Market Access Timber Framed Residential Housing: Thermal Bridging & The path to 7 Star - Forest and Wood Products Australia

Market Access

 Timber Framed Residential Housing:
 Thermal Bridging & The path to 7 Star
 NatHERS

 Project number: PRA526-1920 May 2021

Level 11, 10-16 Queen Street
Melbourne VIC 3000, Australia
T +61 (0)3 9927 3200 E info@fwpa.com.au
W www.fwpa.com.au

Timber Framed Residential Housing:
Thermal Bridging & The path to 7 Star NatHERS

 Prepared for

 Forest & Wood Products Australia

 by

 Philip Christopher, Khuong Bui & Tuan Ngo

Publication: Timber Framed Residential Housing: Thermal
 Bridging & The path to 7 Star NatHERS

Project No: PRA526-1920

IMPORTANT NOTICE

This work is supported by funding provided to FWPA by the Department of Agriculture, Water
and the Environment (DAWE).

© 2021 Forest & Wood Products Australia Limited. All rights reserved.

Whilst all care has been taken to ensure the accuracy of the information contained in this publication,
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ISBN: 978-0-9586704-1-8

Researcher/s:

University of Melbourne, The Department of infrastructure Engineering:

Dr. Philip Christopher, Dr. Khuong Bui, Prof. Tuan Ngo

Final report received by FWPA in April 2021

Forest & Wood Products Australia Limited
Level 11, 10-16 Queen St, Melbourne, Victoria, 3000
T +61 3 9927 3200 F +61 3 9927 3288
E info@fwpa.com.au
W www.fwpa.com.au

Contents
Table of Tables ................................................................................................................................................6

Version Control ...............................................................................................................................................8

Executive summary .........................................................................................................................................9

 1.1. Introduction .................................................................................................................................11

2. Scope of Assessment ...........................................................................................................................11

 2.1. Assessment Methods ...................................................................................................................11

 2.2. Houses Plans ................................................................................................................................11

 2.2.1. HIA Standard Home .............................................................................................................12

 2.2.2. The volume builder two storey home – “Lynvale” ..............................................................15

 2.3. Wall Construction Types ..............................................................................................................17

 2.4. Windows and Glazing ...................................................................................................................18

 2.5. Flooring Systems ..........................................................................................................................20

 2.5.1. Timber Sub Floor (Suspended).............................................................................................20

 2.5.2. Concrete Slab on Ground (CSOG) ........................................................................................20

 2.5.3. Waffle Pod ...........................................................................................................................20

 2.6. Other Parameters Assessed .........................................................................................................21

3. Results..................................................................................................................................................22

 3.1. Melbourne based parametric assessments. ................................................................................22

 3.1.1. HIA Standard House .............................................................................................................23

 3.1.2. Lynvale Standard House ......................................................................................................30

 3.2. Australia Wide Parametric Assessment .......................................................................................33

 3.2.1. HIA house with Low-E windows and CSOG ..........................................................................35

 3.2.2. HIA house with double glazing and waffle pod ...................................................................42

4. Discussion ............................................................................................................................................50

 4.1. House plan and passive design ....................................................................................................50

 4.2. The Importance of Window Selection..........................................................................................51

 4.3. The Impact of Floor Type .............................................................................................................54

 4.4. The Impact of Wall Type ..............................................................................................................54

 4.5. Additional Variations....................................................................................................................56

5. Thermal Bridging Assessment..............................................................................................................57

 2

5.1. Introduction to thermal bridging standards ................................................................................57

 5.1.1. NZS 4214 (AS/NZS 4859.1) Method .....................................................................................57

 5.1.2. ISO 6946 Method .................................................................................................................60

 5.2. Wall Profiles Assessed ..................................................................................................................63

 5.2.1. Light Weight Direct Fix (LWDF) Timber frame .....................................................................63

 5.2.2. Light Weight Direct Fix Steel Frame.....................................................................................65

 5.2.3. Brick Veneer Timber frame ..................................................................................................66

 5.2.4. Brick Veneer Steel frame .....................................................................................................68

 5.3. Thermal Bridging Results .............................................................................................................70

 5.3.1. Parametric Assessments ......................................................................................................71

 5.3.2. Mitigating thermal bridging for steel wall frames ...............................................................73

 5.4. Thermal Bridging Summary ..........................................................................................................77

6. Conclusions ..........................................................................................................................................78

7. Further Work .......................................................................................................................................80

8. Appendix ..............................................................................................................................................81

 8.1. Climate Zone Details ....................................................................................................................81

 8.2. Wall Construction Types ..............................................................................................................81

 8.2.1. Standard Brick Veneer Wall 90 mm studs ...........................................................................81

 8.2.2. Standard Brick Veneer Wall 90 mm studs and reflective air cavity .....................................83

 8.2.3. Brick Veneer 140 mm studs .................................................................................................84

 8.2.4. Brick Veneer 70 mm Studs ...................................................................................................85

 8.2.5. Cross laminated timber (CLT) XLAM ....................................................................................86

 8.2.6. Light Weight Direct Fix .........................................................................................................87

 8.2.7. Light Weight Direct Fix 70mm .............................................................................................88

 8.2.8. High Performance 140mm ...................................................................................................89

 8.2.9. Reverse Brick Veneer ...........................................................................................................90

 8.2.10. High Performance Light Weight ...........................................................................................91

 8.2.11. 75mm Hebel with R 2.0 .......................................................................................................92

 8.2.12. 75 mm Hebel with R 2.7.......................................................................................................93

 8.3. HIA Standard Home Plans ............................................................................................................94

9. References ...........................................................................................................................................97

 3

Table of Figures
Figure 1: 7 Star NatHERS house (Australian Government 2018) ....................................................................1

Figure 2. Floor plan of the HIA home ............................................................................................................12

Figure 3. Floor plan of the Lynvale home .....................................................................................................16

Figure 4: Timber sub-floor and standard insulation .....................................................................................20

Figure 5: Waffle Pod Construction ................................................................................................................21

