Mike’s team have started on the corrugated tin roof installation, this is quite a delicate operation as we are leaving the underside of tin exposed around the edges.
We also started installing the lovely Smartwin windows. It took us nearly all morning to install the first one as there was a lot to go through – pre-taping for airtightness, fixing (using adjustable Essve screws), stuffing the gaps with sheepwool insulation, closing the external reveals with additional woodfibre insulation and finally external taping for windtightness. Eventually, the external timber reveals will fully cover the frames.
During the ‘unwrapping’ of timber/ straw panels we discovered that one piece got wet during the installation. We had a membrane going over this window with a taped joint, unfortunately there must have been a gap in the joint and water leaked down to the cill panel. Water and straw is not a happy combination, so we’ve put some fans on the panel trying to dry it out, but after a couple of weeks we were still getting new green shoots appearing. As we had to prepare the window opening for window installation, I decided to remove the wet straw from this panel. The gap will later be filled with Warmcel and capped off with woodfibre board so we can continue the clay plaster across. This incident was a reminder that straw is an organic material which reacts to humidity, but when this issue arises, it can be dealt with relatively easily.
This week’s weather has been kind enough to allow us install woodfibre boards on top of roof I-beams, and wrap the boards with windtightness membrane, held down by timber counterbattens. Larger timber battens will provide support for the corrugated metal roof. It’s good to have two layers of protection above the straw panels.
We have been tweaking the design of junctions between timber cladding and roof with Mike, and decided that it’s best to finish off installation of external woodfibre boards to walls and insect mesh to close off vented cavities before the corrugated roof goes on.
On Saturday Joyce & me finished off sealing the last charred cedar cladding boards, which was very satisfying to see. It’s now all stacked and ready to use.
There was a bit of excitement when a herd of escapee cows passed our site – I wonder if they wanted to have a peek at this straw filled passivhaus? 😉
As if the week wasn’t quite packed enough with action, we took delivery of our Smartwin passivhaus windows & doors on Friday. It’s been a bit of a logistical conundrum – due to recent wet weather the artic lorry could not park along the verge near the site, so we offloaded half the windows in a layby and the big sliding doors & main antrance door at the nearest industrial estate with a help of forklift truck. Those triple glazed sliding doors are pretty hefty at 300+ kg!
It was very satisfying to see the sliding door put in place only 9 days after starting the timber frame. All the planning, coordination and detailed design over the past few months has definitely paid off!
Hopefully next week is going to be dry enough to allow us install woodfibre boards on roof and provide the much needed protection for the straw panels.
Things have been moving at a pace on site. Wet weather at the beginning of the week slowed down the progress somewhat, but come mid week, Mike’s team (Mike, Henry, Bisto, Petras, Liam and part time me) got on to taping all the airtightness membranes (particularly around tricky corners), installed timber wall plates and started with the roof installation. It was critical to do all the taping for airtightness before wall plates were in place, otherwise access would be impossible. The strategy is for airtightness layer to switch from outside (walls) to inside (roof), and this swap happens on top of straw timber panels, below wallplates. Unlike walls, which were pre-fabricated as insulated panels, roof is installed as individual timber I-beams, spanning between glulam wallplates and central glulam ridge beam. These 400mm deep I-beams were pre-cut and reinforced in the Ecococon factory, hugely speeding up the installation process on site. Later on they will be fully insulated with blown cellulose insulation. The south canopy overhang is formed with a combination of Douglas Fir rafters cantilevered over wall plates and smaller, 200mm deep I-beams. A team of four of us had all the beams tacked into place in about two hours and Mike’s apprentice Liam topped the house just after lunch on Thursday. This made a huge transformation to the shell – we can really start to appreciate the feel of internal spaces now.