BIM + Building Performance Analysis Using Revit 2009

Transcription

1 Integrated Environmental Solutions / Revit 2009 BIM + Building Performance Analysis Using Revit 2009 and IES <Virtual Environment> February 2009

2 1.0 Table of Contents 1.1 Introduction Checklist for Translating Revit 2009 to IES<VE> Basic gbxml information gbxml essential diagram Project Information Rooms Surfaces Walls Roofs Floors Ceilings Columns Curtain Systems Room Separation Lines Openings Doors Glass Doors Elevator Doors Windows Shading Surfaces Shading Devices Obstructions Adjacencies Defi ning the Upper and Lower Boundary Room Volume Computations Linked RVT Files Design Options Families Lighting Fixtures Furniture Clean out Existing Revit Model

3 1.1 Introduction One of the most time-consuming aspects of any Building Performance Analysis is the setup required to carry out the analysis. This often is a process of re-creating the building geometry as well as setting the conditions necessary to properly represent the environment both inside and outside of the building. Integrated Environmental Solutions (IES) specially developed a plug-in toolbar which allows Revit Architecture, Revit MEP, and Google Sketchup users to translate their models directly into IES s software and conduct sustainable performance analysis. The <Virtual Environment> is a unique software system developed by Integrated Environmental Solutions (IES). It is a suite of building performance modelling and analysis tools based around a single integrated data model. The purpose of the system is to provide the high quality information required to design, build and operate better performing, more sustainable buildings. The tools available include thermal simulation with a proven capability for natural ventilation, displacement ventilation, chilled beams and ventilated facades studies, energy analysis for LEED accreditation, daylighting (for LEED) and electric lighting, solar analysis, internal and external CFD airfl ow studies, occupant evacuation and many more. It can be applied from the earliest stages of the design process, when greatest opportunity often exists for making improvements right through to detailed design and even into operation of the building. In order to take advantage of this advanced workfl ow between the platforms, the Revit model must be properly prepared for analysis. Like any type of analysis, the usefulness and accuracy of the results depend greatly on the quality of the inputs. This white paper is intended to give you guidance when modelling in Revit in order to carry out Building Performance Analysis successfully. 1 2 This diagram illustrates a typically workfl ow using Revit. mechanical thermal hybrid ventilation CFD Model in Revit electrical evacuation 2. Set Model Properties 3. IES <VE> Toolkits 4. IES <VE> Figure 1 - Workfl ow from Revit to IES<VE> lighting solar daylighting x x compliance costs value 3

4 1.2 Checklist for Translating Revit 2009 to IES<VE> The following checklist are items that is necessary in your Revit model before the translation to a design / building performance model. The following pages of this document will describe in more details regarding each items. 1. Rooms Make sure all rooms are place in every space, and adjacency of Rooms are correct. 2. Room Bounding Elements Check or uncheck room bounding elements that is necessary for design / building performance model. 3. Define all Upper and Lower Boundary Make sure all the Upper and Lower Limits and Offsets are correct 4. Project Information Make sure Project Information is fi lled out correctly 5. Room Volume Computations Make sure Room Volume Computations is checked 4

5 1.3 Basic gbxml Information Green Building XML schema, referred to as gbxml, was developed to facilitate the transfer information from building information models to integrate with design / energy performance analysis. Since it is not a direct conversion from Revit to IES<Virtual Environment>, there are many areas users need to take notice while modelling their Revit model to successfully translate into a design/building performance model. Refer to for more detail information regarding gbxml documentation. 1.4 gbxml Essential Diagram A gbxml document organizes information according to the following hierarchy: Location, Building, Space, Surface and Opening. Each category in the hierarchy diagram will be describe in more details in the order they are showing. Location Section 1.5 Geographically Building Section 1.5 Building Type Space Section Rooms Section Shading Surfaces Rooms Shading Surfaces Surface Section 1.7 Walls Floors Roofs Ceilings Opening Section 1.8 Doors Windows Skylights Figure 2 - Hierarchy Diagram 5

6 1.5 Project Information Defi ning the location of the project is very important for design / energy performance analysis. Location and climate dictate the performance of the building. Settings > Project Information, the Element Properties dialog opens. Under Energy Analysis category, Energy Data, Click on Edit Figure 3 - Settings - Project Information Figure 4 - Element Properties 6