Figure 6: HIA house with sub floor - wall type assessment results for Melbourne ......................................25

Figure 7: HIA house with sub floor - Window Type Assessment Results for Melbourne .............................26

Figure 8: HIA House With Sub Floor - Additional Parametric Assessment Results for Melbourne ..............27

Figure 9: Lynvale Standard home wall type assessment results for Melbourne ..........................................31

Figure 10: Lynvale Standard home wall type assessment results for Melbourne ........................................32

Figure 11: Parametric Assessment Results of the HIA Economical house in Melbourne .............................35

Figure 12: Parametric Assessment Results of the HIA house with Low-E windows and CSOG in Brisbane .37

Figure 13: Parametric Assessment Results of the HIA house with Low-E windows and CSOG in Hobart ....38

Figure 14: Parametric Assessment Results of the HIA house with Low-E windows and CSOG in Sydney ....39

Figure 15: Parametric Assessment Results of the HIA house with Low-E windows and CSOG in Perth.......40

Figure 16: Parametric Assessment Results of the HIA house with Low-E windows and CSOG in Canberra 41

Figure 17: Parametric Assessment Results of the HIA house with double glazing and waffle pod in
Melbourne ....................................................................................................................................................43

Figure 18: Parametric Assessment Results of the HIA house with double glazing and waffle pod in Brisbane
......................................................................................................................................................................45

Figure 19: Parametric Assessment Results of the HIA house with double glazing and waffle pod in Hobart
......................................................................................................................................................................46

Figure 20: Parametric Assessment Results of the HIA house with double glazing and waffle pod in Sydney
......................................................................................................................................................................47

Figure 21: Parametric Parametric Assessment Results of the HIA house with double glazing and waffle pod
in Perth..........................................................................................................................................................48

Figure 22: Parametric Assessment Results of the HIA house with double glazing and waffle pod in Canberra
......................................................................................................................................................................49

Figure 23: Impact of Eaves on Home performance for the HIA house with sub floor..................................50

Figure 24. Impact of Glazing Type on HIA High Performance Home - Star Rating and approximate costing
for Melbourne, ..............................................................................................................................................52

Figure 25: Impact of Glazing Type on HIA High Performance Home - Star Rating and approximate costing
for Brisbane...................................................................................................................................................53

 4

Figure 26. Results of the HIA with subfloor home's parametric assessment for wall type in Melbourne ...55

Figure 27. Results of the Lynvale home's parametric assessment for wall type in Melbourne ...................55

Figure 28: Impact of wall and window performance on wall system R value ..............................................56

Figure 29: Transformation method for metal frame sections (NZS4214-2006) ...........................................58

Figure 30. Sections and layers of a thermally inhomogeneous component ................................................60

Figure 31: LWDF Timber frame wall build up ...............................................................................................63

Figure 32: Light Weight Direct Fix External Wall Elevation Profile (Timber Frame) .....................................64

Figure 33: LWDF Steel frame wall build up ...................................................................................................65

Figure 34: LWDF Steel Frame Wall Elevation Profile ....................................................................................66

Figure 35: Wall Build up for Brick Veneer Timber frame ..............................................................................67

Figure 36: Brick Veneer Timber Frame Elevation Profile ..............................................................................67

Figure 37: Wall Build up for Brick Veneer Steel frame .................................................................................68

Figure 38: Brick Veneer Steel Frame Elevation Profile .................................................................................69

Figure 39: Comparison of R-value of system ................................................................................................70

Figure 40: The effect of thickness of the contact resistances on the total R-value of a wall system. ..........71

Figure 41: The effect of thickness of steel on (a) Light Weight Direct Fixed Wall, (b) Brick Veneer Wall ....72

Figure 42 The effect of Thermal break on (a) Light Weight Direct Fixed Wall, (b) Brick Veneer Wall..........74

Figure 43 The effect of insulation on (a) Light Weight Direct Fixed Wall, (b) Brick Veneer Wall .................76

Figure 44: ABCB climate zones (Australian Bureau of Statistics, 2013) ........................................................81

Figure 45: Brick Veneer External Wall Construction and Insulation .............................................................82

Figure 46: Brick Veneer with reflective air cavity shown here with R 2.7 Batts ...........................................83

Figure 47: Brick Veneer 140 mm External Wall Construction and Insulation ...............................................84

Figure 48: Brick Veneer 70 mm External Wall Construction and Insulation .................................................85

Figure 49: Cross Laminated Timber XLAM External Wall Construction And Insulation................................86

Figure 50: Light Weight Direct Fix External Wall Construction And Insulation.............................................87

Figure 51: Light Weight Direct Fix 70 mm External Wall Construction And Insulation ................................88

Figure 52: High Performance 140mm External Wall Construction And Insulation ......................................89

Figure 53: Reverse Brick Veneer External Wall Construction And Insulation ...............................................90

Figure 54: High Performance Light Weight External Wall Construction And Insulation ..............................91

Figure 55: 75mm Hebel with R 2.0 External Wall Construction And Insulation ...........................................92

Figure 56: 75mm Hebel with R 2.7 External Wall Construction And Insulation ...........................................93

Figure 57: HIA Standard HOME (HIA 2013)...................................................................................................94

 5

Figure 58: HIA Standard Home Sections (HIA 2013) .....................................................................................95

Figure 59: HIA Standard Home Site Map (HIA 2013) ....................................................................................96

 Table of Tables
Table 1. Details of the HIA home ..................................................................................................................12

Table 2. HIA economical house with subfloor baseline building envelope details.......................................13

Table 3. HIA house with Low-E windows and CSOG - Building Envelope Details .........................................14

Table 4. HIA house with double glazing and waffle pod - building envelope details ...................................15

Table 5. Details of the Lynvale home ............................................................................................................15

Table 6. The properties of the baseline model of Lynvale home .................................................................17

Table 7: Summary of wall types assessed .....................................................................................................18

Table 8: Window Types in Assessment (Sustainability Victoria, 2020).........................................................19

