DCV stands for Demand Controlled Ventilation. This is a term used to describe a ventilation system that varies its operation in response to measured levels of occupancy within the dwelling, using humidity sensors, infra-red detectors, etc. This approach can account for up to a 50% reduction in ventilation heatlosses over a constant airflow system.
SAP (Standard Assessment Procedure) is used for rating energy performance of UK dwellings. The calculation looks at aspects of the Part F and Part L of the Building Regulations to show compliance.
Aereco has a range of fans that have been tested to the SAP appendix Q methodology, which allows easy input of the fans SFP (Specific Fan Power) when carrying out energy performance calculations.
Volatile Organic Compounds (VOCs) is a term used to describe a number of indoor air pollutants which arise from the presence of both naturally occurring and synthetic chemical compounds. The compounds can come from a variety of sources which include construction materials, cleaning products, paints, air fresheners, and electrical goods. The BXC extract grille was the world’s first extraction unit to offer an integral VOC sensor.
Aereco can offer retrofit solutions for a variety of different dwelling types, from individual apartments and houses, to entire apartment buildings. We have a range of smaller fans which can be hidden away in cupboard spaces, ceiling voids, or attic spaces which make these ideal for use in individual apartments and houses. Our larger collective fans are capable of being connected to existing ductwork systems of larger apartment blocks, and because only the extraction elements of the system require ducting, the overall ducting used is kept to a minimum. Passive stack systems generally require zero electrical connections (unless using electrical variant of the G2H extract grille), and window inlet installation is also very simple.
If a room contains a heat producing appliance (fire/stove) adequate supply of air to it for combustion and for the efficient working of any flue pipe or chimney is required. This is via permanent background ventilation (6,500mm2 min) or an independent air supply.
Aereco inlets are closable, so are not suitable for combustion. See Building Regulations Part J for details.
It has been shown from studies carried out by Aereco and other organisations, that moisture is a very good indicator of the need for ventilation, because so many indoor air pollutants are accompanied by an increase in the level of relative humidity. (For example, the 1.9 litres of CO2 per hour produced by an average adult’s breath is also accompanied by an emission of moisture). However there are certain applications where humidity sensing alone is not enough, and to address this we have a number variants of our standard extract grilles which offer additional boost functions such as presence detection (PIR), CO2, Volatile Organic Compound (VOC) detection or manual boost (via a pull cord, switch or remote control).
MEV stands for Mechanical Extract Ventilation and describes any form of ventilation that is driven by a powered fan. Aereco Demand Controlled Mechanical Extract Ventilation (DCMEV) systems typically make use of one fan which extracts air through humidity sensitive grilles in “wet rooms” (kitchen, bathroom, wc), with fresh replacement air drawn through humidity sensitive air inlets either mounted on an external wall or fitted to window casements in “dry rooms” (bedrooms, living rooms).
An Aereco Demand Controlled Mechanical Extract Ventilation (DCMEV) system is typically driven by a constant pressure fan motor (which is set between 80pa and 170pa). Airflow is then modulated in line with the variable cross-section of the demand controlled extract grille(s), which change their opening area in proportion to measured relative indoor humidity (or other activation criteria depending upon the variant employed).
Controlling the fan in this way ensures that there is adequate ventilation without incurring heat loss through over-ventilation, electrical power consumption is kept to a minimum, and audible fan noise is reduced to almost zero.
Passive Stack Ventilation (PSV) is a technique that utilises the “natural motors” of thermal draught (the rising of “warm” air through ductwork) and the Venturi Effect (where humid/stale air is drawn through ductwork by an area of low pressure that is created by wind passing over a ridge or tile vent in the roof). Control over this system is provided by humidity sensitive air-inlets and extract grilles.
Passive Stack Ventilation (PSV) relies upon the natural forces of thermal draught (the rise of warm air), and the venturi effect (where extraction is driven by an area of low pressure created by moving air passing over a duct terminal at the top of the building). As these natural forces are not always present or sufficient in all building types and locations, care should be taken in the selection of this particular ventilation solution.
For example PSV is not recommended for buildings that are taller than four storeys (due to insufficient thermal draught), or for buildings which are surrounded by taller structures / trees, or sited in a steep sided valley (due to insufficient movement of air over the stack terminals to create the area of low pressure required for the venture effect).
PSV relies on natural forces (stack effect and venturi effect) in order to drive extraction at low pressure.
For the supply and extract components of the system to balance, the total internal cross sectional area of the stack must be equal to the equivalent area of background ventilation.
