After taping of the last few areas around the window, the BDT could start. We soon realized that the result could not be bad, because the ventilator turned fairly slowly. So we created a low pressure and started checking out the envelope. There was a big disappointment when all the window hinges leaked. I usually take tight windows for granted... after calling the producer, we found the problem: They had forgotten to place small elastic strips over the hinges (the hinges are of a special construction) This can be done later as well, but no such material was available.
We then decided to go forward anyway. The measurement showed at low pressure 0.12 and at high pressure 0.00. The hinges nicely sealed up with the overpressure. With the elastic strips in the hinges I am certain we would have gotten the same 0.00 measurement with low pressure as well...:-)
After a good cheer at the builders the Testers wrapped up their equipment and left. i had some other customer to attend to but returned to the building site 3 hours later. To my big surprise the Testers were back...
They had called the mother company and they said a 0.00 measurement could not be analyzed - the data would display an error... (so much about software!) So they had to make some measurement, even if it meant to punch a hole in the airtight layer.
So we rigged up the equipment again, and now the measurement showed 0.12 at low pressure but 0,20 at over pressure!!! No I said, this can't be right, let's do it again. 3rd test 0.24 at low pressure and 0.20 at over pressure. Now we were really looking for what was wrong - some tape getting loose because of the over pressure? In the end we found the villain: A balloon tightening the oven air inlet had lost pressure and a big leak was fairly evident.
4th test: only overpressure tested, and again 0.00. So definitely the balloon - big relief!
5th test: A building pencil punched in on the side of the baloon, flat side - hoping a small opening will show a measurement 0.05... but again, only 0.00... (so much about precision measuring!)
6th test: The same pencil but standing high side - definitely a bigger gap but still just measuring 0.00...
Now we were really getting annoyed, we all wanted to leave for home, so I opened a 40mm drainage - we had to get some kind of measure. This time at overpressure we got 0.17. For a small house with only 349m3 for the BDT is a good proof that we had a really tight building!
Now we are waiting for the company to analyze the data and issue the BDT certificate - and I wonder what results they will use...?
So, don't make a house too tight, the BDT is a pain to do...!
Here are some pictures from the building site and especially the airtight details:
Because we have a nice massive wooden ceiling for the 2nd floor, which we did not want to spoil, we are taking electricity and ventilation ducts OUT and then back IN trough the Airtight layer. The ducts will be covered with 60cm blown cellulose, so that should not be a problem. I was not sure we would get good airtighness, but the builders did a good job!