Table 9: Melbourne Based Parametric Assessments Summary....................................................................22

Table 10. HIA house with sub floor simulation results for Melbourne.........................................................24

Table 11: Proposed 7 Star solutions for HIA Standard Home .......................................................................28

Table 12: High performance combinations for HIA standard home in Melbourne ......................................29

Table 13. Results of the Lynvale home's parametric assessment at Melbourne .........................................30

Table 14: High performance Lynvale home combinations ...........................................................................32

Table 15: Australia Wide Parametric Assessment Summary ........................................................................34

Table 16: HIA house with Low-E windows and CSOG in Melbourne ............................................................35

Table 17: HIA house with Low-E windows and CSOG in Brisbane ................................................................36

Table 18: HIA house with Low-E windows and CSOG in Hobart ...................................................................38

Table 19: HIA house with Low-E windows and CSOG in Sydney...................................................................39

Table 20: HIA house with Low-E windows and CSOG in Perth .....................................................................40

Table 21: HIA house with Low-E windows and CSOG in Canberra ...............................................................41

Table 22: HIA house with double glazing and waffle pod in Melbourne ......................................................43

Table 23: HIA house with double glazing and waffle pod in Brisbane ..........................................................44

Table 24: HIA house with double glazing and waffle pod in Hobart.............................................................46

Table 25: HIA house with double glazing and waffle pod in Sydney ............................................................47

Table 26: HIA house with double glazing and waffle pod in Perth ...............................................................48

Table 27: HIA house with double glazing and waffle pod in Canberra .........................................................49

 6

Table 28: Costing for Windows and Glazing,.................................................................................................51

Table 29: Material Properties for LWDF Timber Frame................................................................................64

Table 30: Material Properties for LWDF Steel Frame ...................................................................................66

Table 31: Material Properties for BV Timber Frame.....................................................................................68

Table 32 Material Properties for BV Steel Frame .........................................................................................69

Table 33. R-value of each wall type based on NZS 4214 and ISO 6846 ........................................................70

TABLE 34. R-VALUE OF EACH WALL TYPE BASED ON NZS 4214 AND ISO 6846 (SPECKEL 2021, KOMPLI 2021) ...............71

Table 35: Location and Climate Zones ..........................................................................................................81

 7

Version Control
Version Number Comments Date
1.0 Work to date excluding thermal bridging study 07/11/20
 Revisions and updates – supersedes Version 1.0 which
2.1 17/02/21
 should be deleted.
 Window costing updated, further Brick Veneer wall
2.2 23/02/21
 types added, expanded discussion section & addition
 of Further Work section.
 Inclusion of comments from HIA and glazing costs from
2.3 20/04/21
 the Australian Glass and Window Association

 8

Executive summary
With the Australian Governments in the process of considering increasing the required star ratings of
houses and apartments to equivalence of 7 Star NatHERS rating in the next revision of the National
Construction Code due in 2022, this work has investigated how current residential timber framed houses
around Australia can meet this standard. Forest and Wood Products of Australia (FWPA) commissioned
this study to investigate a variety of different floor, ceiling, wall and window types to determine what
combinations will achieve better thermal performance according to NatHERS to meet future requirements.
Additionally, an investigation into the implications of thermal bridging on steel and timber framed wall
systems was to be assessed using both the Australian and international ISO standards.

As such the scope of this study was to (1) investigate realistic and practical measures that can be
implemented to meet the new minimum of 7-stars and hence what impact that has on the nature of timber
framed homes and (2) investigate the impact of thermal bridging for both steel and timber framed wall
systems. Modelling has been performed in FirstRate5® house energy rating software for two house plans
and four baseline homes in six capital cities around Australia with results detailing NatHERS Star rating as
well as the heating and cooling loads for each home in MJ/m2.

Solutions that achieved 7 Star NatHERS ratings in predominantly heating climates comprised either
combinations of double glazing and high-performance wall insulation, single glazing and waffle pod slabs
or high-performance ceiling and wall insulation with single glazing. 7 Star NatHERS rated homes were more
readily achievable in more mild climates such as Sydney and warmer climates such as Brisbane with 7 Star
solutions comprising more moderate upgrades to building insulation or double glazing in select rooms.
These solutions were however contingent on the design of the home such that passive solar heat gain in
winter was sufficient throughout living areas whilst solar heat gain in summer was minimised with either
eaves or awnings. This study also found that homes constrained to a narrower lot and hence reduced
passive design had difficulty in meeting the 7 Star performance band in the Melbourne climate despite
significant building fabric upgrades. This highlighted the need to allow for new regulations to allow for
additional compliance pathways for these homes beyond just heating and cooling energy requirements.

Thermal bridging was found to have a significant impact on both timber and steel framed wall systems
reducing the apparent R value by up to 22% and 40% respectively. Light Weight Direct Fix (LWDF) systems
showed the greatest susceptibility to thermal bridging and the NZS 4214 calculation method yielded higher
overall R values for steel framed systems when compared to the ISO 6946 analytical method. This report
recommends the use of the ISO 6946 method due to its greater accuracy and more robust calculation
method. This report found that if a deemed to comply regulatory approach were adopted for steel and
timber wall frame systems, such that they were to perform comparatively then the steel framing system
would require increased thermal resistance (either insulation or unventilated reflective air cavities)
adjacent to the thermally bridged section. Thermal breaks of approximately R = 0.5 m2K/W would be
required for a typical brick veneer steel framed wall to perform on par with a timber framed system.

Based on the analysis the following general findings have been made:

 • Achieving 7 Star NatHERS ratings will require a combination of approaches which varied depending
 upon climate zone but typically required either double glazing in living and day use spaces or
 upgraded floor, R 6.0 ceiling insulation and R 2.7 wall insulation.