Other factors which can influence the required level of background ventilation can be found in the British Building Regulations Approved Document F: 2010-Table 5.2b, for dwellings.
For buildings other than dwellings, subsidiary guidance should be sought.
Our STF Ridge Vent is no longer available. We recommend the use of tile vent with at least 20,000 mm² free area such as Ubbink UB16 Universal Ubiflex Tile Vent.
The tile vent should be installed no more than 0.5m away from the ridge level and situated on the leeward side of the building.
On a pitched roof, a wet ridge installation uses mortar joints between tiles to ensure weather protection. A dry ridge system has dedicated fixing joints (requiring no mortar) which can be installed faster.
Hybrid Ventilation, also known as Assisted Passive Stack Ventilation (or aPSV), utilises the same “natural motors” of Passive Stack Ventilation in addition to a very low-powered intermittent fan (controlled by a wind gauge, or temperature sensor) which activates when the natural motors of wind and thermal draught are insufficiently powerful to drive the system.
Individual dwelling systems typically require 204 x 60mm “flat” duct, or 125mm diameter “round-pipe” duct. Where duct leg pressure or airflow is high, larger duct sizes may be more appropriate.
For collective dwelling / communal installations, sizes range from 100mm – 630mm diameter (using metal spiral duct for main duct legs, with the option of using plastic duct for final duct legs), connecting to the VEC range fan units. Duct sizes to be recommended by Aereco.
Ductwork for Aereco DCMEV should be installed to Building Regulations: Technical Guidance Document Part F. Please also refer to: HVCA Standard DW/154 for Plastic Ductwork and HVCA Standard DW/144 for Sheet Metal Ductwork.
Current ventilation regulations in England and Wales (Building Regulations: Approved Document F) require that ductwork in passive stack installations has a minimum diameter of 125mm (for round pipe ducting), or is of equivalent cross-sectional area (for rectangular ducting).
For Scotland and Northern Ireland (where domestic ventilation is regulated under the Scottish Technical Standards, and Technical Booklet K, respectively), please refer to BRE IP:13/94.
If PSV is installed in a country where no regulations exist, it is generally good practice to follow the Approved Document F as guidance.
As aPSV (assisted Passive Stack Ventilation) is a hybrid of mechanical and passive ventilation, it is good practice to design the system in accordance with PSV recommendations to achieve a low pressure duct network.
Ventilation regulations in the UK require stacks to have a minimum diameter of 125mm for all rooms where PSV is installed.
Where a collective duct shaft is used, the cross-sectional area should be equal to the total duct internal cross sectional area using the minimum duct diameter.
Alternatively individual ducts can be collated into a single plenum chamber sited directly at the termination point.
Insulated ducting is used to limit the temperature difference between that of the extract air and the surrounding environment. If the temperature difference is significant, condensation will form.
Ducting must be insulated where ever it passes through uninsulated spaces of a building. This most commonly occurs in loft areas where insulation is installed directly over the joists, and the void above is at a colder temperature than the main structure.
Condensation forms when the water content of air becomes saturated, due to an increase of moisture, or a temperature difference causing rapid cooling.
Mould spores are constantly floating about in the air around us. If the humidity rate exceeds 80% for a number of hours, these mould spores can germinate on cold surfaces (usually on external walls or around windows). These spores then continue to grow until humidity falls below 70%, when they will go dormant.
Mould appears in a range of colours, from black, brown, grey and there is even a red one that grows next to glass, although this is steadily becoming less common as it tends to grow on single glazed windows.
In temperatures ranging from 1ºc to 20ºc, mould spores only require water and oxygen to germinate and grow. Below 1ºc much of the moisture is “locked up” as ice, and mould will become dormant. At temperatures above 20ºc the growth of mould is suppressed.
In order to prevent condensation and mould, humidity and temperature must be controlled. This requires good insulation of the building envelope to prevent the occurrence of cold surfaces, and adequate ventilation in order to control excess humidity.
Where mould already exists, this will need to be treated separately with fungicidal agents.
Please note that insulation, heating and ventilation will NOT prevent mould caused by rising damp, thermal bridging, dry rot, water ingress etc.
Where mould already exists, this needs to be treated separately with fungicidal agents. Failure to do so will result in the mould going into a dormant state when humidity is low and growing in moments when humidity is high.
Assuming that this mould is caused by condensation (and not some other structural issue), that all pre-existing mould in the bathroom was cleaned with a fungicidal agent when the extraction system was fitted, and that the extract ventilation is working correctly, this problem may result from an inadequate flow of air from other parts of the dwelling.
