Exterior air flow for condensation boiler

Hi All,

We have had our new condensation boiler in since mid 2014 and have only just been told by a new plumber that the (reasonably large hall) where it is situated, which includes our main door, does not have enough exterior air flow for the boiler. Extraction is via a chimney to the roof, which had new tubing installed at the same time.

He proposes a 10cm diameter circular hole or a 10cm X 20cm rectangular opening, one at the top of the wall and a second at the bottom. However, I can’t find any information or guidelines on this on the internet. Is it absolutely necessary for functionality or efficiency?

Will these openings not cause quite a draught and therefore heat loss? Are specialist grilles needed for each end?

Also, the wall of this room is quite thick (60cm) so will will need to hire (or almost as cheap to buy) a “carotteuse” drill in order to create a neat circular hole. This also will cost about €150 in addition to any other Equipment required.

All information and advice very welcome! Thanks


Hi Danielle

Do you have the fitting instructions /information booklet which would have been with the boiler in 2014 ?
Can you tell us the Make and Model of your boiler (and fuel) ? This info would be useful.

Why not ask the original Fitter/Plumber about the exterior vents … (and perhaps why was this not done in the first place).

It could be that the Norms have changed since 2014… and this is now a requirement in 2017.

If, by any chance, this work should have been done in 2014 (and wasn’t) you may well be able to claim against the original Fitter/Plumber… for not doing the job properly. (All professionals have to carry Insurance to cover them.)…

Frankly, there is no way I would expect to pay a Plumber/Fitter … to buy a tool to drill through the wall. Any professional should have the correct tools to do the work.

(around here walls can be anything from 1 metre upwards.)

There does need to be sufficient air for the boiler to work correctly, carbon monoxide etc. I would be surprised if this wasn’t checked when installed (registered/qualified installer?). There is no need for special vents, just sufficient air for the boiler to work. If the rules have changed, then it would only be for new installations. But yourself a CO alarm for peace of mind😊

It might be worth checking to see if the boiler can be converted for use with a balanced flue. There are systems available to run this via your chimney/flue route & not just straight out through an exterior wall. This would remove the need for any extra ventilation from inside the house. However, such flue systems are not cheap but you seem to faced with high costs already.

Hi, its an E.L.M.leblanc Egalis Ballon NGLB24-4H natural gas boiler and the new plumber has explained to us that it is the cheapest / lowest of the range. We took the recommendation of our original fitter who cale recommended by the house’s previous owners.

The boiler came with only a 5 page booklet, of which 1 page is very general fitting instructions (nothing about ventilation), 1 page about very general usage instructions (totally useless) and the rest is blurb.

The original fitter turns out to be a total bleep which is why we have the new guy in - the boiler kept putting itself into security mode (i.e. switch off) after a few hours at night and 2 other plumbers had not been able to work out why, so we were trying again… He says that the flue from the boiler to extract gases up the chimney was not correctly installed by the fitter (not airtight) and we have both of them round for a meeting on Monday to see if we can resolve it amicably (which I doubt, knowing the fitter…). So we will be asking for a copy of his Assurance Decennale which he didn’t provide at the time!!! Have spoken to insurance’s legal advisor re. newt steps already

Bought a CO monitor yesterday on advice of new plumber because he was concerned that fitter’s ‘dodgy’ flue may be leaking. So far, it is reading zero ‘=less than 10ppm’. We’ll give it a few more days.

Thanks all

Gosh… that is rather worrying… if the original installation was indeed done incorrectly…it could lead to expensive problems, let alone safety concerns.

Glad you are having a meeting with all concerned… and that you have been talking with Insurance…Frankly, whoever you used to install and now to correct the boiler… you need to ensure that they are Registered to work on Gas and Insured to do the work involved…

Best of luck… and please do let us know how it is progressing.

Hi Mark, could you please elaborate upon how I check the registration / qualifications of an installer? Which affiliations should I be asking about?

I have looked about on the internet but don’t seem to be finding anything relevant…

Thanks in advance,


Danielle… did your original Installer give you a Certificate of Conformity of Installation for your Gas boiler ?

If not… what paperwork did he give you… what do his Devis and Facture say about him/his business/siret number etc…??

Easiest thing with Gaz is to use a Qualigaz approved Plumber/Fitter, but not essential.

Although any plumber/installer can fit a Gaz boiler…this site (and many other sites) clearly states that every installation must be verified by Qualigaz, who will then give the installer a Certificate of Conformity of the Installation CCI.


Hi Stella,

Yes, he left us the Certificate which is Qualigaz approved, his SIRET number comes back to a proper company with the correct code NAF etc.

Mmm… yet you say the original fitter was a “bleep”… so what do you mean… was there something which would now make you query his workmanship…???

I think, if it were me… I might be asking Qualigaz for advice…If you have their CCI and there is something wrong… seems best to involve them… at least in a discussion…

Is your current Fitter Qualigaz approved ??

See the rest of paragraph 3 of that same post - it was the original fitter that left us with a badly installed extraction flue, non-airtight, potentially leaking fumes, and a boiler that switches itself off for security after a few hours use at a time.

We used him again for another job afterwards (before we knew we had problems with the boiler) and he did shoddy work and really let us down - never available to come back and finish off or correct errors. We just decided to have nothing to do with him again - hence why we have been using other plumbers to try to diagnose and fix the problem ever since (2 years!). I simply can’t trust the original fitter, no matter what his certificates say!

However, upon advice of the new plumber (very qualified - plumbing teacher for Leroy Merlin) and our insurance company’s legal service, we are having the meeting on Monday to give the original fitter the chance to put things right amicably before maybe having to go down ‘official channels’ such as via his assurance décennale which could be long and stressful.

I have 2 full time jobs and simply don’t have the time - I just need to get it fixed.

Hope this explains better…


Dodgy Gaz over a 2-year span… I’m so glad there has not been an incident/accident during this period.

Be interesting to hear the outcome of the Site Visit…if it is definitely shoddy workmanship by the first chappie… his Decenial Insurance should cover whatever needs to be done…I am sure your own Insurance folk will sort things out for you…and you will get a new CCI once the dust settles…

Best of luck.

So are we - but it had been seen regularly over that period by various plumbers, in addition to its annual inspections of course.

Unfortunately, our insurance company itself doesn’t want to know - they say there hasn’t been ‘damage or an accident’ so not their issue. The legal protection service will only give us general advice as to how to write the fitter a letter etc. They advised against ‘proper’ legal action due to long time delays for results…

Sorry Danielle, no idea how to check if someone is qualified to fit gas boilers. Be surprised if anyone who wasn’t qualified would fit something like that given the ramifications if something goes wrong

No, I can see why the Insurers are not involved as such… but the Insurance Legal side of things… should be a great help. I have first-hand experience of such folk and how they can cut through the muck and rubbish and get things sorted.

(It only costs us about 70 euro a year… and gives me peace of mind to know they will leap in to help us if required…)

As I say… please let us know how things go on…