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Mass-timber as thermal mass

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Improving Thermal Efficiency in
Lightweight Construction:
mass timber as thermal mass
PROJECT NUMBER: PNA289-1213a
February 2016
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Improving Thermal Efficiency in Lightweight
Construction: mass timber as thermal mass
Prepared for
Forest & Wood Products Australia
by
Dr Mark Dewsbury
Publication: Improving Thermal Efficiency in Lightweight Construction:
mass-timber as thermal mass
Project No: PNA289-1213a
This work is supported by funding provided to FWPA by the Department of Agriculture, Fisheries and
Forestry (DAFF).
© 2016 Forest & Wood Products Australia Limited. All rights reserved.
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ISBN: New number 978-1-925213-40-9
Researchers:
This research was completed by the School of Architecture & Design, University of Tasmania. The
research team was lead by Dr Mark Dewsbury, who was assisted by:
Dr Detlev Geard
Dr Tim Law
Miss Clare Dunlop
Mr Maxim Tooker
Mrs Stephanie Edwards
v
Executive Summary
This research task was established to obtain new data to inform opportunities to further
improve the thermal efficiency of light-weight, timber framed, small to medium scaled
buildings. The principle task of this project was to complete an empirical study assessing the
measured thermal performance of mass-timber. This empirical study, within real buildings,
could then be used to corroborate previous published building heating and cooling energy
simulations, which had shown significant thermal performance benefit when mass-timber was
substituted with standard framed systems, and concrete and clay brick thermal mass systems.
The mass-timber as thermal mass research tasks included the installation, detailed
measurement and detailed simulation of two mass-timber systems within a very lightweight
building (unenclosed perimeter, platform-floored with plywood cladding), namely a:
Tasmanian plantation Eucalyptus vertically laminated 90mm partition wall, and
European plantation cross-laminated timber system placed on the floor.
After the mass-timber systems were installed, environmental conditions were measured in
great detail. The detailed measurement included an array of sensors in the subfloor zone, test
building room zone, the roof space zone and a site weather station. The site weather station
data were used in conjunction with other data from the Bureau of Meteorology to create a
site-specific climate file for each experiment. The site data and built fabric data were used to
complete experiment specific detailed building thermal performance simulations, which
included modifications to conductivity values, infiltration rates and conditioned temperatures,
to more correctly reflect the as-built nature of the buildings.
From the outset it must be acknowledged that both mass-timber research tasks documented
thermal performance benefits caused by timber acting as thermal mass. This improvement
came from three pathways.
Firstly, the inclusion of mass-timber elements which provided new thermal mass
within the built fabric of the test building
Secondly, in the case of the mass-timber flooring task, additional insulation in the
flooring system was added by the softwood panels
Thirdly, the inclusion of the built fabric structural elements, (joists, studs, plates,
roofing structure), appear to further reduce peak minimum and maximum internal
zone temperatures.
Additionally, in both research tasks the inclusion of the built fabric timber elements often
lessened the gap between simulated and measured thermal performance data, indicating a
correlation between reality and the capacity of the house energy rating software to model
indirect gain and losses from thermal mass.
Previous building simulation research showed significant thermal performance benefit when
mass-timber elements were added to the built fabric (Dewsbury, Geard et al. 2012, Dewsbury
2013, Dewsbury, Tooker et al. 2013). However, this building simulation based research was
questioned due to the current presumption that masonry elements provide the best thermal
mass. In this research the measured thermal performance of the mass-timber partition walls
and mass-timber flooring provided a strong similarity to the simulated thermal performance.
The strong correlation between the empirical and simulated data supports the hypothesis that
mass-timber does provide effective thermal mass within buildings. Within this context, this
research has shown that carefully placed mass-timber elements within the built fabric of
buildings will provide a pathway to lightweight, low carbon and high thermal performance
timber buildings.
vii
The principle purpose of increased stringency in several components of the national
construction code is to reduce the carbon emissions from the operation of buildings. This
research has shown that the measured and simulated energy needs energy needs to heat and
cool a building have been reduced. The development of the regulations has also included an
objective to reduce peak loads from the operation of heating and cooling in new buildings,
which has a significant impact on Australian power generation and distribution. In these tasks
both the inclusion of the mass-timber and the inclusion of the built fabric thermal mass had a
significant impact on the reduction on the peak energy calculations. Finally, internationally,
there is a desire to reduce the carbon economy. When mass-timber elements are compared to
traditional concrete and clay brick thermal mass elements, the mass-timber has:
A lower embodied energy,
Includes significant carbon sequestration, and
Can provide significantly lighter and structurally adaptable buildings, which leads to
further reductions in the carbon associated with the construction and maintenance of
buildings.
Figure 1: 90mm plantation Eucalyptus nitens partition wall within test building
viii
Table of Contents
Executive Summary .................................................................................................................. vi
Introduction ................................................................................................................................ 1
Mass-timber as thermal mass ................................................................................................. 3
Nation-wide house energy rating scheme (NatHERS) & empirical validation ..................... 4
The solid wood context .......................................................................................................... 5
Methodology .............................................................................................................................. 7
Built Fabric Methodology ...................................................................................................... 7
Task 1: Mass-timber partition walls as thermal mass ........................................................ 8
Task 2: Mass-timber flooring as thermal mass .................................................................. 9
Data acquisition methodology ................................................................................................ 9
Detailed thermal performance simulation methodology ...................................................... 11
Data comparison methodology ............................................................................................. 12
Methodology summary ........................................................................................................ 14
Results and Discussion ............................................................................................................. 14
General non task specific results .......................................................................................... 14
Mass-timber partition walls as thermal mass results ............................................................ 18
Mass-timber flooring as thermal mass results ...................................................................... 19
Conclusion & Recommendations ............................................................................................. 20
Appendices ............................................................................................................................... 22
Acknowledgements .................................................................................................................. 22
References ................................................................................................................................ 23
1
Introduction
Resulting from the global awareness of climate change and its relationship to human activity,
the Australian government has initiated a range of measures to reduce greenhouse gas
emissions since 1992 (Harrington and Foster 1999, COAG 2010). The measures include
regulations to reduce the amount of energy that may be required to condition residential and
commercial buildings (Drogemuller 1999, Tucker, Newton et al. 2002, ABCB 2003). In
response to these legislative changes the Nationwide House Energy Rating Scheme
(NatHERS) was established and in co-operation with state governments and industry,
established 69 Australian climate specific thermal comfort bandwidths, zone specific internal
energy loads and star-bands, (from 0 to 10), for Australian housing (Ballinger and Cassell
1995).