A lack of air inlets in “dry rooms” (such as living room, bedrooms etc.) or a lack of undercuts under internal doors can obstruct the flow of air within the building envelope, and thereby reduce the effectiveness of the extract ventilation in the bathroom.
An Aereco system alone will provide sufficient ventilation for domestic kitchens (and bathrooms) where extract terminals are installed.
If a cooker hood is also fitted, this may be of a type that filers and re-circulates the air. A separate cooker hood that exhausts directly to the outside may also be used, to remove grease and cooking odours.
Air extract terminals should be installed as close to ceiling space as practical, to ensure warm moist air is removed (Domestic Ventilation Compliance Guide:2010). It is recommended that the maximum distance from the ceiling is 400mm. It is also good practice for the grille to be positioned away from the doorway opening, in order to maximise cross flow ventilation.
Extract terminals operating on humidity sensing alone, require no power supply. However extract grilles other boost functions require a power connection. Extract grilles with PIR (infra-red presence detection), remote control, and impulse switch boost functions can either be powered via a hardwired supply (recommended), or by 2x AAA (1.5 V) batteries. CO2 and VOC detection variants can only be hardwired.
A rectifier is always required for a hardwired supply. This is included with remote controlled extract grilles, and CO2 / VOC detecting grilles, and can be purchased separately for other variants (such as the PIR grille).
The rectifier (which also contains an integral 12-3 VAC transformer) provides an output of 3 VDC to supply the powered sensors, and boost facilities. Certain fans have an integral 230-12 VAC transformer (with an integral connection block). Stand alone 230-12 VAC transformers are also available, where required.
All standard Aereco extract grilles and air inlets are white. Window inlets are also available in oak and brown. The EHA2 is also available grey and has a removable cover that can be primed and sprayed.
However, these are also available in a range of RAL colours, subject to minimum order quantities.
Where a purpose provided continuous ventilation system has been installed for extraction from ‘wet rooms’ (kitchen, bathroom, WC etc.), air inlets should not typically be installed in the wet rooms, as cross flow ventilation would be by-passed.
Where intermittent extraction, or no purpose provided ventilation is available in a ‘wet room’, purge ventilation with background ventilators can be installed. This is not considered good practice and was changed in the 2002 Part F Building Regulations.
Cross flow ventilation is typically achieved by extracting from ‘wet rooms’ and supplying renewal air via air inlets fitted in ‘dry rooms’ (living room, bedrooms etc.).
Air is then transferred throughout the dwelling via undercuts in doors. This ensures that all areas of the dwelling are adequately ventilated.
It is recommended that the outer surfaces of extract grilles are periodically wiped with a damp cloth, (twice per year for a grille fitted in a kitchen, and once per year for an extract grille fitted in a bathroom / wc). If more thorough cleaning is required, the front cover of the grille(s) can be removed and washed separately.
It is also recommended that, once per year, dust is removed from the internal components of the fan (where fitted) using a brush or compressed air (see specific maintenance instructions for the fan). ENSURE THAT THE FAN IS ISOLATED FROM THE POWER SUPPLY BEFORE OPENING THE FAN CASING.
Where a collective Demand Controlled Mechanical Extract Ventilation (DCMEV) system is installed (using a collective VEC fan), it is recommended that annual maintenance checks are carried out on the fan to ensure its longevity. Any dust and dirt should be removed from the fan blades using a brush or compressed air, and the drive belt (where fitted) should be checked for correct tension, and replaced if found to be worn. A final audio test should also be carried out once servicing has been completed, to check for unusual noises. ENSURE THAT THE FAN IS ISOLATED FROM THE POWER SUPPLY BEFORE OPENING THE FAN CASING.
A correctly installed room-sealed gas appliance will not need additional consideration, as the air supply intended for combustion is supplied from outside the building envelope. However gas appliances which use air from inside the dwelling for combustion will need an additional supply of air to ensure complete combustion (and thus avoid the production of carbon monoxide). When designing and installing ventilation systems in dwellings with gas appliances it is imperative that reference in made to the Building Regulations Part J.
A chimney that this sealed up and no longer in use can effectively be ignored for the purposes of designing a ventilation system.
To prevent back-draft, a chimney in a dwelling with Mechanical Extract Ventilation can have an automatic device installed to shut off the ventilation when the chimney is being used.
If passive stack ventilation is installed, such an automatic device is unnecessary as the stack effect of the chimney will be greater than the stack effect found in the ventilation ductwork.
For further information please refer to the Building Regulations Part J.