Abstract:
Embodiments of the invention may be used to generate an analysis model of a building for use in thermal modeling and other analyses. A method for generating a model for use in determining environmental requirements includes the steps of receiving a computer-aided design (CAD) model of a building design, parsing the CAD model to identify one or more rooms in the building design, and generating a description for each of the one or more rooms. The description of a given room specifies a set of geometric properties describing the given room. The method also includes the steps of determining an environmental requirement of the building design based on the descriptions generated for the one or more rooms and storing the results of the analysis and the determined environmental requirement for review.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 60/866,940, filed on Nov. 11, 2006, incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to computer software. More specifically, the present invention relates to techniques for calculating an analytical model of a building used in thermal modeling and analysis. 
         [0004]    2. Description of the Related Art 
         [0005]    The architectural design of buildings is commonly performed with computer-aided design (CAD) software applications. Users of CAD applications can design buildings by constructing computer models of the buildings, which includes specifications of construction, dimensions, materials, windows, doors, and the like. However, CAD applications are typically not configured to determine the heating, ventilation, and air conditioning (HVAC) requirements (“loads”) of a building. Instead, the HVAC loads are usually analyzed by using specialized software programs, referred to herein as HVAC analysis tools. 
         [0006]    Typically, an HVAC analysis tool is used to construct an HVAC analysis model of a building. An HVAC analysis model enables the HVAC requirements of the building to be analyzed. An HVAC analysis model requires data on the characteristics of the building, such as the dimensions of the rooms of the building, the materials and layout of the rooms, the number of occupants, the heat generated by electrical devices, the climate conditions at the building location, the solar energy absorbed by the building, and the like. 
         [0007]    Conventionally, an engineer creates an HVAC analysis model by manually loading the model with data taken from a CAD building design. For example, an engineer may print a copy of the CAD building design, measure the appropriate plan dimensions with a ruler (or using tools provided by the CAD application), determine the associated room height, and then input each dimension into the HVAC analysis model. Such manual measurements are time-consuming and tedious. Thus, the manual process of loading an HVAC analysis model is usually only performed twice, at the beginning and end of the CAD building design process. However, it is common that a building design can change significantly during the design process. If an HVAC analysis model is not updated to match a changed building design as it changes, the HVAC analysis model will likely be inaccurate and result in costly mistakes. 
         [0008]    Further, manually measuring print-outs results in an HVAC analysis model that is, at best, an approximation that is likely to contain errors. For example, an engineer may build an HVAC analysis model using centerline wall dimensions (i.e., a point halfway through the thickness of the wall) instead of using the interior room dimensions (i.e., from the inner surfaces of each wall). The interior room dimensions are important for certain HVAC load calculations, such as determining the heat transfer characteristics of the system and the air flow requirements. Thus, the use of centerline wall dimensions alone can lead to significant errors in the HVAC analysis. 
         [0009]    The limitations of manual measurements are magnified by the presence of irregular walls or ceiling topology in the building design. Similarly, manual measurements may fail to account for shading of sun light by surfaces external to the room (e.g., roof overhangs). These aspects of a building design are sometimes ignored due to the effort required to include them in the HVAC analysis model. 
         [0010]    The above-described problems associated with creating HVAC analysis models also occur when analyzing other environmental aspects of a building design. For example, the lighting requirements of a building (i.e., the number of light fixtures, fixture locations, wattage, etc.) may be determined by using a lighting analysis model. However, a lighting analysis model requires many of the same data inputs as an HVAC analysis model. Thus, the process of generating a model from a CAD building design for performing a lighting analysis suffers from many of the same difficulties described above. 
         [0011]    As the foregoing illustrates, there is a need in the art for techniques for generating a computational model of a building design for use in thermal modeling analyses or other facility requirements analyses. 
       SUMMARY OF THE INVENTION 
       [0012]    One embodiment of the invention includes a method for generating a model for use in determining environmental requirements. For example, embodiments of the invention may be used to generate a model of a building for use in thermal modeling and other analyses. A method for generating an analytical model of a building for use in environmental requirements includes the steps of receiving a computer-aided design (CAD) model of a building design, parsing the CAD model to identify one or more rooms in the building design, and generating a description for each of the one or more rooms. The description of a given room specifies a set of geometric properties describing the given room. The method also includes the steps of determining an environmental requirement of the building design based on the descriptions generated for the one or more rooms and storing the results of the analysis and the determined environmental requirement for review. 
