Heat Recovery Ventilation

Heat Recovery Ventilation

What is Heat Recovery Ventilation?

With the energy costs rising the move towards low energy air tight houses and even Passive houses is increasing rapidly. While these houses are cheap to heat and run, the very fact that they’re airtight does not allow the house to breath in the way a conventional house would. Because of this, condensation and a general feeling of stale air or stuffiness can become a problem.
Heat Recovery Ventilation systems allow you to overcome these problems without compromising the energy efficiency of the building. HRV systems work by extracting stale moist air from the wet rooms of your house. This air is dragged back to the HRV unit where it passes through a heat exchanger. Fresh air from outside is pumped through the heat exchanger at 90degrees to the fresh air being extracted. The heat from the warm stale air transfers to the cooler fresh air being pumped into the house with an energy transfer efficiency of up to 90%. This means that the fresh air entering the building is almost the same temperature as the air in the room it enters and therefore does not compromise the room temperature and requires very little additional energy.

Climate Control Renewables are agents for Zehnder Heat Recovery Ventilation systems. Zehnder are a Swiss made system with very high levels of efficiency and production quality. The systems incorporate an innovative ducting system, which allows for low levels of airflow resistance, noise of air movement and duct contamination from dust.

Zehnder manufacturer HRV systems of 200 m3, 350 m3 and 550 m3 and are Passive house approved.

The Zehnder distribution system consists of a supply and extract manifold which are mounted above the unit, above ceiling level or even in the floor construction if required. From this manifold a 75mm semi flexible plastic duct is ran to each individual room. The duct is coated internally with Clinside, a protective coating that discourages dust adhesion to the duct and it therefore remains clean and obstruction free.

The ducting also differs from standard solid duct systems in that the semi rigid duct routes contain no tees or sharp bends which cause restrictions on airflow which must be overcome by running the unit at a higher speed, so higher efficiency levels are experienced. Also, the problem of possible noise movement from room to room experienced with solid duct systems is eliminated, as noise would have to travel from the vent back to the manifold and then back out the ductwork to the next room. Air movement noise is also greatly reduced as each room has its own duct where the air must travel and therefore you do not get sections of ducting where the full volume of air for the house will be travelling all at once.

Summer Bypass: Most of Zehnder’s ventilation units come complete with a summer bypass feature. This means that during warmer months, the supply air bypasses the heat exchanger – especially important if this air has already been pre-cooled by the ground source heat exchanger.


Zehnder HRV units also come with a wide range of options in order to maximise the comfort supplied by your system.

Enthalpy Heat Exchanger

In some instances, the environment within an airtight home can become too dry for comfort. It is possible to upgrade the heat exchanger on selected units to the Zehnder Enthalpy Heat Exchanger. Not only does this product remove heat from extracted air, it also extracts water vapour, which is absorbed by a membrane. This can then be used to regulate the humidity of supply air, ensuring it is optimised for comfort with no transfer of odour or microbes and no loss in performance

Comfond: A Ground source heat exchanger is employed to capture energy in the earth to temper or cool supply air to your home when used with a whole house heat recovery system. At a depth of approximately one to one and a half metres, the temperature of the earth remains almost constant all year round at between 10 and 12°C. By utilising a system, which has been designed to absorb this heat, you can either cool or warm supply to your
habitable rooms through your whole house ventilation system. This has benefits on several levels. By preheating or pre-cooling the air entering the HRV unit it is possible to increase the heating or cooling effect of the unit depending on time of year e.g. Air pre-cooled by the comfond and passed through the summer bypass could be used to cool your home in warmer weather.Designer Grilles: Zehnder have a full array of designer grilles that can be supplied in white or Brushed stainless steel finished and can be fitted in the floor, walls or ceiling depending on your design requirements.

Flat 51 Ducting: When space is at a premium the Zehnder flat 51 ducting system is the solution. At only 51mm high it can provide a duct run in the tightest of areas and is strong enough to be routed in ceiling voids and floor construction.

Comfobox: When space is at an absolute premium the Zehnder Comfobox allows you to fit a heat pump and HRV system in the tightest of spaces. The Comfobox incorporates both the heat pump and HRV into one neat unit. With a COP of 4.4 and heat outputs of up to 10kw these units are perfect for low energy or Passive homes.

Commercial Units: Zehnder have a full range of units to cover even the commercial sector with capacities of up to 4000m3 per hour.

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