Has anyone seen any study on the relative energy costs and savings of sun tubes? I have a client interested in one of these and I’m not sure if it’s a good idea in general.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
I haven't seen such a study.
Here's what I know:
1. All types of skylights make more sense in commercial buildings, institutional buildings, and schools than in residential buildings, because most American homes aren't occupied during daylight hours, at least for 5 days a week.
2. Putting a big hole is your thermal envelope (especially in the ceiling) provides a thermal bridge and is likely to increase air leakage.
My guess is that in most cases, these units are installed for aesthetic reasons (which is fine), but that the owners end up with an energy penalty rather than an energy benefit.