Extractor fan ducting condensation

[masamune]

My bathroom fitter used a flex fan ducting with a standard extractor fan in our bathroom, which goes into one of the disused chimneys.

The problem, one lovely evening after it got colder outside, my fan gave a huge spark and tripped the fuse. Eventually I figured out the steam was condensing and dripping back into the fan. One of my ceilings also got a little damp stain, coming from the two ductings joined together with hose clips in the loft. Obviously they are not designed to carry water but vapour, although this is the side effect and not the issue. I emptied half litre of water from the hose and it also has mold built up inside.

His initial response was that I have to insulate the rafters in my loft because it's cold, causing the hot steam to condense. Well yes, he has a point but that is somewhat silly, as he knew this would happen when installing the ducting. Also I can't imagine I have to spend £2k to insulate the loft rafters, just to save from condensation in the ducting pipe? For the record my loft floor is all insulated with pretty thick rockwool under the boarding.

The issue I believe is with the design, I just think it's wrong. The pipe is too long, about 2.5 meters running across the loft and into the chimney. He covered the entire ducting in rockwool about a week ago, but I doubt this will work.

The first observation was that the rockwool was damp again today around the joint of the two ductings. I opened it up and there was some water build up in there again. I think it sucks alright (no pun intended, so even without the fan not working -fan is fried- the steam goes through and condenses again.

The second problem is that my fan is fried and I am not sure what to buy yet, especially not until the problem is properly resolved. He recommended a silent Vent Axia.

Do I need a different layout? This is a photo I found on the web, is this a better layout,

http://www.ultimatehandyman.co.uk/diy/electrics/extractor_fan/shower_extractor_fan_3.jpg

and if there is water build up, is there a design to collect the condensed water and prevent any leaks or going back into the bathroom?

 

[stef99]

No one can see you picture as it re-directs to warning that hotlinking is theft.
Try uploadng at a normal website like
tinypic.com.

The vent should have gone directly thorugh the roof with some sort of flashing.

Thats the prfessional way in my opinion.

As for the condensation you have, you can try poking holes in the vent to drain any water out. but this is not a real solution as the water will just build up at the bottom of your chimney causing even more damp.

this is how to do it properly

http://www.enter-shop.com.au/information/Versatile.jpg

for details on how to do it just search "roof pipe flashing" in google.

No one should be venting any steam or water in the chimney at all. Chimneys were made for smoke, not water.

Personally I always try to install fans on the wall. and then take the vent straight through the wall to the outside.

This eliminates any bends, or the need for rooing ladders.
Even if the fan is high up from the group, a good set of ladders will be enough to fit the grate.

Also, make sure you cover the hole with mesh or something to stop the birds flying down it.

 

[GoodDIYjob]

Agree with response (stef99) and your comments - that sounds like a bodge in a number of ways but probably not uncommon.

1. If venting via the loft. The vent should go externally through soffit or roof tiles. I have a plain tile clay roof and used a klober roof vent kit edit( more correctly called tile vent). Wasn't cheap at about £55 including the pipe connection but it fits well and is barely noticeable on roof elevation. Venting into a chimney is asking for another damp problem, which you haven't yet seen.

2. Flexi pipe has a lot more surface area resistance which increases the likelihood of vapour condensing before being vented. I always try to use rigid plastic piping.

3. If you use rigid plastic ducting you can then fit a condensation trap and insulate or lag the pipe work as you see fit and much more effectively.

4. Is the fan an inline fan in the loft fitted horizontally or is it in the ceiling. If in the ceiling it will be much more prone to damage from water droplets travelling back down. An inline loft fan would be better.

Attached is what I did for our bathroom fan. Uses rigid piping - the distance between the inlet and the fan was to meet manufacturer instructions saying min 1m.

There is a slight fall left to right and I have a condensation trap installed at the extreme right end. It connects to an old overflow through the soffit.

I used foil therma wrap type insulation and used foil tape to secure tightly.

View media item 86213

 

[masamune]

No one should be venting any steam or water in the chimney at all. Chimneys were made for smoke, not water.

This is what really worries me in the long run. I feel that my fitter was trying to avoid the hustle of working with the roof, although he did a really good job in the bathroom.

With regards to the pic, it shows an inline fan with a camel's back shape layout for the ducting.

Personally I always try to install fans on the wall. and then take the vent straight through the wall to the outside.

This was a problem for my bathroom because of the low pitch of the roof. There used to be an air brick on the side, but it would have been very close to the shower for the fan and it would get splashed with water.

Hmm, I have to talk to the fitter and convince him to do it properly.

 

[masamune]

1. If venting via the loft. The vent should go externally through soffit or roof tiles. I have a plain tile clay roof and used a klober roof vent kit edit( more correctly called tile vent). Wasn't cheap at about £55 including the pipe connection but it fits well and is barely noticeable on roof elevation. Venting into a chimney is asking for another damp problem, which you haven't yet seen.

I think my roof is plain tiles, maybe something like their Plain Tile vents could work in this case.

