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

2021 ◽  
Vol 2069 (1) ◽  
pp. 012007
Author(s):  
N S Bunkholt ◽  
L Gullbrekken ◽  
B Time ◽  
T Kvande
Keyword(s):  
Moisture Content ◽  
Thermal Insulation ◽  
Field Measurements ◽  
Office Building ◽  
Mould Growth ◽  
Laboratory Measurements ◽  
Cold Side ◽  
Load Bearing ◽  
Wood Frame ◽  
Bearing Structure

Abstract 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.

Moisture conditions in well-insulated wood-frame walls. Simulations, laboratory measurements and field measurements

2015 ◽  
Vol 10 (3) ◽  
pp. 232-244 ◽  
Author(s):  
Lars Gullbrekken ◽  
Stig Geving ◽  
Berit Time ◽  
Inger Andresen ◽  
Jonas Holme
Keyword(s):  
Field Measurements ◽  
Laboratory Measurements ◽  
Wood Frame ◽  
Moisture Conditions

scholarly journals Temperature Flows in Railway Tunnels: Field Measurements of Frost Penetration

2020 ◽  
pp. 161-194
Author(s):  
Anna Andrén ◽  
Lars-Olof Dahlström ◽  
Erling Nordlund
Keyword(s):  
Field Measurements ◽  
Fracture Network ◽  
Ice Formation ◽  
Air Velocity ◽  
Railway Tunnel ◽  
Water Leakage ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Frost Penetration ◽  
Bearing Structure

Even though extensive pre-grouting is carried out during the construction of tunnels, certain leakages and drips remain. These remaining leakages are remedied by a combination of post-injection and drainage measures with, for example, frost insulated drain mats, whose function is to prevent the cold tunnel air from reaching a leakage spot and causing water to freeze. Despite these measures, some water may still enter the tunnels and cause problems during winter with ice formations and frost shattering. Icicles, ice pillars and ice-covered roads and railway tracks require constant maintenance. If ice occurs in the fracture network close to the tunnel contour or in the interface between the rock and shotcrete, it can cause degradation of the load-bearing capacity of the tunnel and fall-outs of both materials. In tunnel sections with water leakage problems it is common to protect the load-bearing structure from freezing with insulated drainage systems. To determine where along the tunnel efforts must be made to prevent ice formation, the temperature conditions of tunnels must be investigated. This article presents parts of the results from field measurements in two Swedish railway tunnels. The measurements involves monitoring of air and rock temperatures, air pressure and air velocity. Keywords: Frost penetration, ice formation, frost shattering, temperature measurement, maintenance, railway tunnel.

Analysis of Energy-Saving Architecture with Self Thermal Insulation Structure of Fiber Reinforced Foamed Concrete

2011 ◽  
Vol 71-78 ◽  
pp. 444-446
Author(s):  
Li Guo Ma ◽  
Hong Wei Song
Keyword(s):  
Energy Saving ◽  
Thermal Insulation ◽  
Fiber Reinforced ◽  
Load Bearing ◽  
Building Technology ◽  
New Countryside Construction ◽  
Foamed Concrete ◽  
New Countryside ◽  
Save Energy ◽  
Bearing Structure

It has economical and social value to build energy-saving architectures. Foamed concrete is commonly used as non-load bearing structure to save energy of buildings. With reinforcement of fiber foamed concrete can be used as load bearing structure to build architectures. The load bearing structure of fiber reinforced foamed has ability of self thermal insulation to get the aim of energy-saving. In the paper the excellence and disadvantage of foamed concrete is summarized. Methods are given to build the energy-saving architecture with self thermal insulation structure of fiber reinforced foamed concrete in new formwork. The building technology will be applied in new countryside construction in China.

CLT construction without weather protection requires extensive moisture control

2021 ◽  
pp. 174425912199638
Author(s):  
Lars Olsson
Keyword(s):  
Moisture Content ◽  
Field Measurements ◽  
Scientific Work ◽  
Field Studies ◽  
Microbiological Analysis ◽  
Mould Growth ◽  
Extensive Growth ◽  
Almost All ◽  
Dry Out ◽  
Moisture Conditions

