Installing thermal wrap...insulating our thermal mass!

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Here is the beginning of our thermal wrap, installed on the east wall. Essentially we increase the thermal mass of the tire walls by wrapping them and 3-6 feet of dirt with rigid insulation and poly. During winter, the insulation traps the thermal mass of the tires and dirt and slows down the heat transfer into the rest of the bermed wall, allowing our house to remain warmer longer.

We decided to match the R value of a traditional basement wall, which is 12. This piece of blue styrospan is 2.4 inches thick and is suitable to be buried. Earthship Biotecture recommends doubling the insulation using two, two inch pieces, mostly for added rigidity for backfilling, but also to gain a few extra R values.

We decided to stick with one layer of R12. The original earthship designs did not even include a thermal wrap and as we intend to heat with an auxiliary source, we made the call to stick with a single layer. This picture shows the 2x8 sheet of insulation with the 6 mil poly that will run on the outside of the insulation, into the edge of the drainage system.

Here it is with the second and third piece attached. As each piece is placed, we are leveling them individually and to each other.


















Chris and James extending the insulation along the north wall.


















Here's the insulation (again on the east side), next to the cleanout for the drainage system. The insulation takes a 45 degree turn around the first U (our bedroom!)
















Here it is from the opposite direction with the poly tuck taped to the insulation. Our next layer of poly will overlap by 6 inches. We will take the insulation up to about six feet (as we continue filling tires) and then the rigid insulation will slant inwards to the roof, creating a "ceiling" for the thermal wrap.













Looking east to west. As we turn the corner we add more poly and attach it to the piece already sloping into the drainage system (not shown here).
















We are holding the insulation in place by means of these small wooden "cradles". Made of scrap wood, each is intended to cradle the ends of two adjoining pieces of rigid insulation (thereby necessitating the bare minimum of cradles). Where the insulation turns, we use a dedicated cradle for the end of each piece. We are also tuck taping the joins of the insulation. This also helps keep it aligned. To answer an obvious question: yes we will bury the wooden cradles. Who cares if they degrade down the road. The bermed walls will more than hold the insulation in place over time.


We only set the thermal wrap to about half of the north side of the walls. We need to feed our services through the conduits we placed under the first round of tires and we still need to figure out what some of those are (including the proper gauge wire for renewable electric)! Alvin brought in his amazing excavator to help us with drainage and backfilling, so we had him backfill oh-so-carefully around each side of our thermal wrap. He has a delicate hand on the controls; it's the hours he's spent with kids and grandkids, playing Nintendo since the 80s! Here's a video of him doing the backfilling. We sent him away until Monday when we hope to have the thermal wrap set on the remainder of the building for backfilling.




Tomorrow we lose James. He's been here just over a week, having made his way across Canada from Newfoundland with the intention of settling in Victoria. Before getting himself set up there and looking for work, he decided to make a stop and help us with our home. He's been taking carpentry and has lots of insightful questions for Chris about the construction. At first he worked only with us, before Sean and Anna made their way back from Victoria to rejoin us. They brought Josh last Sunday and the four of them have worked in concert since then. Josh is a story teller and always sees the humour in situations. Despite having very little construction experience, he has been digging in with fervor since arriving. He's headed to Calgary tomorrow for a wedding and then will return to Victoria to his work. Chris and I hope both James and Josh will come back again and help with another aspect of our project. Together with Sean and Anna I will always think of this group of 20-somethings as the "Fab Four", they are relentless workers and were the first ones to sign on to the Darfield Earthship!

We are looking forward to welcoming other volunteers in the coming weeks!