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FAQs----------------------------------------------------------------------------------------------------------- 1. How does it work?
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, offices, studies, 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 95% of the heat from the extracted “wet” air to the incoming fresh air. ----------------------------------------------------------------------------------------------------------- 2. What is involved in installing the system
The MVHR unit is generally located in utilities room such as laundries, garages, or cupboard for easy access to filters and general maintenance. A ducting system is installed to extract air from ‘wet’ areas and is connected to the MVHR unit. Similarly a system of ducts for the supply of air to bedrooms and living rooms is also connected to the MVHR unit. A main control switch is located near the MVHR unit and is generally installed in the utility/kitchen, cupboard or even hallway. Boost/ over-ride switches can be installed outside each bathroom or in the kitchen to boost the unit to full speed if necessary. An ordinary socket is required to power the MVHR unit. -----------------------------------------------------------------------------------------------------------3. What is the difference between MVHR and normal house ventilation
A house fitted with a Mechanical Ventilation Heat Recovery 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 MVHR 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 MVHR house is more secure because there is no need to have windows open. ----------------------------------------------------------------------------------------------------------- 4. Why should I install MVHR?
Your home will have a constant supply of fresh air, lower heating bills, no condensation and increased comfort levels.
----------------------------------------------------------------------------------------------------------- It is recommended that the whole house is covered by the system to offer a maximum efficiency.
----------------------------------------------------------------------------------------------------------- Yes. It is independent of the heating system in the house. In fact, the extraction from wet areas points will lower the moisture contents in the air resulting in a drier air. As a consequence, the efficiency of any heating devices will be enhanced as the vapour laden does not need to be heated.
----------------------------------------------------------------------------------------------------------- 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).
----------------------------------------------------------------------------------------------------------- In order for the MVHR 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.
----------------------------------------------------------------------------------------------------------- On average most people spend over 80% of their time indoors. 50% of all illnesses are either caused by or aggravated by poor indoor air quality. The MVHR System will continuously remove stale moist air from your home reducing the growth of mould mildew and other dust mites thus creating a more suitable and healthy place to live.
----------------------------------------------------------------------------------------------------------- We do advise that the MVHR units should be installed by one of our trained installers.
----------------------------------------------------------------------------------------------------------- Contact one of our offices in Auckland, Christchurch, Wellington or Waikato along with a set of quoted drawings (lay out and cross section drawing in metres are imperative). One of our representatives will contact you within a few days.
----------------------------------------------------------------------------------------------------------- The ideal stage to install a MVHR system is at 1st Fix. We like to be the first fixer. However, well insulated renovated house with double glazing windows can have a MVHR installed too. It is important to note that a MVHR installed in a leaky house will have a severe energy recovery efficiency reduction and as such is not recommended.
----------------------------------------------------------------------------------------------------------- The MVHR unit is generally located in utilities room such as laundries, garages, or cupboard for easy access to filters and general maintenance. However, it greatly depends on the type of house and we will advice at design stage.
----------------------------------------------------------------------------------------------------------- The main control is located normally in the kitchen, hallway, or utility room with additional boost switches (option) outside the wet areas.
----------------------------------------------------------------------------------------------------------- Rigid plastic duct must be used. This is more robust than flexible duct and offer less resistance resulting in the systems using far less power to move the required volume of air. This contributes to the overall efficiency of the system.
----------------------------------------------------------------------------------------------------------- No! We strongly recommend that rigid ducting be installed at all times. Flexible ducting creates too much resistance to air flow and will lower the efficiency of any MVHR unit. It will also be impossible to clean if the situation arises. Finally, the difficulty to stretch flexible duct leads to the creation of “poodles” leading to potential bacteria growth and as a result to air contamination.