This study examines how cross-laminated timber (CLT) constructions, including joints, connections and attachment points, are affected by precipitation during construction. The case studies are based on moisture content measurements and material sampling as well as microbiological analysis during the structure’s construction stage. The study does not include remediation control. The field measurements show microbiological growth in all buildings and almost all floor structures that were investigated. Of a total of 200 measuring points analysed, half had mould growth and around a third had moderate or extensive growth. The moisture content measurements for one of the locations with the largest percentage of elevated or high moisture content was at the top of the floor structure in the bottom gap between timbers in the CLT top layer. This is one example of several materials or construction components where there is limited possibility of dry out. Based on the outcome, it would appear difficult, or impossible, to avoid the appearance of microbial growth during construction with CLT without weather protection. Previous studies indicate that microbiological analysis of CLT is extremely rare in both laboratory and field studies, which implies that there are obvious shortcomings in the scientific work. The fact that mould growth is often invisible needs to be disseminated, especially in practical studies. However, there seems to be a good level of awareness in the literature that theoretical studies often conduct mould growth risk evaluations. There do not appear to be any moisture safety assembly methods or solutions for CLT construction that do not have weather protection or a declaration of the critical moisture conditions for CLT products.

Saturated Hydraulic Conductivity of Clayey Tills and the Role of Fractures

1990 ◽  
Vol 21 (2) ◽  
pp. 119-132 ◽  
Author(s):  
Johnny Fredericia
Keyword(s):  
Hydraulic Conductivity ◽  
American Studies ◽  
Field Measurements ◽  
Present Knowledge ◽  
Saturated Hydraulic Conductivity ◽  
Field Observations ◽  
Laboratory Measurements ◽  
Vertical Hydraulic Conductivity ◽  
Data Field

The background for the present knowledge about hydraulic conductivity of clayey till in Denmark is summarized. The data show a difference of 1-2 orders of magnitude in the vertical hydraulic conductivity between values from laboratory measurements and field measurements. This difference is discussed and based on new data, field observations and comparison with North American studies, it is concluded to be primarily due to fractures in the till.

A comparison of hygrothermal simulation results derived from four simulation tools

2021 ◽  
pp. 174425912098876
Author(s):  
Maurice Defo ◽  
Michael Lacasse ◽  
Abdelaziz Laouadi
Keyword(s):  
Relative Humidity ◽  
Outer Layer ◽  
Growth Index ◽  
Mould Growth ◽  
Simulation Tools ◽  
Assembly Design ◽  
Hygrothermal Simulation ◽  
Moisture Performance ◽  
Wood Frame ◽  
Wall Assembly

The objective of this work was to compare the hygrothermal responses and the moisture performance of four wood-frame walls as predicted by four hygrothermal (HAM) simulation tools, namely: DELPHIN, WUFI, hygIRC and COMSOL. The four wall systems differ only in their cladding type; these were fibreboard, vinyl, stucco and brick. Three Canadian cities having different climates were selected for simulations: Ottawa, Ontario; Vancouver, British Columbia and Calgary, Alberta. In each city, simulations were run for 2 years. Temperature and relative humidity of the outer layer of OSB sheathing were compared amongst the four simulation tools. The mould growth index on the outer layer of the OSB sheathing was used to compare the moisture performance predicted by the respective hygrothermal simulation tools. Temperature profiles of the outer layer of the OSB sheathing were all in good agreement for the four HAM tools in the three locations. For relative humidity, the highest discrepancies amongst the four tools were found with stucco cladding where differences as high as 20% could be found from time to time. Mould growth indices predicted by the four HAM tools were similar in some cases but different in other cases. The discrepancies amongst the different HAM tools were likely related to: the material property processing, how the quantity of wind-driven rain absorbed at the cladding surface is computed and some implementation details. Despite these discrepancies, The tools generally yielded consistent results and could be used for comparing the impacts of different designs on the risk of premature deterioration, as well as for evaluating the relative effects of climate change on a given wall assembly design.

scholarly journals Stochastic Simulation of Mould Growth Performance of Wood-Frame Building Envelopes under Climate Change: Risk Assessment and Error Estimation

Buildings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 333
Author(s):  
Lin Wang ◽  
Maurice Defo ◽  
Zhe Xiao ◽  
Hua Ge ◽  
Michael A. Lacasse
Keyword(s):  
Climate Change ◽  
Risk Assessment ◽  
Error Estimation ◽  
Ventilation Rate ◽  
Climatic Conditions ◽  
Cold Climate ◽  
Mould Growth ◽  
Frame Building ◽  
Wood Frame ◽  
Water Tightness

