Venting multiple flues in disused chimneys

[nebjamin]

Hi,
Recently moved into a 1930s property that has 3 chimneys, all of which have been cut back to below roofline.

The fireplaces have all been blocked up.

Our survey (and other people since) have said we need to install vents to vent the stack. No problem. I'd like the vents installed on the outside of the stack.

My question is that I believe (but not certain) the stacks contain 2 flues (they are pretty wide on the outside of the house - see pic). Does this mean that they need 4 vents, one at the top and bottom of each flue?

Ta,
Ben

Untitled

• nebjamin
• 20 Dec 2012
• 1

 

[Alastairreid]

A vent installed top and bottom of each flue so if there are 4 separate flues that would be 8 vents.

 

[dann09]

What are the projections on the roof plane just above the chimney breasts?
Are they venting something?

Your lower porch guttering, and the main roof guttering - front and side - require cleaning out.

If possible, maintain and retain your original bay windows.

The bay roof has organic debris accumulating and will probably fail in the next few years. Research, or come back here for how to replace it with a better arrangement.

 

[nebjamin]

dann09:

What are the projections on the roof plane just above the chimney breasts?
Are they venting something?

No - they are from a previous owner of the house who was a (bad) DIY nut and installed the loft room. He used wooden beams to support the floor and they stick out through the tiles. The felt caps are there to stop the wood rotting! Great huh?
The whole loft room will be removed over the longer term along with the crappy felt caps (this is a project house).

Your lower porch guttering, and the main roof guttering - front and side - require cleaning out.

Lower porch maybe, but how do you know the other gutters need cleaning? You can't see them well enough from that shot to make a valid judgement about that!?!

If possible, maintain and retain your original bay windows.

Is there any alternative??

The bay roof has organic debris accumulating and will probably fail in the next few years. Research, or come back here for how to replace it with a better arrangement.

Again, how can you make a valid judgement about that. You can't tell from this photo.

 

[joe-90]

What will vents achieve? What benefits are there?

 

[nebjamin]

What will vents achieve? What benefits are there?

There is currently damp in the chimneys. The paint on the chimney breasts is falling off (you can't see it from this shot - it's on a 3rd chimney stack round the back).

AFAIK it's common knowledge that if you block off a chimney (fireplace and top), you need to vent it to allow any moisture to evaporate.

 

[dann09]

Take a magnifying glass to the pic and tufts of organic debris will be visible.

Experience of pre-war, bay, lead flats ( over a 100 properties in one area) informs my judgement - they have no fall and typically pond in the centre until they overflow ( having no guttering ) down the face of the bay.

Please research on here and elsewhere the difficulties that occur ( esp. in bays ) when such sturdy window frames are replaced with PVC alternatives.

As regards venting redundant chimney flues, esp. those that once contained solid fuel fires, it's been common knowledge and standard practice for decades - often included in Regs - to through vent and prevent sulpherisation.

 

[nebjamin]

Dann09:

Thanks for the comments but I have to disagree that you can see organic debris on that flat roof. This pic is from google streetview and the resolution is so low there is no way you can see that. You may be right that there is the likelihood of it up there, but you can't see it.

What you can see is probably distortion in the image where streetview has stitched 2 images together.

It's also felted and not lead.

Anyway - the windows are already PVC (old ones). Been in there about 20 years I think.

Thanks for the tips anyway and confirming what I thought about the flues.

 

[Alastairreid]

the main roof guttering - front and side - require cleaning out.

If possible, maintain and retain your original bay windows.

The bay roof has organic debris accumulating and will probably fail in the next few years. Research, or come back here for how to replace it with a better arrangement.

I'm intrigued! how can you tell from that pic the gutters to the main house need cleaned?

And the bay window???

 

[Alastairreid]

What will vents achieve? What benefits are there?

Nxt joe is going to tell you about the 20million flues in the uk which are unvented!

He thinks he knows better than construction professionals.

 

[joe-90]

If you read the forum Alasair, you will find endless cases of partially vented chimneys becoming damp. Don't take my word for it - have a look.

Until you understand the Venturi Effect, then you will never understand the science behind the problem.


An exterior vent top and bottom is an ornament as there is equilibrium within the system.


It's schoolboy science Alastair.

 

[Alastairreid]

Ok joe i have been here before with you( last xmas i think)

Post a link backing up your theory!!! just 1.


And please do not make assumptions of my knowledge of building physics.

 

[joe-90]

I'm not trawling through it all. If you choose ignorance over knowledge -"cuz that's wot everyone duz" then good luck to you.

 

[Alastairreid]

Your theory is flawed.

I'm not asking you to trawl through anything, just show me a link which legitimises your theory.

You wont because you cant.