Rod Williams (@rodwill08584685 in twitter) has published some thermal analysis on the hexayurt. The following is his tweets in chronological order, and copied without real understanding, so use at your own risk.
- A growing number of UK builders are adopting the PassivHaus standard - space heating reduction by 90%.
- A PassivHaus grade hexayurt would require 150 kWh per year to stay warm (constant 20 degrees in winter), 15 l of oil or 40 kg of wood.
- For East Anglia, a PH Hexayurt with a south 2x1m window and 3 residents would require 200mm of PIR including on ground.
- The window is triple glazed, the airtightness would need to be very good plus a very small MVHR is required. All doable.
- QuadDome, SE UK, 4 x 1x2m window (1w, 1e, 2south), with shading to minimise summer overheating, 4 people, 130mm celotex = PH.
- Same but 5 people, 115mm = PH.
- Same QuadDome with 5 people, space heating increased from 15kWh/m2 per annum to 400 with 11mm ply and 90kWh/m2.a with 30mm PIR.
- The inhabitants would need to burn 4000kg of wood to keep the ply version warm.
- 40kg for PH hexayurt, 150kg for PH QD, 4000kg for 11mm ply QD, Insulation big contribution then airtightness/mvhr halves again.
So, we need to add references, understanding, software, etc. But it does look like insulation sort of pays for itself fast, right? How do we get that insulation? There's the Hexayurt_materials page.