Balanced flu on mid terrace

[Rageyboy91]

Hey guys,

I have a mid terrace property and wanted a gas fire inset, I've heard conventional chimneys can increase radon levels and wondered if any solutions exist to convert a conventional chimney into a vertical balanced flu.

In my head this sounds abit impossible/ impractical but wondered if there was solutions available on the market. Cheers.

Edited this to be clear.

 

[ianmcd]

I've heard conventional flues can increase radon levels

absolute shoite

 

[denso13]

absolute shoite

Actually, I think the OP means open chimneys not flues and there is some evidence for this....

https://www.bre.co.uk/page.jsp?id=3150

"How can I change the way I ventilate my house to reduce radon levels?

Typical examples of appropriate measures include installing trickle ventilators to windows, particularly downstairs, capping off and sealing unused chimneys, draught stripping loft hatches and avoiding use of open fires and solid-fuel-effect open fires."

https://link.springer.com/content/pdf/10.1057/palgrave.jba.2940015.pdf

"As noted earlier, ventilation solely on upper floors should be avoided as it can lower the indoor pressure causing greater ingress of radon from the ground. The presence of chimneys and regular use of open fires can compromise the remedial effect of room ventilation."

 

[ianmcd]

No the OP said increase radon levels, Radon is present in the ground a gas appliance cant produce it

 

[denso13]

a gas appliance cant produce it

An open chimney causing a natural updraft has got nothing to do with a gas appliance. I think that is what the OP is getting at.

I've heard conventional flues can increase radon levels

Swap chimney for flue...

 

[ianmcd]

An open chimney causing a natural updraft has got nothing to do with a gas appliance. I think that is what the OP is getting at.



Swap chimney for flue...

read the post for balanced flue

 

[denso13]

read the post for balanced flue

Yes he/she is asking if they can fit a balanced flue into a conventional chimney (and close it up) as they have heard an open chimney can increase radon levels, which they can.

 

[bernardgreen]

I've heard conventional flues can increase radon levels

Radon is present in the ground a gas appliance cant produce it

A conventional flue or chimney draws air out of the building and if the replacement air comes from under the house then radon gas maybe be drawn into the building increasing the level of radon gas in the building.

 

[ianmcd]

No one can increase radon levels it is a naturally occuring gas

 

[denso13]

No one can increase radon levels

You can if you "pull" more radon into the house by the effects of an updraught through a conventional chimney. How plausible it is in real life I don't know, but that is the theory.

 

[bernardgreen]

Positive ventilation brings fresh air into a home, and dilutes the radon. The flow of air and radon from the ground may also be reduced.

SOURCE

 

[Rageyboy91]

Thanks guys, yeah my worry was creating negative pressure like you stated with the chimney drawing radon gas from the subfloor, where radon would/could be highier in cold conditions.

I am in a higher radon area but It's all abit pie in the sky as I'm yet to have a radon test, but I would like the improved efficiency of the gas fire with a balanced flue anyway, just a win win really.

Positive pressure system would benefit this house as there is some damp on the front solid wall so that could be a good idea cheers, looking at them I'm quite impressed tbh not that much to run overall.

 

[Madrab]

Having a read through a pile of the government advisory stuff, they actually actively encourage drawing fresh outside air into the house, this helps to dilute any build up of radon within the rooms, that may have come from underground. (I was asked this very question about 2 years ago when doing a chimney survey for a large gas fire in Berwick and did a fair bit of digging)

I would look at it like :- .... if the room with the fireplace is well ventilated from outside, through wall vents etc, then it would actually help to remove any radon that may have built up within the room. It seems the consensus is to attempt to try and minimise any the build up of radon to higher percentages into rooms, as this is where the risk arises, from badly ventilated underfloor areas, through concrete foundations, in through cavity walls etc.

If you can make it easier for the external air to ventilate the room other than from under the floor then any draw from underneath, which is where the radon primarily comes from, not outside, should be minimised. I'd also look at whether any radon remedial works have already been undertaken to externally ventilate under floor areas and seal up potential air paths, from below, into the rooms.

Therefore it may actually reduce the beneficial natural ventilation - depending on how the room is ventilated just now - if the chimney is sealed.

I would recommend you get some specialist advice before deciding.

 

[Rageyboy91]

Thanks for the detailed post, the house has no radon measures but the air brick has been covered so that's not helping, I havnt moved in yet but thats my first point of call. I can see what you mean I think it sounds like in a way the chimney acts similar to a radon sump, and as long as fresh air is brought into the property like a piv system, instead of rising stagnant air from the subfloor which has not been ventilated, that's when the radon levels will be at their highest, if I understood correctly.
Really liking these piv systems seem like they save money in the long run.

 

[Madrab]

Yes, in short, the chimney can act like a super vent to remove radon build up in the room, as long as the air that ventilates that room is as clean as possible and taken from as high up off of ground level as can be achieved and not drawn from under the floor.