Thanks, @AbrahamYezioro . I appreciate providing sources and examples since this gives us something that we can discuss and try to understand.
Understanding the Existing Sources
It seems like both cases are not adding a shade “strategy polygon” but are instead trying to draw a “shade line” on the chart, which is just trying to say “shade can be helpful here” and it doesn’t actually make any of the hours more comfortable. So, this at least helps me see that, if we were to try implement something similar in LBT, we probably shouldn’t be doing it with a polygon and we should instead find a way to draw a line on the chart that doesn’t really add to the the total number of comfortable hours.
I’m also at a bit of a loss to understand how this shade line tells us something that we don’t already know. If we just wanted to figure out the number of hours that are in the comfort polygon or warmer, we don’t need to have a line on the psych chart labeled “shade” to do this.
This leads me to a bigger point of confusion, which is that I can’t figure out why these two sources decided to put this “shade line” where the did. Technically, any temperature above the building balance point is one where the solar gain combined with a lack of building shade could make conditions too warm to be comfortable. So I don’t see any satisfactory explanation for why the shade line is at the lower boundary of the comfort polygon and not the lower boundary of the “Internal Gains” polygon. All of this kind of underrepresents how powerful shade is as a strategy since, as my comparison above shows, it can be REALLY helpful and we risk having people walk away with a false sense that “shade is not really that important” when we under-represent it like this.
Lastly, as I said earlier, climate consultant and the strategy polygons in LBT already assume that the building is shaded for all hours above the building balance point (as long as you’re plotting outdoor dry bulb temperature in LBT). So it’s not like shade it something that can be added on top of the existing strategy polygons.
It all makes me think that the creators of the “shade line” might have gotten a little carried away with wanting to represent all of passive design in a single temperature/humidity plot that they didn’t think enough about how informative, useful, or accurate their implementation was.
Proposal for LBT
What do you think about trying to implement “shade” in the following way on the psychrometric chart?
- We can add an option to the Passive Strategies List called “Remove Shading.” Using this “Remove Shading” option will require the user to plug in hourly
solar_data_just like the “Passive Solar” polygon. - Checking this “Remove Shade” option will draw a “shade line” on the chart at the building balance point, above which shade is considered helpful and a lack of shade can make conditions uncomfortable.
- Using methods similar to the “Passive Solar” polygon (with the user-input Solar Heat Capacity and Time Constant), the “Remove Shading” option will try to figure out how much warmer the building is at each hour as a result of not having shade.
- If the temperature delta from the removed shading would put a point outside of all comfort and strategy polygons, these hours will be removed from the “total comfort data” and the total comfort percent output form the component.
I’m open to other suggestions if anyone else has a proposal that would be more helpful or informative. This is just the best one that I could think of that doesn’t mis-represent how important shade is.