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The hygrothermal inertia of massive timber connstructions
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
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.
Series
Trita-BYMA, ISSN 0349-5752 ; 2006:2
Keyword [en]
1H MRI, Building simulation environment, Heat buffering capacity, Heavy timber construction, Indoor climate, In-situ measurement, Magnetic Resonance Imaging
National Category
Construction Management
Identifiers
URN: urn:nbn:se:kth:diva-4200ISBN: 91-7178-460-8 (print)OAI: oai:DiVA.org:kth-4200DiVA: diva2:11208
Public defence
2006-12-11, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100825Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2010-08-25Bibliographically approved
List of papers
1. Contribution of indoor exposed massive wood to a good indoor climate: in-situ measurement campaign
Open this publication in new window or tab >>Contribution of indoor exposed massive wood to a good indoor climate: in-situ measurement campaign
2004 (English)In: Energy and buildings36, ISSN 0378-7788, 281-292 p.Article in journal (Refereed) Published
Abstract [en]

An indoor climate is mainly influenced by factors including heating, ventilation and air-conditioning, building envelope and materials, occupants, furniture, and service life of the building components. These last few years, the usual porous medium provided in wall and flooring constructions have been pointed out as possible passive systems capable of buffering the indoor climate variations in terms of temperature and humidity. The objective for the ongoing project is, therefore, to evaluate the possibility of ensuring an indoor climate within an acceptable range making use of large exposed massive wood surfaces. An experimental study, being performed in four occupied apartments of a multi-storey residential building in Sweden, is described in this paper. A brief analysis of the in situ recordings is also included. The temperature and relative humidity recordings show fairly well-agreement with the ASHRAE recommended values for a good indoor climate excepted during the cold periods revealing low indoor relative humidity. The first results show evidences that a large area of exposed massive wood contributes to buffer the indoor temperature variations. Furthermore, this far it does not shows evidences that a large area of exposed massive wood is able to damp the daily fluctuations in relative humidity.

Keyword
massive wood structure; in situ measurements; heat storage; moisture storage; thermal comfort; indoor climate
National Category
Construction Management
Identifiers
urn:nbn:se:kth:diva-6478 (URN)10.1016/j.enbuild.2003.12.003 (DOI)000220762100008 ()2-s2.0-1542531366 (Scopus ID)
Note
QC 20100825Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2010-12-06Bibliographically approved
2. Heat and moisture buffering capacity of massive wood construction
Open this publication in new window or tab >>Heat and moisture buffering capacity of massive wood construction
2004 (English)In: Proceedings of the 8th World Conference on Timber Engineering, 2004, 1-6 p.Conference paper, Published paper (Refereed)
Abstract [en]

The heat and moisture buffering effect of a massive wood structure directly exposed to an indoorclimate is investigated. An in-situ measurement campaign has been carried out in a massive woodmulti-storey building in Stockholm, and interesting issues are the quantification of heat andmoisture storage capacities of such structures. The aim is to present a clear insight in the heat andhumidity interaction between an indoor exposed massive wood construction and an indoor climate.A website is available (http://www.byv.kth.se/vetenskapsstaden), where hourly updated results canbe followed. The results show evidences that large areas of exposed massive wood might contributeto buffer the indoor temperature variations and at least retard the heat migration to the outdoor. Themoisture buffering capacity of massive wood wall during diurnal humidity fluctuation of an indoorclimate is believed to be a surface phenomenon and further research is needed in this way.

Keyword
Massive wood structure, In-situ measurements, Thermal comfort, Heat buffering capacity, Moisture buffering capacity, Heat storage, Moisture storage
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-6479 (URN)
Conference
8th World Conference on Timber Engineering
Note

QC 20100825

Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2017-04-18Bibliographically approved
3. The buffering effect of heavy timber constructions on the indoor moisture dynamic
Open this publication in new window or tab >>The buffering effect of heavy timber constructions on the indoor moisture dynamic
2005 (English)In: Proceedings of the Nordic Symposium on Building Physics, Reykjavik, 2005, 1-8 p.Conference paper, Published paper (Refereed)
Abstract [en]

Since the renewal of the fire regulations in the 90s, an alternative to the traditional light-weight timber frame structures particularly suitable for multi-storey dwellings has recently emerged in the Scandinavian countries under the generic name of massive wood construction or heavy timber construction. This concept provides manifold architectonic possibilities for the use of wood as a building and structural material, with the particularity among others of creating large areas of wood surface being directly exposed into an indoor environment. Regarding the hygroscopic properties of wood materials, this calls upon the possibility of buffering the indoor environment in term of moisture fluctuations by making use of the structure as a passive system. This paper discusses some insights and thoughts round about the notion of moisture buffer capacity through the examination of the indoor moisture dynamic registered into four apartments during the year 2003 at the Vetenskapsstaden multi-storey dwelling located in Stockholm. Numerical results are also provided to ascertain and highlight the holistic approach lying behind this concept where the control of the indoor moisture dynamic requires taking simultaneously into consideration several aspects of the building as the ventilation strategy, the structure configuration, the building use and the outdoor climate.

