MMC 5541 48 Nov'15 cc

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‘Traditional’ approach to island
PassivHaus properties
MMC Magazine’s Bruce Meechan reports on a substantial low energy development by one of the south-east of
England’s largest housing associations.
Many of our readers will be aware of
the Isle-of-Wight’s desire to become
a Zero Carbon beacon for other
parts of the country – by maximizing the use
of renewable energy sources as well as
cutting usage across its properties – but the
ambition has been brought a step closer
thanks to the decision of Southern Housing
Group to build 28 new homes to PassivHaus
Standard. .
Cameron Close in Freshwater on the island’s
western side is a £4.2 million development of
16 semi-detached family homes and a dozen
sheltered apartments; built on a 1.5 acre site
formerly occupied by an earlier retirement
scheme belonging to the RSL.
Interestingly, the development began its life
being designed by PCKO Architects to satisfy
the higher levels of the Code for Sustainable
Homes, before Southern Housing Group’s
Regional Manager viewed another PassivHaus
project in Portland, Dorset and recognised the
potential for doing the same at Cameron
Close.
As Alan Townshend, Development Director at
Southern Housing Group, explained to MMC
Magazine: “We decided to make Cameron
Close a PassivHaus development as it best
meets the group’s sustainability objectives
without the need to provide expensive
renewable technology. We moved our current
residents to a new modern sheltered housing
scheme, Whitmore Court, that best met their
needs and used the existing site to create
those environmentally friendly family homes.
“As part of our aim to provide sustainable
tenures, the group is always looking at how we
can improve the quality of the homes we
provide, so not only does this ‘fabric first’
approach provide an environmentally friendly
solution for building these homes, it will also
give the residents of Cameron Close
significant and long-term savings on their
energy bills.
“When we decided to go down the traditional
route rather than timber frame, Celcon was
approached, and it was the company that
suggested thin-joint construction as the best
solution. Celcon was very helpful with
technical guidance and providing training for
the operatives from Stoneham Construction
on the Isle-of-Wight who were going to lay the
thin-joint system.”
The exterior walls were finished with a
proprietary render system applied to 230 mm
of insulation, fixed over the 200 thick Celcon
blockwork. This was parge coated on the inside
in order to achieve an excellent level of
airtightness – typically 0.48 m3/m2/hr at 50
Pascals. The contractor then formed a metal
studded batten cavity behind a final lining of
plasterboard which provides a service void.
Also of major importance to controlling air
leakage was the selection of triple glazed,
aluminium clad windows from Munster Joinery,
and exterior doors manufactured by Internorm.
Then at first floor ceiling level, a polythene
membrane was installed above the
plasterboard soffit. Overall the success of all
these measures is also the result of a
‘PassivHaus Champion’ having been employed
on site to monitor all of these details’
execution; along with the multiple service
penetrations.
The ground floor construction features the use
of a beam and block floor system, overlaid with
250 mm of Kingspan Kootherm K3 insulation
and then a further concrete slab which also
helps add thermal mass to the living space.
Of course the main idea of using such high
levels of insulation in a PassivHaus
construction is to keep energy usage down to a
very low level; and often you will find properties
just feature a wood burning stove to ‘top up’
the heating on the coldest days. At Cameron
Close, the solution chosen was to give every
home a small combination boiler to not just
supply the kitchen and bathroom with hot
water, but also to heat a towel rail and a couple
of radiators. One is in the hallway while another
is situated in the lounge; offering visual
comfort as much as physical warmth. Zehnder
Comfoair MVHR units are also installed in every
home to further reduce heat loss and ensure
necessary air changes are achieved.
Work actually started on site in early
September 2013 with final planning permission
having been granted in the previous December,
before going through the OJEU tendering
process. Alan recalled: “The tenders for
building to PassivHaus standards actually came
back higher than we had expected, but we had
already secured HCA funding and the Isle-of-
Wight Council also provided some finance to
support the PassivHaus element to the build as
it was in line with their Green Island agenda.
“Our initial estimation is that the entire
scheme could save up to £25,000 a year in
energy costs, with some residents being able
to save up to £900 in a three bedroom home.”
The PassivHaus Institute has already precertified
all fixtures and fittings to ensure that
the required heating and primary energy limits
are met; the homes are currently going
through the PassivHaus certification process.
Alan concluded saying: “If we were going to
develop another PassivHaus project I think we
might well use the thin-joint masonry again, as
it proved very successful, though we would
probably revert to a traditional brickwork
outer elevation as the render proved difficult
to apply in the poor weather conditions
suffered.”
The properties are now the subject of post
occupation monitoring using heat meters and
other sensors.
• Over the last 110 years, Southern Housing
Group has become one of the largest
housing associations in the south of
England, housing more than 67,000
residents, managing almost 30,000
homes, employing nearly 900 people and
working with more than 70 local
authorities across the South East,
including the Isle of Wight.
• Our vision, ‘A business with social
objectives’, draws on our history and
traditions while recognising the need to
change with changes in the housing
sector.
• Our social and economic regeneration
work is undertaken to improve the lives of
residents in the communities and
neighbourhoods where we build and
manage homes. It provides tangible
evidence of our commitment to building
sustainable communities.
• Southern Housing Group is a member of
the g15, which represents London's 15
largest housing associations. The g15
houses one in ten Londoners and builds a
quarter of London's new homes. We are
working to solve the housing crisis by
delivering good quality, affordable homes
of all types. To find out more about the
g15's work please visit g15london.org.uk
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