Friday, September 21, 2012

Air tightening the extension

20 Sept 2012: [Extension]  The weather has got cold enough to need the heating on and we have got the structure up just in time! Now it's time to make it airtight so that previous heat is retained.
John A Stevens start the day by delivering enough sand and cement to lay the floor screed in the extension - 300 litres of sand cement which I calculate to be 600 kilos. The crane on "Stevo's" truck can reach almost anywhere. I'm sure it would be fun (and a little scary) to operate it, but these guys do it many times a day and have long got over the novelty of it.
Adam and Ken are returning soon and this is all they need, they have a mixer and a barrow!The extension is held to the wall with aluminium angle and wall bolts, but now that is it safely on its feet, the angles can be taken off. The gap is about 10mm all the way up, and you can clearly see daylight through it. This must be filled and expanding foam is the method.
The panels are as close to the wall as we could get them - or so we thought, until I saw this 10mm gap - daylight shining through. There would be no point in having good insulation if benefits are cancelled by high unwanted air draughts. This is the first time I have used foam for a long while, and one has to get used to it. My first efforts are to over pump, and I use up too much of the foam in the first wide gap, and when it has had time, it quietly expands and becomes a swollen monster that I have to cut off and put in the skip (below is my effort to push some of it back into the gap. After a few hours, the foam is set, and one can carve away the excess with a decorator's scraping tool.
Second time of trying, I get it absolutely right, but in the nick of time. As the last droplets go in, the spray can is empty because I wasted too much on the first seam. Not that we are also taping the nylon bolt heads and the seams between the timber panels. When I stand on a ladder high in the extension, I can feel some air slipping between the panels - so I am relentlessly hunting down every possible air infiltration route with metallic tape. 

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