Ventilation Extract Testing

Ventilation extract testing is a requirement on all new dwellings, including those created by a change of use.
The test determines the extract flow rate of the installed ventilation to ensure the system performs as designed.

The requirements to build more energy-efficient and airtight homes make it essential that ventilation systems (and their performance) are considered.

UK Building Regulations require test certificates to be issued on completion of a new build or conversion to provide evidence that the ventilation system is performing to the required standards. The quality of the installation must be considered from the beginning as there are limited cost-effective solutions that can be done once the building is complete if the performance of the system is not adequate.

All of our ventilation extract tests are carried out with UKAS calibrated equipment, with all engineers having completed the NICEIC domestic ventilation course. When booking alongside an Air Tightness Test we offer significant cost reductions.

Types of ventilation systems

There are four types of domestic ventilation systems:

Background ventilators and intermittent extract fans:

This is the most common in the UK as it is the simplest and cheapest to install. We would advise developers to avoid installing this system as it is an old system which is not designed to efficiently cope with the level of humidity created by a modern lifestyle.

Passive Stack Ventilation

This is not recommended as the main ventilation system in a dwelling as it relies on natural pressure differences and weather conditions. This is more commonly seen in commercial buildings as a background ventilation system, such as in atria.

Continuous mechanical extract (MEV)

This can be either a centralised or decentralised system and is the recommended system if the client is not investing in a heat recovery balanced system. The system continually trickles a small amount of air out of the dwelling and can be boosted when required, i.e. during showers or when cooking). Window trickle ventilators will still be required. 

Continuous mechanical supply and extract with heat recovery (MHVR)

The most energy-efficient and highest performing ventilation system, capable of recovering over 90% of heat loss. This system is balanced with extract grills in every wet room and supply points in habitable rooms. Trickle ventilators are not required. 

Installation advice

Fans rarely perform to the level they claim on the box. They are tested in laboratory conditions, much like a car will not achieve the claimed MPG in real life. This means that they don’t account for any backdraft and ductwork resistance that is experienced in real life.

To give the best possible chance of passing the final tests we recommend:

  • Purchase the highest capacity fan that you can
  • Install fans as close to the external wall as possible, if possible install the fan through the external wall itself
  • Use rigid or semi-rigid ducting
  • Keep duct runs as short as possible
  • When using flexible ducting, ensure there is no excess ducting

When installing system 3 and 4 fans (MEV and MVHR) we advise choosing a system which is more powerful than is needed. This results in the fans working to a lower percentage of their total capacity and therefore producing less noise. These systems should be properly designed and commissioned to ensure they operate to the best of their ability.

Frequently Asked Questions

Yes. For intermittent extract fans and continuous mechanical extract you will need to have the flow rates tested. Centralised continuous systems will also require balancing to ensure that extract rates from each room are suitable for that rooms use. Test certificates will need to be provided to Building Control. 

For dwellings which has Mechanical Ventilation with Heat Recovery (MVHR) installed, the system will need to be fully commissioned and the certificate provided to Building Control. 

  • Purchase the highest capacity fan that you can
  • Install fans as close to the external wall as possible, if possible install the fan through the external wall itself
  • Use rigid or semi-rigid ducting
  • Keep duct runs as short as possible
  • When using flexible ducting, ensure there is no excess ducting

Not all MVHR systems are equal, and not all ducting is equal. You can have a poor performing system installed for a fraction of the cost of a quality system however it will be inefficient, costly to run and noisy. MVHR should be properly designed by a reputable company and, ideally, installed by the same company. The system then needs to be comissioned to ensure that it is balanced and achieving the extract flow rate that is required to provide a healthy living space. 

Yes. Without a doubt. Many self builders and developers have no issue spending thousands on areas of the build that can be seen such as kitchens and bathrooms however shy away from spending money on the ventilation system. MVHR will not only significantly reduce heating bills (meaning it will pay for itself over time) but it also has a huge impact on comfort levels. Where your building is insulated well with high quality glazing, MVHR will ensure condensation is a thing of the past and there will no longer be an issue drying clothes inside and the ventilation system will take care of the excess moisture. Air quality will also significantly improve as standard with additional filters being optional for pollutants such as pollen and Nitrogen Oxide (exhaust fumes) where required.