         [0013]    In a particular embodiment, generating a description of the given room may include computing an interior volume measurement of a region of space enclosed by the walls, ceiling, and floor of the given room. Similarly, generating a description of the given room may include computing an analytical volume measurement of the given room specifying an intra-wall space between the given room and an adjacent room in the building design. 
         [0014]    Another embodiment of the invention includes a computer readable medium storing instructions for generating an analytical model of a building for use in environmental requirements modeling, including instructions for performing the steps of the recited method. 
         [0015]    Advantageously, embodiments of the invention may be used to generate analysis model of a building for use in thermal modeling and analysis directly from the drawing elements included in a CAD drawing representing the building design. Thus such an analysis may be performed at any phase of the building design process. Further, the thermal model may accurately reflect a variety of features of the building design typically omitted from a manual or ad-hoc requirements analysis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0017]      FIG. 1  is a block diagram illustrating a computer system for calculating the analysis model of a building for use in thermal modeling and analysis, according to one embodiment of the invention. 
           [0018]      FIGS. 2A-2D  illustrate aspects of an analysis model of an example room, according to one embodiment of the invention. 
           [0019]      FIGS. 3A-3B  illustrate an screen of an HVAC analysis user interface, according to one embodiment of the invention. 
           [0020]      FIG. 4  illustrates a method for calculating the analysis model of a building for use in thermal modeling and analysis, according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Embodiments of the invention provide techniques for generating a thermal analysis model for a building. In one embodiment, a computer-aided design (CAD) model is used to generate an analysis model for determining the heating, ventilation, and air conditioning (HVAC) requirements of a given building design. Additionally, the CAD model may also be used to generate an analysis model for determining the lighting requirements, or other environmental features, for the building. 
         [0022]      FIG. 1  is a block diagram illustrating a computer system  100  for generating a computational model of a building for use in thermal analysis, according to one embodiment of the invention. Note, the components illustrated in system  100  are included to be representative of computer software applications executing on existing computer systems, e.g., desktop computers, server computers, laptop computers, tablet computers, and the like. The software applications described herein, however, are not limited to any particular computing system and may be adapted to take advantage of new computing systems as they become available. 
         [0023]    Additionally, the components illustrated in system  100  may be implemented as software applications that execute on a single computer system or on distributed systems communicating over computer networks such as local area networks or large, wide area networks, such as the Internet. For example, system  100  may include a software program executing on a client computer system at one physical location communicating with a computer-aided design (CAD) application  110  at another physical location. Also, in one embodiment, a CAD application  110  and an analysis engine  120  may be provided as an application program (or programs) stored on computer readable media such as a CD-ROM, DVD-ROM, flash memory module, or other tangible storage media. 
         [0024]    As shown, the system  100  includes, without limitation, a CAD application  110 , an analysis engine  120 , a model converter  150 , and a user interface  160 . The CAD application  110  includes a CAD model  112 , which includes data objects for walls  113 , openings  116 , roofs  117 , other objects  118 , and a building location object  119 . 
         [0025]    In one embodiment, the CAD model  112  may provide a representation of a building design. A user generates the building design of CAD model  112  by designing the overall structure of the building, as well as designing one or more rooms that are part of the building. Typically, the room designs are constructed by specifying drawing elements to model components of the building, such as the walls  113 , ceilings  114 , and floors  115  of the rooms. In addition, a room design may include drawing elements to model room openings  116 , such as windows and doors. The structure of the building may be modeled by adding drawing elements for roofs  117  and other objects  118  to the CAD model  112 . Each drawing element of the CAD model  112  may specify a position, relative to the other elements in the CAD model  112  and to the building site. In some cases, the drawing elements of the CAD model  112  may specify the materials used to construct the corresponding component of the building. For example, a wall  113  may be modeled using drawing elements representing frame members composed from 2×4 studs covered with dry wall. In such case, CAD model  112  may also include elements representing items such as insulation, electrical wiring, and wall receptacles for plugs and light switches. A building location data object  119  may specify the orientation (i.e., north, south, etc.) and geographic location (i.e., latitude and longitude) of the building design. This information may be used in a thermal modeling to simulate the expected temperatures and sunlight exposure the building is likely to experience at the given geographic location and position. 
