Thermal Comfort Index for Multi-Units

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					                                             Thermal Comfort Index for Multi-Units

Thermal Comfort Index in the BASIX Multi-Unit Tool
Information for Accredited Assessors

This document outlines the role of Accredited Assessors in relation to the BASIX Multi-Unit
Thermal Comfort Index. The general role is similar to that for the Single Dwelling version of BASIX
currently in operation, however, there are some key differences outlined below.

The process for completing the Thermal Comfort Index is as follows.
    1. Conduct a rating for each dwelling in the development using software approved by DIPNR.
    2. Record the conditioned and unconditioned floor area (NEW), heating and cooling loads
       and the required shading for the cross ventilation bonus for each dwelling – if bonus is
       claimed by applicant. Do not make any adjustments to these values: BASIX applies the
       floor area adjustment and suspended floor concessions.
    3. Enter the values into BASIX for Multi-Units tool.
    4. Complete the Cross Ventilation details on the BASIX tool if available in that
       postcode/climate zone.
    5. Check that the heating (NEW) and corrected cooling loads are lower than the Maximum
       Loads (“caps”) for each dwelling.
    6. Check that the loads for the Average of all Dwellings are less than the Maximum Loads.
    7. Discuss the impacts of any modifications (i.e. construction, design and cost) required for
       compliance with the client. Make any changes to the dwelling simulation files as
       necessary and repeat process until the development achieves a pass.
    8. Record the relevant details on the Assessor Certificate and ensure the documentation
       (refer below for new requirements) is updated to reflect the information entered in the
       simulation files prior to stamping plans.

Thermal Comfort Protocol
The roles and responsibilities of Accrediting Organisations (eg Association of Building
Sustainability Assessors (ABSA)) and Assessors in relation to BASIX are determined by the
BASIX Thermal Comfort Protocol. This will be updated for the introduction of BASIX for Multi-Units
to provide greater clarification and more specific documentation and certification requirements. It is
important that all Assessors read and understand the Protocol (available on the BASIX website Failure to comply with the Protocol can lead to a withdrawal of

DIPNR has conducted audits of 70 BASIX affected single dwelling and dual occupancy
Development Applications submitted to councils before July 2004. Poor documentation and failure
to follow required procedures are consistent problems. The main areas of concern are
Specification Blocks not being affixed correctly to drawings (stapling is not permissible) and
drawing details (especially glazing, shading and insulation) not matching the Assessor Certificate.
DIPNR will continue to monitor documentation submitted to councils and has asked ABSA to
address these issues.

                                                                                                         April 2006
                                             Thermal Comfort Index for Multi-Units

Floor coverings
A common misunderstanding is that tiled ground floors are required to pass the BASIX Thermal
Comfort performance standard. This has generally arisen from designers and residential
development companies not wanting to change facades to improve shading. Given this restriction,
Assessors are recommending performance glazing and tiles to lower the cooling load. Due to a
lack of communication, the client is led to believe that tiles are mandatory when they would rather
not have tiled floors.
It is important that Assessors, designers and clients are aware of the range of options to reduce
the cooling load, especially effective external shading.
The Thermal Comfort Protocol requires that carpet be simulated on all floors unless a floor
covering is nominated on the plans. The extent of all other floor coverings (including tiles) must be
shown on the plans.

Approved simulation tools
Currently, NatHERS v2.32A is the only approved simulation tool under the BASIX Thermal
Comfort Protocol. Use of Earlier versions of NatHERS or other simulation tools is not permissible.
DIPNR is currently awaiting applications from the developers of BERS and FirstRate to be BASIX
accredited. Other tools can be used once approved by DIPNR. Only Assessors accredited under
the Thermal Comfort Protocol can use these tools. Interstate software users will need to be
accredited before they can issue certificates for BASIX Thermal Comfort compliance.

Heating and Cooling caps
The policy intent for Thermal Comfort for all of NSW is that a dwelling must have an adequate
level of thermal performance for winter and summer. To reflect this policy, the Simulation Method
from 1 July 2005 will have an appropriate heating and cooling cap for each climate zone. The ‘total
cap’ column will temporarily remain but will show ‘n/a’.