Based on the newly developed Star Rating based metric it was agreed that a minimum
performance rating of 3.5 to 4 Stars would be adopted by all jurisdictions in 2003-2004
(ABCB 2003). The minimum thermal performance requirement was upgraded to 5 Stars in
2006 (ABCB 2005), and to 6 Stars in 2010 (ABCB 2010). The change from no or minimal
built envelope thermal performance regulations in 2002 to the 6 Star requirement of 2010 has
had a significant impact on material choices and construction methods in the cooler and hotter
climates (Nolan and Dewsbury 2006). It is expected that by 2020 the regulations will include
other aspects that effect building energy use, including domestic hot water services and
lighting, and a further increase to the minimum Star Rating requirement (Pitt & Sherry 2010).
These regulatory developments are inherently linked to the thermal performance of
lightweight buildings, which rely greatly on the quality of envelope design and construction.
A high quality lightweight timber framed building is achieved through the appropriate use of
insulation within the subfloor, external walls, internal walls, ceiling and roofing built fabric
systems, between unconditioned and conditioned spaces, and through the careful installation
of building membranes to control infiltration (Nolan and Dewsbury 2006, Department of
Industry 2013). The insulation will significantly reduce the unwanted outward or inward heat
flow to occupied and often conditioned spaces. After matters affecting the design of a high
quality envelope are achieved, and subject to climate and access or exclusion of solar
radiation, thermal mass can then be used to moderate temperature fluctuations within each
room (Dewsbury and Nolan 2015, Slee and Hyde 2015).
However, as the Australian design and construction sector has continued to adopt the required
level of thermal performance specified by the Building Code of Australia, there has been a
significant reduction in the use of lightweight timber platform floored construction systems.
This has generally resulted from industry-based recommendations to use more massive
systems in preference to well designed and constructed mixed mass and lightweight systems,
from general marketing literature and the energy rating industry. Within these sectors there
has been a common recommendation to replace lightweight construction systems with more
massive systems such as a concrete slab-on-ground floor (Iskra 2004, Sustainable Energy
Authority 2004, Tony Isaacs Consulting Pty Ltd 2006, Floyd Energy 2014).
The general adoption of these principles appears to be caused by opinions that any thermal
mass is good, regardless of quantity or solar access, and that it is too costly or the construction
process is too difficult to construct well insulated and thermally efficient lightweight
buildings. This Australian pattern appears to be at odds with international design and
construction trends where there are an assortment of methods to provide high quality
insulation and thermal mass within lightweight buildings (Nolan and Dewsbury 2007). Within
this context, there is a significant need for appropriate and specific building science
knowledge and education in the Australian building design, construction and thermal
performance industries (Marceau 1999, Tucker, Newton et al. 2002, HIA 2004, Iskra 2004,
2
Productivity Commission 2004, Henderson 2005, Murphy, Head et al. 2005, Energy Partners
2007, Williamson, Plaves et al. 2007, Dewsbury, Wallis et al. 2009, Wallis and Dewsbury
2009, Dewsbury 2011). Similarly, timber products and lightweight construction should be
considered as complementary elements, which can provide high thermal performance
buildings, and utilises an ongoing sustainability and readily available Australian timber
resource.
Thermal capacitance is not often considered within the context of lightweight buildings as the
traditional materials selected to provide thermal capacitance include clay brick, cement and
concrete based products. These products do provide good thermal capacitance but they are
massive and have a relatively high value for embodied energy. Their significant mass requires
the structural systems of the building to be increased to carry additional load, thereby further
increasing the quantity of building materials, their relative embodied energy and costs.
Looking to the future, the use of these traditional massive materials may reduce heating and
cooling energy but also significantly increase the embodied energy and decrease the carbon
sequestration of a building’s construction materials. Slee et al (2013) have explored the issue
of too much thermal mass. Since 2004 Dewsbury has explored the use of different materials
as thermal mass and the ‘right-sizing’ of thermal mass to reduce the heating and cooling
energy needs for new and existing houses (Dewsbury 2009, Dewsbury 2011, Dewsbury 2012,
Dewsbury 2012, Dewsbury, Fay et al. 2013, Dewsbury, Tooker et al. 2013). This research has
included the construction of low to zero energy homes and the completion of many house
energy rating simulations which have explored built fabric and its impact on simulated
heating and cooling energy. Many of the recent thermal performance simulations were
completed for houses located in Tasmania and Victoria, and compared the relative thermal
performance of typical timber framed, 110mm clay brick, 90mm concrete block, 90mm mass-
timber and 110mm mass-timber partition wall systems (Dewsbury 2012, Dewsbury and Fay
2013). In most cases, the mass-timber partition wall system scenarios provided the best
simulated thermal performance result. However, this is not just an area of exploration in
Australasia, internationally there has been a recent and significant increase in researchers and
practitioners exploring how thermal mass might be retrofitted to existing buildings (Aanestad
2013, Gjerde 2013).
The thermal benefits from mass-timber construction include, but are not limited to, its thermal
conductivity, thermal capacitance, infiltration reduction properties, vapour permeability and
thermal lag properties. Of these five significant benefits, only three are well catered for in the
current house energy rating and building simulation software. Internationally, the design and
manufacture of mass-timber products for use in low and medium rise residential and
commercial buildings has been shown to increase thermal performance, carbon storage and
earthquake resistance (Lattke and Lehmann 2007, Muller 2010, Kotsopoulos, Farina et al.
2012, Kildsgaard, Jarnehammar et al. 2013).
Past empirical validation research within the Launceston test buildings has already verified
construction practices and their impact on thermal performance (Dewsbury, Nolan et al. 2007,
Dewsbury, Fay et al. 2008). However, these two facets of built fabric insulation and timber
products as thermal capacitance were one of many spring-boards for this research task, which
has focused on two tasks, namely:
The measured thermal performance and effectiveness of mass-timber partition walls as
thermal mass.
The measured thermal performance and effectiveness of mass-timber partition walls as
thermal mass.
3
This report covers a vast quantity of research, and an introduction to the research task
reasoning, the nation-wide house energy rating scheme system, and the general methodology.
Research results follow this section. Due to the complexity and quantity of data, task-specific
appendices are included with this report, namely:
- Appendix 1: Mass-timber as partition walls for thermal mass
- Appendix 2: Mass-timber flooring for thermal mass
It had originally been intended that the project would include the measured thermal
performance and effectiveness of mass-timber internal lining as thermal mass. However, due
to financial constraints, this task was not completed. Nevertheless, the positive findings from
the partition wall and floor tasks do assert the need for empirical data on mass-timber as wall
lining.
The final sections to this report are Conclusions, Recommendations (which includes future
research needs), Acknowledgements and Bibliography.
Mass-timber as thermal mass
In many climates, the correct placement of thermal mass within a building is critical for
optimum thermal performance. However, the general principles behind the structural systems
of lightweight timber buildings have normally excluded the use of thermal mass. In response
to this dilemma, the building thermal performance simulation-based research completed by
Dewsbury (2012, 2013, 2013, 2015) explored the use of mass-timber as thermal mass in new
housing, or as a retrofit to existing housing. The earlier research, focussed principally on the
use of mass-timber as partition walls. However the 2015 research also explored the thermal
performance benefits when mass-timber systems were simulated as part of floor, external wall
and ceiling systems. The data from the simulated use of timber as thermal mass found that in
many situations the mass-timber provided a very similar or better thermal performance result
than the traditional clay brick and concrete block solutions.
