Overall:
Firstly, this is a good rendering, and I think rendering style fits the design of the building.
Love your description on how you approached the design, and how you can simply divide the building into two separate units. However, since that is a main idea of the building, I think it should be shown in a rendering also. Not particularly in this perspective, but maybe with a cutout orthographic view.
Also, I would like to give you some rendering tips which I hope can help you improve your rendering skills.
Composition:
Although the horizontal position of the camera is good (catches nicely the important parts of the building), I think it's elevated from the ground a bit too much. It looks like the photographer is standing on a higher ground than the building while taking the photo (or he is 2.50 meters tall :P). That is most often not the case, and I usually place the camera not higher than 1.50 m from the ground. In this case, I would even go lower, somewhere between 40-80 cm from the ground, look up at the building and use two point perspective to correct the vertical lines of the building. That way the building would probably look a bit taller, and more majestic.
Lighting/Shadows - red lines:
I like how soft shadows and cloudy weather influence the mood of the image, but I think the image is a bit too flat. We could improve that by placing the sun on the left side of the image, keeping the right side in shadow. That way, we would create more shadows, which would improve the depth of the image.
1 - Red - You really want to avoid small, unnecessary shadows on your building. The shadow from the roof edge (gutter) just creates confusion. Keeping that whole side of the building in the shadows (by moving the side), is a better choice.
2 - Red - Moving the sun will also change the direction of the shadows in the shaded part of the outdoor sitting area, which will also create more depth.
3 - Red - Building shading device on the left side would cast shadows on the facade, which you probably can guess, would add more depth to the image if the sun was coming from the left side.
4 - When you have boring cutted grass in front of the building, adding a tree shadows makes the image more interesting, and will guide the viewer eyes to the building.
3D Models:
1 - Green - I know it is hard to find vegetation models, but I think a bigger ivy growing along the sun shading device would add to the quality of the image.
2 - Green - That part of the image is a bit empty in my opinion, and adding some pool sitting furniture could add to the whole garden story.
3 - Green - A bit bulkier outdoor furniture would be better visible in the image.
4 - Green - Although the black silhouette people fit very nicely in the overall style, maybe trying some AI generated people would help with the realism of the rendering.
Textures:
1 - Yellow - The texture is a bit confusing. I'm not sure if this is wood (which I would guess), or concrete. The gap between the planks is a bit too big, in my opinion.
2 - Yellow - Roof tiles are a bit too flat. I don't know if it's the design of the tiles, but could be improved by adding some displacement, and probably some slight difference in the color of the individual tiles.
Hope I could help at least a bit :).
