The ventilated space can be assumed to be at outdoor air conditions.Ĭeilings are suspended surfaces below a roof or an intermediate wall. Partitions that separate spaces with different conditions, such as an air conditioned space and a ventilated space such as a boiler room, must be included in the heat gain loss calculations. Partitions that separate spaces with similar conditions can be ignored. Partitions are vertical walls that are not exposed to the outside and are therefore not affected by solar, wind and other weather and environmental conditions. If the conditions are different (example, one side is air-conditioned and the other side is not) then the floor cannot be ignored. If they are the same then there is no heat transfer through the floor and the floor can be ignored or omitted in the heat gain/loss calculations. INTERIOR WALLSįloors: The conditions on either side of an intermediate floor can be the same or it can be different. About 10 feet below grade the ground temperature can vary between 40 oF (above freezing) and 60 oF while the outside temperature varies from -40 oF to 120 oF. #ANGLE ROOF WITH FLAT CEILING IN HOME DESIGNER ARCHITECTURAL WINDOWS#The prescriptive criteria for infiltration through doors (varies with the type of door - revolving, swing, etc.) is greater than for windows (fixed, operable, etc.)įloor on grade (ground) is affected by the ground temperature. If the glass area of the door exceeds 50% then it must be considered as window and the prescriptive criteria for windows must be applied. Infiltration affects heating and cooling loads. Exterior doors have air infiltration rates that depend on the type of door and the usage. They have the same azimuth (orientation) and tilt angles as the roofĭoors that open to the outside are part of the building envelope. A sloped roof with a tilt angle greater than 60 degrees can be considered a wall and the less stringent prescriptive criteria for walls can be applied ASHRAE STD90 has more stringent requirements for roofs. In DOE2, the analysis of an external surface is based on azimuth angle and tilt angle. The DOE2 program does not distinguish between walls & roofs. The tilt angle of a horizontal roof is 0 degrees. The tilt angle can vary from 0 to 60 or 90 degrees. Overhangs, side fins, canopies, the metal or wood frame are considered as part of the window configuration. Windows are affected by solar radiation and infiltration in addition heat transfer. If the window tilt angle is different from that of the wall, then a separate wall with 100% glazing must be defined. They are assumed to have the same azimuth (orientation) angle as the wall it is located on. The tilt angle can be 61 to 90 degrees (ASHRAE STD90) A horizontal roof has an azimuth angle of 0 o and a tilt angle of 0 o. For example increase the tilt angle until it is vertical and it is the orientation looking out from inside. The roof azimuth angle is the azimuth angle of the equivalent wall. So both the roofs shown in the figure have a tilt angle of 60 o. The roof tilt angle is measured from the horizontal within the enclosed building space. If this tilt angle is, say, less than 60 o then you can treat it as a roof.Ī roof has an azimuth angle and a tilt angle. However some walls may be tilted slightly away from the vertical. It is measured from the horizontal which has a tilt angle of 0 o. The tilt angle of a vertical wall is 90 o. This convention is used later in establishing direction of building surfaces relative to other building surfaces. It is the direction that you are looking at when looking out through the window in the wall from inside the building. The term roof exposure is used to include the entire horizontal or tilted surface including the roof and skylights.Ī building's exterior wall azimuth (also referred to as exposure orientation) is the direction faced by the wall. Sometimes the term wall exposure is used to include the entire vertical surface consisting of the wall and also its windows and doors. These components can be considered as part of the space envelope but the outside surface is not exposed to the weather. The term exposure is not usually applied to intermediate floors and interior partitions. It has an azimuth direction (also known as exposure orientation). An exposure is the outside surface of a building envelope component. It provides separation and protection from outdoor weather conditions. The envelope consists of walls, windows, doors, roofs and skylights. Building Envelope (also known as building shell)
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