Internationally, a range of construction systems have been developed that are made from solid
and mass-timber materials which have been used for flooring, internal walls, external walls
and ceilings to significantly improve the insulation value, construction process, building
structural engineering and cost effectiveness of lightweight construction (KLH Massivholz
GmbH 2012). At times the mass-timber floor has been combined with a concrete screed
coating to further improve the fire retardant properties and other regulatory requirements of
multi-use and multi-storey buildings. Internationally, some of these systems have been in use
for more than a decade, but they have had limited use within the Australian market. Rarely
has the discussion on the benefits of mass-timber systems included a critical assessment of its
effectiveness as thermal mass. However, all manufacturers have completed extensive testing,
(within the ISO framework) to publish conductivity and thermal capacitance values for their
mass-timber products (KLH (UK) 2014).
As mentioned in the introduction, researchers in New Zealand and Australia have completed
desktop building simulation research, which has shown positive thermal performance results
when mass-timber elements have been added to buildings as thermal mass (Dewsbury, Geard
et al. 2012, Dewsbury, Tooker et al. 2013, Gjerde 2013, Dewsbury and Chandler 2015). To
ascertain whether the desktop thermal simulation research findings are correct, mass-timber
systems need to be empirically tested for thermal performance benefit within real buildings.
For this initial Australian empirical thermal performance task mass-timber as partition walls
and flooring, was tested within the very lightweight, unenclosed, platform-floored test
building at the Launceston Campus University of Tasmania. Due to the newness of mass-
timber elements within the Australian construction industry, this task provided the
opportunity to display mass-timber made from Tasmanian hardwood plantation E. Nitens in a
4
vertical lamination format in a partition wall, and imported softwood cross-laminated-timber
(CLT) panels were used as mass-timber flooring. In both cases detailed measurements were
taken and a detailed building thermal performance simulation was completed. The simulated
and measured (empirical) data were compared. The methodology of the empirical validation
process is discussed in more detail below in the methodology sections.
Nation-wide house energy rating scheme (NatHERS) & empirical validation
When climatically specific and well-placed quantities of insulation and thermal mass are
used, the impact on energy use to condition a house can be reduced significantly (CSIRO
2009, Aelenei 2010, Slee and Hyde 2015). The first priority in many building designs is to
use passive principles to establish a thermally comfortable internal environment. However,
the internal room temperatures achieved through an unconditioned passive building operation
may often be hotter or cooler than the occupant’s expectation for human comfort, leading to
the use of mechanical heating and cooling systems. Within the NatHERS house energy rating
framework, when a conditioned and occupied room becomes thermally uncomfortable natural
ventilation strategies are invoked (ABCB 2006). When passive ventilation does not provide
an appropriate improvement, generic energy consuming mechanical heating and cooling
systems are simulated. The NatHERS system applies nationally agreed thermal comfort
temperature bandwidths for 69 climate typologies within Australia (Ballinger and Cassell
1995, Delsante 2005, Lee 2005, Marker 2005, ABCB 2006). A NatHERS simulation, for
energy rating purposes, calculates the amount of energy in mega-joules that may be required
to maintain human thermal comfort within each room of a house.
The true benefits provided by appropriate levels of thermal mass and tight well-insulated
buildings can only become obvious when the energy required to maintain acceptable levels of
thermal comfort is reduced. A significant by-product of this research is the acquisition of high
quality data sets which can be used to inform the ongoing improvement and calibration of the
CSIRO developed CHENATH building simulation software, which is the principle tool
behind the Australian AccuRate, BERS and FirstRate house energy rating tools. Two key
components of the NatHERS scheme are within the scope of this research, namely:
The capacity for the software to adequately calculate the environmental temperature
within a lightweight residential type of building
The capacity for the software to adequately calculate the heating and/or cooling
energy required to maintain thermal comfort.
Previous research has established that the occupancy and conditioning patterns adopted by the
NatHERS do resemble modern households (Ambrose, James et al. 2013).
Additionally, recent empirical validation research has documented that the AccuRate and
CHENATH softwares do consider built fabric and climatic variables quite well, but
differences between measured and simulated results indicated the need for continuous built
fabric, thermal mass and heating/cooling energy calculation algorithm improvement (Delsante
2006, Dewsbury, Soriano et al. 2009, Dewsbury 2011, Dewsbury, Soriano et al. 2011, Geard
2011, Dewsbury and Fay 2013, Dewsbury, Geard et al. 2014, Dewsbury 2015). One of the
many recommendations from these previous research tasks was the matter of built fabric
thermal mass, as its non-inclusion in the thermal calculation model may have been one of the
possible causes of observed differences between measured and simulated temperatures. This
is an important issue for the timber industry, as softwood and hardwood framing systems may
provide significant thermal mass benefits within lightweight buildings, especially when the
framing is partially or fully separated from the external environment and thermally connected
to the internal environment. Within this context this research explored the effect of including
the built fabric thermal mass within the detailed building simulations.
5
The resultant heating and cooling energy calculation provides the numeric input for a
NatHERS star rating. For this to occur, the software must firstly calculate the temperature
within each room of a house relative to the external environment. When the simulated room
temperature is not within the accepted climate based thermal comfort bandwidth, the software
invokes cooling and/or heating operation. The annual amount of heating and cooling energy
calculated by the software establishes the star rating for the building (ABCB 2006).
To validate the effectiveness and correctness of building simulation software the results from
detailed building simulations must be compared to measurements from a real building. This
empirical validation methodology is internationally accepted as a requirement for all building
simulation software tools. The empirical validation methodology is discussed below in the
methodology sections.
The simplest method for comparing measured and simulated data is attained from the
unconditioned mode of building operation, where the only energy inputs within the test
building are the internal loads from the data logging equipment and, subject to internal and
external temperatures, the flow of energy into or out of the test building (Dewsbury, Soriano
et al. 2011, Dewsbury 2015). The more complex empirical validation of the heating and
cooling energy calculations requires the building to be operated in heated and cooled modes.
To date there has been no Australian empirical validation research, which has compared the
energy use of a thermally controlled and conditioned test building to the energy calculation
from a detailed simulation from the AccuRate Nationwide House Energy Rating Scheme
approved house energy rating software. The inclusion of the heating and cooling component
within this research allows for software developers to be made aware of differences between
simulated and measured data sets for the ongoing improvement and calibration of the CSIRO
developed building simulation tools.
Finally, although not a part of this research task, most accredited NatHERS software
programs now include an embodied energy and carbon sequestration calculation module.