7 1.5 Project Information (cont) In the Energy Analysis Type Properties dialog box, these are the information gbxml will export from Revit fi le for the use of building performance analysis. NOTE: Under Settings > Manage Place and Locations..., it does not matter the location you choose within that dialog, gbxml will not read the information. Figure 5 - Type Parameters Building Type: Specifi es the type of building according to the gbxml schema 0.34 (similar to ASHARE). Postal Code: Location and climate dictate the design/energy performance, it can dramatically affect the analysis data if the location is incorrect. Postal Code will determines the location of the building. Ground Plane: Specifi es the level that serves as the ground level reference for the building. Spaces below this level are considered underground. The default level is zero Shading Surfaces: Surfaces that are not adjacent to any spaces, and include surfaces that create a solar obstruction Project Phase: Specifi es the stage of construction (Existing, New Construction). Make sure the Rooms that are being placed in the Revit model is in the same phase as the Project Information. Sliver Space Tolerance: Specifi es the tolerance for areas that will be considered sliver spaces. Leave the default that is defi ned within the Revit dialog box. Too much sliver space may allow light, solar radiation, and air fl ow thermal transfer between zones that in reality do not occur. 7

8 1.6 Rooms Revit Architecture 2009 Rooms are the most fundamental and critical element for design/building performance analysis. They are elements that determine the accuracy of your analysis from your Revit model. It is very important to place a Room in every space of your model, even if the room is a shaft or it is not necessary for analysis. In Figure 5 - Rooms, the two rooms that highlighted in red, in reality, we might not place a Room tags in those areas, but for design/building performance model, it is essential to place them in there. If all Rooms are not place, IES software will potentially have diffi culty translating the model correctly, which could impact results or run time of the model (refer to Section 1.10 Adjacencies) NOTE: Within the gbxml schema the Space is the analog for a Room. For the purposes of clarity in this paper we will refer to these items as Rooms in all cases. Figure 6 - Rooms 8

9 1.7 Surfaces Rooms are defi ned by the elements that surround them. During the gbxml translation from your Revit model to building performance model, gbxml will read only room bounding elements. These bounding elements are Walls, Floors, Roofs and Ceilings. Even though columns are bounding elements, they have the potential to cause inaccuracies in the building performance analysis if they are not designated correctly (refer to Section Columns for details). During the translation of your Revit model, these bounding elements are translated into 2D surfaces representing their geometry that enclose the 3D spaces (rooms). (See Figure 7) The following elements are room bounding elements for Room Area and Volume Computations: Walls (Curtain, standard, in-place, face-based) Roofs (Standard, in-place, face-based) Floors (Standard, in-place, face-based) Ceilings (Standard, in-place, face-based) Columns (Architectural, structural with material set to concrete) Curtain systems Room Separation Lines Revit <Virtual Environment> Figure 7 - Revit model translation to <Virtual Environment> 9

10 1.7 Surfaces (cont) Another situation where a Room bounding element is broken up into multiple surfaces is when rooms are adjacent to each other. In order to allow for situations where one room is conditioned while the other is unconditioned, the wall is broken into two surfaces in the Revit model. Walls are split in the middle during translation if rooms are adjacent to each other Revit <Virtual Environment> Figure 8 - Breaking Wall into Two Surfaces in Building Performance Model You can check or uncheck Room bounding instance parameter (Figure 9). If a room bounding element is unchecked, it will not be added to the building performance analysis. Figure 9 - Room Bounding Instance Parameter 10

11 1.7 Surfaces (cont) The following sections will describe some of the items to be aware of when modelling. By understanding each elements, it will help calculate a more accurate analysis model, and this is also where it differentiates a Revit model for documentation purposes versus a Revit model for an energy analysis purposes Walls Revit wall types do not translate directly to the <Virtual Environment>, because they do not contain the thermal properties needed to conduct dynamic thermal simulations. Therefore at the Set Model Properties dialogue, the user will be prompted to identify these at the building and/or room tab Figure 10 - IES <VE> Building Construction Dialogue 11

