nzdan

We will be using the Revit model from the cottage project in ecotect to analyse how the existing living space is performing.

Step1: Exporting the Revit model and importing this geometry into Ecotect

Note: Most Revit models will be quite complicated geometrically in comparison to my simple cottage project and I recommend that you adjust the view properties parameters to show only the walls for your space as this is all we will need as a reference in Ecotect.

To do this, choose a 3D view, right click select “view properties”, Select the “Edit…” button next to “Visibility/Graphics Overrides” category, In the Visibility/Graphics overrides dialogue box turn off all the layers except the walls layer, select ok, ok and then continue with the following steps.

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As we need to remodel the Revit geometry in ecotect for the calculations to work correctly we only want to export the geometry of the space that we want to analyze; To do this we will be using the Section box tool.

I recommend using the simplest Revit project you have available while you are learning the fundamentals of Ecotect.

• In a 3D view right click and select view properties

• Scroll down and turn on the Section box option, click OK

• Drag the arrows until the geometry is suitably cropped

• File -> Export -> CAD Formats

• Choose a suitable location and change the “files of type” to *dxf, save.

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Open up Ecotect

• File -> Import -> 3D CAD Geometry

• In “Files of Type” Select *DXF

• Click the “Choose File” button, browse to your file and select

• Select the “Scale Objects By:” and change to Millimetre (1:1)

• Select “Open as New”

Our exported Revit geometry is now in ecotect, we only want to use it as a guide for creating new native ecotect geometry, so now would be a good time to save.

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Step 2: Modelling the shell in Ecotect using the Zone tool

There are several ways of creating geometry and zones the easiest technique which should work with most geometry is the zone tool…

• Select the zone tool

• With the left mouse button click on the bottom corner of an internal wall, and then start making your way around the room clicking on all the bottom corners of the walls, Notice the planes that are going to be our ecotect walls are appearing.

• Do not click back on the original point simply hit the Esc key on your keyboard to complete the room (zone)

• Rename your zone to whatever suits, click the Ok key and your first zone is done

• Turn off your *dxf layer to see your new zone, and select your visualise tab to see a shaded view.

• Read on if you want to learn how to tweak this geometry otherwise you could jump straight to Step 4:

• How do you change the height of your space?, select the floor or ground (Might need to use the spacebar to alternate between selections)

• In the selection information bar on the right hand side of the screen look for the extrusion vector tab and change the Z axis from 2400 to what suits your project (I selected 3200), and then select Apply Changes at the bottom right of the screen

• Now select a face, right click and choose insert -> node

• Click with your left mouse button somewhere on the edge of the face that you have just selected, you can now drag this point around to suit

• Open the visualise tab to see what you have done to your model

• You can modify your model significantly using and moving exisitng nodes or adding new ones, be careful though as your model needs to be completely “sealed” to work once we begin thermal analysis.

I recommend you undo any changes you have made to the nodes and then continue with step 4

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Step 3: Modelling the shell in Ecotect using the Plane tool

Another technique is to create the individual planes that encompass our space using the plane tool. This technique is useful for circumstances when the zone tool is not appropriate, review the following steps and then continue at Step 4.

• Select the Zone management tab, and select the little + sign to create a new zone

• Create a suitable name

• Double click your new zone to ensure that it is the current zone (Note the Current zone is shown at the top of the screen)

• Select the “Plane” tool

• Select the internal points (corners) of your walls, (Note: you only need to select four points then hit the Esc key on your keyboard to complete the plane).

• Continue creating new planes with all the internal walls of your space

• Go back to the “Zone Management” tab and turn off your original Zone (layer) by selecting the lightbulb

• Check that all your walls are ok, they should be the same colour of your zone i.e. grey in my case, if they are red that means they are not coplaner (have a twist in them) which does not really matter.

• Use the same process to create the ceiling and floor

• Click the “Visualise” tab to see a shaded view to check that you have modelled your space correctly.