These have been developed and implemented to allow for the accounting of built fabric
carbon sequestration and embodied energy. The use of mass-timber for thermal mass, when
compared with other traditional forms of thermal mass, may reduce the embodied energy and
increase the carbon sequestration of the built fabric providing further incentives to use
modern wood products in lightweight and thermally comfortable buildings.
The solid wood context
In Australian there is a significant and established private and public investment of just over
two million hectares of hardwood and softwood plantation forests to help meet future solid
timber, reconstituted wood and pulp product needs. About half of Australia’s plantations are
softwood, mainly radiata pine, largely managed for sawlog production. In contrast, more than
75% of hardwood plantations are managed for fibre production. Only around 7% of the
hardwood plantation estate was established for hardwood sawlog production, with only a
small proportion being managed to maximize sawlog quality (ABARES 2012).
Due to international trends, the expected markets for the output from these plantations is now
in flux, which has significantly impacted demand for pulp fibre. Additionally, the logs from
Australia’s plantation estates are yielding significant quantities of low-grade material that is
unacceptable for Australia’s dominant solid timber construction systems (sawn boards for
appearance, and structural uses). Much of this low-grade plantation material is unacceptable
for appearance applications, and fails to meet either standard and market requirements for
strength or board distortion for structural applications. Internationally, the confluence of the
collapse of the pulp wood market and the increasing quantities of low-grade solid wood has
6
generated significant interest in the design of new mass-timber materials, enabling higher
utilisation rates from plantation forests.
Increasing quantities of low-grade material are being produced from Australia’s softwood and
hardwood plantation forests. In some of Australia’s largest softwood sawmills up to 50% of
the sawn production does not meet structural grade requirements and is categorised as ‘fall-
down’ grade, with limited, and at times unviable, market opportunities. Most of this low-
grade sawn wood is sold at a loss (Stringer, 2012). Additionally, Australia’s hardwood
plantations are yielding significant volumes of low-grade material. Tasmania has the largest
hardwood sawlog plantation estate in Australia, most of which is shining gum (E.nitens).
These sawlog plantations are expected to supply around 150,000 m3 of high quality sawlog
each year in Tasmania from 2025 onwards. However, the remaining sawlog supply, around
780,000 m3 a year, has been found to be of much lower quality. Previous research has
demonstrated the low recovery rate for appearance and marketable structural grade sawn
timber and veneer from plantation hardwoods (Innes and Greaves 2007, Farrell and Blum
2012). This has resulted in the exploration of various composite and solid wood products,
with limited success.
The national plantation log harvest in 2009-2010 was 18.6 million cubic metres with an
approximate value of $1.4 billion. This is forecast to increase to an annual average of 29
million cubic metres a year by 2015. By 2025, plantation hardwood sawlog supply is expected
to increase to 1.3 million cubic metres a year. Using ABARE forecasts for plantation
softwood and hardwood log production, and assuming a conservative 35% of sawn output is
fall-down grade, then by 2015 an estimated 10 million cubic metres of low-grade material,
with a negative financial value, will be produced each year. Significantly, it is predicted that
73% of Tasmania’s hardwood plantation forests will yield poor quality material unsuitable for
traditional solid products (ABARES 2012)
While the low-grade timber has limited marketability under current building practice, due to
low strength and/or excessive deformation, mass-timber products may be able to use this low-
grade plantation timber. Mass-timber elements are large timber panels assembled from sawn
board held together with glue, mechanical fasteners or both in combination (). Significantly
different from glued, peeled veneer and stick constructed glue laminated products, mass-
timber products have the potential to act as a structural system and surface material
simultaneously (Figure 3). Subject to the system design approach taken, mass-timber products
can support multi-directional and multi-planar loads, yielding a product that is significantly
more versatile than traditional timber stick, block masonry and concrete slab construction
systems (Figure 4). Additionally, this dimensionally accurate and lightweight material lends
itself to the use of digital prefabrication systems, which internationally, have been shown to
provide more thermally efficient and economical housing.
7
Figure 2: Photograph of CLT panel (Courtesy of Tilling)
Figure 3: CLT panel wall in multi-storey construction
(www.karakusevic-carson.com/2012/bridport-
house-hackney)
Figure 4: Diagram of cross-laminated timber panel (www.crosslamsolutions.com)
Methodology
To empirically validate the thermal performance of built fabric systems requires the careful
combination of test buildings, detailed building environmental measurement, non-standard
detailed building thermal simulations and the comparison of measured and simulated data, as
shown in Figure 5 (Lomas, Eppel et al. 1994, Strachan 2008, Dewsbury 2011). The
comparison between measured and simulated data sets allow for the identification of building
simulation input variables that may need to be modified and/or algorithms that require
improvement. This research task required the detailed measurement, the detailed thermal
simulation and the analysis of the measured and simulated data sets of the two mass-timber
built fabric systems as described below. The common elements of the methodology are
discussed within this section. Task specific elements are discussed within the Appendix for
each task.
Figure 5: Empirical validation task framework
Built Fabric Methodology
Three purpose built thermal performance test buildings were established on the Launceston
Campus University of Tasmania, in 2006 (Dewsbury, Fay et al. 2007, Dewsbury, Nolan et al.
2007, Dewsbury, Soriano et al. 2009, Dewsbury, Soriano et al. 2009, Dewsbury 2011,
Dewsbury, Soriano et al. 2011, Dewsbury and Fay 2013). They were purpose-built for
material thermal performance analysis and empirical validation research tasks for industry and
8
government collaborators. The three test buildings comprise an unenclosed-perimeter
platform-floored, enclosed-perimeter platform-floored and concrete slab-on-ground floored
construction systems. For this task, Test Building 1, the unenclosed-perimeter platform-
floored test building, as shown in Figure 6, was used.
Figure 6: Unenclosed-perimeter platform-floored test building
Task 1: Mass-timber partition walls as thermal mass
To ascertain if the positive thermal performance benefits from the previous simulation based
mass-timber as thermal mass research is reflected in reality, the use of mass-timber for
thermal mass required empirical validation. In line with the earlier desktop research, the first
mass-timber system to be validated was the use of mass-timber as partition walls. Due to the
limited availability of imported product and a desire from the research team to explore
benefits from Australian plantation timbers, this task utilised Tasmanian plantation
Eucalyptus Nitens. The method of constructing the mass-timber partition wall required:
- The sourcing of kiln dried, 90mm x 35mm E. Nitens plantation grown timber,
- The vertical nail lamination of the boards (as shown in Figure 7), and
- The joining and erection of panels within the test building room to mimic a partition
wall (as shown in ).
A more detailed account of this task is discussed in Appendix 1.
Figure 7: Nail lamination of E. Nitens 90x35 boards
Figure 8: 90mm thick, vertically laminated E. Nitens panels
installed as partition walls
9
Task 2: Mass-timber flooring as thermal mass
As this task was to be completed after Task 1, a significant lead-time was established, which
allowed for a deeper exploration of mass-timber systems that may be available in Australia.