12 1.7.2 Roofs Revit roof types do not translate directly to the <Virtual Environment>, because they do not contain the thermal properties needed to conduct dynamic thermal simulations. Therefore at the Set Model Properties dialogue, the user will be prompted to identify these at the building and/or room tab. (See Figure 10) Always specify the Upper Limit above the top of the roof. It is especially important if you have a slope roof. This will ensure that there are no unnecessary shading surfaces in the building performance model due to the roof. For slope roof, when Areas and Volumes is checked under Area and Volume Computations, Room will automatically wraps around the slope roof Room Volume above the highest point of the room Check Areas and Volumes Automatically wraps around the slope roof Figure 11 - Room Volume at Slope Roof 12

13 1.7.3 Floors Revit fl oor types do not translate directly to the <Virtual Environment>, because they do not contain the thermal properties needed to conduct dynamic thermal simulations. Therefore at the Set Model Properties dialogue, the user will be prompted to identify these at the building and/or room tab (See Figure 10) If openings of the fl oors were drawn as part of the fl oor sketch, you will need to remove these openings before exporting to gbxml, it causes polygon lines to appear in the building performance model Ceilings Although ceilings are Room bounding elements, but in many cases, ceilings are not used as Room bounding elements for building performance analysis purposes. Allowing ceilings to be Room Bounding would result in many voids between ceilings and level above, impacting the accuracy of analysis results. Unless the volume between the ceiling and underside of slab is used as ceiling plenum and need for energy analysis, in many instances, you would want to uncheck Room bounding for ceilings. Floor above Room Volume shown in blue Void Ceiling (Room bounding check) Floor Columns Figure 12 - Ceiling Void Columns as room bounding elements will impact the volume of the building performance model. The volume of the column itself is subtracted from the total Room Volume, thus reducing the room volume. It is strongly recommended that you unchecked Room bounding (Refer to Figure 13) for all columns before exporting the Revit Model to the <Virtual Environment>. Since there is no Room defi ned inside of the columns, and the columns are translate as surfaces for geometry, the room will mistakenly the adjacent space as exterior. If the columns are critical elements for the analysis, you can re-created them within <Virtual Environment>. 13

14 1.7.5 Columns (cont) Figure 13 - Diagram on the left. The Columns has room bounding Checked, during the translation to <Virtual Environment>, the columns caused the volume inaccuracy. Diagram on the right - The Columns has room bounding Unchecked, and it translated successfully into <Virtual Environment> Figure 13 - Columns Translation from Revit to IES<VE> Curtain Walls Curtain walls are translated into surfaces and openings as it translates to a building performance model. A curtain wall will be translated as a Wall surface. For every glazing panel in the Curtain wall, there will be a window opening. If the Curtain wall is curved, it will be faceted to several planar wall surfaces. NOTE: If the glazing panel material is less than 3% transparency, it will be translated as a solid panel. 14

15 1.7.6 Curtain Walls (cont) Revit Figure 14 - Curtain Wall Translation <Virtual Environment> Room Separation Lines Room separation lines are Room bounding elements. They are useful in building performance analysis if a large room needs to be calculate for different HVAC loads. For example, 15-0 from the exterior of the building needs to be calculate differently than the interior of the building. 15

16 1.8 Openings Referring back to the hierarchy diagram (Figure 1 - Hierarchy Diagram), Openings are the next level down. Openings are elements such as windows, doors and skylights. They are usually hosted components in the system families. Like Room bounding elements and surfaces, openings are represented as 2D surfaces during the translation from building information model to building performance model. The model will only translate what is needed to conduct for the analysis. Note that the railings did not translate into <Virtual Environment> from the Revit model, because they have very little, if any, infl uences on the analysis. Window Door Doors It is very important to use a door template when creating custom doors. If a door template was not used, it can cause the Room to extend beyond the area expected Elevator Doors It is recommended to use a door template when creating elevator doors. If an elevator is required, then another template should be used to create that separately. An elevator door should also be placed at each fl oor level the elevator crosses Glass Doors Figure 15 - Openings Translation If the door contains glass in it, it will not export as a glass door during the gbxml translation. Once it is export to <Virtual Environment>, you can defi ne the property of the door to show it contains glass for proper analysis to be calculate. 16

