warm house challenge

SUSTAINABILITY
WARM HOUSE CHALLENGE
Energy efficiency is the catchphrase of today, but recent research reveals that there
are some challenges to achieving a desirable outcome in practice.
By Gleb Speranski, formerly Team Manager Technical, EECA, and now Head of Sales and Marketing, Insulpro Manufacturing Ltd
A
ccording to Ministry of Economic
Development data, electricity prices
have risen by more than 40% since
2000, so it’s important to build energyefficient, well insulated and effectively ventilated
houses. The health and wellbeing benefits
from a dry, well heated and comfortable living
environment make this even more necessary.
Recent changes to the Building Code have
placed more emphasis on energy efficiency.
Clause H1 requires higher levels of insulation
across different construction types and double
glazing to help meet increased energy efficiency
requirements for the building envelope.
But are new houses actually better as a
result of these changes? Recent EECA research
on quality of insulation in new builds revealed
that energy efficiency may be substantially
compromised in new homes. There are six main
areas of concern.
House design
Timber- or steel-framed houses almost solely
rely on insulation installed between the framing
for their thermal efficiency, but frame design
makes little provision for insulation – studs,
dwangs, battens and diagonal bracing elements
partially fill the cavity. Electric wiring and
plumbing often obstruct proper placement of
insulation, so it may be compressed or missing.
SOLUTION
Providing for good insulation performance
during the design stage requires more than
just specifying an insulation product. Framing
should be carefully sized and positioned to
minimise thermal bridging.
Running electric wiring and plumbing
services in internal walls or dedicated service
cavities leaves external walls free for unimpaired
insulation installation. This will also help reduce
potential pathways for uncontrolled airflow
through the building envelope.
Installation quality needs improving
There is a perception that the quality of insulation
installation doesn’t make much difference to
60 BUILD 120 October/November 2010
the energy performance of a house, but the
latest research from BRANZ indicates that
the reduction in the system R-value from poor
fitting insulation can be significant – around
1% per 1 mm gap in insulation. With many
modern homes designed to the minimum Code
compliance, a poor quality job may result in the
house not meeting the H1 requirements.
EECA research found tucks, gaps and missed
areas are common.
SOLUTION
The recently formed Insulation Association
of New Zealand (IAoNZ) runs an introductory
training course for insulation installers based on
NZS 4246:2006 Energy efficiency – Installing
insulation in residential buildings. This training,
along with a wider uptake of NZS 4246, should
improve the quality of insulation jobs in new
builds and retrofits.
Compliance issues
EECA research found that compliance with
clause H1 is not well understood by Building
Consent Authority inspectors – the very people
who are supposed to ensure adherence to it –
but clause H1 doesn’t provide any guidance to
help assess compliance for fitting insulation.
SOLUTION
Referencing NZS 4246:2006 in H1 would
help inspectors to have a more rigorous and
consistent compliance process.
Clearer instructions needed
Some insulation products can be difficult to fit.
These may not achieve the designed thermal
performance and are more likely to fail.
SOLUTION
Each product should be designed for a particular
application. It should be easy to install, should
maintain designed thermal performance in situ
and should not have any detrimental effect on
the building structure. Clear, detailed installation
instructions should be product-specific, verified
and cover all aspects of the installation process.
Having product-specific installation instruc­
tions clearly written and referenced in BRANZ
The insulation is poorly installed in this house, like many new
builds. Note the gaps, tucks and missed insulation.
Appraisals would ensure instructions are relevant
and quality installation achievable in practice.
Lack of quality monitoring
Building a new house is one of the biggest invest­
ments most people ever make, so it is remarkable
that most homeowners rely solely on their trust
in building contractors and council inspectors.
Research indicates that quality control around
insulation installation is essential.
SOLUTION
Independent quality monitoring throughout the
construction process could avoid substandard
installation practices and ensure homeowners
get adequate quality for their investment.
Airtightness of building envelope
To work effectively, air trapped by insulation
materials must be still. Clause H1 requires
account to be taken of the airtightness of the
building envelope, but this rarely happens in
practice, particularly as Acceptable Solution
H1/AS1 provides no further detail. Complicated
junctions and service penetrations in the
thermal envelope can result in air leakage, and
any air moving through the insulation material
reduces its thermal performance.
SOLUTION
Airtightness should be dealt with during the
design stage by minimising service penetrations
and sealing any potential pathways for air
leakage.