The entry into force of Regulation No. RD-02-20-3 changed the rules in the construction sector. Now every new building must be "nearly zero energy" (nZEB). This poses a serious challenge for investors: how to achieve Class A and the required RES share without making the project unnecessarily expensive.
The Challenge: The 95 kWh/m2 limit
The main indicator for obtaining a building permit is the Primary Energy, whose limit value is 95 kWh/m2 per year. In a modern design with a high percentage of glazing and a load of 70 W/m2, traditional systems fail:
- TPP: 191.5 kWh/m2.
- Gas: 167.4 kWh/m2.
Why does geothermal energy win without photovoltaics?
While air-source heat pumps often balance on the edge of the limit (86.3 kWh/m2), geothermal energy offers security with a value of only 49.0 kWh/m2.
- Automatic coverage of the RES norm: The law requires a minimum of 20% of primary energy to come from on-site RES. Geothermal (at COP 6) extracts 5 units of free energy from the ground for 1 unit of electricity. This means an 83% RES share – 4 times above the law.
- Space saving: For a building with a total area of 1428 m2 when heated with a CHP, 273 m2 of photovoltaics are needed to cover the RES norm. For geothermal, the required capacity is 0 m2, as it fulfills the requirement automatically.
Frequently Asked Questions (FAQ)
Question: Can a gas building meet nZEB standards? Answer: Very difficult. At a load of 70 W/m2, the gas exceeds the primary energy limit by 76% (167.4 at a limit of 95 kWh/m2). To compensate for this, you need to install a huge photovoltaic power (about 39.8 kWp), which requires nearly 239 m2 of roof area.
Question: Why do air source heat pumps sometimes require photovoltaics, but geothermal ones do not?
Answer: At low outdoor temperatures (−10∘C to −15∘C) the efficiency of the air pump drops to COP 1.5-2.0, making it almost like a regular electric heater. The geothermal pump uses the constant temperature of the ground (10−12∘C) and remains highly efficient 24/7.