 9

• The greatest influencing factor on the performance of each house was the windows, with double
 glazing typically adding around 0.5 stars and high-performance double glazing adding up to 1.6 Stars
 when compared with single glazed Low-E windows. This was true for both heating and cooling
 climates.
• PVC framed glazing units represented the best value in terms of cost to performance with lower
 cost than aluminium and superior performance with 7 Stars achievable for a typical three bedroom
 with approximately $2,250 of additional investment in double glazed PVC windows
• Predominantly heating climates benefited from glazing with higher Solar Heat Gain Coefficient
 (SHGC) windows whilst cooling climates like Brisbane benefited from lower SHGC windows.
• There was marginal benefit of double glazing in night use spaces (bedrooms) for heating climates
 (around 0.2 Stars) but significant benefit of double glazing in night use spaces for cooling climates
 (around 0.5 Stars)
• Timber frames outperformed non-thermally broken aluminium framed windows (typically adding
 0.3 Stars) and performed slightly better than thermally broken aluminium framed windows
 (typically adding 0.1 Stars).
• Flooring systems demonstrated a large impact on building performance but without a clear trend.
 Frequently waffle pods were the best performing solutions however Timber Sub floor systems
 performed on par (when insulated with R 2.0) in Hobart but significantly worse in warmer climates
 such as Brisbane. Further investigation is recommended into the assumptions and validity of the
 Chenath engine and performance of thermal mass, earth linkage and passive design.
• Wall systems were of secondary importance when compared to windows, however when combined
 with high performance window solutions were able to significantly contribute to better performing
 homes. The high performance 140 mm lightweight cladding and reverse brick veneer were the best
 performing and when combined with other measures were able to obtain over 8 Stars for Sydney,
 Perth and Brisbane.
• Common wall systems such as brick veneer and light weight direct fix (LWDF fibre cement)
 performed relatively similar.
• Good passive design was also found to have a significant impact on the overall performance of the
 homes assessed with the HIA home outperforming the Lynvale home by an average of 1 NatHERS
 Stars given the same building fabric selections. Eaves, natural light in living spaces and a presence
 of a stairwell attached to the living space all played a major part in the home’s performance.
• Higher performing buildings were more readily achievable in more mild climates such as Brisbane,
 Perth and Sydney. Cooler climates such as Melbourne, Canberra and Hobart all were also able to
 achieve 8 Stars but required more significant thermal envelope upgrades.

 10

1.1. Introduction
The Australian and State and Territory Governments will introduce more stringent thermal performance
requirements for residential homes in the next revision of the National Construction Code due in 2022. It
is anticipated that a 7-star minimum (up from the current minimum of 6-stars) NatHERS Star Rating will be
the requirement for new residential homes. Clearly, improvements will need to be made to the thermal
envelope of residential buildings in order to meet the new standards.

As such the scope of this study is to (1) investigate realistic and practical measures that could be
implemented to meet the proposed energy efficiency standards and what impact that will have on the
nature of timber framed homes and (2) investigate the impact of thermal bridging on wall section R values
in order to ascertain requirements for both timber and steel framed systems to perform comparably.

2. Scope of Assessment
 2.1. Assessment Methods
In order to ascertain the performance of each home and subsequent parametric analysis, homes have been
modelled in the FirstRate5® house energy rating software (Sustainability Victoria, 2020). This software
integrates the AccuRate calculation engine (Chenath) to estimate the annual heating and cooling energy
and can be used to rate an existing design or as an interactive tool to optimise the design beyond
compliance. This software can be used to issue certificates of compliance for Energy Assessors, however
for this project formal compliance was not required, and as such the star rating and energy consumption
was recorded for each assessment.

Assessments utilised base case homes as discussed in the next section of this report. These base cases
considered typical building fabric and construction methods. Modifications were then made to this base
case, one at a time, in order to ascertain the impact of changing this parameter on the overall thermal
performance of the home. Upon investigating individual performance changes, measures were combined
in order to obtain greater NATHERS Star Ratings. The benefits of individual measures have been captured
in isolation as well as when combined with other effective measures. A total of six climate zones were
assessed as presented in Table 35 in the appendix.

 2.2. Houses Plans
To account for variation in the layout, size and number of storeys and the impact this has on the thermal
performance of different building fabric solutions, two distinct homes have been selected for analysis. Each
of these homes consist of a baseline where typical minimum building practices have been selected and
compared with subsequent changes in building fabric and improvements in order to meet 7-star and
beyond.

 11

2.2.1. HIA Standard Home
The HIA standard home has been used by HIA for training purposes for over a decade, and it is relatively
representative of common detached housing construction in the southern states of Australia. The floor
plan of the HIA home is shown in Figure 2. This home consists of three bedrooms, two bathrooms, a garage
and an open plan living kitchen area. The details of which including floor area, wall area and window ratios
are provided in Table 1. Full plan details are provided in the Appendix of this report.

FIGURE 2. FLOOR PLAN OF THE HIA HOME

TABLE 1. DETAILS OF THE HIA HOME

 Number of floors 1

 Number of bedrooms 3

 Total floor area 140.6 (m2)

 Total garage area 36.3 (m2)

 External wall area 148.5 (m2)

 Window area 30.8 (m2)

 Window-to-wall ratio 20.7 (%)

 12

A total of three baseline HIA homes were assessed in this report. The first “HIA House with subfloor” was
intended to represent a standard build with a sub floor rather than CSOG. The construction materials were
selected to represent common building practice as well as minimum compliance to the BCA. As such this
home achieved a star rating of 6.0 Stars and was calculated to require 113.7 MJ/m2 for heating and cooling
when located in Melbourne (Climate Zone 21). The baseline wall construction consisted of brick veneer
with insulation and build up details provided in Table 2. As the results section will detail, this home was
used to perform the most comprehensive set of parametric assessments for Melbourne to ascertain the
impact of changing a variety of building attributes.

