**Experimental Evaluation and Numerical Simulation of the Thermal Performance of a Green Roof**

#### **Claudia Guattari, Luca Evangelisti, Francesco Asdrubali \* and Roberto De Lieto Vollaro**

Department of Engineering, Roma TRE University, Via Vito Volterra 62, 00146 Rome, Italy; claudia.guattari@uniroma3.it (C.G.); luca.evangelisti@uniroma3.it (L.E.); roberto.delietovollaro@uniroma3.it(R.D.L.V.)

 **\***Correspondence:francesco.asdrubali@uniroma3.it

Received: 5 February 2020; Accepted: 28 February 2020; Published: 4 March 2020

**Abstract:** In the building sector, both passive and active systems are essential for achieving a high-energy performance. Considering passive solutions, green roofs represent a sustainable answer, allowing buildings to reach energy savings, and also reducing the collateral effect of the Urban Heat Island (UHI) phenomenon. In this study, a roof-lawn system was investigated by means of an extended measurement campaign, monitoring the heat transfer across the roof. Heat-flow meters and air- and surface-temperature probes were applied in a real building, in order to compare the performance of the roof-lawn system with a conventional roof. This experimental approach was followed to quantify the different thermal behaviors of the building components. Moreover, an equivalent thermal model of the roof-lawn system was studied, in order to obtain the equivalent thermal properties of the roof, useful for setting building models for yearly energy simulations. The roof-lawn system revealed its advantages, showing a higher thermal inertia with no overheating in summertime and a lower thermal transmittance with energy savings in wintertime, and, consequently, better indoor conditions for the occupants of the building.

**Keywords:** green roof; experimental investigation; thermal performance; measurements; simulations