Tilling, who were a project collaborator, at this time was exploring a business model, which
included the import of European made cross-laminated-timber (CLT) panels. To help
promote product awareness, Tilling provided three softwood CLT panels for the mass-timber
as flooring task. The methodology followed for this built fabric comprised:
- The mass-timber product was selected by the project steering committee,
- A manufacturer provided a softwood cross laminated timber (CLT) product accessible
to the Australian construction industry,
- UTAS staff received the product in Launceston, and
- UTAS staff co-ordinated the installation of the panels, which were laid on top of the
existing particleboard floor of the unenclosed-perimeter, platform-floored test building
(as shown in Figure 9 and Figure 10).
A more detailed account of this task is discussed in Appendix 2.
Figure 9: 180mm 5 ply softwood CLT panel
Figure 10: Three softwood CLT panels installed inside test
building on top of existing particleboard floor
Data acquisition methodology
For appropriate environmental measurement and data collection to occur, an extensive array
of sensors was placed within the test building and on the timber elements. Additionally, a site
weather station was used to obtain appropriate data for the simulation software climate file.
This type of framework would enable a suitable measurement and data acquisition process to
support the detailed thermal performance simulation and the comparison of measured and
simulated data sets. This framework was developed by Dewsbury at the Launceston test
buildings in 2006 (Dewsbury 2011, Dewsbury 2015).
The generic thermal measurement profile within the test building, for this task, is shown in
Table 1. The measurements taken from the 600mm, 1200mm, 1200mm globe and 1800mm
were averaged to provide an average room temperature. A site weather station collected data
for air temperature, relative humidity, wind speed, wind direction and global solar irradiation,
which were used in conjunction with other data from the Bureau of Meteorology to create
experiment-specific climate input files. Additionally, high quality energy use metering was
collected by one of the research collaborators, Aurora Energy, for comparison to simulated
energy use.
10
The installation of all sensors required an initial calibration followed by intermediate
calibration during the completion of the two research tasks. All temperature sensors were
individually checked for calibration at zero degrees Celsius, room temperature and a
temperature close to boiling point, as shown in and Figure 12. Any temperature sensor that
did not provide a result within 0.2oC was removed. However most temperature sensors were
within 0.1oC of the calibration temperature. The solar radiation, relative humidity and wind
speed sensors were compared to output data from similar, pre-calibrated, sensors. The wind
direction sensor output was compared to synchronous compass bearings taken beside the wind
vane.
Table 1: Test building thermal measurement profile
Description Function
1000mm below ground level temperature Background & supporting data
Ground surface temperature Background & supporting data
Mid-subfloor zone temperature Thermal performance and validation data
Outside subfloor insulation surface temperature Background & supporting data
Inside subfloor insulation surface temperature Background & supporting data
Outside platform-floor surface temperature Background & supporting data
Inside platform-floor surface temperature Background & supporting data
600mm test building room temperature x 3 Thermal performance and validation data
1200mm test building room temperature x 3 Thermal performance and validation data
1200mm globe temperature x 3 Thermal performance and validation data
1800mm test building room temperature 3 Thermal performance and validation data
Inside ceiling surface temperature Background & supporting data
Outside ceiling surface temperature Background & supporting data
Outside ceiling insulation temperature Background & supporting data
Mid-roof space air temperature Thermal performance and validation data
Inside sarking surface temperature Background & supporting data
Outside sarking surface temperature Background & supporting data
Inside sheet-metal roof surface temperature Background & supporting data
Outside sheet-metal roof surface temperature Background & supporting data
With the exception of the energy use data, which was collected cumulatively every fifteen
minutes, all other data was collected at ten minute intervals. All data, once cleaned, was
averaged to hourly data for comparative analysis with the detailed simulation output
temperature files (Lomas 1991). Other data that was collected, but is not included in this
report, included a range of heat flow (flux) measurements, direct vertical north solar
irradiation and diffuse solar irradiation. This data requires significant analysis and will be
presented in future publications.
11
Figure 11: Thermoline calibration equipment for heated
temperature sensor calibration
Figure 12: An ice filled thermos for cooled temperature
sensor calibration
To gain adequate information on thermal performance and relative energy use, the test
building operation for each built fabric task included four operational modes, namely:
- unoccupied and unconditioned (commonly known as ‘free running’ or free floating’)
- unoccupied and continually heated (to a pre-set temperature)
- unoccupied and intermittently heated (to mimic a NatHERS room operation)
- unoccupied and continually cooled (to a pre-set and agreed temperature).
The temperatures measured, and the heating or cooling energy consumed, to maintain pre-set
temperatures was compared to the outputs from the non-standard detailed simulation from the
AccuRate house energy rating software.
Detailed thermal performance simulation methodology
To enable a more correct analysis of simulated and measured thermal performance data
required the completion of non-standard house energy rating simulations. A standard thermal
simulation and energy calculation for house energy rating includes a range of accepted default
values for built fabric, infiltration, internal heat loads, thermostat set points and climate input
data. All of these can vary significantly from the as constructed built fabric and the climatic
conditions during the research task (Clarke, Strachan et al. 1994, Girault 1994, Lomas, Eppel
et al. 1994, Strachan 2000, Dewsbury 2011). To enable a rigorous comparison of the
measured and simulated data set results, changes were made to some front-end input and
back-end scratch file inputs for each simulation, as shown in Table 2. Temperature thermostat
set points for simulating the heated and cooled modes of operation were only established once
the test building room data had been acquired and cleaned.
The initial research proposal only included the use of a modified conductivity value for the
floor, walls and ceiling to account for the reduction in insulation caused by the framing factor
(Syed and Kosny 2006, Kosny, Yarbrough et al. 2007, Dewsbury, Wallis et al. 2009).
However, during the early stages of the research some collaborators requested that two
simulation types be completed. The first simulation type was to include the modified
conductivity values as described above. The second was to model each floor, wall and ceiling
element as components, which allowed for the built fabric (timber framing) to be accounted
for as thermal mass and insulation. For example, a wall might be modelled as:
12
- 10 m2 plasterboard, insulation, cavity, cladding, and
- 1 m2 plasterboard, 90mm softwood, cavity, cladding.
- Table 2: Modified inputs for detailed simulation
Description Reason Experiment Type
Modified floor, wall
and ceiling U-values To account for the reduction in
insulation resulting from timber
framing
All simulations
Modified infiltration
values To use measured infiltration values
rather than the default values All simulations
Modified internal load
values To use measured internal energy load
values rather than the default values All simulations
Modified heating set
points To reflect the thermal condition of the
experiment Zero for free running and
cooled modes of operation.
Measured value for heated
modes of operation.
Modified cooling set
points To reflect the thermal condition of the
experiment Zero for free running and
heated modes of operation.
Measured value for cooled
modes of operation.
Natural ventilation To account for non-ventilated
operation Hours of operation and
thermostat set points set to
zero.
