What can be detected in a blower door test, which house values?

Hello everyone!
We have built a prefabricated house and are moving in this week. A few weeks ago, we noticed that the right side of the attic is wet. We reported this to the [Fertighausfirma] and were told that "the fault has been fixed." Afterwards, the Blower Door Test was carried out. We received a report for this (n50=1.0) and confirmation that the test was successful. In hindsight, we found out that the fault in the attic was not fixed (only the wet glass wool was replaced, but the cause was not addressed) and by now we already have mold on the wooden beams. Now my question is, shouldn't this have been noticed during the Blower Door Test? Were we only shown a Blower Door Test or can open spots in the vapor barrier not be detected by it? I actually thought that a BDT is precisely for this???

Thank you very much for any information regarding this post!

Katrin

Hi,

do you have a converted attic? Insulated and heated? Or just insulated?
No matter what, I doubt that the moisture in the insulation comes from the inside. The house can’t be old if you’re just moving in this week.......

Regards

Hello Katrin,

I actually thought that there is a BDT specifically for this???

With the Blower Door, you have a measuring instrument that helps to assess the airtightness of buildings. During this airtightness test, wind load is simulated and it is determined to what extent the building envelope resists natural wind pressure. The required pressure difference between inside and outside is created by a controllable fan that is installed in a door or window opening.

The controllable fan first generates a negative pressure inside the building. At a constant pressure difference between inside and outside, the amount of air transported by the fan is measured. This volume flow is related to the heated building volume and the air change rate is calculated from this. The same procedure is applied with positive pressure and the two calculated air change rates are averaged.

Kind regards

The blower door test tells you that you know that you know nothing.

A blower door test was also conducted at our place. The result was quite decent, 1.43.

The friendly gentleman also showed me exactly where the leaks were. All minor things (e.g., a roller shutter belt outlet) that actually cannot be the cause of major moisture in the house.
We also have an insulated but not converted attic, which however had more the appearance of a stalactite cave.
Because of this and an intuitive premonition, I opened the vapor barrier last weekend and touched inside. Insulation completely soaked. Everywhere.
In the meantime mold formation on some walls, moisture rising from the floor in the utility room at the exterior wall, etc.

So as you can see, a good blower door test result actually says nothing about the building quality.

Hello,

As you can see, a good blower door test result actually says nothing about the quality of construction.

That is partly true because it is only a snapshot; on the other hand, it reveals leakages and thus helps to prevent heating costs from going through the roof.

The construction quality should be monitored by the site manager during the construction process or – which I often suggest here – if there is uncertainty about the expected performance, it should be outsourced externally to a trusted institution/person.

Kind regards

We also have an insulated, but not finished attic, which, however, rather resembled a dripstone cave.

Hi!

Isn't there the rule: Either insulated and heated or uninsulated and (of course) unheated!?

Otherwise: see above.

Best regards, Tomtom.