FAQs on Heat Recovery Ventilation

Please find below a list of the most commonly asked questions regarding Heat Recovery Ventilation. Please click on the question to reveal the answer.

Q. How does it work?

A. The principle behind whole house ventilation is to change the air continuously in the house and use the recovered heat to warm the incoming air. Extract points are located in wet areas such as bathrooms, kitchen, utility and WC. Supply points are in areas such as bedrooms, living and dining rooms. The fundamental part of the entire system is a high efficiency counter-flow heat exchanger. This heat exchanger transfers up to 90% of the heat from the extracted “wet” air to the incoming fresh air.

Q. What is involved in installing the system?

A. The HRV unit is generally located in a utility or plant room within the insulation envelope of the house. In certain situations it may have to be located in the attic. A ducting system is installed to extract air from ‘wet’ areas. This extract system is connected to the unit. Similarly a system of ducts for the supply of air to bedrooms and living rooms is also connected to the unit. A main control switch is located in the utility/kitchen and boost/over-ride switches are installed outside each bathroom. An ordinary socket is required in the attic beside the unit.

Q. What is the difference between HRV and normal house ventilation?

A. A house fitted with a Heat Recovery Ventilation System will have no background ventilation holes in the walls to the exterior of the building. No trickle vents will be necessary in the windows. Bathrooms will not require mechanical extract fans. Comfort levels are superior in a house fitted with a HRV system. Irrespective of weather conditions draught free balanced ventilation is provided all the time. The right amount of fresh air is available 24/7. Energy costs are lower. Water vapour will be removed as it is produced.Therefore there is no moisture condensation which causes rot, damp, condensation and mould growth. These can have a high allergic potential leading to health problems. A HRV house is more secure because there is no need to have windows open.

Q. Why should I install Heat Recovery Ventilation?

A. Your home will have a constant supply of fresh air, lower heating bills, no condensation and increased comfort levels.

Q. Can I do part of a house?

A. It is recommended that the whole house is covered by the system.

Q. Will it work with all heating systems?

A. Yes. It is independent of the heating system in the house.

Q. How much electricity will it use?

A. The running costs depend on many factors. Among them are the size (volume) of the house, the efficiency of the air handling unit, the design and layout of the ducting system and the number of people in the house. A properly designed, correctly installed and commissioned system in a 5 bedroom, 210m2 2 storey house can be run for as little as EUR35 per annum. See Blog piece for more detail.

Q. Is the system noisy?

A. No. The air handling unit is made of foam. In addition it is generally located in non living space such as a utility room. The ducting layout is carefully designed to optimise air flows. A distribution box is used to reduce the duct size coming from the unit. This box is also acoustically lined. Silencers are inserted to reduce whatever noise there is. During the installation process the speed of the fans is set and the system is balanced. The result is that customers will not be aware that the system is working in the background..

Q. In the course of building what steps should be taken to ensure that a HRV system will work well?

A. The house should be well insulated and well sealed. This means that there will be minimum heat loss and that the air flow through the house can be controlled. (A well insulated house may not necessarily be airtight. Air can easily pass through insulation made from coconut, mineral or glass wool.  An airtight house may not necessarily be well insulated: e.g. excellent air tightness can be achieved with a single aluminium foil but it is not an insulating material).

Q. Does insulation and U values of doors and windows have any influence on the operation of a ProAir Heat Recovery Ventilation System?

A. In order for a ProAir system to work efficiently a house should be well insulated. Good insulation will prevent heat loss through the walls, floor and attic. Windows and doors are generally the weak point in the building envelope as regards heat loss. Even the good triple glazed versions lose around three times more heat per square meter than the walls. So size and orientation of glazing is important. The less heat you lose, the more there is to recover.

Q. Are the results of any independent tests of the ProAir units available when doing Energy Rating calculations?

A. The units have been independently tested at the Building Research Establishment (B.R.E.) at Watford UK, to the relevant EN standards. The test results can be input directly into the DEAP software used by Energy Assessors etc.

Q. What are the Health Benefits?

A. On average people spend over 80% of their time indoors. 50% of all illnesses are either caused by, or aggravated by poor indoor air quality. The ProAir HRV System will continuously remove stale moist air from your home creating a more suitable and healthy place to live.

Q. Can I buy the unit and materials and self install?

A. We do advise that the ProAir HRV units should be installed by one of our trained installers. However if you wish to self-install we will give any guidance that is required..

Q. What size of ProAir HRV unit will suit my house?

A. Generally the ProAir 300 unit will be suitable for houses up to 120m2. The ProAir 600LI unit will serve houses up to 300m2 approx. Houses bigger than 300m2 will be served with a combination of ProAir 300 and ProAir 600LI units.

Q. Should the ProAir system be on all the time?

A. It is recommended that the system runs continuously. This will help keep the air fresh and avoid the build up of smells, moisture etc.

Q. How efficient is the unit?

A. The heat exchanger is 96% efficient. When the ducts etc are connected to it the system is up to 90% efficient.

Q. Why do we use Counterflow Heat Exchangers?

A. For the Irish market we exclusively install air handling units that use a counter flow heat exchanger in its core as opposed to the rotating thermal wheel. With the average relative humidity in Ireland around 88% it is essential that within airtight builds this is reduced, for both comfort and to avoid condensation problems. Counter flow systems resolve these issues by achieving a reduction in humidity. When the warm, moist air moves through the exchanger, it is cooled below its dew-point, water vapour then condenses in the outgoing channels and drains off at the bottom of the unit. The relative humidity is reduced to 50 – 60%. In this way, humidity is controlled and condensation problems eliminated. Rotating thermal wheels, whilst highly efficient return the moisture back into the building. There is no net reduction in the water content of the air and the relative humidity is not reduced. See link for more detail re Indoor Air Quality http://www.proair.ie/the-technology/indoor-air-quality/