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Step 4: Modelling windows in Ecotect

We have created the shell of our space we now need to create the windows.

• Open the “3D Editor” tab.

• Select the “Add window” icon

• Similar process to before snap to the points of your windows of your imported Revit geometry

• Turn off your Revit geometry to check your model

• Select your newly creating window, and select the “Material Assignments” tab, select the Panel option, and choose glass.

• Double click the glass in the “Material Assignments” tab, check the transparency of the glass… I use 0.8

• Close this dialogue box

• Click the “Visualise” tab to see a shaded view to check that you have modelled your glass and applied the material correctly

• Sometimes it is difficult to select the correct points in your Revit model, in these cases I turn off the Revit geometry layer and roughly sketch the window in approximately the correct position.

• Turn the Revit geometry layer on again and enable nodes by hitting the f3 button on your keyboard, grab the nodes and move to suit.

• Turn off your original Revit geometry and check you model in the “3D editor” and “Visualise” tabs.

• Click the little red icon next to the padlock on your current layer so that it changes to a little T, this designates the zone as a thermal zone to be included in later calculations.

The last zone we need to model for this particular geometry is the roof space,

Note: If you have a flat roof you do not need to create a separate “roof:” zone.

• To create a pitched roof turn the zone (layer) containing the imported *dxf file, and select the pitched roof tool.

• Using the left mouse button select two edges of the ceiling diagonally across from each other, then modify the parameters in the Scripts & Wizards dialogue box to suit and select the “Create New Object” button.

• Turn off (and/or delete) the layer containing the imported *dxf, check your roof space has the thermal icon switched on and check your model

• Now we need to check the Normals of our space, while in the 3D editor select Display -> Surface Normals

• Check your model ensuring the arrows (normals) are pointing outwards, if they are not select the object/face and then select from the top menus, Modify -> Reverse Normals.

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Step 5: Applying and defining Materials

Our basic model is now complete we will now apply and check the materials associated to this new geometry, check the north orientation and world location and then we are ready to start analysing our space.

• We will begin with the roof, select this element and then the Material Assignments tab

• In the pull down menu select the roof option, and then choose an appropriate type from the menu

• For this project I used the CorrugatedMetalRoof option, double click to open the properties of your selected material

• Repeat this process for the rest of the geometry, i.e. for the walls pull down and select a wall type…

Step 6: Location, Orientation and loading Weather Data

We will now move onto the North orientation and world location. To ascertain the true North for my site I used google earth. I then overlayed this in photoshop and measured the difference which showed a difference of -10.5 degrees.

• Select the transform tool, note that the origin is to the left of the building, select and drag this origin point to the center of your building

• Rotate the model to suit, Note: the degree are shown in the transform dialogue at the top of the page, where you can also type in specific degrees

• Now for the weather data, select the Project tab on the left of the screen, and double click on the WeatherDataFile line under the “EXTERNAL_FILE_REFERENCES”

• Browse to a suitable weather data file, Note NZ data is not included with the default install, you will need this specific data yourself, or substitute for the closest exisitng location

• Once you have selected your data select yes to “Update global position to match climate file?” and notice how the Site Location information changes.

• Save your file as we are now ready to begin thermal analysis studies.

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Step 7: Thermal Analysis Calculations

The following is based on a Squ1 tutorial click here to download a *pdf copy.

• Select Calculate -> Thermal Analysis

• Hourly Temperatures

• Choose a date, I selected the Hottest Day (Peak)

• Select yes for recalculating the Inter-Zonal adjacencies

• Inter-Zonal adjacencies Step 1: Select High

• Inter-Zonal adjacencies Step 2: Very Close

• Inter-Zonal adjacencies Step 3: Yes, Automatically fix…

• Inter-Zonal adjacencies Step 4: Perform Detailed Shading Calculations

• Inter-Zonal adjacencies Step5: Ok (to start calculation)

Note: Depending on the complexity of your scene and speed of your PC this process can take 30min or longer.