The inclusion of the two simulation methods did provide different results, but also more than
doubled the research task workloads by establishing eight simulation types for each built
fabric type, namely:
- unconditioned with modified U-value (no-mass)
- unconditioned with modified built fabric thermal mass (with-mass)
- continuously heated with modified U-value (no-mass)
- continuously heated with modified built fabric thermal mass (with-mass)
- intermittently heated with modified U-value (no-mass)
- intermittently heated with modified built fabric thermal mass (with-mass)
- continuously cooled with modified U-value (no-mass)
- continuously cooled with modified built fabric thermal mass (with-mass)
The completion of the detailed simulation tasks provided simulation data sets, which were
compared to the measured data sets for comparison and validation. The data sets included
simulated hourly temperatures and energy for the subfloor zone, test building room and the
roof space zone.
Data comparison methodology
The building software simulation tools have been developed to provide guidance on methods
to provide better thermally performing and low energy buildings to building designers,
13
regulators, individuals and organisations. The comparison of the simulated and measured data
sets provide the critical findings for this research, i.e., is the software is producing a similar
result to what has been measured. In this task the measured data was averaged into hourly
values and the output data from the simulations was in an hourly format. To enable a quick
and visually apparent comparison, the time series graphing function within Excel was used.
An example of a time series graph is shown below in Figure 13. Each graph shows the
average measured zone temperature, the with structural mass simulation data, the no structural
mass simulation data and the site air temperatures for the duration of the task. This form of
analysis allows for the quick identification of differences between the simulated and measured
data. Additionally, this method is used to visualise the differences between the maximum and
minimum simulated and measured data sets. This is a different approach from much of the
northern hemisphere research where there is a strong focus on the average values and climates
often require significant and year round heating. However, in Australia the average
temperature may often be within human comfort bandwidths and the heating and or cooling
may be used on a daily basis at times of minimum and maximum room temperature. Within
this context, an awareness of differences that occur at these daily extremes is paramount for
designing better Australian homes.
Figure 13: Example of time series analysis graph
Additionally, the residual values (measured data minus simulated data) were analysed
graphically in a time series graph, as shown in Figure 14. This form of analysis high-lighted
what often appeared to be daily patterns in the differences between simulated and measured
data, which often occurred at times of daily minimum or maximum site temperature. A
positive residual value = and under calculation of zone temperature. A negative residual value
= an over calculation of zone temperature.
14
Figure 14: Example of residual time series analysis graph
These forms of graphical analysis provide an immediate visual representation of the data and
form the basis for representing the data and results. However, to provide a deeper analysis of
the data will require the use of statistical methods (del Mar Izquierdo 1995, Ghiaus 2003,
Dewsbury 2015), which will be completed and published in future documents.
Methodology summary
The discussion above provides a detailed summary of the steps taken to establish built fabrics,
acquire measured thermal performance data and the detailed building simulation process and
the method used to compare the measured ands simulated data-sets. The next section presents
task-specific experiences and findings from the research tasks.
Results and Discussion
The results and discussion for this research come from eight different experiments. Each
experiment ran for a minimum of twenty days. Each experiment acquired seven data sets
which included measured temperatures, measured energy use, site weather data, BOM
weather data, simulated temperatures and simulated energy use. The total research task has
acquired 56 data sets. The data from each experiment was combined within Excel spread-
sheets, to allow for graphical and analytical comparisons. The task-specific appendices
include the graphical analysis of measured and simulated data for each experiment, within
each task. The following section summarises some of the key findings.
General non task specific results
This research has found several matters that are common across most of the experiments
within each of the two tasks. These are presented below in dot point form.
1. There were often significant differences between the measured and simulated
temperatures from the unenclosed-perimeter platform-floored subfloor zone, as shown
in Figure 15.
Figure 15: Unconditioned subfloor measured and simulated temperatures for mass-timber flooring as thermal
mass
The variation between the measured and simulated subfloor zone temperatures, from
the eight experiments, is shown below in Table 3. This significant variation was due to
15
the current assumption within the NatHERS protocol that the temperature of an
unenclosed-perimeter platform-floored building’s subfloor zone is the same as the site
air temperature. However, this research and previous research (Dewsbury 2011)
demonstrates that this assumption is incorrect. Subject to the energy levels within the
building and the floor built fabric system, (structure, lining and insulation), the energy
flows between the room and the subfloor may be significantly different. In the context
of cool site temperature leading to the operation of heating, a significantly warmer
subfloor zone would lead to a lessor amount of energy loss from the heated room to
the subfloor, leading to a warmer room or a lessor amount of energy use.
Table 3: Variation between measured and simulated subfloor zone temperatures
No-mass Simulation With-mass Simulation
Minimum - 9.1 to – 1.5 Minimum - 9.1 to – 1.6
Maximum + 1.1 to + 4.9 Maximum + 1.1 to + 4.9
Average - 0.3 to - 0.6 Average - 0.3 to - 0.6
There were often significant differences between the measured and simulated temperatures of
the roof space zone, as shown in Figure 16. The greatest differences were observable between
the maximum measured and simulated temperatures. The significance of the differences
between simulated and measured maximum and measured temperatures is shown in
2. Table 4, where variations of up to -17.3oC (over calculation) for minimum zone
temperature and +11.3oC (under calculation) for maximum zone temperature. An
analysis of residual values and global solar radiation indicates that some of these
variations may be due to radiant heat flow calculations. In a similar pattern to the
subfloor scenario discussed above, the significant differences in roof space energy
would effect the energy flow calculations between the roof space and the test cell
room.
Figure 16: Intermittently heated task roof space zone measured and simulated no-mass and with-mass
temperatures for mass-timber partition walls
16
Table 4: Variation between measured and simulated roof space zone temperatures
No-mass Simulation With-mass Simulation
Minimum - 17.3 to – 1.5 Minimum - 13.3 to – 1.6
Maximum + 3.9 to + 11.3 Maximum + 3.2 to + 11.3
Average - 0.2 to + 1.7 Average - 0.2 to + 1.8
The detailed simulations established a ‘raw’ energy use to condition the test building room, as
shown in Figure 17. The green line represents the raw simulation result, whilst the orange line
shows the measured energy use. As the software uses a simplify energy calculation,
significant differences were expected. To account for the coefficient-of-performance (COP),
of the reverse-cycle air-conditioner, the raw energy calculation was divided by 4.86, and is
shown by the red line. This action provided a simulated energy use that was considerably less
than the measured energy use. However, several researchers have found significantly higher
energy consumption by air-conditioning systems, as installed in real buildings, and have
called into question the standard method of testing for COP certification (Dunn 2005, Butler,
Curtis et al. 2013, Mavuri 2014). To better estimate the as-built operational COP of the
installed split-system reverse-cycle air-conditioner, the measured energy and output
performance were analysed resulting in an operational COP closer to 2.4, rather than the
laboratory certified 4.86. Considering there was approximately 400mm distance between the
external inverter and the internal fan system, this significant difference in COP is of concern.
