Ventilation

[DIYheadache]

Hello Forum,

I'm looking to improve ventilation in my flat. Currently, there is a loovent fan in the bathroom, which vents to the outside via a boxed in section going through the kitchen and exiting through a square ventilation brick.

Vent 2

• DIYheadache
• 28 Dec 2014
• 1

The fan is the original installed in the flats (1982). I decided to take the fan off to clean away the dust and for a general inspection. I expected the fan to be mounted on a 100mm duct, but when I removed the fan I found nothing connecting it to the outside.

Vent 3

• DIYheadache
• 28 Dec 2014
• 1

The fan just vents into the void and has 30 years of accumilated dust inside. You can just make out the ventilation grill at the other end, but it looks like someone has just bashed a hammer through the plasterboard!The vent is on the NE wall of the building and is pretty sheltered from prevailing the prevailing winds. My questions:

1) Is this an effective setup for extracting moisture from the bathroom? Will the vent on the outside of the wall be sleved through the cavity and how can I improve the ventilation without too much disruption to the decoration etc.

2) There is currently no ventilation in the kitchen. Can I somehow tap in to this duct to connect a cooker extractor hood i.e. could I ventilate the bathroom and Kitchen through the same duct?

Thanks in advance

Peter

 

[EFLImpudence]

1) Is this an effective setup for extracting moisture from the bathroom?

Not really although it does not seem damp.
The bathroom wall and ceiling look in good condition so there does not seem to be a problem.

Will the vent on the outside of the wall be sleeved through the cavity

What do you think?

and how can I improve the ventilation without too much disruption to the decoration etc.

Run the correct sized ducting through the box-section to the outside wall.

2) There is currently no ventilation in the kitchen. Can I somehow tap in to this duct to connect a cooker extractor hood i.e. could I ventilate the bathroom and Kitchen through the same duct?

I would not advise it.
It would require all sorts of flaps to prevent back draughts.
Is there not a window?

 

[sparkwright]

As hinted at, not advisable to share the duct with two fans.

As hinted at, fitting a window fan would be the answer.

As hinted at, the duct seems in remarkable condition. I would expect the air brick at the end to include a sleeve round the cavity, but who can say for sure?

What floor are you on? Sliding a rigid duct or flexi duct through the boxing would be possible, but hardly seems worth the effort in some ways, unless you really want to do it.

 

[DIYheadache]

Thank you for your response.

Shouldn't all vents through a cavity wall be sleeved?

Yes, there is a window.

Peter

 

[EFLImpudence]

Shouldn't all vents through a cavity wall be sleeved?

Ideally, yes.

Yes, there is a window.

Then, perhaps the fan is not required in the bathroom.

It may be more beneficial to use the box-section with ducting just for the kitchen.

 

[DIYheadache]

Thank you Sparkwright.

Thanks for the confirmation. Just looking at increasing ventilation as we have a minor issue in the bedrooms. We tend to get anoying brown patches on the ceiling but no visable signs of condensation, average RH is 55-60%. We are on the 1st floor. I might replace the extractor, as the timer no longer works.

Peter

 

[DIYheadache]

EFLImpudence,

There is a window in the Kitchen, the bathroom is internal and has no windows. Sorry, should have made this clear.

Peter

 

[sparkwright]

I'm intrigued to know how a timed fan would work in conjunction with that unswitched fused spur (more recent than 1982) CORRECTLY.

Is that fused spur serving the fan, or does it control something else?

 

[ericmark]

Ventilation is complex, years ago we had chimneys and bad fitting doors which caused good ventilation or in other words drafts. The balanced flue (combustion air drawn from outside) and electric heating transformed our homes removing the ventilation (drafts) and allowed us to seal nearly every space where air got in. Cavity wall insulation not only insulated but also filled in the vent bricks.

So in the main extractor fans not working is due to no air getting into the home to replace it. There have been moves towards heat recovery units which control both air in and air out but these are expensive.

So job one is work out where the replacement air comes from. In the main that is the problem some where a vent has been blocked stopping replacement air.

As to the kitchen and cooker there are two very different units. With electric cooking the hoods have in the main carbon filters to remove smells, with gas cooking you need to remove the combustion products so needs venting to outside.

I look at my house and the electric and gas points are away from the outside wall and clearly the builder had no thoughts at providing any flues or ducts for the cooking units. He also fitted an open flue gas fire in middle of house on the adjoining wall to next house so no air to replace that which goes up the flue bricks. In other words a very poor designed house.

The poor designs of the 1970 - 1990's is now coming back to bit us. For me to install ducting would also entail fitting all built in furniture to hide the duct.

