Retrofit & Replicate - Hyde Housing Association

Retrofit & Replicate
Mottingham, South London

Retrofit & Replicate
Project Briefing
Project Background: Whilst the environmental focus of the house-building industry has been on new
build and the Code for Sustainable Homes, improving the energy efficiency of the nation’s existing housing
stock presents a far more important challenge in terms of helping to combat climate change. Our existing
stock is typically very inefficient compared to new build housing in terms of energy use, yet less than 20% of
existing homes are likely be replaced by 2050.
ECD Architects have a long-standing interest in this issue and a track record in exemplar refurbishment in
the residential sector. Similarly, Hyde Housing Association have strong policies on sustainability and, with
responsibility for over 40,000 dwellings mainly around the south and south-east of England, they were also
very interested in the potential of low-carbon refurbishment. ECD approached Hyde late in 2007 with a
proposal to undertake an exemplar retrofit project and in January 2008 they identified a suitable void property
- a 3-bedroom mid-terrace house in Mottingham, south-east London, typical of their stock.
Most analysis of retrofit focuses on targets for reducing carbon emissions - the Government’s Energy White
Paper (2007) officially stated the UK’s target to reduce its net carbon emissions by 60% by 2050, which will
become a legal obligation once the Climate Change Bill is passed (currently due late 2008). The Review
of Sustainability of Existing Homes, produced by the Department for Communities & Local Government in
November 2006, declared that the country’s existing housing should fall in line with this target.
However, the Existing Homes Alliance and others argue for greater targets – the EHA Declaration states
“deep cuts of at least 80% in carbon emissions are needed by 2050, with major progress by 2020”. Recent
proposals suggest that the Government is likely to adopt this higher target. The EHA Declaration goes further
to propose the approach that must be taken with regard to our existing dwelling stock - “Government and
industry action should focus on developing a ‘whole house’ approach which applies packages of low carbon
improvements, rather than individual measures, using existing, proven energy efficiency and microgeneration
technology. Improvements to water and other resource use efficiency must be included. A whole-house
approach brings greater economic savings to business and causes less disruption to households over time.”
Retrofit initiatives to date have indeed focussed primarily on installing individual renewables or other lowcarbon
technologies. Hyde and ECD therefore agreed that the aim of this project would be to establish the
most effective overall package of retrofit measures necessary to achieve the 80% reduction in CO 2
emissions
at the Mottingham house and to monitor the performance of the low-carbon improvements in use. In addition,
it will record the impact of the retrofit on the incoming tenants over a 24 month period and, at the end of that
time, develop a full cost/benefit analysis, with a view to ascertaining the optimum expenditure. This will enable
Hyde and others to make the more efficient and effective choices about how best to apply energy saving
as part of large scale retrofit programmes. This project will therefore be of huge benefit both in terms of the
developing national policy and of helping to frame the approach of individuals and organisations to retrofit.
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Design Team: ECD Architects are lead designer for the project and are drawing on their sister company,
Keegans, to provide extensive cost consultancy and CDM co-ordinator services. Further consultancy input has
been forthcoming from Parity Projects, with particular responsibility for the data monitoring aspects of the project.
In addition to this quantitative feedback on energy and water use, another of ECD’s sister companies, PPCR,
will undertake post-occupancy evaluation interviews with the incoming tenant providing valuable information on
comfort and satisfaction.
Following interviews and competitive submissions, Mears Ltd were selected as main Contractor partner and
began working with ECD to develop the specification. Mears, in turn, introduced Travis Perkins and Kingspan as
supply chain and technical partners respectively. We are working to a total capital budget of £80k (including VAT
and fees) funded in the main from Hyde internal resources but with all partners and product contributors investing
significant resources in the project. A full list of supply partners and their involvement has been included at the end
of this document.
The Existing Property: 225 Court Farm Road is thought to have been
originally constructed in the late 1930’s as part of a large estate development.
