Frequently asked questions
In order for the MVHR system to work effectively, 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.
It is important to remember that MVHR provides fresh air (to maintain indoor air quality), whereas indoor temperatures are a result of the performance of the building fabric (insulation), and any heating or cooling applied.
On average most people spend over 80% of their time indoors. Illnesses can be caused by or aggravated by poor indoor air quality.
The benefits of installing a MVHR system are:
- Filtered fresh air (ensuring outside air contaminants that may exist are removed)
- Reduced dust and pollen levels benefiting asthma and hay fever sufferers.
- Continuous removal of moister from the home 24/7
- Control mould and mildew.
- Maintain healthy levels on air contaminatns, such as CO2 and volatile organic compounds (VOC’s)
- Removal of odours.
- Reduced heating and cooling requirements (compared to opening windows for ventilation)
- A smooth antibacterial liner made from pure HDPE, a food grade plastic.
- Low resistance to air flow.
- Is cleanable with a customised cleaning system (speak to your installer).
- Flexible ducting creates resistance to air flow and will lower the efficiency of any MVHR unit, and increase noise levels.
- Flexible ducting is impossible to clean or maintain.
- Flexible ducting is difficult to stretch leading to the creation of low points, and the potential for bacteria growth moisture accumulates.
Air-tightness is the control of air flow through the external envelope of the building. In an airtight building air leaks do not occur at ceiling or wall junctions, plaster board joints, doors, windows, service entry points etc.
Leaks create discomfort, thermal energy loss, and compromise indoor air quality. The result is that your heating system has to operate at a greater capacity to compensate for the losses. Air-tightness is essential in maximising the effectiveness and longevity of thermal insulation, ensuring vast savings over a lifetime.
Air tightness testing highlights areas of infiltration of from outside, and should be minimised by reducing unintentional air paths as far as is practicable by:
- Fitting draught stripping in the frames of the openable parts of windows, doors and roof lights, etc.
- Sealing around loft hatches.
- Ensuring that boxing for concealed services is sealed at floor and ceiling levels.
- Sealing piped services where they penetrate or project into hollow constructions, cavities, or voids.
The unit comes with three main settings.
Low speed: At this setting the unit will replace the air once every 4-5 hours. It is used when the house is not occupied and is designed to provide condensation protection, and maintain freshness.
Medium speed: An air change will take place a minimum of one air change every 3 hours. This is known as your standard or nominal ventilation rate.
Boost: This setting is used when a large amount of water vapour and/or heat is generated in bathrooms etc, or when large numbers of people are present in the building. The unit runs at 70 - 100% of its capacity. Once it is activated, the unit can work at high speed for a period of up to 120 minutes and then reverts to normal ventilation rates. If several boost switches are installed in the house, the last boost switch to be activated will determine when the unit will return to normal working.
It is important to remember that the primary job of an MVHR system is to provide fresh filtered air to you house and extract damp and odorous air. MVHR systems have a limited impact on either cooling or heating buildings. This is something that should be managed via good building design (high performance building fabric, orientation, shading etc).
Better MVHR units incorporate bypass valves that allow outside air to bypass the heat exchanger when it is favourable to do so, in order to help achieve a target comfort temperature. A typical example is night purging during summer. This operation is typically automated and does not require any user action.
It is a DIY job, no tools are needed and full directions are given in the operator manual supplied.
Contact your installer to order replacement filters. You will require replacement filters when filters can no longer be cleaned by gently tapping them to remove dust. The HRV unit should not be run without filters, as this exposes the unit and your building to unfiltered air.
As per standard industry practice a parts only warranty is offered. The following periods apply: Zehnder products:
- 2 years form date of purchase.
- Other Fantech HRV product: 1 year from date of commissioning ( up to a maximum of 18 months from purchase).
This warranty is obviously conditional on equipment being installed and maintained in accordance with the manufacturer’s instructions.
Fantech, the industry leader for over 45 years and continues to be the forefront of fan and acoustics technology by developing and implementing new and innovative products for virtually every air movement and ventilation need.