Completing the Thermal Envelope

All the passive houses that we have seen in New Zealand have the thermal envelope following a continuous line from slab to walls to ceiling to walls and back to slab again. The Theca approach is a little different and instead of following the ceiling it follows the roofline, as illustrated in my very crude diagram below:

Our design was such that Glenn at Theca made good use of his school-days trigonometry to work out the precise angles and side lengths so that the panels fitted perfectly together at the apex and joins in the roof. It would have been much simpler if we had chosen a single orientation roof with a gable at each end, but instead we have four different roof heights, hips and valleys, and in particular the two parts of the roof circled on the diagram below which presented significant complexity in creating a perfectly interlocking structure.

The flatbed truck arrived with the panels for the roof and one by one they were hoisted into place. At each junction, as with the walls, the builders took time to ensure the Intello membrane (for airtightness) was correctly overlapped and taped down.

The roof panels are 300mm thick. Extra Intello wrap can be seen at the far end of this panel ready for overlap with the next panel.


It is quite a complex task to ensure that each and every panel has Intello wrap that overlaps the next and that there are no tiny pinholes where the overlapping is not so good and which cause problems for airtightness. The Ethos team worked very hard to pre-plan these junctions and then to tape and double tape every single one of them.

My next post will cover the technical side of these panels and why they are so special.

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