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Water·validated

Rainwater Harvesting

Why it matters

Municipal water arrives through kilometres of pipe, pushed by pumps, drawn from rivers and aquifers that climate change is making less reliable every decade. Meanwhile the cleanest raw water most sites will ever see falls straight onto the roof. Rain from a clean metal roof takes the shortest path of any water source: sky to metal to tank. The clean surface and the short path leave it almost clear from the start — closer to drinking quality than any pond, stream, or shallow well. Harvesting it turns a building from a consumer at the end of a fragile network into a source, eases the pressure on groundwater, and keeps working through blackouts and everything blackouts stand for. And the resource itself is as future-proof as physics gets: whatever else changes about how we live and build, rain will keep falling on roofs.

Role in 001's holistic picture

Harvesting is the intake of the whole water organism, the generation layer of our Water Innovation Model: roof to storage, storage to treatment, treatment to taps, overflow to the pond and the land. It is also one of the four jobs a roof does at once in our designs — shelter, energy, terrace, catchment (green and usable roofs).

In the world

Everything starts with the catchment surface, and there is one rule: the material must stay stable and inert to the water it collects. A clean metal roof qualifies for drinking-grade collection; old asbestos-cement roofing — a surface that weathers and releases fibres into the runoff — disqualifies outright. The yield is simple arithmetic — annual rainfall × area × runoff coefficient; in a climate with ~800 mm of rain a year, a square metre of metal roof yields roughly 0.64 m³. Where that discipline meets a whole society, the roof stops being a supplement and becomes the waterworks. On Bermuda, catching rain is the law: by a rule centuries old, nearly every building must harvest its own. The island's signature white stepped limestone roofs channel rainfall down into an underground cistern beneath the house, and rooftop rain supplies 50 to 70 percent of household freshwater on an island with no rivers and no lakes (per Enter Bermuda). The white lime coating even helps sterilize the runoff in the sun. An entire jurisdiction proving, for four hundred years, that a roof can be the primary supply.

Brazil proved the same thing as a social programme: between 2003 and 2016, its One Million Cisterns programme equipped the semi-arid Northeast with roughly 1.2 million household roof-catchment cisterns of 16,000 litres each, reaching about 4.5 million people. Families received materials and training and built the cisterns themselves. Its documented outcomes — less childhood diarrhea, hours of daily water-hauling eliminated — are what rooftop harvesting looks like once it is engineered and adopted in earnest.

How 001 engages with it

Rainwater harvesting runs in production at two of our sites, and we have lab data behind it. At Tepla Gora, roof collection feeds the community's water backbone, and a laboratory comparison of harvested rainwater against the local ground-based sources came back in rainwater's favour — excellent quality, validating the harvesting-first approach. Our published water strategy inventoried the site's roofs: the existing 300 m², fully connected, yields about 192 m³ a year. With Unity Hub and the planned tiny houses, the collection surface approaches 800 m² — roughly 512 m³ a year, enough to cover the site's 20-person summer baseline with margin. The strategy's central finding points one link down the chain: what the site lacks is storage. Current priorities on the ground are replacing the remaining asbestos roofs with metal, connecting them into the collection system, and installing first flush diverters.

House 001 harvests from its terraces as part of its push toward year-round water autonomy — and is upgrading its roof right now, after a series of failed attempts to treat organic acids out of the harvested water proved the hard way that quality is decided at the surface. The Hlibivka design runs entirely on rain: 110 m² of catchment serving a fully autonomous water loop.

Maturity: validated. Operating at two sites; harvested-water quality verified by laboratory comparison at Tepla Gora.

Further reading