Energy Efficiency and Sustainability
Energy Efficiency and Sustainability tests CTE DB-HE, the certificado de eficiencia energética and the design choices that reduce demand and consumption.
DB-HE 2019
HE0 limits energy consumption; HE1 limits demand through envelope and glazing; HE2 covers thermal installations (with RITE); HE3 covers lighting efficiency; HE4 requires solar thermal for domestic hot water; HE5 requires photovoltaic generation in larger buildings. The CEE follows RD 390/2021.
Envelope first
Insulation, glazing and solar control reduce demand before renewables are sized. Thermal bridges and airtightness often dominate real consumption, so a good U-value on paper can still fail in practice.
Worked example
A dwelling for 4 people with HE4 demand of 28 litres/person/day at 60 °C, cold water at 15 °C. Annual volume = 28 × 4 × 365 = 40,880 litres. Energy = 40,880 × 4.18 × 45 / 3600 ≈ 2,136 kWh. A 60% solar fraction supplies about 1,282 kWh, leaving about 854 kWh from the backup system.
Traps
- Mixing demand (kWh/m²·year) with installed power.
- Forgetting the 60 °C reference temperature.
- Claiming a solar fraction without checking shading.
- Ignoring thermal bridges and airtightness, which dominate real demand.