         [0026]    In one embodiment, a model converter  150  may be configured to process the data objects of the CAD model  112  to generate an analysis model  130 . Although shown separately from CAD application  110 , model converter  150  may be integrated with CAD application  110 . In any case, model converter  150  may be configured to parse a given CAD model  112 , e.g., parse the data objects and/or drawing elements representing walls  113 , ceilings  114 , floor  115 , openings  116 , roofs  117 , and other objects  118  to generate model  130 . The model  130  may provide a representation of the building design in CAD model  112  suitable for processing by an analysis engine  120 . In one embodiment, the model  130  may be composed according to existing building model standard or description language. For example, the publicly available gbXML format may be used. Model converter  150  is described further below with reference to  FIG. 4 . 
         [0027]    Analysis engine  120  may be configured to perform HVAC load calculations. The HVAC load calculations may be based on a set of target conditions  122 , such as weather data  123 , people loads  124 , electrical loads  126 , and analysis model  130 . As shown, analysis  130  includes interior volume measurements  131 , analytical volume measurements  132 , material properties measurements  133 , room adjacencies data objects  134 , location data objects  135 , and non-room surface data objects  136 . In one embodiment, the measurements and data objects used by analysis engine  120  may be generated by model converter  150  from CAD model  112 . By providing multiple volume measurements, the analysis engine  120  may be used to calculate a sophisticated thermal model of a building design using the interior volume measurements  131  when appropriate and using the analytical volume measurements  132  when appropriate. Of course, the invention is not limited to these two types of volume measurements or any particular mode of thermal analysis and other data may be generated by a particular model converter  150  for use by analysis engine  120 . 
         [0028]    User interface  160  may include any combination of graphical elements such as windows, menus buttons, ribbons, dialog boxes, etc., used to invoke the features and functions of CAD application  110  and analysis engine  120 . Illustratively, user interface  160  includes a model viewer  164  and a load report  166 . The model viewer  164  may be configured to provide a user with a graphical representation of the analysis model  130  generated by the model converter  150 . After the analysis engine  120  completes the HVAC analysis, the results may be presented to a user in a load report  166 .  FIGS. 3A-3B , referenced below, illustrate an example user interface  160  and load report  166 . 
         [0029]    In one embodiment, the analysis engine  120  may, in part, perform HVAC load calculations for a building by determining the amount of heat transfer (i.e., heat gain or loss) from the building to the surrounding environment. HVAC load calculations may require determining the amount of heat transfer from one room to others or to the environment external to the building. As is known, the amount of heat transfer for a room depends on how well insulated the room is from its surroundings, the volume and shape of the room, the amount of sunlight/shade provided by windows, etc. The amount of heat transfer also depends on factors such as the dimensions, geometry, and materials of the boundaries of the room (i.e., walls, floor, and ceiling) as well as the temperatures involved. In addition to calculating heat transfer, analysis engine  120  may also determine what HVAC loads are needed to maintain a particular environmental state. 
         [0030]    The volumes and room measurements may be calculated analyzing the CAD model  112 . In one embodiment, the interior volume measurements  131  and the analysis volume measurements  132  are used to calculate the heat transfer between rooms included in a given building design. The interior volume measurements  131  represent the dimensions and geometry of the interior volumes of rooms in the building, including openings such as doors or windows. The model converter  150  may be configured to determine interior volume measurements for a given room based on the positions of drawing elements representing inner surfaces of the walls, floors, and ceilings within CAD model  112 .  FIG. 2A  illustrates an example of an interior volume  203  of a room  200 . As shown, room  200  includes a window opening  210  and a door opening  220 . The interior volume  203  represents a region of space enclosed by the walls, ceiling and floor of room  200 . 
         [0031]    The analysis volume measurements  132  represent dimensions and geometry of the room volumes at the centerline wall dimensions of the walls, floor, and ceilings. Thus, the analysis volume measurements  132  account for the intra-wall spaces between two rooms. This may include both interior-interior wall spaces, as well as interior-exterior wall spaces. In one embodiment, the centerline dimensions may be measured from a point halfway through the thickness of the walls, floor, and ceilings.  FIG. 2B  illustrates an example of an analysis volume  205  of room  200 . As shown, analysis volume  205  is based on the centerline dimensions of the room and is slightly larger than the interior volume  203  of room  200 . Analysis volume measurements  205  also include a window opening  215  and a door opening  225  that correspond to the openings in interior volume  203  of room  200 . 