TABLE 2. HIA ECONOMICAL HOUSE WITH SUBFLOOR BASELINE BUILDING ENVELOPE DETAILS

 Component Property
 Brick veneer, 90mm timber stud wall and R 2.25 insulation as
 Wall-type
 detailed in Figure 45
 Aluminium Framed High Solar Gain Low-E in Living/Day spaces
 Window-type (U = 5.4 SHG = 0.49) and Aluminium Framed single glazed clear
 in bedrooms and other areas (U = 6.7 SHG = 0.57)
 Floor-type Timber Sub Floor with R 2.0 insulation
 Ceiling insulation R = 4.0 (m2K/W)
 Ceiling type Discontinuous
 Roof colour Medium
 Carpet in Bedroom zones, timber in living and day areas, tiles for
 Floor Coverings bathrooms and laundry and concrete slab on ground (CSOG) for
 garage
 Ceiling Height 2.4 m
 Standard 90mm uninsulated stud wall excluding the internal
 Internal Walls
 garage wall which comprised R 2.0 Insulation
 Additional Fixtures All downlights and ventilation were sealed

 NatHERS Performance [113.7 represents total heating and cooling consumption in
 MJ/m2 whilst 79.9 and 33.8 represent the heating and cooling
 portions respectively]
The second HIA home substituted the timber sub floor with a CSOG and upgraded the windows in the night
conditioned spaces to Low-E. As the results section will detail this home was used to perform the Australia
wide parametric assessments to ascertain the impacts of changing more common building envelope
parameters on the performance for a variety of climate zones. The baseline details and NatHERS Star rating
of 6.9 in Melbourne is detailed in Table 3.

 13

TABLE 3. HIA HOUSE WITH LOW-E WINDOWS AND CSOG - BUILDING ENVELOPE DETAILS

 Component Property
 Brick veneer, 90mm timber stud wall and R 2.25 insulation as
 Wall-type
 detailed in Figure 45
 Aluminium Framed High Solar Gain Low-E in all areas (U = 5.4
 Window-type
 SHG = 0.49)
 Floor-type 100mm CSOG
 Ceiling insulation R = 4.0 (m2K/W)
 Ceiling type Discontinuous
 Roof colour Medium
 Carpet in Bedroom zones, timber in living and day areas, tiles for
 Floor Coverings bathrooms and laundry and concrete slab on ground (CSOG) for
 garage
 Ceiling Height 2.4 m
 Standard 90mm uninsulated stud wall excluding the internal
 Internal Walls
 garage wall which comprised R 2.0 Insulation
 Additional Fixtures All downlights and ventilation were sealed

 NatHERS Performance

The third HIA home “HIA house with double glazing and waffle pod” was selected to provide a high-
performance solution from which to compare the impact of different building materials. As such this
baseline consisted of double glazed Low-E timber framed windows and a waffle pod floor. Timber framed
windows could also be substituted with PVC equivalents to reduce cost and achieve very similar
performance. As detailed in the results section of this report this home was used to compare a variety of
climate zones, window types, floor systems and wall types. This high-performance baseline achieved a
NatHERS Star rating of 7.5 in Melbourne with the full details provided in Table 6.

 14

TABLE 4. HIA HOUSE WITH DOUBLE GLAZING AND WAFFLE POD - BUILDING ENVELOPE DETAILS

 Component Property
 Brick veneer, 90mm timber stud wall and R 2.25 insulation as
 Wall-type
 detailed in Figure 45
 Double Glazed Low E timber framed glazing in all spaces (U = 3.1
 Window-type
 SHG = 0.49)
 175-85 mm Waffle pod with equivalent insulation of R 0.56
 Floor-type
 m2K/W
 Ceiling insulation R = 4.0 (m2K/W)
 Ceiling type Discontinuous
 Roof colour Medium
 Carpet in Bedroom zones, timber in living and day areas, tiles for
 Floor Coverings
 bathrooms and laundry
 Ceiling Height 2.4 m
 Standard 90mm uninsulated stud wall excluding the internal
 Internal Walls
 garage wall which comprised R 2.0 Insulation
 Additional Fixtures All downlights and ventilation were sealed

 NatHERS Performance

 2.2.2. The volume builder two storey home – “Lynvale”
The second home selected for assessment was selected based on publicly available plans for a typical two
storey home to be referred to as the Lynvale home. This house comprises a relatively narrow frontage to
allow for tighter blocks and provides four bedrooms and a cinema or multi-purpose room. This house did
not include eaves nor did it have significant daylighting in the living and kitchen zones, and as such was
expected to perform less favourably than the HIA standard home. The floor plan of the Lynvale home is
shown in Figure 3 with the details provided in Table 6.

TABLE 5. DETAILS OF THE LYNVALE HOME

 Number of floors 2

 Number of bedrooms 4

 Total floor area 152 (m2)

 Total garage area 30 (m2)

 External wall area 243 (m2)

 Window area 50 (m2)

 Window-to-wall ratio 20.6 (%)

 15

First Floor
 Ground Floor
FIGURE 3. FLOOR PLAN OF THE LYNVALE HOME

A baseline model of Lynvale home was also developed, however given the lack of passive design for the
home greater performing windows were required to achieve the minimum 6 Star NatHERS rating. Key
assumptions and parameters for the Lynvale home are shown in Table 6. The same brick veneer external
wall and internal walls were selected as in the HIA home.

 16

TABLE 6. THE PROPERTIES OF THE BASELINE MODEL OF LYNVALE HOME

 Component Property
 Wall-type Brick veneer
 Floor-type Timber sub-floor with R 2.0 Insulation
 Ceiling insulation R = 4.0 (m2K/W)
 Ceiling type Discontinuous
 Roof colour Medium
 Carpet in Bedroom zones, timber in living and day areas,
 Floor Coverings tiles for bathrooms and laundry and concrete slab on
 ground (CSOG) for garage
 Ceiling Height 2.4 m
 Standard 90mm uninsulated stud wall excluding the
 Internal walls
 internal garage wall which comprised R 2.0 Insulation
 Ceiling fan included in the living space whilst all
 Additional fixtures
 downlights and ventilation were sealed

 NatHERS Performance

 2.3. Wall Construction Types
In order to ascertain the impact of a variety of wall build ups on the thermal performance of the two
selected homes a variety of available construction types were selected for assessment. All construction
types were simulated for the HIA standard home in Melbourne before. Through consultation with FWPA,
the list was refined to more common and feasible construction systems that were then further assessed in
the Lynvale home and for the HIA home in other major centres around Australia. Table 7 summarises the
wall types assessed with the full wall build ups specified in Section 8.2. of the Appendix.

