Eco-friendly houses for hostels and apartments

I would to know more about the eco-friendly houses and their implementation. Currently I have a close relative who would like to build a good viable hostel for students but its due completion due to finances. I have seen about your KES 80,000 house design and was interested.

Moreover, the house design I have in mind or like to request from you, has two floors. Can it be firm? Although my relative has built one floor (Ground floor), he wishes to continue with the other floor and finish. Can it be done at a lower cost? The area is situated at Kahawa along Thika Road. If possible you can write to him via email: digivillecomm@gmail.com