Revisão integrativa do uso da madeira através do sistema construtivo wood frame no Brasil

O wood frame se apresenta um grande aliado junto à construção civil, suas vantagens em relação à rapidez e eficiência nas construções, além de todos os requisitos sustentáveis, vem conquistando ainda mais quem busca meios alternativos de construção. Com isso, o objetivo deste estudo, foi descrever o wood frame considerando seus aspectos sustentáveis, sua técnica construtiva, a utilização no Brasil, bem como as vantagens e desvantagens, além dos comparativos em relação a alvenaria convencional. Para a realização deste trabalho foi realizada como metodologia revisão de literatura integrativa. Foram encontrados poucos artigos que abordavam sobre o wood frame de uma forma mais completa e agregada. Assim, a fim de trazer um estudo mais amplo, considerando pontos de grande relevância do wood frame, foram reunidas 56 referências para embasar este estudo. Contribuindo para a apresentação de como a sustentabilidade precisa estar presente nas construções, evidências do wood frame no Brasil, como também, a importância da utilização deste método para as questões sociais, ambientais e econômicas. Empenhando-se para popularização e aceitação desta técnica construtiva, esclarecendo sua efetividade e confiabilidade como material estrutural para as edificações. Concluindo que o Brasil possui grande vantagem na implantação do wood frame, considerando-se que este sistema se apresenta superior nos conceitos sustentáveis.

Development of moisture reference years for assessing long-term mould growth risk of wood-frame building envelopes

A moisture reference year (MRY) is generally used to assess the durability, or long-term performance of building envelopes within a long climatological time period, e.g. a 31 year timeframe. The intent of this paper is to develop a set of moisture reference years that can be used to assess risk to the formation of mould growth in wood-frame buildings over the long-term. The set of moisture reference years have been developed based on 15 realizations of 31-year climate data. Replicated Latin Hypercube Sampling is applied to select 15 sub-realizations with 7 representative years having different levels of moisture index (MI) from each realization. Thereafter, hygrothermal simulations are performed for a brick veneer clad wood-frame wall assembly using the 15 sub-realizations; that sub-realization which produces the highest value of maximum mould growth index over 7-year period is selected as the MRY. The selection process is then implemented for all 15 realizations of the 31-years of data sets, from which 15 sets of 7-year long MRYs are selected to represent the original 15 realizations. It is shown that the 15 sets of 7-year long MRYs can produce the same value of maximum mould growth index as well as the uncertainty as compared to the original 15 realizations having a 31-year climate data set.

Pitched unventilated wood frame roof with smart vapour barrier – field measurements

Unventilated wood-frame roofs may provide smaller roof thickness and less material use compared to conventional unventilated roofs with all the thermal insulation above the load bearing structure. Unventilated roofs are, however, normally built without wooden materials between the vapour barrier and roof membrane due to moisture safety. Field measurements on the pitched unventilated wood-frame roof of an office building in Norway is performed to demonstrate and document the performance of this type of roof construction. Through monitoring of moisture and temperature, the study aims to contribute to verification of simulations and laboratory measurements showing that unventilated wood-frame roofs may be built with wooden materials if a smart vapour barrier is used. The results show moisture levels below 15 weight-% on the warm side of the rafters throughout the first 15 months of measurements. On the cold side of the rafters, the moisture content increased during winter due to built-in moisture in the construction and reached levels close to 25 weight-%. The moisture content decreased to around 15 weight-% when summer arrived, which shows an expected redistribution of moisture and indicates possible drying of the construction. The measurements underline the importance of limiting built-in moisture to reduce the risk of mould growth, but the study also implies that for some given premises an unventilated pitched wood-frame roof may have acceptable moisture risk.

Identifying the critical orientation of wood-frame walls in assessing moisture risks using hygrothermal simulation

Hygrothermal simulations can be used as a reliable tool in analysing moisture performance. For an efficient analysis, it is important to appropriately select the wall orientation in the simulations. ASHRAE 160 recommends to using orientation with highest amount of annual wind-driven rain (WDR) and the orientation with the least annual solar radiation. The objective of this work was to identify the orientation which leads to the worst moisture performance of different wall assemblies under historical climate in different Canadian cities. Four cardinal orientations (North, East, South, and West) and orientation receiving the highest amount of annual WDR (Default) were tested in this study. The simulations were carried out assuming three scenarios of moisture loads for four different wood-frame (2×6 wood stud) wall systems that differ by their claddings: brick, fibreboard, stucco, and vinyl. With an assumption of no WDR, north facing wall always leads to the worst moisture performance. In the presence of WDR, with and without water source, default orientation leads to the worst moisture performance with few exceptions. As default orientation was based on total sum of WDR, it sometimes may not lead to worst performance and hence hourly distribution of WDR should be taken into consideration.

Effects of climate change on the moisture performance and durability of brick veneer walls of wood frame construction in Canada

The objective of this study was to assess the potential effects of climate change on the moisture performance and durability of red matt clay brick veneer walls of wood frame construction on the basis of results derived from hygrothermal simulations. One-dimensional simulations were run using DELPHIN 5.9 for selected moisture reference years of the 15 realizations of modelled historical (H: 1986-2016) and future (F: 2062-2092) climate data of 12 Canadian cities. The mold growth index at the outer layer of the OSB sheathing panel was used to compare the moisture performance under H and F periods. Results for the base design that meet the minimum requirements of the National Building Code of Canada showed that cities within the interior of the country, characterized by a low annual rainfall, are less likely to develop significant mold growth under H and F periods, whereas cities in coastal areas, characterized by high annual rainfall, present a heightened risk to mold growth under both H and F periods. For cities located on the west coast, a possible solution could be to use a 38-mm ventilated drainage cavity as this measure would help dissipate moisture from within the cavity. On the east coast, apart from using a 38-mm ventilated drainage cavity, other measures aiming at reducing the wind-driven rain deposition (i.e., increasing overhang ratio or the height of the roof) could be introduced. However, the feasibility of such measures needs to be considered in respect to whether these are to be implemented as part of a new building or retrofit of an existing one.