The external walls are of cavity wall facing brick construction and the original
dwelling included suspended timber floors and pitched tiled roofs but no
bathroom! Later improvements saw the inclusion of a first floor shower
room, the replacement of open fires with a central heating system of
gas combination boiler with radiators and the addition of a single-storey
rear extension comprising a third bedroom and ensuite bathroom. Fabric
improvements over time have seen the addition of double glazing (though
of poor quality) and 100mm loft insulation to the pitched roof, though the flat
roofed extension included only 25mm mineral wool insulation. A solid concrete
floor replaced the timber in the kitchen and the strip out works found that the
original water supply was via lead piping and an asbestos tank, with no stopcock
found on the premises. Further asbestos was found in the soffit boards.
Initial design proposals investigated the potential for a loft conversion at the property but this was eventually ruled
out due to a lack of headroom. There is an imperative to enlarge the first floor shower room and further space is
required for hot water storage and electrical equipment (inverters, dataloggers etc). SAP assessments were carried
out by ECD Project Services for the property, which was found to have a rating of 60, well above the national
average of 48 and therefore presenting a significant challenge to achieve the 80% reductions. In March 2008,
ECD assigned Heathrow Commissioning to undertake a ‘before’ airtightness test. The purpose of this test was to
provide a ‘base case’ with which to compare the completed scheme and to highlight existing leakage points that
need mitigation. The results were surprising – 9.16 m3/hr/m2 @ 50 pascals, which is better than current building
regulation requirements. The windows were the source of the worst infiltration with poor seals leaking air badly,
followed by incoming services penetrations and the loft access hatch.
According to PHPP software, specific primary energy use (heating, DHW + auxilliary electricity) at the existing
property is estimated to have been 414 kWh/m2/yr with CO 2 emissions rated at 100 kg/m2/yr and space heating
demand rated at 223 kWh/m2/yr.
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The Retrofit Proposals: The ‘Retrofit
and Replicate’ strategy focuses on carrying
out the most straightforward improvements
to reach the 80% target . . . and on doing
them well. The priorities are to minimise
heat losses from the building fabric; to install
an easily replicable, efficient form of space
and water heating; to reduce the energy
requirements for lighting; and to utilise
the most appropriate renewable forms of
micro-generation in reducing CO2 emissions
associated to the property.
Heat loss will be addressed though
significantly improved insulation to floors,
external walls and roofs, replacement
high-performance windows and doors,
consideration to the dwelling’s air permeability
and the installation of a mechanical
ventilation system with heat recovery from the
extract air. In the choice of insulation material,
thermal performance and ease of installation
has been favoured over embodied energy
and material source considerations, although
minimal GWP and ZODP credentials were
pre-requisites. U-value targets for the various
envelope build-ups were set as follows:
· Suspended timber floor – 0.2 W/m2K
· External walls – 0.15 W/m2K
· Pitched or flat roofs – 0.1 W/m2K
mechanical ventilation unit, therefore access
and available headroom were important
factors, as was the poor condition of the
existing roofing felt. Simultaneously, we
were concerned about achieving good
airtightness when recessed light fittings were
introduced to the ceiling below. A combination
of insulation products were therefore
selected – Kingspan Thermapitch, laid on
an airtight vapour barrier over the existing
ceiling joists, and Web Dynamics’ TLX Gold
multi-foil lining the existing rafters and party
walls. The rigid boards are laid to the depth
of an existing central bearer (170mm), thus
allowing a floating floor deck to pass freely
across the loft area. TLX Gold is the world’s
first breathable multi-foil and the Court Farm
Road project will be used as a case study
and test-bed for both its ease of installation
and performance in operation. This material
will also allow the retention of the existing
roofing felt and tiles by providing a secondary
waterproof layer, as well as minimising the
impact on headroom in the loft and reducing
summer heat gains due to its reflective gold
inner layer.
to perform as a low-carbon dwelling. To
ensure a reasonably airtight envelope, Mears
will keep a log and photographic record of
all service penetrations through the external
walls and roofs to ensure they are sealed
effectively.
To provide controlled ventilation, a Vaillant
recoVAIR 275 mechanical ventilation
system is being retrofitted into the property.
Mounted on the party wall in the loft space,
the unit will extract air from the kitchen and
bathrooms, reclaiming around 90% of the
heat to pre-warm incoming fresh air which
is then supplied to the living and bedrooms.
In summer mode, a bypass extracts the air
direct to outside.