----------------------------------------------------------------------------------------------------------- Humidity sensors respond to changes in the humidity of the air and they can be connected to a MVHR. However, it is usually expensive and not required. An MVHR is usually designed at a maximum of 70% of its capacity therefore offering a “boost” function to remove moisture faster when required. This boost function is controlled by the user via the wall controller. Once the boost switch is pressed the unit will work at high speed for a programmable period of up to 120 minutes to clear moisture from wet areas and then revert to normal.
----------------------------------------------------------------------------------------------------------- All ducts in the attic are thermally insulated in order to (i) eliminate the possibility of condensation happening inside or outside of the ducts and (ii) avoid heat losses in the attic All exposed ducts running in attics will be insulated. Normally the insulation being provided as part of the attic insulation will suffice. There is no need to insulate ducts that are within the thermal envelope of the house such as in partitions, under first floor, within cupboard, etc…
----------------------------------------------------------------------------------------------------------- No. The house should be as airtight as possible. This will ensure that all the air is taken in and out through the MVHR Unit only.
----------------------------------------------------------------------------------------------------------- In each room you will find a delivery or extract terminal. These fittings come in different types and styles of diffusers or grilles. The most common model has an adjustable centre disc which is used to balance the system. The system is tested and balanced by our technicians and will need no further adjustment.
----------------------------------------------------------------------------------------------------------- We generally use 150, 125 or 100 round rigid ducts depending on the size of the installation and of the required volume of air. Other ducting used in the Flat 51 system which is an oval type plastic ducting with a special food graded inside coating that reduce air resistance and eliminate water and dust retention. This system can be used inside wall, in concrete, under floor etc…
----------------------------------------------------------------------------------------------------------- The supply and exhaust vents should be located at 2m apart. This is to ensure that the exhausted air is not reutilised. There are 3 options (i) use roof vents and have the roofer install them. They are 150mm or 200mm roof vents. (ii) Have the extract and supply come through grilles on the soffitt (iii) Go through holes in the wall using grilles on the outside. The best option is usually decided at design stage.
----------------------------------------------------------------------------------------------------------- Yes, it can but it requires a special type of range hood equipped with carbon filters that is connected to the MVHR via a purposely designed diverter. Contact our company for more information.
----------------------------------------------------------------------------------------------------------- A manual operated damper can be installed. It is open when cooking is in progress and at all other times it is closed. Fantech can supply this as part of the system installation.
----------------------------------------------------------------------------------------------------------- Yes, as a safety feature we can connect your fire alarm system to the MVHR unit. We will require a two core cable from the fire alarm panel to our unit. Our unit will cut out in the event of the alarm going off.
----------------------------------------------------------------------------------------------------------- Air-tightness is the control of airflow 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 and heat is lost. The result is that the 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.
----------------------------------------------------------------------------------------------------------- A MVHR system relies on warm air from the interior of the house returning to the unit and exchanging its heat to incoming air. If that air is taken in part from leaks and openings in the building shell then the overall temperature of the extracted air will drop affecting the overall efficiency of the MVHR. In the worst case, no heat can be recovered at all.
----------------------------------------------------------------------------------------------------------- Air tightness testing highlights areas of infiltration of cold air from the outside and should be minimised by reducing unintentional air paths as far as is practicable by (i) Fitting draught stripping in the frames of the openable parts of windows, doors and roof lights, etc. (ii) Sealing around loft hatches (iii) Ensuring that boxing for concealed services is sealed at floor and ceiling levels (iv) Sealing piped services where they penetrate or project into hollow constructions, cavities, or voids. (v) Sealing around under floor ventilator grilles, gaps in and around suspended timber floors, extractor fans, etc. Open chimneys are a major source of air leakage.
----------------------------------------------------------------------------------------------------------- We suggest that all buildings should attempt to meet the best practice of 3m³/hr/m² or 1.6 Air Change per Hour. A level of 5 m³/hr/m² is roughly the point where the benefit of MVHR becomes questionable.
