is calculated as the sum of volumes of all spaces in the project. Space volume is calculated as the floor area multiplied by ceiling height.
- The R-value of all walls in conditioned space that are not adjacent to ground is at least R-4.
- Windows in conditioned spaces do not have single-pane glass.
- All heated spaces have window area of 10% to 40% of floor area, which is typical for residential construction.
- All unconditioned spaces have at least one surface adjacent to a conditioned space. Surfaces between conditioned and unconditioned spaces are entered in TREAT as attached to conditioned space and adjacent to unconditioned space. Unconditioned spaces that are not connected to conditioned spaces will be heated only by space heat gain from base load located in these spaces (such as lighting). This may result in unexpectedly low indoor temperature in these spaces and exaggerated losses from sections of distribution system located in these spaces. Heat exchange between unheated spaces and heated space(s) in the project will not be accounted for. Check the Calculation Results tab of the Model Inspector to make sure that the temperature of unheated spaces is close to what you observed during the site visit.
- All unconditioned spaces have a surface adjacent to outdoors. This is important if “Surface Leakage Proportional to Area” infiltration algorithm is selected on Weather/Defaults screen. In this case the infiltration input for unconditioned spaces with no surfaces adjacent to outdoors will be ignored and the resulting building heat loss may be significantly underestimated
- Infiltration of conditioned spaces is between 0.2 and 2 ACH, which is typical of residential construction.
- If “Leakage allocated in proportion to surface area” is selected as the infiltration algorithm on the Weather/Defaults screen, then area of holes in the building should account for at most 10% of overall building infiltration. Due to the nature of algorithms employed in the detailed infiltration calculations, the accuracy of modeling results may be compromised if area of holes in the building accounts for more than 10% of overall building infiltration.