Hi Wylie,
If you sell a building you get back some of the resources (gold/supplies) you spent building it and all of the culture/population that building is using.
To quote the Elvenar Wiki:
"You can sell and rebuild most of your buildings. In order to know which resources you will get back from selling a building, just enter sell mode by clicking the icon
, hover your mouse over the building and you will see a tooltip with that information."
Hope that helps.
P.S.: You can check this yourself by comparing a building's costs during the initial build and then upgrade stages. For example (only using population and culture because I don't have the complete values for gold, supplies and goods - which usually never get returned in full):
A rank 1 steel manufacturer costs 36 population and 0 culture.
Upgrading to rank 2 costs further 4 population and 5 culture.
Upgrading to rank 3 costs further 4 population and 4 culture.
Upgrading to rank 4 costs further 5 population and 7 culture.
If I sell a rank 4 steel manufacturer I receive 3500 gold, 150 supplies, 49 population and 16 culture.
36+4+4+5 population = 49 population
0+5+4+7 culture = 16 culture
I get all my population and culture back.