Keyword
Heavy timber construction, indoor moisture dynamic, moisture buffer capacity.
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-6480 (URN)
Conference
Nordic Symposium on Building Physics, Reykjavik
Note

QC 20100825

Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2017-04-12Bibliographically approved
4. Moisture buffering capacity of heavy timber structures directly exposed to an indoor climate: a numerical study
Open this publication in new window or tab >>Moisture buffering capacity of heavy timber structures directly exposed to an indoor climate: a numerical study
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.

Keyword
Heat transport; Indoor climate; Massive wood wall; Moisture buffering capacity; Moisture transport
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-6481 (URN)10.1016/j.buildenv.2004.10.017 (DOI)000230746000014 ()2-s2.0-21644464868 (Scopus ID)
Note
QC 20100825Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2017-12-14Bibliographically approved
5. Magnetic resonance imaging of moisture distribution in Pinus sylvestris L. exposed to daily indoor relative humidity fluctuations
Open this publication in new window or tab >>Magnetic resonance imaging of moisture distribution in Pinus sylvestris L. exposed to daily indoor relative humidity fluctuations
2006 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, Vol. 1, no 3-4, 116-126 p.Article in journal (Refereed) Published
Abstract [en]

n contact with indoor air, wood materials have a high potential passively to reduce the indoor humidity fluctuations resulting from internal moisture loads and outdoor humidity fluctuations. This ability, characterized by the moisture buffering capacity of building materials, has attracted increasing attention within building physics, but a suitable method to appraise and quantify this phenomenon is still sought. In this study, a non-invasive spectroscopic method of accessing information about the interaction between indoor air and Scots pine was investigated. A comprehensive account is given of spatially resolved moisture absorption (desorption) into (from) Scots pine by proton magnetic resonance imaging ([1H]MRI) based on an effective single-point imaging (SPI) sequence. SPI images of bound-water distribution in Scots pine with a spatial resolution on a sub-millimetre scale were acquired when one of the orthotropic directions of the wood material was exposed to typical indoor day-to-day moisture fluctuations. The nuclear magnetic resonance imaging measurements presented in this study clearly show the potential of the method to provide accurate spatial information about the wood-water interaction below the fibre saturation point and hence to characterize the moisture buffering capacity of wood materials.

Keyword
[1H]MRI; moisture buffering capacity; moisture profiles; nuclear magnetic resonance; SPI; Scots pine
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-6482 (URN)10.1080/17480270601150578 (DOI)
Note
QC 20100825Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2012-02-14Bibliographically approved
6. Influence of coating system on the moisture buffering capacity of panels of Pinus sylvestris L
Open this publication in new window or tab >>Influence of coating system on the moisture buffering capacity of panels of Pinus sylvestris L
2007 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 2, no 3-4, 97-105 p.Article in journal (Refereed) Published
Abstract [en]

The indoor relative humidity in dwellings and offices is an important factor in building physics. The ability of hygroscopic materials and especially wood materials to store and release moisture helps to regulate the indoor climate naturally and to avoid extremes of humidity. In the present study, cyclic sorption experiments with coated Scots pine were performed. Materials with different coating compositions were exposed to day-to-day relative humidity changes. The moisture buffering capacity was estimated by a gravimetric method and the moisture buffer value was computed. The results show that the coating has a significant impact on the moisture buffering capacity of the underlying Scots pine. The moisture distribution in the wood sample was appraised for each coating system using a proton magnetic resonance imaging technique. This study confirmed that the dynamics of moisture exchange between the indoor environment and the wooden material during typical daily moisture fluctuations is confined to a few millimetres behind the air-wood interface.

Keyword
[1H]MRI, Bound-water distribution, Coating, Moisture buffer value, Moisture buffering capacity, Nuclear magnetic resonance, Scots pine
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-6483 (URN)10.1080/17480270801906167 (DOI)2-s2.0-49549099538 (Scopus ID)
Note

Uppdaterad från submitted till published: 20100825 QC 20100825

Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2017-12-14Bibliographically approved
7. Toward sustainable multi-storey timber constructions
Open this publication in new window or tab >>Toward sustainable multi-storey timber constructions
2005 (English)In: Proceedings ofthe 2005 World Sustainable Building Conference, Tokyo, 09–012., 2005Conference paper, Published paper (Refereed)
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-6484 (URN)
Note
QC 20100825Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2010-08-25Bibliographically approved

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Citation style
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