details as used for Harnett Dome
The Harnett Dome is a 24m diameter (80ft) 3v oblate ellipsoidal icosahedron, squashed in the Golden Ratio of 0.618:1.000. The largest size of timber used was 100x50 (2"x4").
Window details and window pictures
The materials used in the above schematic sections are butylnitrile rubber (red), plywood (orange), glass (blue), framing (light green), finishing timbers (brown) and shingles (dark green). Yellow represents the wedge fillet and pink for Batts. The glass is embedded in silicone sealant, which adheres well to the Butylnitrile rubber, especially if the correct primers are used. Check with manufacturers for specifications.
Opening windows should only be point down triangles. They to not need to open far to give excellent ventilation. The Butylnitrile rubber (in NZ we have two brands, Dunlop Butynol and Skellerup Butylclad) should be fixed by registered applicators to ensure the 20year guarantee which goes with this product.
1. Timber shingles -- imported Western Red Cedar shingles with Butylrubber or Bituthene flashings.
2. Asphalt Shingles -- available in New Zealand and able to be imported from the U.S.A. or Canada.
3. Butyl rubber either as a sheet or as shingles, glued to the plywood skin. Excellent for lining gutters which have been formed out of plywood and timber.
4. Sprayed polyurethane foam over plywood and protected from ultra-vlolet by an over-spray of Hypalon or Monolar. Very good thermal and acoustic insulation properties are a benefit.
5. Or, for an area where building codes will allow it, discarded aluminium offset printing plates applied over the bituthene product which has adhesive both sides.You need a sympathetic building inspector for this approach -- it works brilliantly but you need to overcome the inertia of the status quo.
6. A fibreglass system very carefully thought out and expertly applied, coated with a polyurethane reaction lacquer in any colour you like as long as it's white.
Pictured below are some different ways of doing a zenith ventilator.
Clockwise from the left: Vent/cupola being lowered into place on Tony Whitton's dome at Havelock North, NZ; Vent/Cupola using a single blade louvre on Mark Verhoeven's dome in Umina, NSW, Australia; Inside view of Mark's vent.