#8 further developed: I've removed the orange color – I think it´s maybe a bit too aggressive for your purpose – and added a more "greenish" color scheme. The roots are more a part of the ground now, and the solid blue sky depicts a clean and healthy environment (= energy efficiency). I'd rather not add more graphic elements like a leaf – this would imo complicate the logo too much, and I think the altered color scheme does the trick :-). Thanks for giving me feedback on this.
(This comment references Entry #38)