Draughty house with high CO2

I have recently visited a draughty house with ill fitted doors and windows with one occupant. The gas heating had not been on all day and no cooking had been done (electric). Why would this house have an internal CO2 reading of 1790ppm?

I have heard that some CO2 monitors also pick up other gaseous compounds of carbon.

If the heating system is old there might be a pilot light, but that shouldn’t account for so much CO2.

By one occupant you don’t mean one human and 100 cats?

Edit: Are the draughts definitely external air and not internal convection and other air currents?

Hi, one male nearly 40 yrs and no animals. House built 1995 and IR camera clearly shows infiltration at external doors and windows. In fact a window in the bedroom was permanently ajar when closed and had mould growing on the frame. Co2 monitor picked up <10ppm PM 2.5

That’s a huge difference in CO2 concentration that I cannot explain unless perhaps it comes from an external source. Is the house built above a mine or an old industrial site?
If terraced or a semi, what is next door and if possible what is their air like?

Hi, It is a terraced house and I think the CO2 source might be external, which is why I reached out for an alternative explanation. Readings were similar upstairs and down.

My guess, without onsite testing is that a neighbour has a leaky flue. The occupant is lucky there are 2 “O”s to each “C”. It could be much worse.

If both neighbours have adjoining chimneys they will both need examination and testing, if only one then initially concentrate on that one. 1995 houses shouldn’t have leaking chimney linings but there may be a gap between gas appliance and flue lining, so that would be a first place to look.

There is a possibility that the neighbour isn’t affected themselves if the flue gasses are all sealed from their living area.

This might need to go through the local council’s Environmental Health Department.

Did you take an outside air CO2 measurement? It might be that something nearby is creating a small CO2 cloud that you are picking up because of the air leakage.

I did not take a measurement outside but it was close to an industrial area. It would be exceptional if this was a microclimate! Any chance that this could be caused microbial activity /(mould) growth under floor? But I am not sure why a similar reading was obtained upstairs in a bedroom where the window could not be shut properly. I could not see any air bricks.

All three properties have through the wall gas flues. At least the right hand half of the picture has no chimneys, so that blows my theory.

Do you have remote sensors to leave in place and monitor the CO2 levels. Ideally inside the three properties and outside front and back.

No airbricks, so solid floor, but maybe gas permeable. Even if it was, I wouldn’t expect sudden changes by that route.

There seems to be a general lack of planned ventilation

I’ve had a thought. It’s very unlikely but possible that if the boiler flu(s) have not been correctly installed, that CO2 is being transferred in the cavity walls.

I agree with the lack of planned ventilation . The bathroom extraction goes across the loft floor and disappears on the front of the house?!!

Thanks for the suggestions I will look into it.

:monkey_face: :see_no_evil: :speak_no_evil:      

I have had a mull and relooked at images of this house and there are no soil pipes or drain pipes on the external walls.

There are are no soil pipes or drain pipes on the external walls of my house either. That was a deliberate plan when I extended and modernised almost 20 years ago. Having lived in Norway I know the risks of severe weather in external pipework.

Did you get to the bottom of this? It’s quite astonishing. I feel stuffy at 900 ppm. I would feel atrocious living in a house with CO2 levels that high. What does the occupier say?

Unresolved and ongoing. I will update when I have more information.

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Are you able to log data over a whole week? If it varies it might give a clue.

What CO2 monitor are you using? Are able to confirm that its not another gas triggering the CO2 sensor?

I used the Airgradient PCB v2 kit I had assembled in an Eco home lab session. I am happy with this as a reasonable reading.

Could it be to do with the boiler flue? It looks like a change has been made to the standard flue pipe on the outside to the right of the front door- looks more like a waste water pipe/ periscope.

Welcome to the forum Ruth.

Flue extensions are fairly common, in this case maybe fitted to avoid flue gasses entering the adjacent window when open.

That’s not to say that this one could be badly fitted and be a cause of the problem, however:

This does make the flue an unlikely candidate.