What Are the Regulations for Flexible Ducts?

According to the National House Building Council, otherwise known as the NHBC, whose aim is to raise construction standards of new homes in the UK. These are the regulations regarding ductwork, which includes flexible ducts…

• Must be fixed in accordance with manufacturer recommendations.
• Must be routed as directly as possible. (As few bends as possible in the ductwork).
• Only be located adjacent to fan units or air valves.

And more.

Part F of UK building regulations, which specifically relates to ventilation, does not have specifications on the ducting required. This is because ducting is subject to the home it is installed in.

That being said, flexible ducts should be used as the ‘final connection’ and be no longer than 1500 mm.

By ‘final connection’ we mean that it should be the ducting that connects directly to the ventilation mechanism, or the ducting that leads directly to the outside. Of course, this is subject to the environment the ducting is placed.

Flexible ducting should not be the only ducting you use. It should be a combination of flexible and round ducting, as much as possible. If you only use flexible ducting, you will have to account for supporting the ducting to prevent any unnecessary bends which will affect the airflow.

Unspoken rules of ducting

The following points aren’t exactly a regulation, but is a logic that is applied with any reputable ducting installer.

• Replace ducting after fires — If you are unfortunate enough to have a house fire, even if the fire was limited to one area of the house, the likelihood is that most, if not all, the home is smoke damaged.

Smoke damage penetrates surfaces and often requires the whole home to be redone in order to remove the pungent odour and carcinogens that have stuck into the fabric of the home.

This also applies to ducting, smoke damage will have penetrated the ducting, usually leaving residue. When getting your home repaired, some sneaky builders may try to overlook ducting in order to finish the job quickly, be sure to remind them to change the ducting.

• Check the area before installing — Installing ducting in an area with damp, or with a structural problem that creates moisture, even if it is an occasional instance, is a bad idea.

If ducting is placed by this area, especially if mould is already present, you are more than likely going to have mould growing on the outside, and eventually the inside of the ducting.

Having mould in your ducting not only reduces the effectiveness of the ventilation mechanism at hand, but also spreads the mould, which can further affect your health.

Can ducting be made to last longer?