Phenolic foam insulation offers the best
performance of any readily available panel
and therefore has less impact on internal
room dimensions where dry-lining is
concerned – an important consideration for
Hyde. Kingspan’s Kooltherm phenolic range
was therefore selected for both suspended
floors and external walls. For the main
body of the house, insulation-backed K17
plasterboard dry-lining panels were specified,
whilst for the rear extension external K5
wallboards with a silicone render finish
provides the best solution. This element
of the works was supplied and installed by
Wetherby Building Solutions.
For the rear extension roof Kingspan
Thermapitch rigid polyurethane boards
(220mm) were preferred, in conjunction with
Knauf Carbon Zero glasswool in the eaves
location.
For the pitched roof element, a number of
other factors came into play rather then
straightforward thermal performance.
The loft is to be used for locating plant
such as the proposed thermal store and
The existing double-glazed windows were
shown to be the weakest building element
during the airtightness test: they will be
replaced with aluminium-clad NorDan Ntech
Passive windows, which are triple-glazed with
warm edge spacers and composite insulated
timber frames, achieving an overall Uw-value
of 0.7 W/m2K. Front and rear doors will also
be replaced with insulated replacements with
a Uw-value of 1.0 W/m2K.
Details have been considered in terms of
the abutment of insulation, avoidance of
thermal bridging and continuity of the air
barrier. As well as communicating installation
requirements on 1:5 detail drawings, ECD
held a workshop on site with Mears site
team to explain the importance of their
workmanship to these issues, together with
background on how the building is intended
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With these measures in place, the space
heating requirements at the property are
estimated to reduce from 17,238 kWh/yr to
2,410 kWh/yr – a drop of over 86%. With such
low levels of heating required, tenant fuel
bills will be significantly reduced. Capital cost,
ease of retrofitting and ongoing maintenance
requirements therefore become the most
important driver in the choice of fuel source.
Ground source heat pumps are relatively
expensive to install and need to be located
in a substantial, and preferably soundproofed,
cupboard. Furthermore, to operate
efficiently they work best in conjunction with an
underfloor heating system, which in itself has
inherent problems in a retrofit situation.
The feasibility for underfloor heating was
explored by ECD and Mears and found to be
technically possible but only with a reduction
in underfloor insulation levels and an increase
in installation time and cost. When further
confronted with a solid concrete floor in the
kitchen, the concept was rejected in favour of a
conventional wet radiator system. Heat pumps
require electricity to operate, which in the UK is
particularly carbon intensive – more than twice
the kgCO 2
/kWh than mains gas. Therefore to
produce carbon reductions in comparison with
an efficient gas condensing boiler, heat pumps
need to achieve a Coefficient of Performance
greater than 2.5 measured across the whole
year – the recent trials at the Barratt EcoSmart
show properties recorded a CoP of 2.6. Air
source heat pumps are unlikely to improve
upon these results at present and would also
require underfloor heating. A biomass boiler
was also ruled out by Hyde as it was thought
to place an undue burden on the tenant to
source and store a supply of wood pellets,
and would again require additional plant
space. With these considerations in mind, the
decision was made to upgrade the existing
gas boiler for a more efficient condensing unit
and the Vaillant ecoTEC system was selected,
with low NOx emissions and programmable
controls. This was relocated to a hall
cupboard since the existing flue outlet position
contravened modern guidelines.
The gas condensing boiler will also supply hot
water to the property but will be supplemented
by solar thermal collectors located on the
pitched roof. The system is to be supplied
and installed by Kingspan Renewables in
conjunction with a twin-coil 250l Range Tribune
thermal store located in the loft space. Two
flat plate collectors mounted either side of
the ridge will face east and west but will be
controlled intelligently to favour the better
performing panel as the sun tracks around
the house to the south. It is hoped that 50-
60% of the tenant’s hot water needs will be
met by this system. All connecting pipework
between boiler and thermal store will be well
insulated to prevent heat transfer to the internal
environment.
