25270 version 1
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Describe heat, moisture, air-flow, corrosion, and wind loadings relative
to roof structures
Level
4
Credits
10
Purpose
People credited with this unit standard are able to describe: the effect of
ventilation on heat and moisture in a roof cavity; how water vapour forms and
how the movement of water vapour is controlled in roofs; corrosion on roof
structures; how wind loading affects building design; and loads on roofs.
Subfield
Plumbing, Gasfitting and Drainlaying
Domain
Roofing
Status
Registered
Status date
23 January 2009
Date version published
23 January 2009
Planned review date
31 December 2013
Entry information
Open.
Accreditation
Evaluation of documentation and visit by NZQA and
industry.
Standard setting body (SSB)
The Skills Organisation
Accreditation and Moderation Action Plan (AMAP) reference
0227
This AMAP can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Special notes
1
Legislation relevant to this unit standard includes but is not limited to – Health and
Safety in Employment Act 1992, Building Act 2004.
2
The New Zealand Building Code (NZBC) is a schedule to the Building Regulations
1992. It provides requirements for compliance with the Building Act 2004 when
constructing a new building or altering an existing one. The Building Code sets out
performance standards that building work must meet and covers aspects such as
structural stability, fire safety, access, moisture control, durability, and services and
facilities.
3
AS/NZS 1170 Structural Design Actions Set is available from Standards New
Zealand – http://www.standards.co.nz/.
 New Zealand Qualifications Authority 2016
25270 version 1
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Elements and performance criteria
Element 1
Describe the effect of ventilation on heat and moisture in a roof cavity.
Performance criteria
1.1
The description identifies thermal insulation types and the effect that the
insulation has on temperature.
Range
cold, warm, inverted roofs;
insulation types – bulk, reflective.
1.2
The requirements of the NZBC are described for cavity ventilation.
1.3
The description identifies the advantages of proper ventilation.
Range
evidence of four advantages is required.
Element 2
Describe how water vapour forms and how the movement of water vapour is controlled in
roofs.
Performance criteria
2.1
The description includes the relationship between night sky radiation, water
vapour, and condensation.
2.2
The description identifies how condensation is formed in roofs and the effect
condensation has on roofing materials and structures.
Range
2.3
includes but is not limited to – metal, timber, translucent sheeting,
underlay; roof types – attic, skillion.
The description identifies how condensation can be managed or minimised in
roof structures.
Range
insulated, uninsulated roofs; structure configurations – attic,
skillion.
Element 3
Describe corrosion on roof structures.
Performance criteria
3.1
The description includes atmospheric corrosion and its effects on roof
structures.
 New Zealand Qualifications Authority 2016
25270 version 1
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3.2
The description includes galvanic corrosion and its effect on roof structures.
3.3
The description includes elimination and minimisation techniques that can be
used.
Element 4
Describe how wind loading affects building design.
Performance criteria
4.1
The description identifies the purpose of AS/NZ 1170 and where information
can be obtained about localised wind zones.
4.2
The description identifies the impacts of wind loading on building design and
components.
Range
fasteners, roof structures, structures.
Element 5
Describe loads on roofs.
Performance criteria
5.1
Loads on roofs are described in terms of cause and minimisation of effect.
Range
includes but is not limited to – uniformly distributed load, point
load, peripheral load, snow and hail load, load of the structure,
design load.
Please note
Providers must be accredited by NZQA, or an inter-institutional body with delegated
authority for quality assurance, before they can report credits from assessment against
unit standards or deliver courses of study leading to that assessment.
Industry Training Organisations must be accredited by NZQA before they can register
credits from assessment against unit standards.
Accredited providers and Industry Training Organisations assessing against unit standards
must engage with the moderation system that applies to those standards.
Accreditation requirements and an outline of the moderation system that applies to this
standard are outlined in the Accreditation and Moderation Action Plan (AMAP). The
AMAP also includes useful information about special requirements for organisations
wishing to develop education and training programmes, such as minimum qualifications for
tutors and assessors, and special resource requirements.
 New Zealand Qualifications Authority 2016
25270 version 1
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Comments on this unit standard
Please contact The Skills Organisation info@skills.org.nz if you wish to suggest changes
to the content of this unit standard.
 New Zealand Qualifications Authority 2016