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Whole House Ventilation Why do we need ventilation? Building regulations require a minimum rate of ventilation equivalent to one air change for the whole building every two hours. General improvements in house construction, building regulations and much higher levels of insulation in modern dwellings mean that houses are becoming almost airtight. Consequently, the air inside becomes stale with a build up of moisture and smells. The moisture can result in condensation and mould, and a generally ‘stuffy’ atmosphere. What types of ventilation are available? 1) Single room extractors Traditionally, ventilation has been provided by individual extract fans fitted to bathrooms and other ‘wet’ rooms. These provide short term ventilation, usually very noisily. The extracted air is replaced by fresh air entering the house through trickle vents in the window frames. These are neither attractive nor particularly sensible (having spent a lot of money on a well insulated house with high specification double glazing, a hole is made in the window frame in order to create a draught!) 2) Central Extract Ventilation As modern houses have more wet rooms, so it becomes more economical to replace several individual extractors with one Central extract ventilation unit. With a CEV unit, only one vent to the exterior is required (via wall grill or roof vent) in order to expel the stale air & only one electrical connection with the obvious savings in installation costs over individual extract fans. The extract unit is usually placed in the loft or a cupboard. The (warm) stale air from the wet rooms & the (cold) fresh air from the exterior both pass through a heat exchanger, in opposite directions & without mixing. The heat contained in the extract air is transferred to the incoming fresh air, which is introduced back into the living areas of the building. Heat Recovery Ventilation does not produce heat, but minimises the amount of heat which would otherwise be lost through ventilation, with degrees of efficiency varying between 70 97%. In doing so, it reduces the amount of heat that needs to be produced to keep a house warm. Heat Recovery Ventilation systems are designed to run continuously, virtually silently, providing clean fresh air throughout the building. Normal operation is at a very low speed, allowing the gentle movement of air from dry rooms to wet rooms and then to the exterior. Heat recovery units have two or more speed settings so that larger quantities of air can be extracted as the need arises. Depending on which system is chosen, humidistats, digital programmers, CO2 sensors and timers can also be used to control the ventilation. Heat Recovery Ventilation offers the added bonus of filtering the incoming air so that there is less dust internally (and therefore less dusting to be done). Pollen filters are available, which is a real boon to those who suffer from allergies, asthma and hay fever. An HRV system can also be used to extract air from rooms which get uncomfortably warm ( garden or sun rooms, kitchens with range cookers, etc.) and redistribute the heat from this air, via the heat exchanger, to other rooms which are not so warm. Heat Recovery Ventilation Why every home should have Heat Recovery Ventilation Prevents condensation and mould by removing the moist air from wet areas such as bathrooms, kitchens and utility rooms. Reduces the humidity so carpet and dust mites don't breed - a great help for those with asthma and other allergy sufferers. No draughts Up to 95% of the heat is recovered from the air extracted (from the wet rooms) to warm the incoming fresh air. (This feature can be switched off in the summer months as required) No need for unsightly trickle vents on windows How does it work? Heat recovery ventilation is basically the same as central extract ventilation but instead of the air entering the house via trickle vents in the windows, a second fan draws fresh air in and passes it through a heat exchanger and then sends it to the dry rooms in the house. Ideally the central unit will be sited in the roof space or garage or a cupboard. Flexible ducting in the ceiling void runs from this unit to each wet room, extracting the stale air, and to the dry rooms supplying fresh air. The extractor will provide a continuous low rate of air change, giving a steady flow of air throughout the house. What Heat Recovery Systems are available? CVC Direct supply a number of different Heat Recovery Units, the three most popular ranges being the AKOR, Itho and the Ubbink equipment.The Akor HRI is a high volume French system with a 70% efficiency. It uses flexible ducting which makes the installation easier. It is also one of most economical systems available. The Ubbink range of high efficiency units uses rigid ducting (although semi-rigid or flexible can be used). The Ubbink range is made & tested in the Netherlands, and is probably the most efficient range of heat recovery units on the market (quoting from Ubbink). Helpful tip: If you are building a new house, then we strongly advise that you make provision for ducting the ventilation system to the exterior while the the building is under construction. This greatly simplifies the installation of this item, as it avoids having to cut a 150mm hole in the wall at a later stage, and probably when the scaffolding has been removed. There are 3 common ways to do this. 1. Build the wall vent grill and a short length of 150mm rigid duct into the wall as it is being constructed. 2. Fit the vent grills into the soffit board with a length of flexible ducting 3. Alternatively, fit a roof vent tile, with the appropriate connection, to the roof while it is being tiled. The roof vent is normally a spigot with a coloured cowl on top and 500x500mm lead skirt. Cowl available in Terracotta (orange/red), Red (brick red) Sepia (brown) and Charcoal (dark grey) Wall grills, ducting and roof vent tiles are available separately from CVC Direct. Roof vent tiles are available as a special order to match specific types of tile. Send details of the tile to be used.