A significant proportion of the property’s
electricity load will be for lighting therefore
the retrofit proposals will seek to minimise
this component. Other major demands for
electricity, eg for household appliance and
entertainment use, are typically beyond the
control of any RSL refurbishment scheme
and down to tenant behaviour. The ‘Retrofit
and Replicate’ exemplar project therefore
concentrates on minimising electrical lighting
loads through the installation of low energy
lighting to every room. However, unlike
typical low energy lighting solutions, the use
of compact fluorescents will be avoided in
favour of the latest in LED technology. Unlike
CFLs, LED lamps contain no contaminants
such as mercury or phosphor and can be
safely disposed of or recycled. Although they
are much more expensive currently, they
are very robust and offer 50,000 hours of
use (compared to 10,000 for CFLs or 3,000
for halogens) meaning no need to change
then for at least 20 years! In this way, energy
use is significantly reduced without the
customary start-up delays and only a small
reduction in efficacy. ECD have worked with
Gloucestershire-based specialist GreenLED
to develop the layouts and specifications.
GreenLED will supply 3.7W Antares GU10
lamps for installation by Mears into standard
recessed fittings.
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Despite all the carbon reduction measures
described above, the scheme was still
estimated to fall short of achieving the
80% target, largely because of its relatively
good SAP rating at the outset. Bridging the
shortfall would require the input of renewable
electricity micro-generation, with photovoltaics
considered the only viable solution. Working
with Solar Technologies, proposals for an
array of eight panels located on the rear
extension roof were developed. Bearing
in mind the short lead-in time, product
availability and the need for grant funding,
Solar Technologies recommended Sharp
170W polycrystalline panels, to be laid at
a pitch of only 5° to limit any impact on the
neighbouring property. A single inverter
has been located in the existing ‘electrical’
cupboard and a wall-mounted display will
inform the incoming tenants of its electrical
contribution.
The graph opposite shows the impact that
each of the measures implemented at
the property have on the associated CO 2
emissions. The insulation measures alone
account for over a quarter of the original
emissions, or a third if the triple glazing
is included. The greater efficiency of the
condensing boiler then takes the improvement
to over 50%, after which the returns on
investment are less dramatic. Nevertheless,
the introduction of MVHR and airtight
construction should contribute a further 15%,
with the solar thermal and LED lighting taking
our overall reduction to 76%! The photovoltaic
contribution allows the refurbishment to easily
achieve the target with a built-in contingency
for actual performance in use. The high levels
of energy conservation and generation are
reflected in the provisional EPC rating of 92,
placing the property in the highest Band A.
Predicted specific primary energy use at the
refurbished property is estimated at 67 kWh/
m 2 /yr with CO 2 emissions reduced to 17 kg/
m 2 /yr and space heating demand reduced to
32 kWh/m 2 /yr. Fuel poverty should never be a
concern for one lucky tenant!
Though driven primarily by low-carbon
targets, the project offered an opportunity to
incorporate other sustainable refurbishment
measures. Water conservation measures
are also a key interest for Hyde and the two
bathrooms will subsequently be fitted with
Twyford Galerie Flushwise (2.6l/4.0l dualflush)
wc’s, aerated basin taps, Mira Eco
shower handsets and a low volume bath. The
project team did not consider conventional
rainwater harvesting, stored underground
and pumped up to a header tank, to be
viable for a stand-alone property - primarily
in terms of the installation and maintenance
costs but also in terms of energy and carbon
savings. A recent study by the Centre for
Alternative Technology (CAT) has proven
that the embodied energy consumed in the
manufacture of buried tank systems is never
paid back through its life by the savings made
from utilising rainwater. However, ‘Retrofit
and Replicate’ partners Parity Projects have
experience of installing simple gravity-fed
harvesting systems and have designed a
proposal based around a filtered 318 litre
tank located in the void above the stairs.
The tank is fed directly from an external
downpipe, requires no pumps and therefore
requires no parasitic electricity and next to no
maintenance. Parity Projects’ calculations
indicate that virtually all of the water required
for flushing could be supplied from the annual
average rainfall locally. A meter on the backup
supply will determine actual annual mains
water consumption.
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Materials specifications generally reflects the
environmentally-friendly aims of the project,
for example:
• FDT Rhepanol pvc-free single-ply roof
membrane to the rear extension
• Finnforest Thermowood fascia cladding
boards
• Lindab Rainline steel guttering
These materials have been selected because
their manufacture and processing avoids
the use of toxic materials. Typically they
are durable products that require minimal
maintenance and can be easily recycled at
the end of their life.