 17

TABLE 7: SUMMARY OF WALL TYPES ASSESSED

 Wall Description Insulation Insulation Air Overall Overall R Value (excluding
 thickness R value Gap Wall any thermal bridging) 1
 (mm) (m2·K/W) (mm) thickness (m2·K/W)
 (mm)
 Brick Veneer 90 2.25 50 260 2.65
 Brick Veneer High 90 2.7 50 260 3.10
 Performance
 Brick Veneer with 90 2 or 2.7 50 260 2.77-3.47
 reflective air cavity
 Brick Veneer 140 140 3.5 50 310 3.97
 mm studs
 Brick Veneer 70 70 1.75 50 240 2.15
 mm studs
 Cross Laminated 66 1.5 20 205 2.78
 Timber (XLAM)
 Light Weight 90 2.25 N/A 113 2.39
 Direct Fix 90 mm
 Light Weight 70 1.75 N/A 93 1.89
 Direct Fix 70 mm
 High Performance 140 3.5 20 + 221 3.87
 140 mm 45
 Reverse Brick 90 2.25 N/A 220 2.49
 Veneer
 High Performance 180 4.09 N/A 199 4.18
 Light Weight
 75mm Hebel 80 2.0 35 200 2.8
 Standard
 75mm Hebel High 108 2.7 35 228 3.5
 performance

 2.4. Windows and Glazing
Window types that were assessed included a variety of different glazing types as well as frame systems in
order to identify the benefit of each. Three different window frames were also assessed including timber,
aluminium and aluminium with a thermal break. A summary of the glazing performance for each type
assessed is shown in Table 8.

1
 NatHERS software currently does not take into account thermal bridging for wall, ceiling or floor framing

 18

TABLE 8: WINDOW TYPES IN ASSESSMENT (SUSTAINABILITY VICTORIA, 2020)

 Glazing Type Frame Thermal Abbreviation U Value Solar Heat Gain Approximate
 Type Break (W/m2 K) Coefficient Cost/m2
 (SHGC) ($AUD)2
 Single Aluminium No SG-Al-CLR 6.7 0.57 124
 glazing clear
 Single Aluminium No SG-Al-LE 5.4 0.49 218
 glazing,
 Low-E
 Single UPVC No SG-UPVC-LE 4.3 0.5 376
 Glazed Low-
 E
 Double Aluminium No DG-Al-CLR 4.8 0.51 224
 glazing clear
 Double Timber No DG-Tb-CLR 3.0 0.48 451
 glazing clear
 Double Aluminium No DGAr-Al-LE 4.1 0.52 376
 Argon filled,
 Low-E
 Double Aluminium Yes DGAr-Al-LE- 3.1 0.49 526
 Argon filled, TB
 Low-E
 Double Timber No DGAr-Tb-LE 2.0 0.31 564
 Argon filled,
 Low-E
 Double Air UPVC No DG-UPVC- LE 2.3 0.26 356
 filled, Low-E
 Double UPVC No DGAr-UPVC- 2.0 0.25 376
 Argon filled, LE
 Low-E
For the HIA standard home two key configurations were used, the first was upgraded high performance
glazing only in the living and day use spaces and the second incorporated fit out of the entire home with
the high-performance glazing. This was done to determine the additional benefit of installing high
performance glazing in spaces that are only conditioned at night.

2
 Costing is approximate only and will vary according to location and other factors. These costs are based on
supply only and exclude installation. Local data sourced using Rawlinsons Construction Guide (Rawlinsons, 2019)
and the assumption that timber frames cost 50% more than standard aluminium frames whilst thermal broken
aluminium frames add approximately 40% to the cost (Home Improvement Pages, 2020).

 19

2.5. Flooring Systems
Three different base flooring systems were included in the assessment as detailed below:

 2.5.1. Timber Sub Floor (Suspended)
Two variations of raised sub-floors were assessed. The first of which comprised timber with R 2.0 EPS
insulation and the second increased this insulation to R 3.0. The baseline case is shown in Figure 4.

 FIGURE 4: TIMBER SUB-FLOOR AND STANDARD INSULATION

 2.5.2. Concrete Slab on Ground (CSOG)
For the CSOG solution a standard 100mm concrete slab with no insulation was selected. An additional
parametric to investigate the additional benefit of including slab edge insulation was also investigated and
discussed in the subsequent section.

 2.5.3. Waffle Pod
A standard 175-85 mm waffle pod was selected for this flooring system which yielded an R value of 0.57 as
shown in Figure 5 below.

 20

FIGURE 5: WAFFLE POD CONSTRUCTION

 2.6. Other Parameters Assessed
Several additional parameters were included for the baseline HIA home in Melbourne including:

 • Continuous and reflective roof/ceiling types
 • Roof colour variation of Light and Dark
 • Ceiling insulation increased to R 6.0.

The results of these and other parametric are presented in the subsequent results section of this report.

 21

3. Results
 3.1. Melbourne based parametric assessments.
As this study evolved, focus shifted from exploring a wide variety of wall and floor systems in Melbourne to exploring the impact of more commonly available systems
and construction methods throughout Australia. Table 9 shows a summary of the parametric assessments performed for homes in Melbourne. This study’s principal
aim was to investigate the impact of changing window, wall, floor and other building fabric parameters on the performance of a two distinct Melbourne based homes.