Previous studies have shown that the effects of climate change on building structures will increase the mould growth risk of the wood-frame building envelope in many circumstances. This risk can be controlled by wind-driven rain deflection, improving water tightness of the exterior facade, and improving cladding ventilation. However, the effectiveness of these risk mitigation strategies are subject to various uncertainties, such as the uncertainties of wall component properties and micro-climatic conditions. The objective of this paper is to apply stochastic hygrothermal simulation to evaluate the mould growth risk of a brick veneer-clad wood-frame wall with a drainage cavity under historical and future climatic conditions of Ottawa, a Canadian city located in a cold climate zone. An extensive literature review was conducted to quantify the range of stochastic variables including rain deposition factor, rain leakage moisture source, cladding ventilation rate and material properties of brick. The randomised Sobol sequence-based sampling method, one of the Randomized Quasi-Monte Carlo (RQMC) methods, was applied for risk assessment and error estimation. It was found that, under the climatic condition of Ottawa, limiting the amount of wind-driven rain to which walls are subjected is a more robust mitigation measure than improving cladding ventilation in controlling mould growth risk, the improving of water tightness of exterior façade is not as robust as wind-driven rain deflection and cladding ventilation, however, the reduction of rainwater penetration can reduce the mould growth risk at different levels of rain deposition factor and cladding ventilation rate.

Aerosol Properties and Processes: A Path from Field and Laboratory Measurements to Global Climate Models

2007 ◽  
Vol 88 (7) ◽  
pp. 1059-1084 ◽  
Author(s):  
Steven J. Ghan ◽  
Stephen E. Schwartz
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Field Measurements ◽  
Substantial Improvement ◽  
Global Climate Models ◽  
Department Of Energy ◽  
Lower Atmosphere ◽  
Laboratory Measurements ◽  
Successive Generations ◽  
Aerosol Properties

Aerosol particles in the lower atmosphere exert a substantial influence on climate and climate change through a variety of complex mechanisms. Consequently, there is a need to represent these influences in global climate models, and models have begun to include representations of these influences. However, the present treatment of aerosols in global climate models is highly simplified, omitting many processes and feedbacks that are thought to be climatically important. Thus, there is need for substantial improvement. Here we describe the strategy of the U.S. Department of Energy for improving representation of the properties, processes, and effects of tropospheric aerosols in global climate models. The strategy begins with a foundation of field and laboratory measurements that provide the basis for modules describing specific aerosol properties and processes. These modules are then integrated into regional aerosol models, which are evaluated by comparison with field measurements. Issues of scale are then addressed so that the modules can be applied to global aerosol models, which are evaluated by comparison with satellite retrievals and other observations. Finally, the validated set of modules is applied in global climate models for multicentury simulations. This strategy is expected to be applied to successive generations of global climate models.

Assessment of Moisture Content in Sandy Beach Environments from Multispectral Satellite Imagery

2021 ◽  
Author(s):  
Julie Paprocki ◽  
Nina Stark ◽  
Hans C Graber ◽  
Heidi Wadman ◽  
Jesse E McNinch
Keyword(s):  
Moisture Content ◽  
Laboratory Data ◽  
Field Measurements ◽  
Weather Conditions ◽  
Sandy Beaches ◽  
Percent Error ◽  
Moisture Contents ◽  
Multispectral Satellite Imagery ◽  
Factor C

A framework for estimating moisture content from satellite-based multispectral imagery of sandy beaches was tested under various site conditions and sensors. It utilizes the reflectance of dry soil and an empirical factor c relating reflectance and moisture content for specific sediment. Here, c was derived two ways: first, from in-situ measurements of moisture content and average NIR image reflectance; and second, from laboratory-based measurements of moisture content and spectrometer reflectance. The proposed method was tested at four sandy beaches: Duck, North Carolina, and Cannon Beach, Ocean Cape, and Point Carrew, Yakutat, Alaska. Both measured and estimated moisture content profiles were impacted by site geomorphology. For profiles with uniform slopes, moisture contents ranged from 3.0%-8.0% (Zone 1) and from 8.0%-23.0% (Zone 2). Compared to field measurements, the moisture contents estimated using c calibrated from in-situ and laboratory data resulted in percent error of 3.6%-44.7% and 2.7%-58.6%, respectively. The highest percent error occurred at the transition from Zone 1 to Zone 2. Generally, moisture contents were overestimated in Zone 1 and underestimated in Zone 2, but followed the expected trends based on field measurements. When estimated moisture contents in Zone 1 exceeded 10%, surface roughness, debris, geomorphology, and weather conditions were considered.

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