NSD uses 3/4″ thick plywood for the exterior panels instead of OSB (orientated strand board- which is often considered the better environmental choice). However, in our 35 years of dome building, we have discovered that OSB will deteriorate when exposed to moisture. Plywood does not lose its structural strength when it gets wet. In fact, the plywood will dry out and OSB will not. So for moist climates, heavy rains, snow, hurricanes etc. plywood is the better choice.Also, OSB uses substantially more glue and contains more formaldehyde than plywood. The plywood NSD uses has a southern yellow pine veneer which does not come from old growth forests but, instead from sustainably managed forests. By relying on the long term structural ability of plywood, we are able to eliminate bracing within the triangle of the dome. This saves the use of approximately 3,000 lineal feet of 2″ x 6″ lumber in an average sized dome.