Found this website on a search of the net for some good discussion/opening type question on surface area: http://mrpiccmath.weebly.com/blog/3-acts-pop-box-design
Thanks to the author there who has created some nice little videos and even accompanying worksheets to go along with the lesson. I mixed things up a little, but still had fun going through the process with the students.
Later on I came across another question prompt from Dan Meyer on surface area/volume… it’s ‘Dandy Candies‘: working out what design is most efficient for wrapping.
There’s also Robert Kaplinsky’s lesson on working out how much paint on a space shuttle! Incorporates surface area, volume… other measurement.
The other one I’ve tried before is the ‘filing cabinet activity‘ with stick-it-notes, described