TABLE 9: MELBOURNE BASED PARAMETRIC ASSESSMENTS SUMMARY

 Baseline House Windows Options Wall Options Floor Options Additional Variations
 • SG-Al-CLR • Brick Veneer (BV) • Concrete Slab on • Ceiling insulation R 6.0
 “HIA Economical House
 • SG-Al-LE • Brick Veneer 140mm Studs (BV- Ground (CSOG) • High performance wall
 with subfloor”:
 • DG-Al-CLR 140mm) • CSOG with R 1.0 edge insulation R 2.7
 • Window: SG-Al-LE
 • DGAr-Al-LE • Cross laminated timber XLAM (CLT) insulation Subfloor • Double glazing in day
 • Walls: Brick Veneer
 • DGAr-Tb-LE • Light Weight Direct Fix (LWDF) Timber with R 2.0 EPS use spaces only
 • Ceiling: R 4.0
 • High Performance 140mm (HP-140mm) insulation • Roof light and dark
 • Roof: Medium
 • Reverse Brick Veneer (RBV) • Subfloor Timber with R • Continuous roof with
 discontinuous
 • High Performance Light Weight (HP- 3.0 EPS insulation reflective sarking
 • Floor: Sub floor R 2.0
 180) • Waffle Pod
 • 75mm Hebel with R 2.0 (AAC-75 R2.0)
 • 75 mm Hebel with R 2.7 (AAC-75 R2.7)
 • Brick Veneer • Concrete Slab on • Ceiling insulation R 6.0
 “Lynvale Standard House” Single Solution:
 • Brick Veneer 140mm Studs Ground (CSOG) • Continuous roof with
 • Windows: see window SG-AL-LE in night
 conditioned • Cross laminated timber XLAM • CSOG with R 1.0 edge reflective sarking
 options
 spaces and DGAr- • Light Weight Direct Fix insulation • Roof light and dark
 • No eaves
 Tb-LE in day • High Performance 140mm • Subfloor Timber with R
 • Walls: Brick Veneer
 conditioned • Reverse Brick Veneer 2.0 EPS insulation
 • Ceiling: R 4.0
 spaces • High Performance Light Weight • Subfloor Timber with R
 • Roof: Medium
 • 75mm Hebel with R 2.0 3.0 EPS insulation
 discontinuous
 • 75 mm Hebel with R 2.7 • Waffle Pod
 • Floor: Waffle Pod
 *SG – Single glazed; DG- Double glazed; DGAr – Double glazed Argon filled; Al – Aluminium frame; Tb – Timber frame; CLR – Clear; LE – Low-E.
 22

3.1.1. HIA Standard House
The Baseline HIA standard home as discussed in Section 2 was designed to achieve a 6 Star Rating
(minimum compliance). The subsequent parametric assessment was performed by modifying a single
parameter at a time in order to ascertain the impact on energy performance and NatHERS Star Rating. The
results of the parametric assessment of HIA standard home at Melbourne are shown in Table 10 on the
following page. The impact of wall, window, roof and floor selections on the heating and cooling energy
demand are subsequently presented.

 23

TABLE 10. HIA HOUSE WITH SUB FLOOR SIMULATION RESULTS FOR MELBOURNE

 Total Heating Cooling
 Energy
 Parameter Variation Energy Energy Energy
 rating
 (MJ/m2) (MJ/m2) (MJ/m2)
 BV (Baseline) 6.0 113.7 79.9 33.8
 BV-140mm 6.1 109.5 76.4 33.1
 CLT 6.2 107.3 76.6 30.7
 LWDF 5.9 118.6 83.2 35.4
 Wall Type HP-140 6.0 113 78.2 34.8
 RBV 6.3 104.5 75.8 28.7
 HP-180 6.0 113.4 78.8 34.6
 AAC-75 (R2.0) 5.9 114.1 80.1 34
 AAC-75 (R2.7) 6.0 113.8 79.8 34
 Single clear 5.7 125.5 87.6 37.9
 Single Low-E (baseline) 6.0 113.7 79.9 33.8
 Double clear 6.2 107.1 74.5 32.6
 Window
 Double argon 6.3 104 71.7 32.3
 Double argon low-e 6.6 95.9 66.2 29.7
 Double argon low-e (Timber) 7.1 81.2 61.5 19.7
 Sub floor with R 2.0 (baseline) 6.0 113.7 79.9 33.8
 CSOG: Slab on Ground 6.2 106.1 88.4 17.7
 Floor Waffle pod 6.6 95 73.3 21.7
 Sub floor with R 3.0 6.2 109.2 75 34.2
 CSOG edge insulation 6.4 100.6 82.8 17.8
 Ceiling R 4.0 (baseline) 6.0 113.7 79.9 33.8
 insulation R 6.0 6.2 106.1 73.9 32.2
 Discontinuous (baseline) 6.0 113.7 79.9 33.8
 Ceiling type
 Continuous & Reflective 5.9 114.7 80.2 34.5
 Light 6.0 113.4 82.3 31.1
 Roof Colour Medium (baseline) 6.0 113.7 79.9 33.8
 Dark 5.9 114.7 78.3 36.4
 Sub Variations
 Window None (baseline) 6.0 113.7 79.9 33.8
 arrangement Day and living 6.4 99.7 69.2 30.5
 for double
 glazing All rooms 6.6 94.9 65.4 29.5
 Insulation Thermal Conductivity 0.42
 performance in (Glasswool) 6.0 113.7 79.9 33.8
 walls
 High Performance R = 2.7 6.0 112.8 79 33.8

 24

Wall Type

The selection of wall builds up and associated insulation in the wall cavity had a minor effect on the overall
star rating of the home as depicted in Figure 6. Thermal mass was shown to improve the performance of
the homes with reverse brick veneer leading to the greatest reduction in heating and cooling loads followed
by CLT. Higher performance wall systems including both the 140mm and 180mm (double stud) solutions
did not add any tangible benefit when compared to the brick veneer wall system. This is further discussed
in Section 4 of this report and is largely attributed to the poor glazing performance accounting for the vast
majority of thermal gains and losses.

