LIFE CYCLE ASSESSMENTS OF WHITE FLAT AND RED OR WHITE PITCHED ROOFS FOR RESIDENTIAL BUILDINGS IN ISRAEL

Historically,white flat roofs have been used in Israel due to the intense solar radiation and long,hot,rainless summers.However,red pitched roofs have also been frequently used for aesthetic reasons.It has been recently observed that red pitched roofs have been recolored white by homeowners.The goal of this study was to compare the life cycle assessments(LCAs)of white flat roofs versus red or white pitched roofs through their production(P),operational energy(OE),and maintenance to disposal(MtoD)stages.EnergyPlus software was used to evaluate the OE stage.The ReCiPe method was used to evaluate the environmental damages in all the stages.A two-stage nested ANOVA was used to determine the significant differences between the ReCiPe result of a white flat roof and the ReCiPe result of a red/white pitched roof.It was found that(i)selection of the best roof technology(flat or pitched)requires consideration of the LCA,including the P,OE,and MtoD stages;(ii)the white(flat and pitched)roof was the best technology,while the red pitched roof was the worst technology;and(iii)the combination of the ReCiPe endpoint hierarchical six methodological options method with two-stage nested hierarchical mixed ANOVA is the best approach for assessing the differences related to the LCAs of roof technologies.

Influence of Local Weather Conditions on Ventilation ofa Pitched Wooden Roof

This paper investigates the influence of temperature and wind conditions on ventilation of the air cavity beneath the roofing in a full-scale pitched wooden roof construction.The potential for condensation in the air cavity is studied.The relevant roof construction is equipped with 81 thermocouples and four air velocity measurement devices.A weather station at the site records outdoor temperature and wind conditions.Five periods between 2016 and 2018 are investigated.The findings show distinct periods of below-ambient temperature and positive condensation potential in the ventilated air cavity of the roof.A relation between low wind speed and positive condensation potential is shown.Difference in size of periods with below-ambient temperature and periods with positive condensation potential implies that the materials in the roof regulate the humidity in the air cavity.Large negative peaks in the condensation potential indicate dry-out of the construction.

Wind Pressures on Structures by Proper Orthogonal Decomposition

Proper orthogonal decomposition （POD） is an effective statistical technique for data reduction and feature extraction of the random field including the wind field. This paper introduces the theory of the POD and illustrates engineering of structures. Using the POD technique, it is shown that wind pressure data can be accurately reconstructed with a limited number of modes using the wind pressure data from wind tunnel test. Comparing the reconstructed values by POD with the original measured values from the wind tunnel test both in the time and frequency domains, it is concluded that the proper orthogonal decomposition（POD） is an efficient and practical technique for deriving the random wind pressure field from limited known data as shown in the pitched roof example in this paper.