The importance of ventilation

As a plumbing and heating professional, it is important to understand the requirements of ventilation and the need to comply with Part F of the Building Regulations. However, ventilation doesn’t just stop at Part F, it falls in to many other approved documents:

Part B – Fire Safety
Part C – Site preparation and resistance to contamination and moisture
Part E – Resistance to the passage of sound
Part L – Conservation of fuel and power
Part J – Combustion appliances and fuel storage systems
Part P – Electrical safety

All are freely available via on the web at

Who is responsible for ventilation?

It’s important to note that as the installer/designer of a plumbing or heating system, you have the responsibility to ensure that the work complies with all Building Regulations. The person responsible will be the main contractor; for example, a building contractor may have specified a new extension which includes a new bathroom installation involving multiple trades such as a plumber, an electrician, a plasterer or a tiler; however, which trades person is responsible for the ventilation?

“It is important to remember that if you are the person e.g. designer, builder, installer carrying out building work to which any requirement of building regulations applies, you have a responsibility to ensure that the work complies with any such requirement. The building owner may also have a responsibility for ensuring compliance with building regulations requirements and could be served with an enforcement notice in cases of non-compliance.”

(Source: Approved document F – means of ventilation 1.10)

Ventilation: The good, the bad and the ugly?

The purpose of ventilation is to limit the accumulation of moisture which could lead to mould growth and pollutants originating within a building becoming a hazard to health. However, there is a disconnect between the minimum required ventilation for health purposes and the effect on the heating system plant size due to excessive heat loss. The challenge is creating an efficient home with healthy climate conditions.

How does ventilation affect the plumbing and heating professional?

The equipment we install impacts upon the buildings provision for ventilation. These factors need to be considered:

Airborne pollutants and odours, e.g. in bathrooms and kitchens

Control of humidity – bathrooms, kitchens, utility rooms

Provision of air for fuel burning – open-flued appliances, ranges

Accurate calculation of ventilation heat loss.

How to select the correct bathroom fan

Firstly, you need to measure the total volume of air in the bathroom in m3.

Example (see figure 1):

A bathroom with a total floor area of 3 m (L) by 3 m (W), that is 2.4m high (H), gives a total air volume of 21.6 m3 in the room.

Part F of the building regulations stipulates for intermittent extract ventilation (figure 2), that a minimum requirement of 54 m3/hr (15 litres a second) is required. The amount of air to be extracted using the above example is:

21.6 m3 (the volume of the bathroom) x 6 air changes an hour

= 129.6 m3/hr or 36 l/sec

This is above the minimum recommended extraction rate of 54m3/hr (15 l/s) stated in part F of the building regulations. Most bathroom fan manufacturers publish the fan performance in m3 per hr or litres per second (l/s).

Important note — building regulations state that “in a room with no openable window, an intermittent extract fan should be used with a run-on facility set to a minimum of 15 minutes”.

The table above is guidance from Part F for new-build and existing extract ventilation rates.

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

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