Bathroom fan

[John.Stitch]

4 years ago I converted two garages and a toolroom into annexe accommodation. One garage is a lounge the other is the kitchen and there are two bedrooms with a bathroom inbetween.

The bathroom is 7'6 x 6' with a shower, toilet, bath and basin, so pretty compact.

The bathroom has no window and use a Screwfix fan to vent smells and steam up into the loft and outside via a rectangular gap between the external wall and a covering length of wood. A length of silvered ducting supplied with the fan vents the air outside.

The smells in particular do not clear and I have to leave the bathroom door open to clear smells and steam.

I want to get better venting presumably using a more powerful fan.

The current fan is I think a 6" square one, cost about £10 or so.

So can anyone recommend a better fan and I assume the power is measured in cubic metres a minute shifted.

 

[noseall]

The current fan is I think a 6" square one, cost about £10 or so.

I would think at that price just about any other fan available will be better!

Clicky.

 

[JohnD]

centrifugal fans are generally quieter and more powerful

if you have room above the ceiling this sort of thing is very good

http://www.screwfix.com/prods/98482.../Manrose-In-Line-Centrifugal-32W-Bathroom-Fan

 

[ajrobb]

I am considering the Silent 100 CHZ with backdraft shutter, timer and humidistat. It has a brushless motor and resilient mounting and is 16dB quieter than the Manrose. At about £65 it's the same price. It is only an 8W, 4" fan but shifts 95m3/h. Can anyone comment?

For air to be extracted effectively, it has to get in somewhere. I'd consider a passive vent outside the bathroom door.

Considering fresh air inlet, the Nuaire Drimaster for instance, blows filtered air from the loft into the dwelling but cost over £200. Is there a passive shutter/filter that allows air to be drawn from the loft by the extractor?

 

[JohnD]

The one I linked has
Extraction Rate 180m³/hr

100mm fans with an extract rate of about 85cu m are pretty weedy, and in real life will not extract this much, especially if there is a duct or backdraught flap. BTW rigid duct (you can use soil pipe) can be laid with a slight fall to the outside, and is not so prone to accumulate dust and condensation. You can flop loft insulation over the duct to keep it warm and reduce condensation.

It is more normal for bathrooms to draw fresh warm air from the house through the gap under the door, to replace that sucked out by the extractor.

A positive pressure device is quite different and is not relevant to the OP

 

[ajrobb]

It is more normal for bathrooms to draw fresh warm air from the house through the gap under the door, to replace that sucked out by the extractor.

Agreed. The trouble is that the existing fan does not clear the smell. A more powerful fan will do a better job. The important thing is to have a timer so the fan runs on to clear the smell. However, if I'm running a fan for 20 minutes after going to the loo in the middle of the night, I want it to be very quiet. (I'll often use a shaving light in a hotel bathroom just to stop a noisy fan from coming on.)

I was thinking a fresh air inlet outside the bathroom should help with the smell and make it easier for the extractor. As you say though, any shutter will reduce air flow, so it might be better to run a second duct outside for such a vent. Oh, and don't make the gap under the door too tight.

The Silent 100 fan includes its own back-draft shutter, so the flow quoted will include the shutter (but not a long duct).

 

[noseall]

I'll often use a shaving light in a hotel bathroom just to stop a noisy fan from coming on.

You mean you don't use the basin? No need for lights less chance of missing......

 

[JohnD]

the one I showed can be mounted in the loft, and you can even put it in a box and stand it on insulation to muffle the noise still more

it also has about twice the extract rate of the little one.

 

[ajrobb]

the one I showed can be mounted in the loft, and you can even put it in a box and stand it on insulation to muffle the noise still more

it also has about twice the extract rate of the little one.

I don't dispute the 32W centrifugal fan is powerful and reasonably quiet. None of that matters if it is not on a timer. After flushing the source of the smell down the lavatory, I doubt the light will be on for much more than a minute.

Incidentally, the MAN125M with a 5" duct is 5dB quieter than the MAN100M with 4" duct and extracts 220m3/h for the same power.

 

[John.Stitch]

Thank you for all your posts.
Can I ask a further question.
I removed the flexible hose in the loft from where it was lodged and put my hand over it and the air flow is pretty feeble,so a change of fan looks on the cards.
If I changed the fan where would be the best place to put the vent?
Could it just vent into the loft which is not sealed from the outside and is a cold loft, if that's the right phrase? The loft does get quite hot in summer with the sun on the tiles and the black felt as well.

I could cut a hole through the external wall in the loft but it is double skin and stone faced.
I have a 4" core bit and an SDS drill.
At ground level the soil is 18" higher outside than the floor inside so I am wary of drilling through it. Before converting the property a man from Cotswold Treatments came to look at the walls for damp he took dampness readings and it was very dry on the inside at the floor level.

 

[JohnD]

Could it just vent into the loft

no

it must go outside

you can go through a wall or a soffit. If needs be you can get a roofer to put a vent tile in, but this has to be done well as holes in rooves tend to leak

 

[John.Stitch]

Well I am finally doing this. I will have a centrifugal fan arriving shortly.
http://rover.ebay.com/rover/0/e1100...170535312694&ssPageName=ADME:B:EOIBSA:GB:1123

The plan is to put it in the loft above the bathroom and have the vent pipe going through a blockwork wall.

The other side of the blockwork wall is a piece of 7x1 timber nailed to the ends of the rafters which conceals the top of the stone wall or cladding next to the blockwork.

The blockwork is about 9" higher than the stone.

The hole will go through the top most block under the wall plate, I am not sure whether I can get away using a 4" core bit or I will have to chain drill it as it is the top of the wall?

Also not sure whether I need to drill through the 7x1 or I can allow the fan to vent into the gap between the blockwork and the 7x1. There is gap between the stone and the 7x1 I can get a large finger into.
I thought about putting some foil on the inside of the 7x1 with mastic to prevent rot?