Multi-Unit caps
The policy for multi-unit developments is to set a good average level of thermal performance
across all dwellings in the development but to allow some dwellings to achieve a lower level of
performance. This acknowledges the difficulty in designing all dwellings with a high level of
performance due to site shape, orientation, privacy/views and overshadowing constraints.
Therefore, the caps for Individual Dwellings in a multi-unit development are higher than for the
Average of all Dwellings. Some dwellings will need to be below the Average caps to compensate
for the ones that are above.
For example, in the table below, all units pass the individual dwelling caps but Unit 1 only just
passes. The overall development passes the ‘Average of all dwellings caps’ because Units 2 and 3
compensate for Unit 1.

                             Your          Max         Your         Max         Your      Max
                            Heating       Heating     Cooling      Cooling      Total     Total
         Average all
                               80            96         46.6          49        126.6      n/a
            Unit 1             130          135          65           70         195       n/a
            Unit 2             50           135          40           70         90        n/a
            Unit 3             60           135          35           70         95        n/a

                                                                                                        April 2006
                                             Thermal Comfort Index for Multi-Units

Floor Area Adjustment
The floor area adjustment for multi-unit development is set based on the dwelling type selected on
the Project Details page:
    1. separate dwelling house (the floor area adjustment will change from the current single
    2. Attached dwelling houses – eg, townhouse, semi-detached dwelling, attached villa
    3. Unit – flat or apartment with another dwelling or building above or below
Refer to the updated cap charts to see the different floor area adjustment curves for the different
dwelling types.

Suspended Floor Concessions
From 1 July, BASIX will award a concession to dwellings required to have a suspended floor in
flood prone areas. Proof of this requirement must be provided to Assessors before this can be
indicated on the Assessor Certificate. The overshadowing concession has been withdrawn from
BASIX from 1 July as it was rarely used, Assessors found the documentation requirements
complex and it discouraged improving building design/location to achieve better solar access.

Construction Issues for multi-unit residential development


Ceiling Insulation
For framed ceilings, the same systems used for houses are generally appropriate. For concrete
ceilings, check that the specified insulation type and R-value can be accommodated in the
ceiling/roof detail. In some high mass dwellings, ceiling insulation may actually increase cooling
loads. In this case it is particularly important to test a combined insulation, glazing, shading

Wall Insulation
The Building Code of Australia (BCA) requires that external walls of Class 2 buildings of Type A or
B construction be ‘non-combustible’. This means any insulation in the external wall must comply
with AS1530.1.
At present, DIPNR is aware of compliance for glasswool and rockwool bulk insulation only,
although other insulation types may have certification. Any insulation that does not have
certification of AS1530.1 compliance should not be specified for Type A or B construction. This
has significant impacts on the wall construction system that can be used in multi-unit dwellings.
The options are:
   • Use any wall system and don’t use insulation – if compliance can be achieved
   • Use a framed wall system that can accommodate thick glasswool batts. Wall systems with a
     thin (eg 32mm) furring channel won’t accommodate glasswool and compression of batts is
     not permitted under the BCA.
   • Use a wall system with a high inherent R-value. For example, some developers are using
     external cavity brick and internal autoclaved aerated concrete (AAC) to address both
     thermal and acoustic insulation issues.
Higher density thin rockwool products are under development/investigation by insulation
manufacturers for multi-unit developments.

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                                               Thermal Comfort Index for Multi-Units

Floor Insulation
Be aware of services that may be located within or under framed floors and concrete floors. In
many carparks the network of services (eg sprinkler systems and ventilation ducts) can mean it is
extremely difficult to insulate under the floor. If floor insulation is required for compliance, it may be
necessary for the insulation to be on top of the floor structure depending on the location of

Glazing and shading
For most multi-unit developments, the glazing and shading will need particular attention in order to
pass Thermal Comfort.
Performance glazing will assist with controlling both heating and cooling loads. Even with
adequate shading, glazing with a low Solar Heat Gain Coefficient (SHGC) will assist with
controlling conductive gains through large areas of glass. Performance glazing, while more
expensive than standard single clear glazing, may be the most cost effective solution in many
cases if design changes are not feasible.
To comply, some developments will require the use of different types of performance glass in
different orientations. Assessors are required by the Thermal Comfort Protocol to record certain
information (detailed in the Protocol) on the Assessor Certificate and ensure other information is
recorded on the development documentation.

