Marco D'Orazio

Assessment of the effectiveness of cool and green roofs for the mitigation of the Heat Island effect and for the improvement of thermal comfort in Nearly Zero Energy Building

The effectiveness of cool and green roofs to improve thermal comfort could be strongly dependent on the U-value of the roof itself and on the way it has been constructed (ventilated or unventilated, lightweight or massive, etc.). Recent strict limits on the U-values of building envelopes run the risk of reducing the effectiveness of cooling strategies in roofs which could be employed in warm and temperate climates to reduce surface temperatures and consequently to cool internal environment. In this paper, we experimentally analyse some roof systems (a high-albedo membrane and a green roof) compared to traditional ones in a Nearly Zero Energy Building, in order to provide new information concerning their effect on the internal comfort and the air temperatures of the surrounding environment. Experimental results confirm that, while the effectiveness of green and cool roofs for the mitigation of the Urban Heat Island effect is well established, the use of high-albedo materials on roofing systems with very low U-value is of little effectiveness for internal comfort. The green roof is distinguished by its passive cooling ability due to the evapotranspiration phenomena of the vegetation and the storage capacity of the substrate.

In-life prediction of hygrometric behaviour of buildings materials: an application of fractal geometry to the determination of adsorption and suction properties

Abstract In order to describe the hygrometric behaviour of a porous material such as mortar, it is quite common to resort to the diffusion process theory [1] . The equations that are obtained depend on the parameters that linearise the dependence on the gradient of the potential P adopted. Such parameters are not constants, but they greatly depend on the hygroscopic content of humidity inside the material. The hygroscopic content u inside the material depends on the relative humidity of the environment φ in a non-linear way. In short, we indicate the mass flux by m : m=f(u)× grad P, with u=u(φ) . Current research obtains the constitutive link between u and φ by fitting experimental data and there is no theoretical model which can interpret the curves obtained. This paper shows the results of research that, on the basis of fractal geometry, has worked out a mathematical model in order to express the existing link between the water content inside a porous material and the relative humidity of the environment at a given temperature. It shows that the knowledge of the fractal dimension of the pores’ space in a porous medium is enough to work out the suction and adsorption curves characteristic of the medium.

The properties and durability of adobe earth-based masonry blocks

This chapter deals with adobe technique and its materials for making eco-efficient masonry block. In particular, after a brief historical digression, it presents how manufacturing adobe earth-based masonry blocks, their dimensions, which soil is suitable and which stabilization materials are currently used for enhancing their properties. Then the principal mechanical and hygro-thermal properties of adobe blocks, how to determine them and which parameters influence them are provided. In addition, the present methods of testing adobe blocks for durability are presented and practical advice on maintaining or improving them are suggested. Finally, environmental and economic benefits potentially associated with the use of adobe earth-based masonry blocks, including new ways to reuse bulk industrial waste as stabilizers, are provided.

Light Vaults With Frescoes or Stuccoes Strengthened by Glass Fiber-Reinforced Polymer (GFRP) — the Role of the Reinforcement on Intrados Strains: First Experimental Data

In many historical buildings built between the 16th and 19th centuries, light vaults are present made by wooden structures and mats of reeds and plaster carrying frescoes or stuccoes of architectural and historical value on the lower surface. Some of these structures today are in a precarious state of conservation, and a wide program of rehabilitation has started, especially with the use of glass fiber-reinforced polymer (GFRP) bandages on the upper surface. This article experimentally evaluates the effect that GFRP extrados bandages may have on the mechanical behavior of this system. In particular, the main issue is to evaluate how GFRP extrados reinforcement affects the intrados surface strains of the fresco or stucco plaster. Results show that GFRP reinforcement changes the mechanical behavior of the original system. In particular, under a particular load condition, intrados plaster surface — and thus frescoes or stuccoes — may deform more in the reinforced case than in the original case. Thus, looking forward to have more experimental results, GFRP strengthening should be carefully applied to this historic system to avoid frescoes and stuccoes on the intrados surface that could more easily crack for loads that were carried with no fissures before GFRP strengthening.