Heat Recovery Ventilation — Save Energy with an HRV System

Heat recovery ventilation (HRV) is a system that recovers heat energy from exhaust air and transfers it to the supply air. In practice, this means that the heat from warm indoor air being expelled is transferred to the incoming cold outdoor air, so the supply air does not need to be heated as much.

A modern HRV system achieves an efficiency of 70 to 90%, which means significant savings in heating costs. In cold climates where the heating season lasts 7 to 9 months per year, heat recovery is a particularly worthwhile investment. An HRV system can save up to 30 to 50% in heating energy compared to ventilation without heat recovery.

There are several types of heat recovery ventilation systems, each with its own strengths:

• Rotary heat exchanger (rotor): Highest efficiency (75 to 85%), but a small amount of exhaust air may transfer to the supply air. Well suited for residential buildings
• Cross-flow plate heat exchanger: Reliable and low-maintenance solution, efficiency 50 to 70%. Does not transfer exhaust air to supply air
• Counter-flow plate heat exchanger: High efficiency (70 to 90%), compact size. The most common solution in modern air handling units
• Liquid-coupled system: Suitable for buildings where the supply and exhaust air units are located in different places. Efficiency 40 to 60%

The right choice of HRV type depends on the building's characteristics, the ventilation system, and the budget. We help you choose the best solution for your property.

The heat recovery core requires regular maintenance to operate efficiently. A dirty core reduces heat transfer and increases the energy consumption of the ventilation system. HRV core maintenance includes:

• Core washing: The plate heat exchanger is washed with water and mild detergent every 1 to 3 years
• Rotor cleaning: The rotary heat exchanger is brushed and vacuumed to remove dust
• Seal inspection: The core seals are checked and replaced if necessary
• Frost protection: In severe cold, the core can freeze, so the defrost function is important

A well-maintained HRV core maintains its high efficiency throughout its service life. The typical lifespan of a core is 15 to 25 years, after which it should be replaced. Core replacement is often a more affordable option than replacing the entire air handling unit.

Installing a heat recovery ventilation system is a worthwhile investment that typically pays for itself in energy savings within 3 to 7 years. Installation and equipment costs vary depending on the project:

• HRV core replacement in existing unit: 400 to 1,000 euros
• New air handling unit with HRV: 3,000 to 6,000 euros installed (detached house)
• Apartment-specific HRV unit: 2,000 to 4,000 euros installed

The profitability of the investment can be assessed by comparing current heating costs with the savings provided by HRV. For example, in a detached house where the ventilation heating requirement is 5,000 kWh per year, an HRV operating at 80% efficiency saves 4,000 kWh of energy, which is approximately 400 to 600 euros per year.

Replacing the HRV core should be considered when its efficiency has dropped significantly despite maintenance. Signs that the core has reached the end of its service life include:

• Temperature efficiency has dropped: Supply air no longer warms up sufficiently, even though the core is clean
• Core is leaking: Exhaust air passes to the supply air side as seals fail
• Mechanical wear: Rotor bearings are worn or plate heat exchanger fins are damaged
• Condensation problems: Condensate continuously builds up in the core and freezes in winter

A new HRV core immediately improves the energy efficiency of the ventilation system. Modern cores are made of more durable materials and offer better efficiency than older models. Core replacement is generally a more worthwhile solution than continuous repairs, and it is significantly more affordable than replacing the entire air handling unit.