I’m new in Sefaira. After wathcing all videos and testing it in a building design, it seems everything works fine except the shading. I can’t make the shading impact at the EUI or cooling results. I’ve tried both modeling the shading or setting it at the Sefaira web app configuration, and it doesn’t have any impact on the results.
To make sure it’s not the modeling, I created a simple box with the a glass openning at the south side, and I tested both with and without shading and the results are exactly the same, even placing it in Barcelona, and removing most of the glass solar heat gain coeficient to make sure shading is important.
this is Vlad from Sefaira team. Would you mind sharing the project url with me so I can see if your overhang shading device is properly interpreted? In the mean while I just want to point out that people sometimes have high expectation for overhang shadows when it comes to reducing cooling load or cooling consumption. But before I get to that, a project url would be really needed as I need to see your other cooling loads as well. Thank you
Ok. So one has to be carful when considering overhang shading to reduce cooling peak load and cooling energy consumption. In your case you window is covering 100% on the south facade. It is a big glazing area and the size of the overhang just doesn’t really do very much to reduce cooling loads. For overhang to be effective it has to be very aggressive in size. I am sending you a similar example where I have standard windows and overhang that is aggressive in size for the size of the window and as you can see, overhand does make some but still small difference. I hope that this helps.
I’ve tried also agressives overhangs, as long as the window height plus vertical shading on sides, and I believe the impact on solar heat gains is too small and not according to reality. In our weather avoiding sun from south is essential, and specially on office or retail crowded spaces, where there are high internal loads and most of the year the HVAC works on cooling. In our office we’ve had external dynamic simulations made with DesignBuilder or EnergyPlus that comfirm this point, but we wanted to use Sefaira to improve our shading design in early stages and it seems it’s not really helpful since it doesn’t show the real impact of shading.
If you try changing the glass solar heat gain you will see changes on the EUI of 15-20% or even higher. The shadows we are creating should be as effective as a glass with solar protection and in your example there is almost no difference between the two options.
Do you think shading has such a small impact in hot and sunny weathers?
Has anyone managed to get a higher impact on the building EUI by shading it?
Hi. It’s a 150cms long shading in a 3 meters tall glass. Now I’ve tested a 3 meters long shading and there is a 10% improvement. It’s obvius that having a 150cms shading means during winter lots of sun will come into the building. But it’s still hard to believe that having a 150cms long shading becomes 0% improvement on a building, specially considering that during the hot months and hot hours the sun comes in a very vertical angle.
Maybe I’m wrong and the software is right. I really believed this kind of shading had some effect in our weather (Barcelona).
I assume that there is only so much that can be done using the typical retail construction from the template to combat the ambient temperate of the locale and volume of equiptment and people in the building - These are all factored in I believe.
If I use the same basic model in enscape impact, I get a similar small change from shading alone, so I think that the numbers are crunching correctly.
Maybe I’m doing something wrong. I’ve tested the results with a 300cms shade, 150cms shade, no shade and a wall instead of a glass, and the first three get exactly the same number in cooling needs, and the last one reduces a lot these needs. See the results with each 3d model next to it
I’m using Barcelona weather, and I haven’t changed any equipment configuration, but I’ve placed the U-factors of each elements according to a slightly better requierement than spanish legislation.
I think I have the answer for you. Sefaira/EnergyPlus doesn’t handle 100% WWR glass very well as glass (fenestration) has to point to an opaque parent surface. What you should do is offset that glass little bit and try it again. Here is an example that I did when glass was not 100% exactly. I hope that this helps.
I’ve tried your solution and now the results make sense. Sefaira uses by default a glass with a very strong sun protection. I’ve tried using a regular glass and U-values and the south solar gains during cooling hours get reduced by a 40% when shading.
Now the results make sense to me.
I believe this solves my main problem. I will check this issue in my bigger model.
