Here is my answer:
According to Cambridge Dictionaries Online, the word 'renewal' has 3 different meanings.
- The act of making an agreement continue for an extra period of time after it has come to an end: contract/license renewals
example) The purchases are subject to annual renewal.
- The act or process of making changes to something in order to improve it so that it becomes more successful.
Ex.) The country is going through economic renewal.
- A situation in which something begins again after having stopped for a period of time.
Ex.) Pharmaceutical shares also benefited from the renewal of interest in growth stocks.
For this case, you could technically say ‘Our shop is under renewal’ or ‘Our shop is undergoing a renewal process’ based on the meaning 2 above. There is nothing wrong to it and it is totally understandable to most English speakers.
However, as the 3 commenters mentioned above, using the word ‘renewal’ in this case is not idiomatic and it could be a bit awkward. So it will be much better to say ‘under renovation’ or ‘being remodeled’ for your sake.
Thank you guys for all your help!