How does Central Extract Ventilation (CEV) work?
Central Extract Ventilation works by continuously extracting from the kitchen and wet rooms within the property boosting and, if necessary, removing the pollutant air quickly and effectively at its source.
It is a central system containing one fan with multi-spigot adapters that are used to connect with each extract valve via ductwork. The fan extracts from each kitchen and wet room, this air is drawn into the unit and then pushed out to atmosphere via one 125mm diameter opening (e.g. an external wall louvre or roof vent).
This type of system works in collaboration with window ventilators within a property, the extraction of air within each of the wet room creates negative pressure within the property causing fresh air to be drawn in via the window ventilator.
These systems can be linked to various switches/ sensors that can instruct the system to boost when needed. Typical examples include humidistats, lighting circuits, shower circuits, motion (PIR) sensors, and boost switches.
What are the benefits of Central Extract Ventilation (CEV)?
Some of the main benefits of Central Extract Ventilation (CEV) system are:
• Cost effective – a Central Extract Ventilation system replaces the need to have a local extractor fan in each wet room, put simply, you are only paying to run one fan instead of 2, 3, or more, which saves considerably on the general running costs
• Quiet solution – local extractor fans must be located in the wet room itself and are typically noisy in operation. Brookvent Central Extract Ventilation (CEV) systems are the quiet solution. They have one single fan, fully sealed within a polypropylene casing which provides great insulation for properties and typically located out of the way in an attic/storage cupboard to ensure minimal intrusion
• Continuous ventilation – unlike local extractor fans which are typically intermittent in operation, Central Extract Ventilation (CEV) systems are designed to extract from the wet rooms in the property, running continuously at a trickle rate and boosting to a higher rate when necessary. This continuous operation means that there is constant change of air within the property, pollutant air is removed at source and fresh air is drawn into the property via window vents due to the pressure difference created by the system
• Aesthetically unobtrusive – there is only one exterior vent required on the outside of the property with a Central Extract Ventilation (CEV) system, as opposed to local extractor fans which require an exterior vent for each fan. This helps to maintain the aesthetics of the property and reduce the amount of times you have to exit through the shell of the building
• Gain SAP points – Brookvent airstream Central Extract Ventilation (CEV) systems are SAP Approved and successful in reducing CO2 Dwelling Emission Rate (DER). Specifiers , Low Carbon Consultants and Architects can gain SAP points for your property by using our product’s specific performance information instead of standard default information provided in the SAP register
How is Central Extract Ventilation (CEV) installed?
Design: it is absolutely vital to have your Central Extract Ventilation (CEV) system installed properly. This begins with a good design. Brookvent is very experienced in system design and provides professional guidance on ducting routes across a wide variety of residential properties.
Installation: CEV systems are generally installed in two stages – 1st and 2nd fix. At 1st fix stage the majority of the ducting is installed, as per the system design, and any wiring requirements are provided for, including the tracking of remote sensors such as humidistats. At 2nd fix stage the system is installed, all ducting and wiring is connected, ceiling valves are fixed to the ducting point in each room, and the condensation drain from the system is installed. Finally the system is commissioned as per the appropriate Building Regulations.
Performance: the size and location of the CEV unit is extremely important. The unit must be fit for purpose, taking into consideration the size of the property and associated airflow rates. Brookvent is a BPEC Centre of Excellence and installs to the highest standards to achieve best performance.
Commissioning: Brookvent issue commissioning certificates detailing the measured installed airflow performance of each system against design requirements. Finally, each unit’s operational and maintenance requirements are clearly defined and demonstrated to ensure competent user operation and optimum system performance. At Brookvent we have adapted our products based on customer feedback so they can be installed easily, often in compact spaces, and accurately commissioned.
What does the term Specific Fan Power (SFP) refer to?
Mechanical systems require electrical power to operate, including power to the fans, any compressor(s) and transformer(s) and control and safety devices. The term ‘specific fan power’ is used to compare the electrical energy use for different ventilation systems as installed (i.e. allowing for system resistance).
Specific Fan Power is defined by the Energy Savings Trust as: “The power consumption, in Watts, of the fan (plus any other electrical system components) divided by the air flow through the system, in Watts per litre per second (W/l/s)”.
Specific Fan Power Calculation: Central Extract Ventilation
For a small house with a Kitchen + 1 Wet Room the minimum extraction airflow rate is 21 l/s (Part F: Eng & Wales 2010)
If the unit consumes 3.5 watts to achieve this rate of air flow then:
Specific Fan Power (SFP): 3.5 / 21 = 0.16 W/l/s
The Energy Savings Trust ‘Best Practice’ recommendation for SFP is 0.6 w/l/s or lower. Brookvent’s airstream Central Extract Ventilation units can achieve a SFP down as low as 0.16 W/l/s.
What are the typical running costs?
All Brookvent airstream Central Extract Ventilation systems (CEV) are SAP approved and use EC fan technology which helps to ensure a low Specific Fan Power (SFP) meaning our systems run as efficiently as possible.
Running Cost Calculation
Brookvent airstream 1.1 E Central Extract Ventilation System
Dwelling Type: Kitchen + 2 wet rooms
Assumptions: The system operates at trickle speed for 22 hrs per day, and at boost speed for 2 hrs per day.
Speed 3 (Trickle) 22hrs @ 0.0046 kW = 0.102 kW.h
Speed 7 (Boost) 2hrs @ 0.01 kW = 0.02 kW.h
Total 0.122 kW.h x 365 days = 44.53 kW.h
110.96 kW.h @ £0.15 per kW.h = £6.68 per year
In this scenario the Brookvent airstream 1.1 E would cost as little as 1.8 pence per day to run.
