Model checklist for SketchUp models

Below is a checklist to help with setting up your model for Sefaira analysis, both to avoid errors and to ensure that your results are correct.

If you are running into error messages related to Sefaira being unable to process your model correctly, this is likely down to an issue with the model setup.

 

Aside from the checklist below, please also follow this guide to ensure that your entities are tagged correctly. 

 

1) Always place your model at the origin and orientate correctly

If the model is placed far away from the origin, this might interfere with both the daylight and energy simulation.

To orientate your building correctly, Sefaira will assume that the default green model axis always points North.

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2) Use a realistic scale

Both energy and daylight analysis rely on a realistic floor area, and also a realistic internal ceiling height to calculate results correctly. 

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3) Use single-plane elements

Energy analysis assumes that any surface tagged as 'wall' (for example) will have all the physical properties of an actual wall with corresponding thickness. If you tag two surfaces that are parallel to each other, e.g. a wall, roof, ceiling or glazing modeled with thickness, then energy transfer will be calculated across both surfaces, leading to incorrect results. 

This is not relevant for walls, ceilings and floors in daylight analysis only, as for daylight we are only interpreting opaque and transparent faces, which either block (and reflect) or transmit light.

If you have a complex model with double-faced elements, here are some ways to manage these:

  • You could redraw a simple outline of the complex building
  • You could tag all internal faces as 'internal wall' or 'ignore' (in the case of double floors or ceilings). Note that 'internal wall' is interpreted as an opaque face for daylight analysis, but ignored for energy analysis

Some notes regarding internal zone separation:

  • Internal walls are required for correct daylight analysis, however if you are only interested in energy analysis you can simply divide the floor planes and internal walls will be assumed along those boundaries
  • To stick with single-plane floors and avoid internal walls below cutting into the floor area above, simply Group your building floors or stories

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4) Tag external elements correctly

Any wall, roof, floor or window area should be part of the building envelope, and never outside it. Sefaira will always assume that there is heat transfer between the outside and inside (with the exception of internal floors) across these elements.

Any elements that do not separate the inside from the outside and are outside of the building, should be tagged with either Shading, Internal Glazing (for external transparent surfaces) or simply Ignore. As a rule of thumb:

  • Any external floor areas should be set to Ignore, unless they provide shading to the building (e.g. balconies)
  • Any external glazing should be set to Internal Glazing if they provide some shading to the building (e.g. on balconies or double-skin facade)
  • Any context geometry (walls, surrounding buildings, etc) should be set to Shading only if they provide substantial shading to the building you are analyzing - but take care to stay well below 500 shading planes in total!

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5) Skylights must be framed

If a skylight finishes flush with the edge of a wall, this causes issues with the model interpretation algorithm. Please always create a frame around the skylight to ensure that the edge of the glazed area is inside the floor area below, and that the two edges are not directly in line or overlapping.

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6) Below grade walls and Cantilever overhangs

To ensure best results, you should tag these as follows:

  • Any below-grade walls should be tagged as shading
  • The floor of a Cantilever overhang should remain floor - this will be treated correctly, and energy transfer with the air will be calculated with the same insulation as the ground floor

 

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