2. Flexi pipe has a lot more surface area resistance which increases the likelihood of vapour condensing before being vented. I always try to use rigid plastic piping.

This something I also thought. Maybe it's best for the pipe to go out as soon as it exits the bathroom, reducing the risk of condensing.

3. If you use rigid plastic ducting you can then fit a condensation trap and insulate or lag the pipe work as you see fit and much more effectively.

Sounds good

4. Is the fan an inline fan in the loft fitted horizontally or is it in the ceiling. If in the ceiling it will be much more prone to damage from water droplets travelling back down. An inline loft fan would be better.

It is in the ceiling unfortunately. Do you know of an inline fan you would recommend, something with low dB noise?

Attached is what I did for our bathroom fan. Uses rigid piping - the distance between the inlet and the fan was to meet manufacturer instructions saying min 1m.

There is a slight fall left to right and I have a condensation trap installed at the extreme right end. It connects to an old overflow through the soffit. I used foil therma wrap type insulation and used foil tape to secure tightly.

There may be an overflow exit from the old tank in the loft up there. We could potentially use it for this purpose.

I am not confident to do this myself. How much would it roughly cost for the entire package ? i.e the tile vent, the inline fan with a condensation trap and the work required.

 

[OwainDIYer]

I am not confident to do this myself. How much would it roughly cost for the entire package ? i.e the tile vent, the inline fan with a condensation trap and the work required.

As you've already paid your fitter for time and materials to install a working ducted bathroom fan, with an implied term of the contract being this will be to a reasonable standard of workmanship, why would you pay any extra to have the shoddy work corrected?

It should be redone at the fitter's expense and if that requires additional duct or parts because he mis-measured or under-estimated on the job that will fall to his costs not yours.

 

[GoodDIYjob]

Yes, shorter runs and keeping turns and bends to a minimum is best. Keep flow as free as possible. For some reason the manufacturer stated min 1M from inlet to fan unit in instructions on my unit, so I followed this. Useful to have a small horizontal section either side of the inline fan, will help with longevity.

There are quite a few posts discussing options for fans in these forums if you search inline fan, loft fan or bathroom fan. Often posts in electrical or plumbing sections.

There are lots of models available, I use an aiflow aventa 100T on low setting. It is two speed selectable.

It is at the cheaper end of options. The suction doesn't feel hugely strong but with overun set to 15min it clears out the bathroom well and has resolved flaking ceiling paint and condensation spots.. There is at least one recent posting where someone complained of it not being powerful enough, but I find it more than satisfactory. Excess ventilation has downsides too.

The specs say 27db at 3M on low setting. It is pretty quiet.

The manrose MF100T looks good spec wise but is more expensive.


Cost

Now that's a very good question. It was a bit more work than running a bit of flex to a chimney. I spent the best part of 2 - half days completely setting it up. So put an hourly rate of your choosing on that for start.

A professional may well work faster. Nothing was particularly hard but measuring and cutting the plastic duct, insulating, running condensation trap waste and terminating electrics all takes time.

I had a roofer fit the roof vent, which cost £120, because I didn't fancy crawling on the pitch of the tiled roof and I didn't have proper ladders anyway which would of cost to hire anyway.

The tile vent pieces complete - I recall was £55, possibly plus VAT.

8 hours @ £35?? fitting?
Tile vent £55 plus vat
Fan £40 to £100
Roofer £120
Edit: plus duct and fittings, bends, grill and misc.£50

So it certainly does add up - with the time taken - labour being the biggest component. When I finished I wondered no longer as to why someone hadn't installed a fan into the bathroom already in the preceding 90 years.

 

[masamune]

I am not confident to do this myself. How much would it roughly cost for the entire package ? i.e the tile vent, the inline fan with a condensation trap and the work required.

As you've already paid your fitter for time and materials to install a working ducted bathroom fan, with an implied term of the contract being this will be to a reasonable standard of workmanship, why would you pay any extra to have the shoddy work corrected?

It should be redone at the fitter's expense and if that requires additional duct or parts because he mis-measured or under-estimated on the job that will fall to his costs not yours.

I completely agree, just preparing myself to call someone else in case he doesn't want to do it properly, because one shoddy job after another will probably end up with me footing the bill for more damage.

 

[masamune]

I had a roofer fit the roof vent, which cost £120, because I didn't fancy crawling on the pitch of the tiled roof and I didn't have proper ladders anyway which would of cost to hire anyway.

That's the toughest me thinks. At least if it's done I could pretty much do the rest. But best to get someone who does this every day to do the whole thing properly.

edit: any caveats for an 1930s roof with felt?

When I finished I wondered no longer as to why someone hadn't installed a fan into the bathroom already in the preceding 90 years.

Which I believe is the reason why my fitter decided to put it into the chimney, but at the time I didn't understand this was a botch.

 

[masamune]

Tile vent £55 plus vat

It may be a stupid question, but does the tile vent allow enough throughput for the steam to come out reasonably fast?

 

[stef99]

This was a problem for my bathroom because of the low pitch of the roof. There used to be an air brick on the side, but it would have been very close to the shower for the fan and it would get splashed with water.


