Rooflight Properties

Contains controls used to view and define properties for rooflight surface types. Rooflight surfaces are sub-surfaces which are placed on surfaces like exposed roofs. Their construction layers affect the thermal properties of the rooms in which they exist. The rooflight contains properties that all surface sub-types share as well as properties specific to the rooflight sub-type.

The Properties For: Rooflight dialog opens when the Rooflight Project Tree object´s pop-up menu is activated in the OpenBuildings Energy Simulator Project Tree and the Properties menu item is selected.

Note: The Rooflight Construction details properties panels under the Construction details heading contain controls used to view the selected rooflight construction details. The properties displayed here are saved in the materials database’s constructions definitions. Constructions can be viewed, manipulated and created using controls and settings found on the Materials Manager.

Property heading	Properties
Category	Displays the surface category. Category is a read only property.
Sub type	Displays the surface sub-type as Rooflight. This property is disabled, and can not be changed.
Name	Used to enter a name for the window. The name entered here appears appended to the window object on the project tree dialog.
Construction	Used to view of change the rooflight material construction definition.
Curb mounted	When on, the rooflight is considered to be Curb mounted or raised off the surface of the roof. When off, the rooflight is considered to be flush to the roof.
Dimensions	Displays overall dimensions of the selected rooflight. Length — Disabled for the rooflight sub-type. Width — Disabled for the rooflight sub-type. Height — Disabled for the rooflight sub-type. Area — Displays the total area of the selected rooflight. Volume — Disabled for the rooflight sub-type. Orientation — Displays the orientation of the rooflight relative to the building orientation. Building orientation is defined in the Properties For: Building dialog.
Blind shading	Contains controls used to define how shading from blinds is controlled. Control type Always off – Controls for the selected rooflight’s blinds are always off. Selecting this options disables the blind schedule property. Always on – Controls for the selected rooflight’s blinds are always on. Selecting this options disables the blind schedule property. Depending on schedule – Controls for the selected rooflight’s blinds are always turned on or off based on the selected schedule. Selecting this options enables the blind schedule property. Schedule — Used to select a blind shading schedule. All available blind shading schedules are provided on the Schedule pick list.
Common	Displays common construction details for all surface sub-types. Common construction details are read only properties. Category — Displays the construction category associated with the surface. Total thickness — Displays the surface total thickness which included all the material layers (solids and air gaps) that make up the construction. Decrement factor (internal) — Displays a Decrement factor associated with the construction’s inside surface. The Decrement factor is used to calculated the amount a thermal wave is decreased in intensity during its propagation process from the outside to the inside of the surface construction. Decrement factor (external) — Displays a Decrement factor associated with the construction’s exterior surface. The Decrement factor is used to calculated the amount a thermal wave is decreased in intensity during its propagation process from the outside to the inside of the surface construction. Fixed thermal properties — Used to display the surface construction setting related to its thermal properties which are defined in the Materials Manager dialog. When on, calculated surface emissivity and absorption coefficients are overridden, enabling you to define your own thermal properties (in the Materials Manager dialog). When off, the calculated transmission values are used. Admittance (internal) — Displays the amount of heat that passes through a unit area of the constructions’s inside surface, when its external face is subject to a unit temperature change. Admittance (external) — Displays the amount of heat that passes through a unit area of the constructions’s external surface, when its inside face is subject to a unit temperature change. Time lag (internal) — Displays the time it takes for heat generated by the sun to transfer from the outside, through the construction, to the inside surface of the construction into the building envelope, and affect the internal conditions. Time lag (external) — Displays the time it takes for heat lost to transfer from the inside, through the construction, to the external surface of the construction from the building envelope. Weight (internal) — Displays the construction inside surface’s weight per unit area. Weight (external) — Displays the construction external surface’s weight per unit area.
Glazing	Contains controls used to display solar heat gains, gains coefficients and transmittance properties for the Rooflight surface type. Glazing Construction details properties are read only properties. Glazing Construction details are defined using the controls on Materials Manager dialog. Glazed amount — Displays the amount of glazing the window has as a percentage or as a ratio. Light transmittance — Displays the amount of daylight striking the window glazing that passes through to the inside as a ratio. Glazings with a high light transmittance appear relatively clear and provide sufficient daylight and unaltered views; however, they can create glare problems. Glazings with low light transmittance are best used in highly glare-sensitive conditions, but can create gloomy interiors under some weather conditions and diminished views. Average solar gain factor air — Used to calculate total heat gain through the window, the Average solar gain factor air property represents the average solar gain over a 24 hour period for the air space between the inside surface of the window glass and internal shading. Solar gain factor refers to an estimate of the heat gain due to transmitted and absorbed solar energy through a benchmark glazing (1/8 or 3 mm clear glass) at a specific latitude, time and orientation. Cyclic solar gain factor air — Used to calculate total heat gain through the window, the Cyclic solar gain factor air property represents the hourly swing of the solar gain over a 24 hour period for the air space between the inside surface of the window glass and internal shading. Solar gain factor refers to an estimate of the heat gain due to transmitted and absorbed solar energy through a benchmark glazing (1/8 or 3 mm clear glass) at a specific latitude, time and orientation. Shading coefficient — Displays the Shading coefficient value associated with the window. This dimensionless indicator is the ratio of the solar heat gain of the selected glazing compared to a benchmark glazing (1/8 or 3 mm clear glass) under identical conditions. The Shading coefficient along with the Solar heat gain coefficient indicate the total solar heat gain and are used in cooling load calculations. Solar heat gain coefficient — Displays the Solar heat gain coefficient value associated with the window. This dimensionless indicator is the ratio of the total transmitted solar heat energy to incident solar energy. It typically ranges from 0.9 to 0.1 where lower values indicate lower solar gain. The Solar heat gain coefficient along with the Shading coefficient indicate the total solar heat gain and are used in cooling load calculations. Average solar gain factor env. — Used to calculate total heat gain through the window, the Average solar gain factor env. property represents the average solar gain over a 24 hour period for the air inside the room (inside the internal shading). Solar gain factor refers to an estimate of the heat gain due to transmitted and absorbed solar energy through a benchmark glazing (1/8 or 3 mm clear glass) at a specific latitude, time and orientation. Cyclic solar gain factor env. light — Used to calculate total heat gain through the window, the Cyclic solar gain factor env. light property represents the hourly swing of the solar gain over a 24 hour period for the air inside the room (inside the internal shading) for thermally light rooms. A thermally light room retains the transmitted solar energy to a lesser degree from a thermally heavy room. Solar gain factor refers to an estimate of the heat gain due to transmitted and absorbed solar energy through a benchmark glazing (1/8 or 3 mm clear glass) at a specific latitude, time and orientation. Cyclic solar gain factor env. heavy — Used to calculate total heat gain through the window, the Cyclic solar gain factor env. heavy property represents the hourly swing of the solar gain over a 24 hour period for the air inside the room (inside the internal shading) for thermally heavy rooms. A thermally heavy room retains the transmitted solar energy longer from a thermally light room. Solar gain factor refers to an estimate of the heat gain due to transmitted and absorbed solar energy through a benchmark glazing (1/8 or 3 mm clear glass) at a specific latitude, time and orientation.
Layers	Contains controls used to display the surface’s construction material layers in a read only table. The table displays thermal properties for each layer such as the thickness, density, conductivity, specific heat and vapor resistivity.