Improving bathroom ventilation

Whether it’s a new build or an older property, avoiding the build-up of condensation in a bathroom is vital to prevent damage caused by damp and mould.

Increasing demand from customers for power showers and wet rooms presents a challenge to installers, particularly in properties where the bathroom does not have a window. Large tiled areas also contribute to the generation of higher amounts of condensation.

Achieving a balance A balance has to be reached between getting a reasonable airflow and keeping the room warm. Getting the calculations right to decide airflow is critical to ensuring the problem is solved and there are minimum standards that must be met. This is set out in the government’s Approved Document F, which covers ventilation and indoor air quality.

Following these requirements on a new build is vital to ensure the installation is signed off by building control inspectors.

Ongoing advice Best practice will also help ensure that the customer cannot later blame the installer for a problem like condensation, as the rules request that the property owner must have been given advice on how to use the room and any equipment in the room, such as extractor fans. This has to be done within five days of the installation being completed. The regulations say: “The owner shall be given sufficient information about the ventilation system and its maintenance requirements so that it can be operated to allow adequate airflow.”


Summing up

Measurements of airflow

Airflow can be measured in terms of: - volumetric flow - mass airflow

Units of volumetric airflow rates are generally expressed in:

- litres per second(l/s) - cubic metres per second (m3/s)

- litres per hour (I/h)

- cubic metres per hour (m3/h)

NOTE: 1,000 litres = 1m3.

Mass airflow rates are frequently used for air conditioning calculations but are rarely used for general mechanical ventilation calculations.

Mass airflow rates are generally expressed in kilograms per second (kg/s).

Where a mass airflow rate is used, it can be converted to volumetric airflow by multiplying the value by the density of the air being considered.


Read more

Read the Building regulations, Ventilation, Approved Document F at tinyurl.com/y5zhd6mx


This article first appeared in the May/June 2019 issue of P&H Engineering, the magazine for members of the CIPHE. Find out how to join here.

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