Figure 17: Measured and simulated with-mass energy use for test cell room during the continuously heated
mode of operation
There is a need for simulation tools to allow for the input of heating and cooling
equipment, which accounts for plant and equipment efficiency. However, this research
has shown a significant difference between the laboratory test result and the measured
installed energy use. This difference requires further investigation as the operational
efficiency of the air-conditioner, the thermal resistance of the built fabric, or the
thermal capacitance of the built fabric may all be contributing to the significant
differences.
17
3. One of the key aspects of the implementation of thermal performance regulations is
the capacity to reduce peak energy demands. This research has established three key
aspects, namely:
- the correlation between the simulated and measured test cell room results show that
the software is considering the thermal mass effect of the mass timber elements. This
provides empirical data to support the previous simulation based thermal performance
research, which showed lower energy needs, (or higher star rating results), when
mass-timber improved buildings were compared to normal low mass buildings and
traditional concrete or clay brick thermal mass buildings.
- By further including the built fabric thermal mass, peak energy demand can be
further reduced, as shown below in Figure 18.
- The significant difference between measured use and simulated raw energy
demonstrated that energy efficient appliances would play a significant role in the
reduction of peak energy demand for heating and cooling Australian homes.
Figure 18: Simulated heating energy use for no-mass and with-mass built fabric variations
4. The reverse-cycle air-conditioner was selected based on its efficiency and its capacity
to provide cool air, to allow a comparison of measured and simulated energy use for
cooling. However during this research it was established that the on-board computer
that forms a part of the equipment’s efficiency and compliance, would not allow the
room to be cooled to less than 18oC. Attempts were made to over-ride this control
mechanism but they were unsuccessful. This doomed some of the continuously cooled
tasks, leading to some limited success. Future research must consider the timing of
experiments relative to site climate, to enable the completion of an effective and
productive cooled operation experiment.
5. This research collected surface temperature data from the mass-timber partition walls
and mass-timber flooring, which showed a consistently higher temperature than the
room air temperature, indicating that the mass was storing energy for the air. This data
requires deeper analysis to establish patterns of energy storage that are occurring.
6. This research collected surface flux measurements, which revealed the absorption and
release of energy by the mass-timber walls and mass-timber flooring, which confirms
the mass-timber is acting as a thermal capacitor. This data requires deeper analysis to
18
establish the rate of energy absorption and release relative to the mass and air
temperatures.
To provide a better and more detailed report on the results from each task, they are listed
below in dot point form. In all cases there is further information within the appendix for each
task.
Task specific mass-timber as partition walls as thermal mass results
In this research task, a 90mm thick mass-timber partition was constructed from E. nitens
plantation timber and installed within the very lightweight, unenclosed-perimeter platform-
floored test building, as shown in Figure 7 and Figure 8. Extensive environmental and energy
measurements were taken to provide a measured data set. The building was operated,
unoccupied, in unconditioned, continuously heated, intermittently heated and continuously
cooled modes of operation. The continuously cooled mode did not work as expected but has
still provided valuable data for comparison. Detailed, as-built, no-mass and with-mass
simulations were completed to provide a simulated data set. The analyses in this report have
compared the measured and simulated thermal performance and the relative energy use to
condition the test building room in its four modes of operation.
Initial analysis has revealed several findings, namely:
As mentioned above, there were significant differences between the subfloor
measured and simulated temperatures.
As mentioned above, there were significant differences between the roof space
measured and simulated temperatures.
There were regular, and at times, significant differences between the test building
room’s measured and simulated temperatures. Often the average difference was quite
small, but differences between the simulated and measured maximum and minimum
temperatures were from -1.5oC to +3.2oC, which may have a significant impact on
cooling and heating energy calculations.
The inclusion of the built fabric thermal mass had a variable impact on the test
building room simulations. Subject to operational mode and climatic conditions, the
closeness of fit was generally better from the no-mass simulation type. However, this
does require further analysis.
The detailed analysis, as presented in Appendix 1, shows a reasonable correlation
between simulated and measured temperatures, which confirms the thermal
performance characteristic that mass-timber partition walls can provide effective
thermal mass.
Generally, as much as there were differences observed between the measured and
simulated temperatures, the software did respond to hourly changes in environmental
inputs.
As mentioned above, the simulated raw energy use data was significantly different
from the measured reverse-cycle air-conditioner energy use during heated modes of
operation. This aspect of the software requires further empirical validation and
calibration.
For further task specific information refer to Appendix 1.
19
Task specific mass-timber flooring as thermal mass results
In this research task, three cross-laminated timber panels made from European softwood
species were provided by Tilling. The three panels were laid on top of the existing 19mm
particleboard floor within the lightweight, plywood clad, unenclosed-perimeter platform-
floored test building. Extensive environmental and energy measurements were taken to
provide a measured data set. The building was operated, unoccupied, and unconditioned,
continuously heated, intermittently heated and continuously cooled modes of operation. The
continuously cooled mode only collected thirteen days of relevant data due to a power
fluctuation that caused the reverse-cycle air-conditioner to turn off. Detailed, as-built, no-
mass and with-mass simulations were completed to provide a simulated data set. The analyses
in this report have compared the measured and simulated thermal performance and relative
energy use to condition the test building room in its four modes of operation.
Initial analysis has revealed several findings, namely:
As mentioned above, there were significant differences between the subfloor
measured and simulated temperatures.
As mentioned above, there were significant differences between the roof space
measured and simulated temperatures.
There were regular, and at times, significant differences between the test building
room measured and simulated temperatures. During the unconditioned mode of
operation the average difference was +0.2oC, but the differences between minimum
and maximum temperatures were more significant with a range of -3.2oC to +3.4oC.
Generally, the measured room temperature was warmer than the simulated no-mass
and with-mass data. This could be caused by the mass-timber providing greater
thermal capacitance and/or insulation, or other external influences from the built
fabric, subfloor zone or the roof space zone could be providing more energy than
assumed. This requires further investigation and analysis.
The inclusion of the built fabric mass had a variable impact on the test building room
simulations. Subject to operational mode and climatic conditions, the closeness of fit
was generally better from the no-mass simulation type. However, this does require
further analysis.
The analysis, as presented in Appendix 2, shows a reasonable correlation between
simulated and measured temperatures, which supports the thermal performance
characteristic that mass-timber flooring can provide effective thermal mass and
additional insulation.
Generally, as much as there were differences observed between the measured and
simulated temperatures, the software did respond to hourly changes in environmental
inputs.
As mentioned above, the simulated raw energy use data was significantly different
from the measured reverse-cycle air-conditioner energy use during heated modes of
operation. This aspect of the software requires further empirical validation and
calibration.
For further task specific information refer to Appendix 2.
