First, thanks for all the info on this site. I just acquired a longere watch with a closed fireplace (insert cased in the old duct) old enough. It does not have a fresh air inlet outside the house (on the draft hatch insert only). The house does not have a VMC. Can I install one without risk? I could see that this is sometimes a problem. In the bathroom and toillette I posed extractors, it remains the stay (with the insert) / American kitchen and the floor to ventilate.
You yourself have seen the problem: a powerful VMC can effectively disrupt the draft of an insert without external air intake, as can, indeed, the hood of your American kitchen. If it does not disturb him, it is because the draw is good; but the conjunction of the two can accentuate the phenomenon.
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