There are some heat recovery units now where the heat exchanger fits in the duct so the air is both feed in and out of the room through the same hole. But these are a fixed length designed to go through a cavity wall likely too short for you.

Again as original design my mothers house has single glazed windows with metal frames at the bottom of each frame was a small tray with a small hole to the outside. The cold windows would condense moisture in the room air and it would run down the window into the tray and outside. Replacing these with double glazed windows and a insulating frame even if vents were included removed the very effective de-humidifier afforded by the original windows.

I have thought about this a lot. A radiator connected to the cold water supply in the bathroom with a tray below and small pipe to outside would be cooled every time the bathroom was used and the water would condense on it and be directed outside. However it would look hideous and would need to be of a material able to take fresh water not the treated water of a central system.

Maybe I should design and market a mini dehumidifier for a bathroom but this does not help you. However I hope although it may seem daft it will spark something which points you to the real problem.

 

[EFLImpudence]

EFLImpudence,
There is a window in the Kitchen, the bathroom is internal and has no windows. Sorry, should have made this clear.

Ah. ok.

 

[DIYheadache]

Sparkwright,

The fan is supplied via one 3-core + E cable. The cable goes into the back of the fused unit. Blue and Yellow are looped through (not cut), red is cut and connected to the fuse L terminals. I assume the red is Live from the light and the Yellow is the switched live. I have not yet removed the light fitting to see if the red and yellow are connected correctly, the timer has not worked since we moved in and I have never checked the wiring at the light end. I shall cjeck this first.

Peter

 

[phatboy]

If you were going to replace and uprate the fan, I would recommend installing a pipe in that boxing. It may not be getting damp because barely anything getting sucked through.

A really good solution would be to fit an inline ducted fan half way along, with a suitable access hatch cut in the kitchen to access it. Extending cables would be pretty straightforward, using the fused unit below the current fan. Although ideally it would be replaced with a 3 pole isolator.

Inline duct fans are a lot more powerful, and a lot quieter than wall mounted units.

 

[Adam_151]

The fan is supplied via one 3-core + E cable. The cable goes into the back of the fused unit. Blue and Yellow are looped through (not cut), red is cut and connected to the fuse L terminals. I assume the red is Live from the light and the Yellow is the switched live. I have not yet removed the light fitting to see if the red and yellow are connected correctly, the timer has not worked since we moved in and I have never checked the wiring at the light end. I shall cjeck this first.

Then its dangerous, Someone could think that removing the fuse had isolated the extractor, and it could even appear so when tested if the bathroom light was switched off. If the bathroom light is turned on to see what one is doing with the fan then the yellow will become live.

You must replace this with a 3pole fan isolator before replacing the fan

 

[phatboy]

The fan is supplied via one 3-core + E cable. The cable goes into the back of the fused unit. Blue and Yellow are looped through (not cut), red is cut and connected to the fuse L terminals. I assume the red is Live from the light and the Yellow is the switched live. I have not yet removed the light fitting to see if the red and yellow are connected correctly, the timer has not worked since we moved in and I have never checked the wiring at the light end. I shall cjeck this first.

Then its dangerous, Someone could think that removing the fuse had isolated the extractor, and it could even appear so when tested if the bathroom light was switched off. If the bathroom light is turned on to see what one is doing with the fan then the yellow will become live.

You must replace this with a 3pole fan isolator before replacing the fan

Really? This is a pretty common setup in my experience. Not much different to assuming any other service is properly disconnected before working on it.

If one wanted to improve the situation, a sticker on the fan stating that there are multiple points of isolation would probably suffice, although I don't think it's necessary.

 

[JohnW2]

Then its dangerous, Someone could think that removing the fuse had isolated the extractor, and it could even appear so when tested if the bathroom light was switched off. If the bathroom light is turned on to see what one is doing with the fan then the yellow will become live.

That is all theoretically true, although I suspect it's a fairly common situation.

You must replace this with a 3pole fan isolator before replacing the fan

At least for the rest of this year, if the MIs demand a 3A fuse, then the FCU cannot be "replaced" by a 3-pole isolator - strictly speaking, the isolator would have to be installed in addition to the FCU.

This is really a possible hazard created by the MIs' demand for a 3A fuse (and maybe also '3-pole isolator') for the fan. It is arguable that neither are really necessary, and if one does not have an FCU, then it is apparent that the only way of making the fan safe to work on is to isolate the entire lighting circuit (or operate a '3-pole isolator', if there is one) - which, IMO, would be safer.

Kind Regards, John