Toilet and bathroom ventilation solutions

Traditionally the smallest room in the house, a WC can quickly become unpleasant to those who have to use it afterwards unless special care is taken to provide adequate ventilation. An opening window is an effective solution but is sometimes uncomfortable, especially in cold weather when there is the additional problem of household draughts and resulting heat loss.

A power extractor fan, operated either by the light switch or independently, is a simple solution and a provision considered essential—by law in the UK—for Wcs that do not have windows.

A slightly different problem exists when it comes to bathroom ventilation. Here, the high moisture content of the air produced by running a bath or shower quickly condenses to form water droplets and puddles which are not readily removed simply by opening a window for a few minutes. The problem is aggravated by the fact that the room is likely to be used only for a short time, thus discouraging opening of the window both during and after bath time.

An efficient extractor fan is the only convenient solution, and its cost can be weighed against the improved atmosphere of the bathroom when it is being used, and the reduced risk of damage to fixtures and fittings resulting from the lower levels of condensation that then form.

About 15 to 20 air changes an hour is considered satisfactory for a bathroom, with 10 to 15 for an enclosed toilet. Find the volume of your room by multiplying height by width and length. Then multiply this figure by the recommended number of full air changes, and use the result to determine which make and model of fan is best for your needs.

Some models are specifically intended for low-volume work, so always err on the side of a more powerful unit if you are in any doubt. Most of the ‘ fan manufacturers provide precise I guidelines on choosing one or other of their models.

Siting the fan

The best place to put an extractor fan is on the wall opposite the main doorway for the room, as high up as you can and above any source of moisture. Replacement air then has to travel across the room, ensuring that ventilation is complete.

You can mount the fan in a non-opening section of window, either by cutting a hole in the glass , or by replacing the whole pane with a suitable sheet of wood and fitting it within this.

Window mounting is not normally much of an aesthetic problem as far as interior WC design is concerned but in most cases, there is only one window. Since opening capability should be preserved, this sometimes rules out using the window as a site for the extractor fan. A similar problem exists in most small bathrooms and the additional loss of window light normally means that the fan has to be located elsewhere.

The wall position which best meets the ventilation requirements is high up, next to the window, where there is often an air-brick or ventilator grille. This can be removed and the ventilator fan installed in its place.

Take care to prevent too much rubbish falling down the cavity—it could cause damp problems.

The covering of a timber-framed wall is usually easy to cut away with a jigsaw or similar. Avoid positioning the fan over vertical studs. Find studs by tapping or drilling small trial holes.

When assembling the fan components, use a length of sleeving to line any cavity and prevent moisture-laden air from discharging into it. The sleeve should slope slightly to the outside, which can usually be arranged during final fixing of the fan.

Follow the manufacturer’s assembly instructions to install the fan unit itself. Much of the making good will probably have to be done beforehand, which means shaping the surrounding brickwork, repositioning cut bricks, and finally using heavy-duty filler or a suitable mastic to entirely eliminate through-wall draughts.

Inner walls usually present much less of a problem but additional work may be involved in providing suitable ducting to the outside, where again a hole must be made. For health reasons and personal comfort a WC ventilator should not be vented to another room or an accompanying corridor. To avoid unnecessary ducting—strictly speaking necessary only for moisture-laden air—consider installing a ceiling mounted fan so that foul air can be discharged into unused roof space.

This position also permits ducting between floors in the case of downstairs toilets and bathrooms. Raising and refixing floorboarding on the floor above—instead of boxing in a duct—is often a small price to pay for the improved looks of the installation.

Panel mounting

If a wall fixing is required, it is sometimes more convenient to use some method of panel fixing—especially if a purpose-built boxed-off duct has to be constructed with the room design in mind. A similar approach could be used for a ceiling mounted fan.

A panel-mounted fan can also be installed where additional work may prove difficult. So instead of bricking up a small and useless WC ‘high window’, you could use inner and outer panels of suitably-treated exterior grade plywood to seal up the window after removal of the glass. The wood could be cut to accept the extractor fan And, later, if it was decided to re-commission the window no permanent damage will have been done to the frame at all.

Fitting a ceiling mounted fan

The best place to put a ceiling mounted fan is right above the bath or shower enclosure, as most of the problem moisture is likely to originate from these. The fan must be located between the joists and requires a hole in the ceiling of up to 300mm diameter, the exact measurement varying between models and makes.