         [0032]    As stated, heat transfer calculations may be preformed using the thermal properties of room boundaries. The thermal properties may specify, for instance, how well insulated a room is from heat transfer. For example, a model of a wall constructed of steel beams and cement board of a certain thickness possess a thermal conductance, commonly referred to as a “U” value. In one embodiment, the “U” value, or other thermal properties data, may be stored in the material properties data objects  133 . Additionally, heat transfer calculations are preformed using data regarding the temperature differences between the interior and exterior of the walls, floors, ceilings, and openings of the rooms. Accordingly, the data used by analysis engine  120  includes the target conditions  122 , which may specify the desired temperatures inside a room, as well as the desired humidity and airflow values. For instance, the desired temperature inside a room in an office building is commonly set to 72 degrees Fahrenheit. 
         [0033]    Further, the exterior conditions such as expected sunlight and average temperate for a given location affect the HVAC calculations for a given building model. In the case of a heat transfer analysis of a wall (or other boundary) that is part of the exterior of the building, the temperature outside the room is the ambient temperature around the building. In one embodiment, the ambient temperature may be derived from weather data  123  and from the geographic location specified for the building. The location of the building may be provided as part of location data objects  135  included in the analysis model  130 . The weather data  123  is based on historical measurements, and may specify expected values for ambient temperature, humidity, and sunlight for various times of the year and at various geographic locations (e.g., for a given longitude and latitude.) Thus, the target conditions  122  and the weather data  123  provide the temperature differences between the interior of a room and the exterior of a building, as required for some heat transfer calculations. 
         [0034]    However, some walls or other boundaries of a room may not be external, and may also be a boundary of an adjacent room of the building. In one embodiment, such shared boundaries are specified in the room adjacencies data objects  134  included in the analysis model  130 .  FIG. 2C  illustrates an example of a first analysis volume  206  and a second analysis volume  207  of two adjacent rooms. As shown, the volumes  206  and  207  represent the volumes of two adjacent rooms sharing a common wall  230 . In this example, the temperature difference across the common wall  230  is generally expected to be less than the temperature difference across an external wall  231 . That is, the temperature difference between the two analysis volumes  206  and  207  is typically less than the temperature difference between the interior of the analysis volume  206  and the exterior of the building. 
         [0035]    Other inputs that may be used in performing heat transfer calculations include the amounts of heat generated by sources other than the HVAC facilities of the building. The heat sources that are internal to the building are usually specified in the people loads  124  and the electrical loads  125  of the analysis engine  120 . The people loads  124  estimate the heat created by the bodies of the occupants. The electrical loads  125  estimate the heat created by electrical devices inside the building, such as electric lights, refrigerators, computers, etc. 
         [0036]    One common source of heat includes sunlight shining directly on the building. The amount of heat gained from sunlight at the building location may be derived from the weather data  123  and the location data objects  135 . However, if there are any sources of shade from sunlight covering a portion of the building, the amount of heat gain from sunlight is likely to be reduced. Thus, in one embodiment, the analysis model  130  includes data objects for non-room surfaces  136 . These data objects represent components of the building structure that are not part of specific rooms, but which may impact the thermal analysis of the building design.  FIG. 2D  illustrates an exemplary non-room surface  240 . In this example, the non-room surface  240  is an overhanging roof that extends over the analysis volume  205  of room  200 . In some situations, the non-room surface  240  may shade the walls of the room from sunlight, and thus reduce the amount of heat gained by the room. 
         [0037]      FIGS. 3A-3B  illustrate an exemplary screen  300  of a user interface (e.g. user interface  160  of  FIG. 1 )  160 , according to one embodiment of the invention. As shown in  FIG. 3A , the screen  300  includes a model viewer  164 , property tabs  320 , and control buttons  330 . Illustratively, model viewer  164  displays a graphic representation of an analysis model  130 . As part of the building property tab, the user is provided with a set of property selection controls  324 , which may be used to set specific properties of the analysis model  130  prior to running an HVAC analysis. In this example, the selection controls  324  allow a user to specify a building type, a building construction, a building service (i.e., the type of HVAC systems available), and the location of the building to use in a thermal analysis. Of course, the selection controls  324  provided by user interface  160  may be tailored depending on the type of thermal (or other analysis) to be performed. Control buttons  330  allow the user to select interface commands, such as running the HVAC analysis. 