 0.5 90
 Change in Star Rating from Base Case (BV)

 80
 0.4

 Energy Requirements (MJ/m2)
 70
 0.3
 60

 0.2 50

 0.1 40

 30
 0
 20
 -0.1
 10

 -0.2 0

 Change in Star Rating from Base Case Heating Energy Requirements
 Cooling Energy Requirements

FIGURE 6: HIA HOUSE WITH SUB FLOOR - WALL TYPE ASSESSMENT RESULTS FOR MELBOURNE

 25

Window Selection

The selection of windows had a significant impact on the overall performance of the home as detailed in
Figure 7. Here it can be seen that double glazing increased the overall star value by 0.2 stars with increased
benefits resulting from argon filled glazing, low-e glazing and a significant improvement in thermal
performance when utilising timber framed windows. The impact of window selection on the whole of
home performance is discussed in further detail in Section 4.

 1.2 100
 Change in Star Rating from Base Case (BV)

 90
 1
 80

 Energy Requirements (MJ/m2)
 0.8
 70
 0.6
 60

 0.4 50

 40
 0.2
 30
 0
 Single clear Single low e Double clear Double argon Double argon Double argon 20
 -0.2 (baseline) low-e low-e (Timber)
 10

 -0.4 0

 Change in Star Rating from Base Case Heating Energy Requirements
 Cooling Energy Requirements

FIGURE 7: HIA HOUSE WITH SUB FLOOR - WINDOW TYPE ASSESSMENT RESULTS FOR MELBOURNE

Additional Assessments

A variety of additional parameters were also assessed to determine the impact on overall star rating, as
well as annual heating and cooling requirements of the HIA home. As detailed in Figure 8 changes to the
roof (either colour or material) had marginal impact on the overall star rating of the home. The use of a
concrete slab on ground (CSOG) instead of the sub floor resulted in a slight improvement of 0.2 stars in the
overall home rating but by reducing cooling loads and increasing heating demand. A Sub floor with R 3.0
or upgrading the ceiling insulation to R 6.0 also managed to achieve the same improvement of 0.2 Stars
through a reduction in heating loads. Although uncommon in Melbourne it was also determined that CSOG
with edge insulation of R 1.0 managed to improve the overall star rating by 0.4 Stars, whilst the waffle pod
had the greatest impact with an improvement in the star rating of 0.6.

 26

0.7 100
 Change in Star Rating from Base Case (BV)
 0.6 90

 80

 Energy Requirements (MJ/m2)
 0.5
 70
 0.4
 60
 0.3
 50
 0.2
 40
 0.1
 30
 0 20
 Continuous Dark Roof Light Roof Slab on Sub floor Ceiling CSOG edge Waffle pod
 -0.1 & Color Color Ground with R 3.0 Insulation R insulation 10
 Reflective 6.0
 -0.2 Roof 0

 Change in Star Rating from Base Case Heating Energy Requirements
 Cooling Energy Requirements

FIGURE 8: HIA HOUSE WITH SUB FLOOR - ADDITIONAL PARAMETRIC ASSESSMENT RESULTS FOR MELBOURNE

7 Star Recommendations

Based on the findings of the parametric studies a series of 7 star building envelopes have been developed
based on selecting the most practical changes. For example, reverse brick veneer, 140mm studs or
concrete slab edge insulation are relatively uncommon and bring about significant added costs and hence
have been excluded from the assessment. The below table details the changes in building fabric from the
base case in order to achieve a 7 Star Rating.

 27

TABLE 11: PROPOSED 7 STAR SOLUTIONS FOR HIA STANDARD HOME

 Star Heating Cooling Windows and Wall System Ceiling Floor
 Rating Energy Energy Glazing and Insulation Insulation Details
 (Mj/m2) (Mj/m2)
 7.1 54.6 26.4 Double Glazed Brick Veneer R 4.0 R 3.0
 Argon Timber with R 2.7 Sub
 framed windows Floor
 7.0 63.0 18.9 Double Glazed Air Brick Veneer R 4.0 R 2.5
 Filled Low-E UPVC with R 2.7 + Sub
 Reflective Floor
 Foil 3
 7.0 53.7 28.5 Double Glazed Brick Veneer R 5.0 with R 3.0
 Low-E Argon with R 2.7 + reflective Sub
 Aluminium framed Reflective Foil roofspace Floor
 windows
 7.0 53.5 28.2 Double Glazed Brick Veneer R 6.0 with R 3.0
 Low-E Argon with R 2.0 + reflective Sub
 Aluminium framed Reflective Foil roofspace Floor
 windows
 7.0 66.7 16.1 Single Glazed Low- Brick Veneer R 4.0 Waffle
 E timber framed with R 2.7 Pod Slab
 windows
 7.2 61.8 15.8 Double Glazed Brick Veneer R 4.0 Waffle
 Low-E thermally with R 2.25 Pod Slab
 broken aluminium
 framed windows
 7.0 64.0 19.0 Double Glazed Brick Veneer R 4.0 Waffle
 Aluminium Clear with R 2.7 + Pod Slab
 Reflective Foil
 7.1 67.3 13.3 Single Glazed Low- Brick Veneer R 6.0 CSOG
 E UPVC windows with R 2.7 100mm
As shown in Table 11 a combination of approaches is required in order to achieve 7 + NatHERS star rating
without employing very high-performance glazing (which is relatively costly). Upgrading the wall insulation
to higher performance batts, combined with better performing glazing and flooring allowed the standard
HIA home to attain 7 stars. Reflective roof space and additional ceiling insulation also enabled the home
to reach 7 Stars whilst utilising R 3.0 Sub Floor systems and high performance (but not thermally broken)
aluminium windows. UPVC framed windows also enabled the HIA standard home to meet the 7 Star rating
even with single glazing, when combined with high performing wall and ceiling insulation and a CSOG
solution. The higher performance from the waffle pod system allowed for single glazed windows in
addition to R 2.7 wall batts to also achieve 7 Stars whilst a sub floor with R 3.0 insulation required double

3
 Full details of the reflective air cavity is provided in the Appendix Section 8.2.2. and is based on CSR
THERMOSEAL™ WALL WRAP XP product guidance document (CSR, 2015)

 28