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• Select the Hourly Temperature Profile under the “Thermal Calculation” tab, the displayed graph should now show a number of solid and dashed lines

• This graph displays the hourly temperature within each zone at the current date. The dotted and dashed lines represent the climate data on that day, as shown in the legend immediately below the graph, whilst the solid colored lines show internal environment temperatures Note: The solid BOLD magenta line and the thin grey line below it, these are our Thermal zones (Roof and Living room and the colours are dictated by the colour associated with these zones)

• Click the little coloured square to the left of the Living Room zone, this brings up a colour swatch, choose a new colour and select ok.Notice the colour of the grey line has now changed.

• Now change the date that the graph is representing, you can do this two ways… i.e. drag the slider at the bottom of the screen or type in dates at the top of the screen (to the right of the help menu)Notice the graph changes accordingly to the weather data of the new day

We will now cover the basics of the zone settings.

• Select a zone in the “Highlight Zone” pull down menu, (in this example I selected the Living Room zone) and select the “Zone settings” tab

• Change the settings accordingly, for this example i simply changed the number of occupants to two

• Under the ‘Thermal Properties” tab, again change the settings appropriate to your scene.

These changes to the zone settings will automatically update your graphs.

• Choose the Hourly Heat Gains/Losses in the “Thermal Calculation” pull down menu at the bottom of the screen.

• Select “Temperature Distribution” from the “Thermal Calculation” pull down menu and click recalculate.

• Select “Fabric Gains” from the “Thermal Calculation” pull down menu and click recalculate.

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Step 8: Thermal Analysis Charts

When this calculation process has completed select the Analysis tab.

Our first graph shows that the peak outside temperature for the 9th of Feb is 25°C, this corresponds to a internal temperature of approx 30°C in our Living space and approx 40°C in our Roof… but how much of an effect is the temperature in the roof space having on our Living room?

To display the contribution of all the different sources of heat loss and gain for our Living space we need to choose a different graph.

This graph shows the relative effect of each source of heat flow for each hour of the day, and is very useful to track down why a zone is behaving the way it does. In our zone it illustrates the dominant loads are Solair (gains due to indirect solar exposure, i.e. the building materials heating up when exposed to solar radiation) and Direct solar gain through the windows…

If we want to improve the performance of our space we can start considering the size or type of the glass, shading devices and thermal massing of the building materials. The whole point of these graphs is to anaylse our design and then have the ability to test different designs and materials quickly to improve the performance of our zones.

For more information on the Heat Gain Loss Graphs click me to download a *pdf tutorial from the Squ1 website.

In addition to temperatures and loads on specific days throughout the year, it is often useful to statistically analyse the annual performance of a building, This means displaying how often zones attain particular temperatures and the average daily distribution of losses and gains.

This graph shows temperature along the bottom axis and the number of hours per year spent at each temperature int he vertical axis. This particular graph shows the our zones are often too cool for our comfort bands with the spaces predominantly been 15°C or less… (The blue and red bands represent the boundaries of the selected zones comfort band).

For this particular design/zone it is important to try to achieve some internal heating in the mid-late evening to prevent th occupants relying on an active heat source. One way to do this is to use exposed thermal mass in the walls to store external heat and solar radiation. If the thermal mass is thick enough, the time taken for this heat to flow through can be up to seven hours (thermal lag). This means that seven hours after the sun has fallen on the external surface, the internal surface starts to warm up.

The last test I will be completing for the initial thermal anaylsis is Fabric gains

This graph shows an average day each month, with months along the horizontal axis and the hours of the day along the vertical. The colour of each grid square represents the average gain or loss.

As expected our zone is performing quite predictably with the current materiality and design, the fabric gains peak around midday in Summer and are the least early/late in the day in Winter.

This concludes our thermal analysis of our existing space, run these tests on your own spaces, change the materiality and design and run the tests again to ascertain how a particular design and materiality will actually perform.

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I have created a *pdf of this Ecotect Thermal anaylsis tutorial,