         [0038]      FIG. 3B  illustrates a screen  300  displaying an exemplary load report  166  generated from CAD model  112 . Illustratively, load report  166  summarizes the results of the HVAC analysis of the analysis model  130  shown in  FIG. 3A . As shown, load report  166  includes a project header  354 , which includes the project name, location, and date. The load report  166  also includes summary data for each room on the first and second floor of a building design, as well as the load totals for the building. For example, a first report line  356  describes the analysis results for the room “101 Office.” As shown, the analysis of room “101 Office” results in an airflow load of 358 cubic feet per minute (CFM,) a cooling load of 3000 British Thermal Units per hour (BTU/h,) and a heating load of 2200 BTU/h. Similar data is available for the other rooms of this building design. 
         [0039]      FIG. 4  illustrates a method  400  for calculating the analysis model  130  of a building for use in thermal modeling and analysis, according to one embodiment of the invention. The method  400  may be carried out by model converter  150  configured to generate analysis model  130  from CAD model  112 . However, persons skilled in the art will understand that any system configured to perform the steps of method  400 , in any order, is within the scope of the present invention. 
         [0040]    The method  400  begins at step  410  where interior volumes of the rooms included in a given building design are determined from a CAD model, such as CAD model  112 . For example, model converter  150  may determine interior room volume  203  of the room  200  shown in  FIG. 2A . At step  420 , the analytical volumes of the rooms included in the given building design are determined. For example, model converter  150  may determine the analytical room volume  205  of the room  200  shown in  FIG. 2B . At step  430 , the adjacencies of the room are determined from the CAD model. For example, model converter  150  may determine the adjacency  230  between rooms  206  and  207  shown in  FIG. 2C . At step  440 , the material properties of the elements (e.g., walls, ceiling, floor, openings) of the room are determined from the CAD model. In one embodiment, the drawing elements, e.g., data objects and/or drawing elements representing walls  113 , ceilings  114 , floor,  115 , openings  116 , roofs  117 , and other objects  118  in CAD model  112  serve as the drawing elements. At step  450 , the locations of the rooms are determined from the CAD model. That is, the geographic locations to use in performing a thermal analysis are determined. At step  460 , non-room surfaces that are part of the building are determined from CAD model  112 . For example, the roof surface  240  of room  200  shown in  FIG. 2D  constitutes such a non-room surface. 
         [0041]    Once the CAD properties and elements of a building design represented by the CAD model are determined (steps  410 - 460 ), then at step  470 , a description of the building configuration is generated for an analysis engine  120 . Any thermal (or other) analysis engine may be used, e.g., the IES &lt;Virtual Environment&gt; building analysis tool available from Integrated Environment Solutions. At step  480 , the description of the building configuration generated from the CAD model is passed to the analysis engine  120 . At step  490 , a thermal analysis (or other analysis) is performed based on the generated description. At step  495 , the analysis results are presented to the user. For example, the analysis engine may be configured to generate and render a display similar to the load report  166  of  FIG. 3B . 
         [0042]    Advantageously, embodiments of the invention may be used to generate a thermal model of a building design represented by a CAD model. Such an analysis may be performed at any phase of the building design process. Further, the thermal model may accurately reflect a variety of features of the building design typically omitted from a manual or ad-hoc requirements analysis. As described, the embodiments of the invention may be used to generate a model used as input for a thermal or other analysis, of a building. The model generally describes features of the building relevant for a given analysis. For example, for a thermal analysis, the model may describe the rooms, the room size, the thermal characteristics (e.g., insulation “U” values), and the geographic location of a building design. 
         [0043]    Further, embodiments of the invention may be used to generate models for other types of environmental analyses of a building design. For example, the lighting requirements of a building or the safety equipment requirements of a building may be analyzed using the teaching of the present invention as set forth herein. When analyzing lighting requirements, the location, shading, and shape and structure of the rooms in a building may be analyzed to determine what natural lighting levels may be expected based on the location, position, and number of windows, sunlight or other openings in the building. Similarly, such an analysis may specify what artificial lighting requirements are necessary to achieve a desired lighting level. 
         [0044]    While the forgoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.