17 1.8.2 Windows When creating custom windows, it is also very important to use a window template. If a window template was not used. It can affect the analysis calculations by allowing air fl ow where none is present. 1.9 Shading Surfaces Shading surfaces are necessary to use as shading devices, overhangs of roofs, balconies, or even surrounding buildings as part of the analysis, etc. These surfaces are generated when Room bounding elements are not bounded/enclosed by a Room. Exceptions to using the proper templates would be shading devices, for documentation purposes, many users might use a generic model template to create a solar shading device family, but that will not translate into the building energy model. Users will need to create the shading devices as an obstruction with a Room bounding element, such as walls, ceilings, fl oor, columns, or roofs. NOTE: Within the <Virtual Environment>, Shading surfaces, shading devices, surround buildings are known as obstructions. For the purpose of clarity here, these items are referred to as shading surfaces throughout. Figure 16 - Shading Surfaces Translation 17

18 1.10 Adjacencies In order for the building performance model to read if the adjacent space is exterior or interior, placing Rooms accurately will be critical. If there is not a Room placed adjacent to the another space, then the room is considered as an Exterior. If Rooms are placed on all sides, then it is considered as Interior. Even if the space is a shaft or an unoccupied space, where you might typically not place a Room in it, it is important in this case or else the rooms surrounding the shaft will consider as exterior spaces. Figure 15 - Adjacencies, if Room 16 was not placed in the Revit model, the Stair will consider as Exterior, and it could affect energy analysis dramatically. That is why it is critical to make sure all Rooms are correct in terms of their adjacencies. Figure 17 - Adjacencies 18

19 1.11 Defi ning the Upper and Lower Boundary Together, the Upper Limit and Limit Offset parameters defi ne the upper boundary of the room. It is important to make sure the Upper Limit and Limit Offset is set correctly for design/energy performance analysis. If the Upper Limit and Limit Offset leave a void between the defi ne area and the level above, this void area will recognized as Exterior in the design/building performance model. As a general rule, it is a good practice to set the Limit Offset to 0-0, and set the Upper Limit to the next level, or the height that covers the highest point in the space. Use the Base Offset parameter to indicate the distance between the base level and the lower boundary of the room. Enter a positive number to move the lower boundary above the base level. Enter a negative number to move the lower boundary below the base level. Figure 18 - Upper and Lower Boundary 1.12 Room Volume Computations Compute Room Volumes determines the room volume and room height. Room volume computations affect Revit performance, it is turned off by default. Before performing analysis, it is critical to go to Settings > Area and Volume Computations, in the Computations Tab, Areas and Volumes need to be checked instead of Areas only (faster). NOTE: Room volumes are computed to the wall fi nish, regardless of the Room Area Computation setting. Figure 19 - Room Volume Computations 19

20 1.13 Linked RVT Files In Revit 2009, Rooms recognized Room bounding elements that are placed in linked RVT models. After linking the Revit model into the project, select the linked model, go to Type Parameters in the Element Properties and make sure Room Bounding is checked. Figure 20 - Linked RVT fi les - Room Bounding 1.14 Design Options If design option is used in Revit, the primary option is typically the preferred design. It is usually displayed in the project views by default. All others are secondary. During the export to gbxml, primary option is the option that will be export. If another option needs to be export for design/energy performance analysis, click tools menu > Design Options > Design Options or click on the Design Options toolbar. In the Design Options dialog, select the secondary design option to promote. Under Option, click Make Primary Families Most of the families does not export during the gbxml translation. Below are a couple of common families types users should take notice Lighting Fixtures Light fi xtures will not carry over to <Virtual Environment> using the sustainability toolkits. Light fi xtures export to <Virtual Environment> is only a feature of the Revit MEP 2009 direct link under Mechanical in the design tab, Heating and Cooling Loads. 20

21 Furniture Since most of the furniture are not create with a room bounding element family template, furniture will not export out as part of the building performance model. Components can be placed separately in <Virtual Environment> Cleaning Out Existing Revit Models As mentioned earlier regarding families, since most of the families does not export during the gbxml translation. It is best to clean out all the unnecessary families from the model. It reduces the fi le size, the amount of information exporting out to gbxml and runtime for analysis. 21