No-no, Airbricks shouldn't be blocked up. they provide ventilation in older houses to prevent the damp seeping into your walls.

The fan should have been placed on the wall. with a connecting pipe pointing straight out to the outside.

The fan should be well away from any possible splashes from the shower.
If the shower is too close, it can contrvene the zoning permissions, which would render your electrics as dangerous.

Let forget the scary stuff for now though.

You can exit the fan through the roof, but generally i find it excessivly difficult, and going through the wall is much easier.

(except from drilling a 150mm hole).

As for the low ceiling height, that shouldn't matter.

Just get it is high as possible (even if its at the other end of the room.

Without the pics, I can only advise on what I know and on what you have said.

But generally, sticking the pipe up the chimney is basically a botch job.
(and to be honest, I would expect problems with it eventually).

 

[GoodDIYjob]

The fan should have been placed on the wall. with a connecting pipe pointing straight out to the outside.

The fan should be well away from any possible splashes from the shower.
If the shower is too close, it can contrvene the zoning permissions, which would render your electrics as dangerous.

If a wall mount is preferred and it must be within a safe zone, or uncomfortably close to one, you can get selv fans with remote transformers. I used one in a shower over bath in a flat where space was exceedingly tight.

Like:

http://www.xpelair.co.uk/catalogue/xpelair/domestic_ventilation/shower_fans/lv100/index.htm

I agree with Stef99 in that wall mount will be cheaper and easier if you can. But if bathroom already finished and tiled electrics might be a problem....

In answer to masamune question about flow through on the tile vent. It seemed very good. The outlet covers virtually the entire width of the 2 tiles profile it covers and is fairly large.

There is a minimum roof pitch required to guarantee watertightness but this is normally consistent with tile requirements anyway - you may want to check.

See.

http://www.roofingsupplies4u.co.uk/...uct/663-klober-universal-plain-tile-vent.html

PS not endorsing this supplier but it is cheaper than what I paid at a roof merchants, you will need the adaptor / pipe too.

[
Edit: pitch requirement not actually shown on that link here's the datasheet. 35 degrees.

http://www.klober.co.uk/products/datasheets/House_Ventilation/uk.datasheets.Uni_Plain_Tile_Vent.pdf
]

My roof is 1920s original clay plain tiles and still close boarded. So we had to just remover a section of close boarding between the raters and the tiles.

If you have felt underlay it would be a matter of carefuly slitting the felt on the underside to allow the spigot through.

 

[masamune]

Thanks for all the suggestions and links.

I think the only option now is through the loft, with a vent tile. I don't think there is any room for someone to reach the soffit.

It is going to be an inline fan, with vibration absorbing material and then a pipe with a condensation trap (can I add one on flex ducting by the way?) possibly going out from the old overflow hole at the end of the loft. I just have to talk my fitter into accepting this, worst case we may split the cost.

Normally people advise you to take the fitter's option so that he can take responsibility. But this is my house after all and I can't accept a flowed design that will produce recurring issues.

 

[OwainDIYer]

I am not confident to do this myself. How much would it roughly cost for the entire package ? i.e the tile vent, the inline fan with a condensation trap and the work required.

As you've already paid your fitter for time and materials to install a working ducted bathroom fan, with an implied term of the contract being this will be to a reasonable standard of workmanship, why would you pay any extra to have the shoddy work corrected?

It should be redone at the fitter's expense and if that requires additional duct or parts because he mis-measured or under-estimated on the job that will fall to his costs not yours.

I completely agree, just preparing myself to call someone else in case he doesn't want to do it properly, because one shoddy job after another will probably end up with me footing the bill for more damage.

You have to give him an opportunity to remedy the defective works.

If he fails to do so, inform him that you will appoint another contractor and sue him for the cost. Then do so.

 

[GoodDIYjob]

Thanks for all the suggestions and links.

I think the only option now is through the loft, with a vent tile. I don't think there is any room for someone to reach the soffit.

It is going to be an inline fan, with vibration absorbing material and then a pipe with a condensation trap (can I add one on flex ducting by the way?) possibly going out from the old overflow hole at the end of the loft. I just have to talk my fitter into accepting this, worst case we may split the cost.

In my opinion the condensation traps do not work well with flexi pvc pipe. You may be able to improvise and get it connected but it will be very reliant on tape to stay in position. Eventually in the environment it is in, it will come adrift.

Also because the pipe work is not fixed and flexible any movement will cause the pipe to move and settle differently causing the fall you had carfully set up to move. The flexi is easily disturbed in the loft space too. And you really need the trap to be secured to connect it to its drainage pipe work in turn....

All much more effective with some rigid pipe work around it.

The tile vent connection and pipe is a sort of plastic flexi which allowed me to directly connect to the outlet side of the fan. I used the other horizontal run, with a slight fall and rigid plastic duct to set up the condensation trap.

A backdraft gate would also be highly desirable and included in my other misc costings. Edit: They're only about 7-£10 and with the tile vent facing down the roof slope will be a wise idea.