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Heat Recovery Ventilation

Heat recovery ventilation , also known as a heat exchanger is a ventilation system that extracts the warm moist stale air from the building and replaces it with clean filtered fresh air, without letting the heat escape.

HRV provide fresh air and improved climate control by improving air quality and protecting the fabric of the building.

As building are intentionally made more air-tight, they become less ventilated. Inorder to get more fresh air into the house, windows can be opened but this can cause a problem both in summer and winter due to the heat and humidity that will be lost.

Therefore it may not be a practical solution as far as the climate and energy efficiency for the indoor climate.

Heat Recovery Ventilation provides high efficiency ventilation throughout the house and are economical to run.

The system recovers up to 95% of the heat from the extracted stale air through a heat exchanger, the incoming air is filtered to reduce the incidence of pollen and dust.

This kind of systems can be very beneficial to people who suffer from alergies to dust and also those who are asthmatic as the air in the house stays fresh. Sick Building Syndrome

Therefore if you wish to live in a house that always has clean fresh air, you should seriously consider a Heat Recovery Ventilation system.

Demand Controlled Ventilation (DCV)

Demand Controlled Ventilation (DCV) is a way of looking at ventilating buildings that is a little different. Instead of there being a fixed rate of air exchange for a building or room on a best guess. DCV measures the air quality and adjusts the rate of air exchange minute by minute, room by room, based on actual need. A technical definition is: a system that provides automatic regulation of the ventilation system by sensing the Indoor Air Quality (IAQ) and determining the required air change rate. It does this without user intervention, in other words it is automatic. This provides for better indoor air quality and saves energy.

Humidity is a very good indicator for air quality in dwellings. There are the obvious issues like showering and cooking, but even breathing creates moisture and CO2. So, by monitoring humidity we can adjust and control the movement and volume of air exchange in a building, based on air quality. By following the needs of a building rather than a best guess, you also eliminate unnecessary ventilation, which in turn saves energy.

DCV, as a technology, is not new. It was invented nearly 30 years ago, when a humidity sensitive strip was invented, that could accurately and consistently open and shut an inlet or extract based on the relative humidity in the room. No power is required to operate the humidity sensitive strip.

Both the inlets and the extracts react to IAQ and adjust the rate of airflow. The fan detects the pressure changes and adjusts the airflow accordingly. The fan is very quiet and very efficient. It does not require filter changes or regular service and should give years of trouble-free running. Because DCV only needs ducting from wet rooms, it makes the system ideal for cost effective installation of a whole house ventilation system. It is also ideal, therefore, for refurbishment and retrofit work.

The net result with DCV is a system that is comparable in efficiency to heat recovery, cost effective and simple, but most importantly, quietly monitors and manages air quality, preserving a healthy indoor environment.

DCV is not constrained by air tightness levels, so it is suitable for all house types and all ages, new builds and retrofits.

Decentralised Heat Recovery Ventilation

Another option for the sufficient supply of fresh air is the use of decentralised heat recovery ventilation systems.

In a nutshell: Decentralised  Heat Recovery Ventilation (HRV) consists of a number of BVU (bidirectional ventilation units) which ensure air exchange without the need to install extensive ducting. The units have to be installed in the external walls of the building.

This is how it works in detail:

The stale air is being extracted from the room through the fan in each unit and discharged outside. As the air passes through the built-in heat buffer, this buffer gets heated by the warm indoor air. After roughly 70 seconds, the buffer is optimally charged with heat.

The fan then automatically switches from exhaust mode into supply mode, thus taking in fresh air from outside

The fresh air passes through the heat buffer, and the stored energy of the heat buffer is released into the fresh air in order to heat it. Thus fresh, unused and pre-heated air is inserted into the building until the fan changes into the exhaust mode again after another 70 seconds.

SEVi 160 reveal - decentralised HRV Unit for External Wall Insulation

Internal Cover for all types of SEVi 160 decentralised HRV Units

External Stainless Steel Hood for SEVi 160 decentralised HRV Units

Our thanks to Prodomo Ireland for the above information on decentralised heat recovery ventilation systems.

Prodomo Ireland

Unit 9 - Ridgeview, Monavalley Business Park, Tralee,
Co. Kerry, V92 W2TH

Phone:   +353 (0)66 4014045    Mobile:  +353 (0)87 7082982

It is highly recommended to run an even amount of decentralised HRV Units in order to prevent vacuum or overpressure. Every second unit operates contraryly to the other – one unit extracts stale air out of the room whilst the other one inserts fresh air at the same time.

Decentralised HRV Systems are equipped with separate control units which allow easy and useful adjustments, such as variable fan speeds.

In comparison to so called single-room-ventilation solutions, decentralised HRV Systems deliver proper air exchange for the entire building in a more comfortable manner. Most systems can be retrofitted with humidity and carbon-dioxide sensors to allow a fully automated regulation.

The noise of the units is almost inaudible. Good systems are quieter than the noise of a personal computer cooling fan.

Due to the use of low-wattage DC fans, the annual energy consumption for an entire decentralised HRV System will not cost more than an average three-course-dinner for two.

Thanks to their easy maintenance and the absence of ducting, decentralised HRV Systems are very popular for retrofit.

Our thanks to Aereco DCV for the information.

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