Glazing specification
 Assessors will be required to nominate the U-value and SHGC of the total glazing system (frame
and glass) and the total area used in the development on the Assessor Certificate. Generic or
Custom Windows names or numbers should still be used in a simulation, however, the values
associated with those selections need to be recorded on the Certificate. The values for each
window system will be available from distributors of approved software. These values must be
calculated according to NFRC100 test conditions – see software distributors for further details.
The use of U-value and SHGC allows clients to shop around for a product that matches these
values after the simulation is conducted instead of being locked into a particular product at DA
Assessors will be required to ensure that the areas, locations, U-values and SHGC are nominated
on the plans and specifications prior to certifying. Building certifiers will be checking these details
against certification from the glazing supplier or builder.

Shading specification
A number of adjustable external shading systems are commonly used in multi-unit developments.
Details that affect the assumed shading level (i.e. pergola schedules) must be nominated on the
plans and specifications. For example, a pergola detail must be provided to support the assumed
pergola schedule. Adjustable shading devices must have the level of shading assumed in the
approved simulation tools (i.e. the software user manual).

Roof colour
The roof colour range (light, medium or dark) and the solar absorption range associated with that
colour as provided in the BASIX Definition must be nominated on the Certificate. This allows
certifiers to more easily match the solar absorption of the colour of the chosen roof (roofing
manufacturers should provide this) with the commitment on the Assessor Certificate.

                                                                                                             April 2006
                                             Thermal Comfort Index for Multi-Units

Cross ventilation
A cross ventilation bonus can now be claimed in the Simulation for dwellings in coastal climate
zones. If the dwelling complies with the Cross Ventilation criteria, the entered cooling loads will be
reduced by a certain amount depending on the number of breeze-paths nominated. The entered
and corrected cooling loads will be nominated on the BASIX Certificate.

Cross Ventilation Criteria
To qualify for the Cross Ventilation bonus, the dwelling must have both adequate shading and
cross ventilation. The shading criteria are included so that the benefit of the cross ventilation to
occupant comfort is not overwhelmed by high solar gain, thereby increasing the likelihood of
airconditioning use. The shading criteria are mandatory only for those that want to claim the cross
ventilation bonus, in which case they are mandatory even if the cooling cap has been met.
The shading criteria must be nominated on the Assessor Certificate and appear in the required
detail on the plans, whereas the cross ventilation criteria are selected within BASIX. It is strongly
advised that Assessors check compliance with the cross ventilation criteria as the cooling load
bonus will reduce the need for additional shading and/or performance glass and thereby reduce
compliance costs.
A minimum level of shading must be provided to all glazing over 1m in the East, North-East,
North, North-West and West orientation sectors, as defined by the Thermal Comfort Protocol.

The cross ventilation criteria use the breeze-path concept. A breeze-path flows between two
ventilation openings through the dwelling. The ventilation opening area is the part that can be fully
opened – eg half a sliding door. Criteria for openings size, distance between openings and
obstructions between these ventilation openings are set for each breeze-path.
A breeze-path can be claimed for the main living area and up to 3 bedrooms. Additional breeze-
paths through other living areas cannot be added. A pair of ventilation openings can only be
claimed in one breeze-path, although a single ventilation opening may be used in up to 2 breeze-
The applicant is responsible for nominating complying ventilation openings, the breeze-path length
between them and labelling of the spaces on the plans, however Assessors should discuss this
with their clients.

                                                               BASIX Contacts
                                                               T: 1300 650 908

                                                                                                         April 2006

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