Superficial bodywork may make the actual diameter of the appliance greater than the distance separating the joists, so check styling and measurements carefully when choosing a suitable fan.

The next stage is to make a pilot hole through the ceiling. Go into the roof space first to check the area for pipes, wiring and obstructions around where the hole is to be made. Use support walling and lamp wiring roses to get your bearings. If necessary make a sketch of the joist plan and take any useful measurements from key details. Cross-check these when you go back to the bathroom.

In older houses, settling and condensation effects often show up the joist pattern in the ceiling plaster, and really it is only a matter of precaution that the loft space area is inspected for obstructions. But where this is not so, take plenty of time over locating the fan; before you cut the hole for the fitting, you always start by drilling a pilot hole safely in the waste area.

Drill the pilot hole from the bathroom side. Check its position from above, if necessary drilling another hole from below until the true centre of the fitting aperture is obtained.

When you have an accurate centre, mark the cutting line for the aperture. This is likely to be a circle, so rig up a simple compass affair using two pencils and a length of string to produce this Alternatively, use a suitable template such as a large diameter biscuit tin lid or similar.

The hole must be cut very carefully, both to avoid cracking and damaging the plaster beyond it and to minimize the amount of making good required after the fan is fitted.

To be absolutely safe, drill further pilot holes along the circumference, then gently chip away the plaster from the middle. Use an old cold chisel or small bolster to nibble away the plaster until you reach the edge line. Offer up the fan fixing to check it for correct fitting as you near completion.

If other materials such as softboard or plasterboard are used for the ceiling, it may be possible to use a pad saw or power jig saw to cut the hole. But do use the correct blade for the job.

From here onwards follow the specific installation instructions that apply to your fan. If you have been careful, you are likely to find that the fixing flange and the bodywork of the fan are sufficient to conceal small irregularities in the hole, so that making good becomes unnecessary except to strengthen the fixing. Use general purpose filler for making good unsightly cracks and dents which remain exposed. If you plan to decorate the ceiling, do this before fixing the fan base permanently.

Providing ducts

Ducting has to be used when the fan is mounted on an internal wall and needs to be discharged to the outside, and also when steam and condensation occur. Moisture-laden air must not be discharged into the roof space or eaves as damp damage may occur over a period of time. If the ducting cannot go through a wall, but must pass through the roof, a roof cover must be fitted at the outlet.

For the small-sized WC ventilator shown, standard 102mm plastics ducting is used. This can be led along the inside of a deep stud-partition wall, beneath floorboards and between joists, or along purpose-built boxing to an outside wall where it ends in a special grille. Similar forms of ducting are used for ceiling-mounted extractor fans when moisture-laden air has to be led to the outside. You can use rigid PVC pipework components in place of flexible ducting, but additional bracing will probably be required to hold the pipework firmly in place.

Where possible, use flexible ducting hose. Try also to keep the route as short and straight as possible, and angled slightly downwards to prevent collection of condensed moisture.

Moisture content is much less of a problem with WC ventilation, so the ducting can be terminated high up in unused roof space, or in the eaves.

Electrical connections

It is important to follow manufacturer’s specific instructions when you come to make the electrical connections, particularly where a fan is being used in damp conditions such as a bathroom or separate shower. Details here are basically for UK electrical systems. In Canada, check if you are allowed to do the work yourself or have to employ a nrofessional.

The WC fan is connected to the supply via a suitable on/off double-pole isolating switch using 0.5mm three-core cable. Protection is provided by a 3 amp fuse if a 13 amp plug is used for the connection, or a 5 amp fuse if wiring is carried from the distribution board. Alternatively, install it on a fused spur. The fan must he earthed properly.

This fan has a timer and remains activated for up to twenty minutes after the light is switched off if connected in this way.

In the UK, the ceiling mounted bathroom fan must be wired to the supply in such a way that plug and socket are outside the bathroom itself. Either run a fused spur to the ceiling—perhaps via adjacent walling—or use existing supply wiring in the roof space.

The electrical connections for heavy-duty fans with variable control devices are more involved, as additional wiring is normally necessary. In this case, running the wires through conduits makes for a neater job and protects the connections from the effects of future improvements.

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