Old fireplaces - must have air vent?

[Londoner]

Hi all, wonder if someone can answer this question. Been looking at some 1930's houses recently and have noticed that most have sealed up the old fireplaces in the dining rooms etc. However, with some, a small air vent has been left in the wall whereas with others there seems to be no vent. I understand the logic of having a vent but does that mean that ones where there is no vent might cause problems in years to come?Assuming that in most cases, a professional would have done the work, is there ever justification for not leaving any vent in the sealed fireplace?

 

[nstreet]

If the chimney has been capped, it shouldn't need an air vent. Air vents are normally used if the chimney is open, to stop damp problems.

 

[Londoner]

I see, thanks.

How do you tell if a chimmney has been capped?

 

[nstreet]

Get on a ladder and have a look.

 

[Nige F]

Get on a ladder and have a look.

If the pot is gone and the top sealed completely-it`s capped....if it`s done with a rubber membrane it`s Dutch capped

 

[Londoner]

Could someone please post a link to an image that shows what I should look for (to determine whether a chimney is or isn't capped)?

A picture is worth a thousand words, as they say... TIA

 

[SD Carps]

I think what the lads mean by 'capped' is that it has been filled in on the pot,ie,the pot has been usually filled with ballast and then usually a 50-75mm cement slab on top of it,the only way you'll find out is to get up and have a look and see if the top of the pot is capped over with cement.
Dunno why but i thought it that air vents/air bricks were needed after being capped,can someone confirm this.
SD Carps

 

[Thermo]

yes it should if its been capped to help ventilate any build up of damp

 

[Londoner]

If the chimney has been capped, it shouldn't need an air vent. Air vents are normally used if the chimney is open, to stop damp problems.

yes it should if its been capped to help ventilate any build up of damp

Sorry, just to clarify...

Capped chimney = no need for vent in a sealed fireplace

UNcapped chimney = DOES need a vent in a sealed fireplace

Is that right?

 

[srs]

Yes thats right.

 

[SD Carps]

No!!!
Capped chimney should be vented(if its capped it obviously means its not in use),this is for some air to circulate within the chimney breast to avoid damp,we recently had to do this on a site to comply with NHBC.

SD Carps

 

[Londoner]

So... basically, if I see a sealed-up fireplace in a house and it has NO vent in it, then I need to make sure the chimmney ISN'T capped.

CAPPED Chimney = MUST have vent in sealed up fireplace

Is that correct?

 

[nobody]

I think that the chimney needs air flow in it regardless. So there should be a vent (although it might not be visible - may be under floor) or the fireplace should be open.