Ceiling cooker hood - query re fitting

Uplander1111

We have just moved and inherited a ceiling cooker hood.  It is fitted in the middle of the kitchen and vents through the roof via a large pipe (not up with technical terms I'm afraid).

The ducting has come off at both ends which of itself is not too much of a problem.  However, the pipe that goes through the roof is not rigid.  There seems to be about 1/2 " - 1" of "play" side-to-side and it also seems possible to move it up and down to some degree.  I say "to some degree" because I am reluctant to be too rough with it.

My queries are these:

Is this amount of movement normal or does it indicate something awry with the roof aspect?

Should the ducting be insulated?

Thanks for any guidance. 

tacpot12

I've seen vent tiles and duct outlets that do allow some movement at the roof line, but generally I would expect a fairly rigid installation. The main issue though is water-tightness. It it's not currently letting in water, I wouldn't change anything. 

Ideallt the duct should be insulated, but whther it really needs to be will depend on the length of the duct and the power of the fan. If the duct is short, and the fan is powerful (and is left on long enough), all the damp air should be ejected outside the property so there is no risk of condensation. if the duct run is quite long or if the fan is weedy, damp air could remain in the duct long enough to form condenstation. You can look for signs of condensation at the lowest part of the duct, where it meets the cookerhood. If there is no sign water damage and no standing water, tehn you are probably ok not to insulate it. 

WIAWSNB

Uplander1111 said:

We have just moved and inherited a ceiling cooker hood.  It is fitted in the middle of the kitchen and vents through the roof via a large pipe (not up with technical terms I'm afraid).

The ducting has come off at both ends which of itself is not too much of a problem.  However, the pipe that goes through the roof is not rigid.  There seems to be about 1/2 " - 1" of "play" side-to-side and it also seems possible to move it up and down to some degree.  I say "to some degree" because I am reluctant to be too rough with it.

My queries are these:

Is this amount of movement normal or does it indicate something awry with the roof aspect?

Should the ducting be insulated?

Thanks for any guidance. 

The pipe is a 'duct'. This can be flexible - usually a quite thin plastic 'film' over a wire spiral - or 'rigid', ie solid plastic pipe, like your gutters or sink waste pipe. The latter is far superior, since it doesn't have any ridges, so allows better flow, and can also be held secure.

I'm going to say, 'non', there should not be any significant movement in this ducting as it exits the roof. Assuming it's 'rigid' type, then it should be supported with one or more brackets in the roof space, so it cannot move either sideways up upski and downski. 

Can you get into the 'roof' - loft or whatever - space to check on it? 

Uplander1111

Thanks for the posts.

I have been in the loft , that's how I found the problem.  To clarify, there is the extractor unit mounted into the ceiling, a rigid pipe going through the roof into the outside world and between the two there was flexible (wire and plastic) ducting (not insulated).  The run is short almost straight up from the extractor.

There is some staining but no real evidence of a recent water ingress and we have had quite some rain in Devon.  That said and I am not knowledgeable in these areas, I would have thought the rigid pipe should be rigidly mounted as it passes through the roof itself.

I cannot get on the roof or I would take a look and understandably, nobody wants to come out for a non-job like this.

Anyway, thanks for the posts and thoughts.

  

WIAWSNB

Any chance of a pic? Is there room to work on it up there?

I would suggest that any significant movement, in particular up and down, will very likely cause problems in the not-too-distant.