Commercial tenants in Connecticut have few of the legal rights that residential tenants have. However, if conditions in the property are really bad or if the building is destroyed or damaged badly enough that it's unfit for occupancy, the tenant has the right to get out of the lease. If the landlord fails to provide an essential service that is covered in the lease, this is a violation that can result in a criminal charge.
A typical office lease will be a triple net lease, under which the tenant pays for everything except structural repairs. So any costs incurred by the landlord in connection with the space or the building (including common area maintenance costs, insurance and taxes) will be passed through to the tenant.