IEV
the Basics.
The most basic extract ventilation systems are the ones that most of us have in our wet rooms at home. They are usually either manually operated by using a pull cord or light switch, or they are sensor-activated. This is known as intermittent extract ventilation.
Building Regulation Part F – Covers intermittent extract ventilation (IEV)
What is Intermittent extract ventilation?
This describes a ventilation system the user can control. This control can be via switches, movement sensors or linked services (comes on when room light or shower is activated).
They are installed in wet rooms (bathroom, kitchen, utility, shower room, WC.) and help with the intermittent removal of moisture or odours.
Intermittent extract ventilation (IEV) to the outside should be provided in all the following spaces and be ducted to meet the requirements of the manufacturer. The below are all classed as wet rooms.
Kitchens. Extraction directly to outside, recirculating unit is not an extraction method
Utility rooms. Rooms with water using appliances, washing machines, dishwashers etc.
Bathrooms. Rooms that contain bathing facilities, shower, bath.
Sanitary accommodation. Bathrooms, shower rooms, washrooms, and toilets.
This ventilation needs to be room-specific, and regulations exist to ensure the required extraction rate is met.
IEV is primarily used to remove moisture, odours, and pollutants from specific areas such as kitchens, bathrooms, and utility rooms. These areas tend to produce higher levels of contaminants and humidity. Extractors are activated at set intervals or in response to certain conditions (like high humidity). This can be achieved through timers, humidity sensors or manual controls. If a room contains only a toilet and no windows exist, then the extraction unit should not rely on a moisture sensor only.
IEV units are energy efficient and by operating only when necessary they use less energy compared to continuous ventilation systems.
Now let’s put this together!
When extraction units are used in wet rooms, they expel moist air at a specific rate. To maintain proper airflow, this expelled air must be replaced with a fresh supply inside the property.
This is achieved through recommended measures such as 10 mm door undercuts (ensure compliance if fire doors are involved) and the installation of background ventilation. These features allow fresh air to be drawn in simultaneously, enabling it to circulate throughout the property and replace the indoor moist air.
Improving Indoor Air Quality (IAQ) depends on effective ventilation to eliminate pollutants such as volatile organic compounds (VOCs), carbon monoxide, allergens, dust, and mould spores.
By replacing stale indoor air with fresh outdoor air, ventilation creates a healthier environment and helps reduce respiratory risks.
Tips on controlling moisture and condensation.
Open Windows. Regularly open windows to let fresh air circulate and reduce humidity.
Use Extractor Fans. Turn on extractor fans in bathrooms and kitchens to remove moisture from showers and cooking.
Install Trickle vents. Easy and cheap solution to introduce background ventilation if required.
Check door to floor clearances. This should be around 10 mm from finished floor covering to allow fresh air to circulate from room to room. (fire doors have different regulations)
Avoid drying clothes indoors. Try to dry your clothes outside or in a well-ventilated area.
Use Dehumidifiers. Consider using a dehumidifier in damp areas to reduce moisture levels. If you cannot avoid drying clothes inside, then a dehumidifier can help with the moisture control.
Keep your home at an even temperature. At 18-21 °C, the dew point will very rarely be reached. As we know, affordability can have a huge impact on achieving this.
Use pan lids. Always try to use lids on cooking pans, not only will this reduce moisture, but it makes cooking more energy efficient. If extraction is available when cooking, then try to use it.
Fix leaks. Repair any leaks in your roof, walls, or pipes to prevent dampness.
Insulate Well. Proper insulation helps prevent condensation by keeping your home at a consistent temperature.
Vent Appliances. Ensure dryers and other appliances are vented outside to avoid trapping moisture indoors.
Avoid using portable gas appliances(LPG). Moisture from burning LPG can lead to condensation, which can cause mould and mildew.
Installation guides.
From June 2022 the building regulations (Part F) introduced a more robust commissioning regime with ventilation. All new mechanical ventilation systems should be commissioned, and a copy of the commissioning report should be left on the premises. A link to the BEAMA checklist is here. Building control should be notified unless the installers are members of a self-certifying competent person scheme (i.e. NAPIT, NICEIC).
