Airtightness nerdery and yet another disaster. 

Today we achieved an airtightness value of 2.54. This means that, under the 50 Pascales pressure applied during the test, the house exchanges 2.54 volumes of air with the outside world every hour. This might seem like a lot, but when you compare that with current building standards, which is 10, this is very respectable indeed.

It’s not passive house standard which is 0.6, but I’m feeling happy, especially given the state in which Scotframe’s builder left the house after the panel erection. And it’s down to Jamie who has also been fitting the Mechanical Ventilation Heat Recovery system. This is a system of pipes taking hot humid air from areas like kitchens and bathrooms, exchanging the heat with that in new air coming into the house. And it keeps hot air from escaping from the house while maintaining the air quality.

He did a great job. And it’s made me almost forget the horror I experienced when I arrived to see the first stage of the MVHR work to find that three 100mm holes had been drilled through the substantial beam that is holding up the whole roof. These holes had the MVHR ventilation pipes passing through them, instead of (as was planned) underneath the beam within a false ceiling in the utility/plant room.

IMG_0173
The swiss-cheese beam is amazingly that same beam which was missing the vital and substantial piece of metalwork when it was first erected (see previous blog). So I was NOT happy.  And I as rather flabbergasted it could have even happened, as I had spent an hour on the phone the previous evening talking through every thing with Jamie. And the design for the lowered ceiling came from Paul Heat recovery, who designed the MVHR system for the house, rather than from my architects. And they had contracted Jamie to install it.
Jamie had been anxious about drilling a row of 100mm holes through the OSB I-joists keeping the floor cassettes rigid. He’d asked me to go back to Scotframe to confirm that would be ok. So you can imagine my surprise that he had drilled three 100mm holes through the middle of the main wooden supporting beam without checking. (It would have taken quite some time to do that – some thinking time to consider the engineering implications….)
Jamie was there that evening so we chatted through his plan to go back to Scotframe engineers to seek a solution. In the end he did a great job sorting it all out with little hassle to me. The Scotframe engineers came up with a solution which was then OK-ed by my engineer involving bolts coming through the beam top and bottom and holding all the laminations of the wooden beam together.  It’s yet another thing to add to the growing resource of dinner-party anecdotes. II’m still standing (as Elton John once said)

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