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The surface temperature of the sub-roof beneath the ventilation layer and the tiles is one of the most important factors for the hygrothermal performance of pitched roofs. The air layer between tiles and sub-roof and the air exchange with the outdoor air influence the heat transfer and therefore affect the moisture level inside the roof construction. The paper aims to discuss these issues.

This paper provides the results of a research project performed at Fraunhofer-Institute for Building Physics, based on field test results. The investigations analyze the thermal behavior of different vented and ventilated roof constructions.

It was found that for a detailed model with roof cladding and ventilated air layer normally too many parameters are unknown. For that reason a simplified approach was set up, especially to consider the radiation exchange between the tiles and the underlay as well as the effects of the ventilation.

Now, effective surface transfer parameters can substitute both cladding and air layer in the simulation, while the approach still provides a high accordance with the measured values. The paper provides characteristic values for different roofing situations to simulate ventilated roofs by means of hygrothermal simulation in a simplified way.

Understanding the dynamic hygrothermal behavior of building elements is very important to ensure the optimal performance of buildings. The Laboratory for Quality Control in Buildings of the Basque Government tested a flat roof designed by a construction company that developed a building to be constructed using prefabricated modules. This is a five to eight floor building with ventilated façade and a flat roof covered by gravel with the possibility of changing it to a green cover. The paper aims to discuss this issue.

The interest of this research was threefold. The first objective was to accurately test, under real dynamic weather conditions, the roof design in a PASLINK test cell to obtain the U-value and the thermal capacitance of the different roof layers, and of the roof as a whole, through the precise calibration of resistance-capacitance mathematical models of the roof. Based on the parameters and experimental information of these calibrated models, a second goal was to calibrate and validate a Wufi model of the roof.

This second calibrated model was then used to simulate the dynamic hygrothermal behavior of the roof, obtaining the roof’s hourly thermal demand per square meter for a whole year in different locations considered in the Spanish Building Code. These simulations also permitted the authors to study the risk of condensation and mold growth of the tested component under different climatic conditions.

The successful combination of the PASLINK method to calibrate the Wufi hygrothermal model is the main novelty of this research.

The purpose of this paper is to present the results of an experimental study aimed at analysing the effect of the roof tile air permeability on the thermal performances of ventilation ducts in the roof. The main reason underlying this study is the fact that the theoretical reference assumed for the manufacture and sizing of ventilation ducts (the accepted theory on roof ventilation) is clearly limited when applied to ducts which are not perfectly airtight (Hens) and results in an oversizing of the ventilation ducts.

A section of roof is built, covered with different tiles and environmental and meteorological data collected. The data are analysed statistically.

The results show that the permeability of the layer of tiles determines heat losses which are in addition to those connected with the stack effect in a perfectly airtight duct with the same features. The results also confirm the correlation which has already been demonstrated between the geometric ratio of the length of the duct divided by its height and the amount of heat dissipated by the roof (Sandberg and Moshfeg).

This study analyses the performance of the roofs only during the summer season. The research is therefore continuing with a long‐term (one year) analysis of the roofs characterised by a high level of roof tile permeability so as to understand the consequences that the presence of a ventilation duct in systems with air permeable roofing may have on the thermal efficiency of the roof.

IN today's battle for greater productivity management is cast in a cardinal role. Like a military commander, it has first to recognize the nature and purpose of the opponent and then formulate the best strategy to encompass his defeat. One element in that is to know the strength and quality of the available resources, ways in which to improve both, and then deploy them to the best advantage.

The timber frame is not a new form of building construction. Until the middle of the 18th century timber was the basic structural material used in this country. The method was gradually superseded by the use of brick and stone. This was caused by a decline in the availability of home grown timber and the improved social status of owning a brick built property. At the present time it is anticipated that half of the annual production of houses will be of timber frame by the end of next year.