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Moisture buffering capacity of heavy timber structures directly exposed to an indoor climate: a numerical study
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
2005 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 40, no 10, 1400-1412 p.Article in journal (Refereed) Published
Abstract [en]

This paper introduces a hygrothermal model accounting for the moisture and heat transport in a massive wood envelope directly exposed to an indoor climate. A better knowledge of the passive interaction between an indoor climate and a heavy timber structure could lead to presenting an alternative to high air exchange rate, and to increasing the thermal comfort of the inhabitants. So far, the model is developed as a stand-alone application with a finite difference method, and is written in a Neutral Model Format, enabling a later implementation in a modular environment for indoor climate energy calculations, called IDA ICE. A numerical simulation is provided to depict the buffering capacity of a massive timber structure as a function of the air exchange rate and the effective wood wall area.

Place, publisher, year, edition, pages
2005. Vol. 40, no 10, 1400-1412 p.
Keyword [en]
Heat transport; Indoor climate; Massive wood wall; Moisture buffering capacity; Moisture transport
National Category
Building Technologies
URN: urn:nbn:se:kth:diva-6481DOI: 10.1016/j.buildenv.2004.10.017ISI: 000230746000014ScopusID: 2-s2.0-21644464868OAI: diva2:11204
QC 20100825Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2011-11-09Bibliographically approved
In thesis
1. The hygrothermal inertia of massive timber connstructions
Open this publication in new window or tab >>The hygrothermal inertia of massive timber connstructions
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The work presented in this Doctoral dissertation concerns the ability of heavy timber structures to passively reduce the fluctuations of the indoor temperature and of the indoor relative humidity, through the dynamic process of heat and moisture storage in wood. We make the hypothesis that the potential offered by the hygrothermal inertia of heavy timber structures is significant, and that it could provide a passive way of regulating the indoor climate. This ultimately could results in a decrease of the energy demand from the Heating, Ventilating and Air Conditioning systems. In this Thesis, the author tries to characterise and quantify the significance of the hygrothermal inertia providing by the heavy timber constructions.

The experimental studies contain an in-situ measurement campaign carried out at the Vetenskapsstaden building located in Stockholm and erected in 2001. The results from the test campaign show that a heavy timber construction may contribute to buffer the indoor temperature. A direct quantification of the moisture stored in the wood structure is measured regarding the year-to-year indoor humidity fluctuations. It was however hardly possible to directly quantify the moisture storage potential offered by the structure regarding the day-to-day indoor relative humidity fluctuations because of the low sensitivity of the measuring technique used.

In regard to the limitations noticed during the in-situ measurements, laboratory measurements were launched to develop new methods to determine the day-to-day hygric performances of wood exposed indoor. A new method based on the Magnetic Resonance Imaging technology was developed and is intended to provide information about the Moisture Buffer Value measured according to a NORDTEST protocol, and about the moisture distribution in wood with high spatial resolution. The Moisture Buffer Value of untreated Scots pine measured with this method is in accordance with the gravimetric method provided by the NORDTEST protocol. The Moisture Buffer Value of coated Scots pine was also investigated and it is normally assumed that any coatings will decrease the Moisture Buffering Capacity of the structure. The results show however that for specific coating such as waterborne alkali silicate coating, the Moisture Buffering Capacity of the structure may on the contrary be improved.

At last, numerical simulations were carried out. They were based upon the extension of a modular simulation environment IDA ICE 3.0, with the implementation of a specific model for heat and moisture transport in a wood. The results obtained pinpoint the highly synergetic effects between the indoor moisture loads, the ventilation rate, the outdoor climate and the moisture interactions with the structure. The outcomes also show that the Moisture Buffering Capacity of a heavy timber structure is appreciable. The structure is able to even out substantially the day-to-day indoor relative humidity fluctuations for a certain range of ventilation rate.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. x, 85 p.
Trita-BYMA, ISSN 0349-5752 ; 2006:2
1H MRI, Building simulation environment, Heat buffering capacity, Heavy timber construction, Indoor climate, In-situ measurement, Magnetic Resonance Imaging
National Category
Construction Management
urn:nbn:se:kth:diva-4200 (URN)91-7178-460-8 (ISBN)
Public defence
2006-12-11, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00
QC 20100825Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2010-08-25Bibliographically approved

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