Internally, the focus has been on responsible
sourcing and avoidance of materials prone
to off-gassing wherever possible. This is
especially important in a dwelling where air
leakage and draughts are very low. Timber
used throughout the house is either softwood
or occasionally temperate European
hardwood, with FSC or PEFC accreditation.
Natural products have been selected for
floor finishes as far as possible, with Tarkett
Marley Veneto XF linoleum flooring in the
kitchen and an eco-wool carpet to bedrooms
and hall areas supplied by the Alternative
Flooring company. The latter has even been
laid on a recycled rubber underlay!
The access door to the rainwater harvesting
cupboard was fabricated in MDF for ease but
the zero-formaldehyde Medite Ecologique
was used in lieu of conventional fibreboard.
In the garden and driveway the tenant has
been provided with the tools to help with a
greener lifestyle, for example:
• raised planter to encourage home-grown
vegetables
• twin composting bins
• rainwater butt to store water for use in
the garden
• a rotary
washing
line
• recycle
box
storage
Internal decoration has been carried
out throughout the entire house postrefurbishment
– paints were generously
supplied by Dulux Trade from their Ecosure
and Light&Space ranges. Working with
consultants from their in-house team,
the specifications have been selected to
highlight their performance credentials,
whether that be low VOC levels in the
bedroom environments, improved durability
and lifespan in the hallways or increased
light reflectance in the living areas. The
Dulux team will then benefit from the tenant
feedback on the performance of these paint
finishes over the two year monitoring period.
In addition to carrying out the
comprehensive eco-refurbishment, Hyde
will provide the incoming tenants with an
understanding of how to best maximise
energy savings and to optimise use of the
property. We will then comprehensively
monitor the property’s performance whilst in
occupation, in order to give us a thorough
understanding of what technologies best
work in terms of CO 2
savings, energy
efficiency and cost effectiveness. Working
with Parity Projects, thermocouples are
being installed across all wall and roof
constructions. These temperature readings
will be recorded and uploaded directly to a
datalogger, together with ongoing electricity,
gas and water usage. Furthermore, a heat
meter linked to the output of the Vaillant
ecoMAX condensing boiler will provide
details of the actual energy used for space
heating and supplementary hot water at
the property. Uploading this information to
a PC-based software package will allow
continuous remote monitoring and analysis
of the property’s energy use and emissions.
In addition to the quantitative data PPCR
will undertake post-occupancy interviews
conducted throughout the monitoring
period to assess resident reactions to
the eco measures employed and their
impact on comfort and satisfaction. The
refurbishment can greatly reduce carbon
dioxide emissions, but another crucial
question is: ‘What’s it like to live in?’ PPCR
will conduct a complimentary exercise
with a family living in a nearby similar but
non-refurbished property as a comparator.
They will discuss general aspects through
a questionnaire type agenda with each
household member able to contribute, for
example:
· Does living here seem any different to
another home of this type?
· Does the ‘ecohome’ present any
requirements for lifestyle changes?
· Are there any aspects of the measures
that are difficult to use/understand?
· Are there any measures you would like
to change? Why?
· Do you think it would work for all
tenants/families?
· What are the benefits of living in an
eco-home?
Of equal importance to reductions in
carbon emissions are the financial savings
to residents resulting from the significant
reduction in energy consumption. We
estimate that energy consumption will be
reduced by up to 85% with a saving to
the residents of around £600 per year as
a result of the retrofit we are carrying out
(at current energy costs). This project can
therefore make a major contribution to the
growing problem of tackling fuel poverty.
At the end of the project we will be able to
produce cost benefit analysis for each of
the eco measures adopted. This information
will be disseminated publicly and will
specifically inform Hyde’s future stock
investment and refurbishment plans.
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The Hyde Group
30 Park Street
London
SE1 9EQ
Tel: 020 3207 2600
If you would like more information on our sustainability
projects, please contact Peter Maddison on
020 3207 2657 or peter.maddison@hyde-housing.co.uk
or visit www.hyde-housing.co.uk