----------------------------------------------------------------------------------------------------------- It is recommended that the system run continuously. This will help keep the air fresh and avoid the build-up of smells, moisture, condensation, etc…
----------------------------------------------------------------------------------------------------------- The heat exchanger is 95% efficient. When the ducts etc are connected to it the system is up to 90% efficient (independently tested).
----------------------------------------------------------------------------------------------------------- It depends on the system itself. Fantech systems have been independently tested at 0.30 Watts/m³/hour. For a modern house using 160m³/hour, it is the equivalent of 48W bulb on, in an average size house. This works out at NZD$96 approximately per annum. This is just a guide; consumption will depend on your house size and usage pattern.
----------------------------------------------------------------------------------------------------------- This varies depending on how airtight the house is and how the system is used. Payback can be achieved over 7 to 10 years
----------------------------------------------------------------------------------------------------------- The unit comes with three main settings.
Low speed: At this setting the unit will effect an minimum air o replace the air once every 4-5 hours. It is used when the house is not occupied.
Medium speed: An air change will take place a minimum of one air change every 3 hours.
Boost: This setting is used when a large amount of water vapour and heat are generated in bathrooms etc… The unit runs at 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 revert to normal. 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 a dry system in that no connection is required to a water supply.
----------------------------------------------------------------------------------------------------------- Any water that condenses is drained off through a condensate drain. This is a 15 or 20mm plastic hose from the unit to the outside.
----------------------------------------------------------------------------------------------------------- No. The MVHR unit is acoustically lined. Silencers are inserted to reduce whatever noise there is. At the end of the installation process the system is balanced. The result is that customers will not be aware that the system is working in the background.
----------------------------------------------------------------------------------------------------------- A MVHR system is not a cooling system and can never be, despite what some suppliers might claim. All Fantech system comes standard with a summer by-pass. It automatically switches on when the outside temperature reach a certain point i.e. 20 or 21. At this time of the year, thermal efficiency will not be an issue and windows can be opened.
----------------------------------------------------------------------------------------------------------- In order for the system to work correctly and effectively it is important that approved maintenance procedures are followed. Full details are in the manual supplied. The main component of maintenance is filter changing. The frequency of this will depend on the following (i) Your geographical location. (ii) The number of people in the house and (iii) System usage. Filters are generally cheaper to replace than clean.
----------------------------------------------------------------------------------------------------------- It is a DIY job, no tools are needed and full directions are given in the operator manual supplied.
----------------------------------------------------------------------------------------------------------- A 1 year warranty starts from the day of commissioning. It includes parts and labour for the first year. Replacement filters should be ordered from Fantech for the end of Year changes. This warranty is conditional on planned maintenance being undertaken as scheduled in the Maintenance manual.
----------------------------------------------------------------------------------------------------------- Yes, because we use solid ducting that can be cleaned.
----------------------------------------------------------------------------------------------------------- It is recommended that any fuel burning appliance should be in excess of 86% efficiency. An open fire is estimated to be 20% efficient. An open fire will reduce the efficiency of a MVHR installation by up to 10%. When the fire is burning air is being taken from the room and by convection goes up the chimney. This causes negative pressure in the house. As a result, cold air will be sucked in as soon as a door is opened. The availability of suitable fuel for an open fire in the future is also an issue. If it is proposed to burn timber we suggest using a wood burning stove. These can be sourced with a pre-designed combustion air inlet. This combustion air must come from the outside, via a duct that has a minimum diameter of 100mm, is suitably insulated and controlled by a damper. This duct can travel under the floor, directly through a wall (if fire is on an outside wall) or is now available down through a specially built balance flue chimney.
----------------------------------------------------------------------------------------------------------- If it has an independent external air supply as described above the effect will be nil.
----------------------------------------------------------------------------------------------------------- Gas fires should be of the enclosed type (they look much like a flat screen TV). These can be fitted with a balanced flue down through the chimney. The fuel burning appliance must have a permanent external air supply available to it. By this, it means a hole in the wall or a balanced flue as described above. Flame effect fires are not usually suitable for a balanced flue.
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