You’ve seen the TV show (if you haven’t, it’s a documentary following people building their own houses), now you can do the unit of work!
At the start of Year 9 we do a full term (12-14 weeks) based around the designing and promoting of a new housing estate. The students plan the estate, design the houses in Google Sketchup, do some financial modelling, create some form of advert and finally present their work to a board of directors (because only 1 proposal will be successful and only one student will be paid!). There are also easy tie ins for data handling and even sequencing (using some of the house-based Flowol mimics).
If you’re interested, you can see all of the resources and even download them as a full Moodle course at Mukoku.