20
Conclusion & Recommendations
This research undertook an empirical thermal performance assessment of two built fabric
systems in conditioned and unconditioned modes of operation. Each of the built fabric
systems was modelled within a building energy simulation program and used to complete as-
built, experiment specific, detailed thermal performance simulations. From the data discussed
above, and within Appendix 1 and Appendix 2 there were many findings.
Firstly, the general patterns of the measured and simulated data sets for the subfloor, room
and roof space zones were similar, which indicates that the CHENATH software is
considering many built fabric and climatic inputs but requires ongoing improvement and
calibration.
In the unconditioned tasks there were significant differences between the measured and
simulated data sets of the subfloor, room and roof-space zones. The differences often occur at
minimum and maximum temperatures, which would also correspond with times when heating
or cooling operation would be called upon to maintain thermal comfort. If the roof space were
consistently warmer, then more energy would be flowing into the room, similarly if the
subfloor zone were warmer, but cooler than the room; there would be a lesser flow of energy
to the subfloor. Furthermore, the heating and cooling energy calculations may be significantly
affected if the test building room is storing more energy or has a slower loss of energy. All
these instances would impact on the energy within the test building room and corresponding
heating and cooling energy to maintain human comfort. However, some of the differences
appear to be linked to climatic variables, and this requires further investigation.
The Australian building simulation methodology adopts the site air temperature as the
subfloor zone temperature within an unenclosed-perimeter platform-floored building. Past
research has questioned this approach (Dewsbury, Soriano et al. 2009, Dewsbury 2011). This
research has also identified significant differences between the measured subfloor zone
temperature of the 6m x 6m building and the site air temperature. One could presume that the
differences would be greater for a larger building. This aspect requires software improvement
and calibration.
This research developed two simulation types, no-mass modified U-value and with-mass built
fabric thermal mass. This research did show that this variation in the simulation input often
produced significantly different results for the test building room and roof space, with a much
less apparent effect on the subfloor temperatures. However, the two simulation types provided
varying qualities of better fit between the simulated and measured data sets. This requires
further analysis to establish probable benefits from, or problems with, the inclusion of the
built fabric thermal mass, and to ongoing software development and algorithmic
improvement.
The analysis of the measured and simulated energy use raised more questions than answers.
As a reverse-cycle air-conditioner was used to provide heating and cooling it was expected
that there would be significant differences between the measured and simulated data sets.
However, it was expected that when a COP multiplier was used the differences between the
measured and simulated data sets would reduce. However, the application of the COP
multiplier allowed the measured energy use to be greater than the simulated energy use. This
is a complex issue and requires further investigation, as the built fabric or the true efficiency
of an installed reverse-cycle air-conditioner could be the cause the differences. One of the
challenges that may face the deeper analysis of the reverse-cycle air-conditioner coefficient-
of-performance is the current approved laboratory based testing method. The differences
between a laboratory and the variability of a site environment and installation practise may be
providing systemic losses that reduce the COP. This does require further investigation.
Furthermore, one of the key aspects of thermal performance legislation is to reduce both
21
general and peak energy demands. The use of reverse-cycle air-conditioners in this task
showed a significantly lower measured peak energy demand when compared to the raw
simulated energy needs, indicating that high efficiency appliances need to be included within
the regulatory mix for heating and cooling of buildings.
The two tasks, mass-timber as partition walls and mass-timber as flooring, both produced
results which confirmed the ability for mass-timber to act as a thermal capacitor, an additional
insulator, reduce general heating and cooling energy loads and reduce peak heating and
cooling energy loads. This confirms the potential for mass-timber elements to improve the
thermal performance with small to medium buildings, which was established in the previous
desktop-based building simulation research. This potential is corroborated by the reasonable
correlation between the measured and simulated data sets, which provides initial empirical
validation. The additional data, which included the surface temperatures and surface flux
measurements provide additional supporting documentation of the thermal capacitor and
thermal insulation properties. However, as discussed in the introduction, further research
needs to occur to ensure that the right climate specific amount of mass-timber, as thermal
capacitance, is designed into new and retrofitted to existing buildings.
Additionally, when used as a component of the external structure mass-timber elements
provide additional thermal resistance and reduce the opportunities for unwanted infiltration
and exfiltration. The thermal resistance benefits were validated within the mass-timber
flooring as thermal mass task. However the benefits that may be achieved from infiltration
and exfiltration reduction have not been tested yet.
This research task has raised many questions but some key areas of future research have been
identified, namely:
Mass-timber
This task collected data on mass-timber surface temperatures and flux. This data needs
to be further analysed as it included Tasmanian plantation hardwood and European
softwood mass-timber materials. The data requires further analysis to establish the rate
of energy absorption and release subject to the test cell room temperature.
This task has not had the capacity to explore the thermal performance benefits that
may be achieved from mass-timber as insulation and thermal mass as in internal
lining, or as a ceiling, or as a combined floor, external wall lining, partition wall and
ceiling system. This focused research must occur to provide an informed marketing
advantage over traditional concrete and clay brick massive elements.
The opportunity to construct a small building with mass-timber elements as floor,
lining and ceiling needs to occur to test and validate the infiltration and exfiltration
benefits that may occur from this comprehensive building system.
Further research needs to occur to support the development of Australian low-grade
plantation wood use as locally made mass-timber materials.
CHENATH & AccuRate calibration
A newer version of AccuRate with algorithmic improvements within the CHENATH
program has recently been released. These simulations described above should be
completed a second time to establish if the CHENATH improvements have reduced
the differences between measured and simulated data sets.
22
The tasks completed within this research need to be continued, so as to test other built
fabric systems and the accuracy with which Australian thermal performance tools
simulate temperatures and energy used to maintain human comfort.
Heating and Cooling Energy
The reverse-cycle air-conditioner measured and simulated raw and COP applied
energy uses are significantly different. This requires further investigation to ascertain
if it is a built fabric or appliance-based issue.
The test buildings have fan heaters installed. Now that the data acquisition process
and test building room control has been demonstrated, it would be beneficial to
collect a comparison energy use data set from less efficient heating sources.
Similarly, other forms of heating and cooling could be tested.
Finally, this research task collected a large amount of data that needs further analysis and
publishing within research and industry based publications to ensure the continuing
increase in building science knowledge in Australia and internationally. This data and its
analysis are needed by software developers to ensure thermal simulation algorithms and
concepts are continuously improved.
Appendices
Supporting documents to this research report are included as appendices. Each appendix
focuses on a particular research task, namely:
- Appendix 1: Mass-timber partition walls as thermal mass
- Appendix 2: Mass-timber flooring as thermal mass
Acknowledgements
This research was made possible by the significant technical and financial support provided
by:
Forest & Wood Products Australia
The University of Tasmania
CSIRO
Department of Industry
CSR Bradfords
Aurora Energy
Tilling
Carawah
Daikin
Jessups Solar Squad
23
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