Unmet Loads Analysis aka. Passive Design Simulation

[Andy Thomson]

Some resources to learn Unmet Loads Analysis - this is when you run an energy model using EcoDesigner with NO mechanical equipment specified. What you want the Architecture/Fabric to do is keep internal temperatures from freezing or cooking your occupants. Buildings that do this well can truly be called 'Passive' Buildings, or Houses, or Häuser, as preference dictates. Video here: https://www.youtube.com/watch?v=8cPlm1AKk-0 - Textbook for why this matters here: https://academic.daniels.utoronto.ca/pbs/wp-content/uploads/sites/13/2023/04/Thermal-Resilience-Guid...

The whole trick is in your Energy Model Report, ADD every month of the year in your daily temperature profile, and watch that your indoor line represents reasonable habitable temperatures, when compared with your outdoor line! That's it!

PS - the sample below shows my internal light blue line is well outside of my pink/habitable zone, so I better improve the architecture or put some more clothes on!

[Strawbale23]

Hi Andy,

In your video you have a very simple design to evaluate. I found that with anything remotely complex, AC ran into issues. This thread pretty much spells it out.

https://community.graphisoft.com/t5/Sustainable-design/upper-walls-not-recognized-in-energy-model-st...

Would be interesting to see the same type of video but with a more "realistic" building situation, and if it can address these issues.

[Andy Thomson]

Hi @Strawbale23  - I'm not having the issues you explain. I can sympathize that building a watertight file for zones to work properly in ED/EE is not easy (ie. overlapping walls will cause issues, zones not touching surfaces will cause issues, and generally modelling for EE/ED to capture everything can be really fussy - but it is still FAR easier than manually entering information in another platform where elements will also be missed). As for my models being realistic or not - these are real projects under construction - realism has everything to do with LOD - and for schamatic phase modelling, LOD100 to 200 is all you need to get an idea of how a building form will perform.... I showed a single-zone model for schematic convenience but also a multi-zoned model alongside it. The attached image is from a 48 unit MURB - again no issues recognizing all structures in all zones and applying aggregate U-values to them appropriately - except for a few patches at balconies that have overlapping wall types - user error! Knowing what the tool is looking for may help - one can't expect it to capture values from 2 different wall assemblies within one-storey however, but one can easily model workarounds and it is still faster than jumping to another energy modelling software. If you are interested in more of our results we did have a LUND University master's student publish a white paper on this here. 

https://lup.lub.lu.se/student-papers/search/publication/9053944

Imho GS needs to update their instructional materials to cover how the tool functions, and what it can and cannot do. 

[Strawbale23]

Hi Andy, sorry, it was not my intention to intimate that your projects are not realsitic or real world. It is just that on the modestly complex projects I have worked on and tried to implement the energy modelling, I ran into a deadend because of issues with the zones being correctly recognised and calculated. However, it has been a while since I tried so perhaps things have improved now.