Blower-Door-Test - Is the fireplace room-air dependent?

We have already received the positive approval for the [Bausparvertrag]. Everything is OK on that side. The question was whether the chimney can even pass the [BDT] since the door does not lock. Hark told us that this is not a problem, but we have not received any technical specifications or standards regarding the pressure the chimney door must withstand and are therefore uncertain!

let's ask differently: do you have a ventilation system and/or a [dunstABzugshaube] (note: not recirculation but exhaust)?

whether a chimney can be room air-dependent or independent depends less on whether you have a ventilation system or something similar, but rather on how the fresh air supply is designed. in old buildings with poor insulation, the fresh air supply can be justified by, for example, air slots in the masonry. in new buildings, it is difficult to account for this properly. the ventilation system is not considered a fresh air supply because it can be switched off by the pressure monitor.

in new buildings, there is basically no reason not to build room air-independent. the appropriate chimney is selected, and that's it. a dependent masonry chimney is no longer installed in new builds. the chimney can then be chosen quite freely. the only thing to consider is the so-called "dibt" approval, which allows a pressure difference of 8Pa instead of 4Pa. the final word here is with the district chimney sweep, whom you need to contact anyway for the combustion application. you should ask him what he requires. then the acceptance will immediately work.

with a ventilation system, there are basically 2 methods:

1. room air-independent chimney with dibt approval and that's it
2. any chimney + pressure monitor; for room air-dependent, proof is required that enough fresh air is supplied – difficult

method 1 means the ventilation system is always running but can be rejected by the chimney sweep because proof is needed from the ventilation system that the pressure difference never exceeds 8Pa. this proof does not exist... another disadvantage is that the choice of chimneys is very limited.

method 2 cannot be rejected by the chimney sweep because it is exactly what is required. disadvantage: the ventilation system does not run in bad wind conditions. but theoretically even safer than method 1.

we got method 1 approved immediately without any fuss from the chimney sweep. up here in the north, it’s all a bit simpler.

Now I am completely confused and I also believe that I did not explain it well enough. The chimney has a LAS system with which room air-dependent wood stoves can also be operated.

This also makes it possible to install heating appliances in buildings that, due to their airtight construction, would not provide sufficient combustion air for room air-dependent heat generators.

I do not understand why I then have to provide proof that enough fresh air is supplied. Since we are building a passive house, it is clear that the extractor hood will be recirculation.

Again: The chimney sweep has already approved the chimney. My concern is whether I will pass the BDT with this chimney, which in my opinion is not 100% sealed because of the door that opens upwards.

This also makes the installation of heating appliances in buildings possible that, due to their airtight construction, would not provide sufficient combustion air for room air-dependent heat generators.

this is the definition of room air-INdependent chimney and not dependent. yes, the other word is written there, but it is actually used the other way around.

so: you have a room air-INdependent chimney, just as is actually only allowed in new buildings today. thus, the matter is settled. if you also have a pressure monitor, this will definitely be approved with proper installation.

room air-INdependent: the chimney is supplied with fresh air from the chimney.

about the bdt: the opening for the chimney is normally only drilled during the installation of the chimney. thus, the chimney is nowhere connected to the interior, so this does not play a role. if the opening is already open, the tester carrying out the work will of course notice and somehow close the opening.
therefore, you do not have to worry about the bdt. however, it would still generally not hurt to be present during the test. this way you also get a feeling for what he is doing and you can be sure that everything is in order. the tester surely knows all the typical problems.

Hello,

thank you for the explanation. I think then it will be fine.

We will have the opening made by the chimney builder on the advice of Hark as this would be cheaper. I am now considering whether we should do it only after the [BDT], then these questions wouldn't arise at all.

We had purchased the fireplace from Hark before the shell construction. Therefore, we already knew the height of the opening on the chimney. We gave this information to the shell builder, who built the chimney.

If the ceramic breaks, it’s not so bad.

Later, it would be the worst case.