nZEB Retrofit of a Concrete Large Panel Apartment Building

The paper discusses energy renovation scenarios from major renovation to nZEB level for apartment buildings in Estonia (cold climate). The study analyses energy usage and economic viability taking into account a possible increase in the lease income after renovation under apartment building renovation scenarios. Our results show that deep renovation of old apartment buildings enables the energy performance requirements of nearly zero energy apartment buildings to be achieved. With nZEB renovation, reductions are ca 70% in delivered energy (heating energy + electricity) need and ca 60% in primary energy need. Payback period of nZEB renovation without increased lease income is around 30 years. In the best scenario case, the payback period of nZEB renovation is around eight years when the increase of the annual lease income is taken into account.