Ventilation valve operating principle

Fresh air valves are required to provide a controlled supply of fresh outdoor air whenever a building is equipped with natural ventilation or mechanical exhaust ventilation. Velco fresh air valves are a reliable and proven solution for supplying replacement air in apartment buildings, detached houses, and terraced houses. They are also ideally suited for holiday homes and sauna buildings.

The operation of a Velco fresh air valve is based on a wax thermostat that responds to thermal expansion, automatically adjusting the valve opening according to the outdoor temperature. The thermostat continuously regulates the airflow opening within the temperature range of +10°C to –5°C.



At outdoor temperatures above +10°C, the valve is fully open. Below –5°C, it operates at its minimum opening. During installation, the valve is adjusted so that it never closes completely. The minimum opening can be fine-tuned to suit the building and local conditions if required. Because the Velco fresh air valve operates entirely without electricity, it provides a maintenance-free and long-lasting solution for controlled replacement air.

Sound silencers

Velco fresh air valves are available with a range of sound silencing solutions designed to effectively reduce the transmission of outdoor noise, including road traffic and aircraft noise, into indoor spaces. Sound silencers can be supplied as part of a new fresh air valve or purchased separately for retrofit installation.

Air filtration

Velco fresh air valves offer market-leading filtration performance. The filter used in the valve significantly reduces the amount of outdoor pollutants entering the indoor environment by capturing 100% of pollen and providing highly efficient filtration of fine particles that are harmful to health.



The exceptional performance of the Velco filter is based on electrically charged fibres within the filter media. Unlike conventional filters that rely solely on mechanical filtration, the electrostatically charged filter attracts even microscopic particles like a magnet and effectively captures them within its fibre structure. The filters are manufactured from patented 3M Filtrete™ filter media, renowned for its outstanding filtration efficiency and low airflow resistance.

Customizable according to the installation requirements

Velco offers a comprehensive range of installation solutions for various applications. The valve can be installed in a new wall mounting or in a wooden ventilation window. The range also includes products for renovating and upgrading existing fresh air valves.

Velco fresh air valves are available as ready-made solutions designed for the most common installation situations. Thanks to the wide range of components, Velco valve solutions can also be customized to meet the specific requirements of each installation. Application-specific configurations allow control over factors such as sound attenuation level, airflow rates, the appearance of exterior grilles, and the technically optimal installation method.