An archaeological and historical exploration of the origins of green roofs

- Archaeological and historical studies from diverse lands can trace green roof origin.
- Extreme Arctic climate and limited resource challenge effective weather-proof shelter.
- Earth daubed on primitive shelter colonized by plants incurs spontaneous meadow roof.
- Portable sod pieces transferred from nature to rooftop signifies intentional sod roof.
- 18 ecosystem-utilitarian services of sod roofs are comparable to modern green roof.

The origin of green roof could be interpreted as old wine in new bottle and traced to antiquity. Archaeological and historical records and contemporary geographical-ecological assessments provide ample evidence to interpret the birth and progressive evolution of the cultural heritage. Studies in different places find early shelters using different natural materials. Humans living in harsh climates need particularly effective weather-proof enclosures to survive. The Arctic region with natural resource deprivation furnished the cradle for green roof initiation and refinement. The versatile and rather ubiquitous earth, widely used since Neolithic times to build dwellings, offered learning opportunities regarding properties and applications. The primitive flimsy conical shelters were sealed by earth daubing, permitting nature's seed rain to establish a vegetative cover to form the spontaneous meadow roof as green roof precursor. Subsequent progression to the house form, separating walls from roofs, required innovations to enhance weather-proofing and durability. Cutting from natural meadows mat-like sods with soil bound by dense fibrous roots into portable strips for roofing was better than plastering. Tantamount to transferring the sod ecosystem en masse from nature to roof, it permitted instant vegetation establishment and bypassed the erosion-vulnerable bare-earth stage. The invention denoted birth of the intentional sod roof. The materials and construction methods of the traditional multiple-layered sod roof are explained with the help of preserved technology. Employing research findings, eighteen hypothesized ecosystem services of sod roofs are identified and explained vis-à-vis modern counterparts.