Ventilation

Heat recovery and controlled ventilation

This page is for anyone dealing with air exchange in an apartment or house, whether due to dampness, allergies, or because new windows have sealed the building so tightly that natural ventilation no longer works. We explain how heat recovery ventilation works, when it makes sense, and what affects its operation.

What is heat recovery ventilation

Recovery ventilation is controlled ventilation with heat recovery: the unit draws in fresh air from outside while simultaneously extracting used air from inside, transferring heat from the extracted air to the incoming air via a heat exchanger. The result is a constant supply of fresh air without opening windows and without the significant heat loss caused by conventional ventilation.

Centralised versus decentralised systems

Central The system has one unit, usually in the utility room or attic, and distributes air via ductwork to all rooms. It handles larger houses and allows you to monitor the balance between air supply and exhaust, but requires space for the distribution network and is more demanding in terms of design and installation.

Decentralised The system consists of one or more independent units built directly into the external walls of individual rooms, without central ducting. Installation is simpler and better suited to refurbishments where there is no space for distribution lines; the disadvantage is slightly lower heat recovery efficiency and the need for multiple units for multiple rooms.

	Central	Decentralised
Where it fits	new build, major renovation	renovation, flat with no space for ductwork
Installation complexity	higher, project and distribution required	lower, one unit per room
Ventilation balance	controlled for the entire building at once	by room, depending on the number of units

For which house or flat does it make sense

Heat recovery is most cost-effective in well-sealed new builds, where tight windows and the building envelope otherwise prevent natural air exchange. In the renovation of older flats, it makes sense where new plastic windows have replaced leaky wooden ones and humidity or stale air have become a problem. In an unsealed older building without further modifications, the benefit is usually smaller because air escapes outside the controlled system.

Kvalita vzduchu a vlhkost

Controlled ventilation maintains more stable CO2 and humidity levels than intermittent window ventilation, and with a suitable filter it also captures some dust and pollen from outdoor air, which is particularly appreciated by allergy sufferers. However, the result depends on correctly setting the ventilation intensity relative to the number of occupants and the size of the apartment.

What affects the price

For central systems, the price is driven up by the length and complexity of the ductwork, the location of the unit, and the building modifications required to route them. For decentralised systems, the main factor is the number of units based on the number of rooms. An indicative range can be found at page with price guides, an accurate quote requires a project tailored to your home.

Subsidies

Installation of controlled ventilation with heat recovery is among the supported items of the programme. Nová zelená úsporámoften in combination with other energy-saving measures. The conditions and scope of eligible buildings change over time; please verify the current status directly on the programme's website.

Operation and maintenance

Filters must be changed regularly according to the manufacturer's recommendations; otherwise, efficiency and air quality will decline. The ductwork of the central system requires periodic cleaning, the unit needs a check of the heat exchanger's function, and during freezing periods it also needs working frost protection to prevent the heat exchanger from becoming blocked by ice.

Common mistakes

The most common problem is underestimating the distribution design in central systems, where undersized ductwork increases noise and reduces efficiency. Other issues include an improperly balanced supply and exhaust air ratio between rooms, and missing or non-functional frost protection, which in winter leads to freezing and system shutdowns.

Frequently Asked Questions

Do I need a heat recovery ventilation system if my windows have micro-ventilation?

Microventilation does not control the actual volume of air flowing into a room, and heat from the extracted air is lost without benefit. Recuperation maintains a constant supply of fresh air while simultaneously recovering most of the heat that would otherwise escape through open windows.

Can a heat recovery system be retrofitted into an older flat?

Decentralised units are feasible and relatively easy to install. They are fitted into individual rooms via penetrations through the external wall, without extensive structural modifications. A central system with air ductwork requires more space and is more demanding to implement in an already finished flat; therefore, decentralised solutions are often preferred for renovations, or a central system is chosen only during major refurbishments.

Is a heat recovery ventilator noisy?

It depends on the design, pipe sizing, unit placement and the use of silencers. A poorly designed or undersized system is noticeably noisier than a high-quality installation, so it pays to have the system designed, not just installed according to the catalogue.

Do I need to ventilate through windows in winter if I have a heat recovery system?

No, the system runs continuously and ensures air exchange without opening windows. Occasional window ventilation remains an option, for example during cooking or cleaning, but it is not necessary as in a house without controlled ventilation.

How often should filters be changed?

Depending on the environment and the manufacturer's recommendations, usually several times a year. Neglecting filter replacement reduces heat recovery efficiency and the quality of supplied air; this is felt most quickly by allergy sufferers.