Ventilation rate. The minimum ventilation rate required by UK building regulations is within part F and currently set at 0.3 litres per second per square meter of floor area.
Outlet terminal. The outlet terminal should have a free area that’s at least the same as the duct’s cross-sectional area. It should also be designed to prevent rain, insects, and birds from entering the duct. Most units will provide a steady draught when not in use, so flap vent covers are always a good addition.
Flexible ducting. Flexible ducting should be pulled taut and kept to a minimum length, should be supported and installed to manufacture instructions if passes through loft space etc.
Placement. Should be placed as high as practically possible and no less than 400 mm from the ceiling. If placed near a background ventilation point like a trickle vent, then these should be at least 500 mm apart. When installing electrical appliances in a bathroom, zones need to be considered.
Extract ventilation to the outside should be provided in all the following spaces at the following rates.
- Kitchens @ 60 L/s Kitchen cooker hood to outside @ 30 L/s
- Utility rooms @ 30 L/s
- Bathrooms @ 15 L/s
- Sanitary accommodation @ 6 L/s
If a wet room has no external walls, the intermittent extract fan should extract at four air changes per hour, to meet purge regulations.
Gas and open flued appliances.
If the fabric of the property is being improved and open-flued gas appliances exist, then a gas spillage test should be carried out on each appliance.
Rules exist that give an average unimproved property a certain amount of leakiness (adventitious air) to allow open-flued appliances to operate safely.
This all depends on how much fuel burns over a period of time, for example: 7.5kw/hr, 9kw/hr, 6.9kw/hr. You will see this on the data badge of the appliance (gas rating of an appliance here.). The more fuel used, the more leakiness is needed. Multifuel appliances are treated in roughly the same way but do not come under gas safe legislations. HETAS and building regulations govern multifuel installations and ventilation.
This is the reason combustion ventilation is sometimes needed. This allows the air to be replenished (with an open flued appliance we are burning the oxygen in the room that we use to breathe)
With the introduction of insulation, extraction ventilation should be installed as part of the process, we now have a different factor to add in with gas safety. Extraction fans either pulling or pushing air (PIV) can now effect the performance of the appliance.
Open flued gas appliances should be checked to prove they are not spilling products of combustion into the property. This is verified by performing a spillage test.
Part J states. “Extract fans lower the pressure in a building, which can cause the spillage of combustion products from open-flued appliances. This can occur even if the appliance and the fan are in different rooms”.
Any funded insulation work now includes ventilation upgrades as part of the current PAS, so extract ventilation will be installed. This should have been factored in as part of any ventilation work carried out. A competent person is required to perform spillage tests.
Part B, 8(1) of the Gas Safety (Installation and Use) Regulations 1998 states that no person can make any changes to a premises that contains a gas fitting or storage vessel if the changes would compromise the safety of the fitting or vessel.
This basically means if the fabric of the building (walls, floors, roofs) are being insulated then appliances need to be checked by a suitably competent and qualified person.
PAS 2035 is a comprehensive standard and not a regulation. It was introduced in 2019 as part of the UK government’s commitment to improving energy efficiency in buildings. If work being carried out on a UK funded scheme then the current PAS should be followed aswel as building regulations.
Part F of the UK Building Regulations, sets out requirements for ventilation in buildings to ensure adequate indoor air quality and prevent issues such as condensation, mold growth, and the buildup of pollutants.
The primary objectives of Part F are to.
Provide Sufficient Ventilation, Control Condensation and remove pollutants.
Click here for more on regulations
Electrical certificates.
The two types of electrical certificates you will come across as a customer who is having any electrical work as part of installing EEM’s (energy efficient measures)
- Electrical Installation.
- Minor Works Certificate.
Electrical Installation Certificate.
An electrical installation certificate is the type of certificate a customer receives after an electrician has installed one or more new circuits. Other examples include a complete rewire, a replacement consumer unit or an additional consumer unit. Generally, any time electrical work is done at the consumer unit, a new installation certificate will be issued.
Minor Works Certificate.
A minor works certificate is issued after an electrician has made an alteration to an existing circuit. Minor works certificates are often used to certify work such as adding additional sockets to an existing circuit or increasing the number of light fittings in a room. It can also be where a fused spur has been installed for an appliance or boiler connection.
