Green roofs (GR) are roof-hoisted structure to make the roof partially or completely covered with vegetation. This study was done to test the feasibility and the technical applicability of GR with a novel capillary siphoning irrigation system in Oman, to investigate whether the designed siphon-pot coolers are economically efficient at the existing electricity and water prices in Oman and to report on laboratory tests with siphoned GR modules as hydrological flood buffers. In this study, a mathematical model, was used to describe the capillary siphoning by some of the capillary rise equations. The green roof experiments with roof-mounted siphons were conducted in January 2009 - June 2009 on the roof of the College of Agricultural and Marine Sciences (CAMS) building at Sultan Qaboos University (SQU). The pots were placed in that open area. Water was diverted to the pots from plastic containers through siphons made of used T-shirts which were rolled and filled with soil. Siphoning flow rate, moisture content in the pots, hydrological parameters and the development of the plants were measured and monitored. The results showed that siphons are feasible and technically suitable for irrigation on Omani roofs. Also, the results indicated that siphons convey water to the pots continuously at of 0.35 to 0.65 L per day per siphon per day. GR proved to have high thermal insulation efficiency. This is because the soil pots reduce the heat fluxes and improve the cooling conditions under their base. Under existing water and electricity prices the suggested GR irrigation-cooling system is economically viable. The least heat-resistant plants (e.g., tomato) planted in January developed well and perished in May. Most heat-tolerant plants (e.g., petunia) şurvived until the end of the experiments. The pot soil profile exhibited good buffer capacity to intercept and retain typical rain and it could utilized in urban water management measures for flood mitigation. The Washburn equation would be appropriate for the interpretation of capillary penetration rates for most systems of practical interest. The Szekely equation is applicable at any stage but gives realistic predictions at very early stages of penetration. If the pore structure characteristics of porous media are not taken into account the applicability of the Washburn or Szekely theories is limited. Temperature has a certain influence on the water, soil and siphons properties. This influence can be examined through the dependence of each particular parameter (e.g. viscosity, contact angle, density, etc) on temperature however to understand the combined effect further studies are necessary