Am I being an unreasonable landlord here?

[Lloyd Spencer]

Upstairs tenant in my 2 family brought to my attention a problem with water coming into the property above their front door.  A $400 report says the problem is that the roofing wasn't finished properly plus the windows all need removal and reinstallation, a $20k job.  

I am trying to schedule the work, tenant is away in August, so I propose to do it then.  No, they want it done while they are there because they don't trust contractors.  Fair enough.  So I scramble to find someone in July who can start this week.

Now tenant is demanding to not pay rent during the time of the construction.  I agree it will be a major hassle, but what are the options?  I've already offered to do it when they aren't there.  Only other option is to do it a year from now when the tenant's lease expires.

I even offered the tenant to break the lease but they think I am being unreasonable.  Am I?  Is it reasonable for a tenant to demand to pay no rent during repairs?  (We have a standard NJ lease with a rider based on the The Book on Managing Rental Properties.)

Need to know where the market is on this situation...

Thanks in advance for your thoughts.