Heat pumps in older homes: When to prioritize insulation or the aerothermal system first

Radiators, underfloor heating, and the question everyone dreads: do I have to replace my radiators?

Air-source heat pumps work optimally at supply temperatures of 35–45 °C. Older radiators—especially pre-2000 models—were designed for boilers reaching 70–80 °C, so they need much hotter water to heat a home efficiently. To make your pump perform well (and keep power bills reasonable), you have three options: (1) replace radiators with low-temperature models designed for 40–50 °C; (2) install underfloor heating in renovated areas or throughout; (3) upsize existing radiators to work better at lower temps, which usually means rewiring and often isn't feasible in apartments.

The most practical option for apartments is swapping radiators for large, energy-efficient low-temperature models (aluminum multi-fin type) and keeping a zoned system. The cost is €500–1,500 per radiator installed (size and complexity matter), but payback comes in 5–7 years of energy savings. Underfloor heating is more comfortable and efficient, but requires lifting floors, which is disruptive and expensive (€8,000–15,000 for 60–80 m²). Many families choose it when renovating kitchens or bathrooms anyway.

Noise, outdoor unit placement, and homeowner associations: what you must know before installing

Every air-source heat pump requires an outdoor unit (condenser) installed on a facade, terrace, roof, or balcony. This unit emits noise (typically 40–50 dB, like a loud fridge). Spanish local regulations vary, but many municipalities require it not to exceed 55 dB daytime and 45 dB nighttime at a neighbor's property line. In homeowner associations, you must obtain prior agreement at a meeting (or at least formal notification) before installation. Some bylaws prohibit visible outdoor units; others mandate placement in common areas under association supervision.

Practical tip: consult your board first and request a noise report from the manufacturer (many modern pumps are 42–45 dB). Choose models with inverter compressors (quieter) and avoid placing units near neighbors' bedrooms. On shared balconies or community rooftops, associations may charge a fee for common-area use. In single-family homes you have more freedom, but respect minimum distance from property lines (typically 0.5–1 m per region). If a neighbor complains, the municipality may order removal, so good neighborly relations are an investment.

Frequently asked: costs, noise, renovations, and regulations