Wednesday 21 September was a big day as we finally started assembling Ecococon straw/ timber panels. One of the main benefits is the speed of construction: it took us only three days to assemble all the external walls, two internal load bearing walls and the main glulam ridge beam. It was helpful that all panels were referenced to colour coded Sketchup renders – this was really easy to follow on site, just like a giant LEGO set. Each panel has a couple of holes at top & bottom, and wooden dowels are used to locate the adjacent panels accurately (like IKEA shelves) before they are screwed together. Unlike ‘traditional’ timber frame, Ecococon system has the airtightness layer on the outside face of the wall, covered with further layer of woodfibre insulation and, in our case, timber rainscreen cladding. Airtightness layer is a vapour open membrane with Sd value of less than 0.2m – this is important in terms of moisture control in the wall assembly. Airtightness membrane is taped to DPM at low level, which in turn is sealed to concrete slab under the sole plates, ensuring no unwanted air leakage. It is critical to keep the straw panels dry – we had a few ‘moments’ during Day 1 when sudden showers forced us to stop assembly and quickly cover the panels up with plastic sheeting.
It is the first time this system has been used in UK and we didn’t quite know what to expect in terms of accuracy of panels. We needn’t have worried – the walls fitted perfectly onto the timber sole plates, even over the longest 17m walls the tolerances were measured in milimeters rather than inches. Very impressive. It was great to have Bjørn Kierulf from the Slovakian architectural studio Createrra available to answer some technical questions during the first day – Bjørn was originally the one who introduced me to the Ecococon system several years ago (thanks!) and I have wanted to find use for it ever since.
Hopefully we will be able to fully wrap the walls up and install the roof over the next week or so, fingers crossed for some dry weather!