Significant delay of runoff's center of mass and lowering of peak runoff was measured in all types of green roof as an average over monthly periods. In bigger events the lowering and delay was insignificant and therefor it should not be assumed that green roofs can decrease the load on stormwater systems in heavy rain events.
Marktæk seinkun á massamiðju afrennslis og lækkun afrennslistoppa mældist í öllum gróðurþökunum en varlegt er að treysta á að gróðurþök minnki álag á frárennslikerfin þegar álagið er mest, þ.e.a.s. þegar úrkomuatburðir eru mjög stórir og tíðir.