FAQs

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The most frequently asked questions. Answered.

Whatever your level of knowledge or expertise, when it comes to modern home ventilation, you are going to have questions about equipment, cost, suitability, regulations, and how these systems can reduce energy bills and carbon emissions. Here, we answer the questions we get asked the most. If you have one you don’t see listed, feel free to get in touch.

General Topics

Generally it is recommended that you change filters every 6-12 months however this will also vary depending on location of your home and proximity to trees and other foliage.

You should leave the system running 24/7 even when you are away. However you can set it to holiday mode which will reduce the flow rate to just the right amount to keep your house fresh, saving energy in the process.

MVHR systems require a filter change every 6 to 12 months, depending on where the houses is located and the surrounding environment. It is also recommended that every two to three years the heat exchanger and the blades of the fans are cleaned to ensure efficient and long term performance of the system. Filters can be ordered online or phone.

Yes you can however in winter it will reduce the efficiency of your unit slightly. During the summer it really doesn’t make any difference. Your unit will be in bypass mode anyway thus preventing heat transfer. Some might ask if they can turn the unit off during the summer when they open windows. It is important to note the extract function will also be lost so turning the unit off should be avoided.

The idea that you will save hundreds on your heating bills is somewhat of a myth.  After all most new houses only cost several hundred euro to heat in the first place. Unlike heat pumps or photovoltaic panels your MVHR system will never pay for itself, not ours or others. While a heat recovery system may recover several hundred euro worth of heat this typically only covers the cost of the electricity to run the unit and a 12 month filter change.

Yes, heat recovery is a valuable aspect to any MVHR system but it is important to understand that it is only secondary to the ventilation function which ensures excellent indoor air quality and prevents mould or condensation issues in the home.

There are many things to consider when designing a house to ensure the heat recovery system can be installed correctly and will perform as efficiently as possible.

  • Location of the MVHR unit.
    • The unit should be installed within the thermal envelope of the house to ensure maximum efficiency.
    • The MVHR unit itself should be installed centrally within the house as this assists in the correct distribution of air.
    • MVHR units should not be installed near bedrooms where possible. If installing in the attic or other space the unit a suitably insulated unit should be chosen.
    • Safe access to the unit should also be ensured to allow for regular maintenance of the system.
  • Access to atmosphere.
    • Every MVHR system must be ducted to atmosphere. One duct to carry the fresh air in to the house and another through which the stale air is exhausted. These ducts can be anywhere between 150mm and 250mm in diameter depending on the volume of air required. Cowls can be wall or roof mounted. Ventilation poles can also be installed where MVHR units are installed in basements. (link to ventilation poles here)
  • Condensate drain.
    • Most MVHR units, except for units that use rotary wheel units, need to have a condensate drain fitted. This should be plumbed into the waste water system within the house. It should not be piped directly to atmosphere such as a down pipe or gutter as it may freeze in cold conditions causing the water to overflow from the MVHR unit.
  • Prevailing winds.
    • It is important that the air intake and exhaust are as sheltered as possible.
  • Distance between supply and exhaust cowls.
    • A minimum of 1.2m is recommended between them. Consideration should also be given to the prevailing wind by keeping the exhaust cowl downwind where possible.
    • The supply cowl should be kept as far away from the chimney as possible, again, with consideration given to prevailing wind direction.

Demand Controlled Ventilation

A DCV system is a controlled method of ventilating your home that links the amount of fresh air supplied to the occupancy of the home. DCV systems continuously monitor indoor air quality measuring parameters such humidity (H2O), carbon dioxide (CO2) and Volatile Organic Compounds (VOCs) which are harmful to our health. As these levels fluctuate daily so too does the DCV system ensuring that the flow rates are sufficient when levels are high. The system runs in trickle mode when air quality is good. This ensures optimum ventilation throughout the home using the minimum energy to do so.

  • As the system is demand controlled each room is ventilated at the optimum level.
  • DCV systems are significantly more cost effective to run than other ventilation systems using as little as .2 to .5 w/l/s. This translates to running costs less than €50 p/year.
  • No user interaction required. DCV systems are automatic.
  • Ensures no mould/ condensation issues throughout the house.
  • Suitable for new and existing buildings.
  • They are very quiet when operating, running at approx. 25-30db.
  • DCV systems do not require filters.
  • They provide security as you do not need to open windows to ventilate your home.

The fan unit is installed in the attic/ utility or plant room. A separate duct is installed from the fan unit to the wet rooms such as the Kitchen, Utility, Bathrooms & WCs. Sensors, fitted inline in the duct, or in the room, depending on the brand used, measure air quality in each area.Based on these readings humid or stale air is extracted from the wet areas and fresh air is drawn into to the house through wall or window vents strategically positioned in each habitable area such as bedrooms, living rooms etc.

Mechanical Ventilation with Heat Recovery

Simply put, heat recovery systems are the lungs of our homes. In the past, our houses were leaky and difficult to heat. Recent changes to building regulations and modern building practices have resulted in us building ultra-low energy houses, some even capable of heating themselves. However, none of them are capable of ventilating themselves which is why mechanical ventilation is such a critical component of the modern-day home.

MVHR systems are designed to re-use the waster energy from your home. In some, ultra low energy houses, MVHR systems which are fitted with an optional post heater can provide sufficient heat however in most houses a primary heat source such as a heat pump is still required.

The standard of MVHR system is very high nowadays. Features to look out for include:

  • Greater than 90% efficiency
  • High Efficiency EC Fans
  • Counter Flow Polystyrene Heat Exchangers
  • Automatic Summer Bypass
  • Built in Humidity Detection
  • Frost Protection
  • Digital Controller
  • Extended Warranty

MVHR systems should be installed within the thermal envelope where possible. This should be considered at design stage to ensure adequate provision of space for the MVHR unit and duct system throughout the house.

  • Ensure excellent indoor air quality
  • Protect against mould & condensation issues within the home
  • Recover up to 98% of heat typically lost with passive systems
  • Clinically proven to help sufferers of asthma and other respiratory problems
  • No trickle vents or bathroom fans required.
  • Allow you to ventilate your home securely without having to open doors or windows.
  • Your home will be quieter and draught free
  • Remove unwanted cooking smells and other odours.
  • Helps prevent build-up of potentially lethal radon gas
  • Are environmentally friendly and are a recommended in Part F of Irish TGD.

You can order filters from us either online at  www.theventilationstore.com or by calling us on 058 20005.

It is not recommended as grease will still penetrate the filters in the cooker hood and cause damage to MVHR unit. We recommend installing aa conventional hood ducted to atmosphere in conjunction with a Flow Star or Thermobox flue closer. Both products will maintain an air tight seal in the duct when the hood is not in use.

No. Sized correctly our MVHR systems will run very quietly. Fan manufacturers say that their fans should not run continuously above 60% approx. We design systems so they won’t have to run at more than 50% on normal mode.

As all of our MVHR units use the latest in high efficiency EC fans electrical consumption is minimal. Approx €20-€30 per year will power an MVHR system required to ventilate a standard 3 bed house. Not bad considering it is the lungs of your home.

At a minimum MVHR units can be controlled with a speed controller but nowadays most come with remote digital controllers. Boost buttons are also an option outside bathrooms however humidity/ VOC and CO2 sensors can be connected to offer a “demand controlled” element to the system.

We recommend installing a stove with an external air supply. This means that the air required for combustion comes from outside rather than from the room.

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