Renovate over Tenant Vacation - Rent Abatement?

[Joshua Kaster]

Would like to hear how others handle optional renovations during tenant vacations and if they apply rent abatement for any loss of use.

Backstory: Renting out a basement apartment with painted concrete walls. It looks nice, attracted many interested viewers, and was rented within 2 weeks of listing. However, humidity is high in Ohio summer and the walls get condensation without dehumidifier on constantly. Also costing more in utilities which I pay. Both tenants are students and decided to visit family for 2 months and return for classes ( lease is 1 year). We asked their plans to return and permission to put up drywall to make the apartment even nicer. Both agreed enthusiastically and are returning weekend before classes start. No increase in rent or change in lease or signed statement was imposed, just written text message communication. 

We messaged multiple times that we would start construction soon and confirmed they wouldn't  move back for a few week. However, 4 days after we start, the tenant announced she would be coming back intermittently and need to sleep in apartment - could we pause construction? We replied yes, but it's full of tools and electrical and isn't safe - Please give us 24hr notice. She responded angrily and requested rent back for that month. We denied request and outlined reasons why - listing dates of communication and current dangerous state of apartment. Other tenant isn't upset, specifically stated doesn't wanting rent back and thank you for renovations. 

Had a follow up phone conversation with angry tenant a few days later where she references our lease. It has a line about restoring property after catastrophic damage, at owner's option, and rent abatement until restored. We stated that was not applicable because apartment wasnt destroyed, she agreed to renovations, and she hadn't told us she needed apartment intermittently. Ended the call with polite but flat refusal to return rent.

Anyway, wanted to know others would handle it, what steps should be taken now, and how to avoid issue in future. Thanks!