Windows and Doors

Windows and doors are openings in the building envelope that affect both transmission heat transfer and solar heat gain.

You work with windows on the Windows tab, and doors on the Doors tab, in Building Model → Envelope. Both are placed on wall segments.

Adding Windows

1. On the Windows tab, click Create Windows
2. Enter the window Width and Height, or turn on Assign as percentage of wall area and set the percent
3. Choose a Window Type
4. Click walls on the canvas to place the windows
5. Click Done when finished

Window Properties

Dimensions

• Width - Horizontal dimension
• Height - Vertical dimension
• Sill Height - Distance from floor to bottom of window

Window Type

Links to the window type definition. Determines:

• U-value for transmission heat transfer
• SHGC (Solar Heat Gain Coefficient)
• Infiltration rates

Shading

Each window can have external and internal shading enabled, which reduces its solar heat gain.

Solar Heat Gain

Windows are the primary source of solar heat gain. The calculation considers:

SHGC (Solar Heat Gain Coefficient)

The fraction of solar radiation that enters through the window:

• Values range from 0.2 to 0.8
• Lower SHGC means less solar gain
• Affects cooling loads significantly

Orientation

Solar gain varies by wall orientation:

• South - Highest gain in winter, moderate in summer
• West - High afternoon gain in summer
• East - Morning gain
• North - Lowest direct solar gain

Shading

External shading reduces solar gain:

• Overhangs and fins
• External blinds or screens
• Adjacent building shadows

Adding Doors

Door Entry

1. On the Doors tab, click Create Doors
2. Enter the door Width and Height and choose a Door Type
3. Click walls on the canvas to place the doors
4. Click Done when finished

Door Properties

• Width and Height
• Door Type - Links to the door type definition, which determines the U-value, surface absorptance, open fraction, and whether the door has seals

Glazed Doors

Door types do not model solar heat gain through glazing. For doors with significant glazing, add the glazed portion as a window at floor level so its SHGC is included in the solar calculations.

Interior Windows

Windows between interior spaces:

• Transfer grilles and vision panels
• May affect airflow between spaces
• Usually no thermal impact if spaces are conditioned

Skylights

Skylights are windows in the roof:

• See Roof for skylight configuration
• Higher solar gain due to sun angle
• Significant impact on top-floor loads

Best Practices

1. Verify areas - Check that window areas match specifications
2. Use accurate SHGC - This significantly affects cooling loads
3. Consider shading - Account for overhangs and external shading
4. Don’t forget doors - Include exterior doors in the envelope
5. Check orientations - Solar calculations depend on correct orientation