Development of thin membrane isolators for attached housing enhancing building performance, wellbeing of occupants, resource efficiency and reducing costs.
Submitting InstitutionEdinburgh Napier University
Unit of AssessmentCivil and Construction Engineering
Summary Impact TypeTechnological
Research Subject Area(s)
Engineering: Civil Engineering
Summary of the impact
Edinburgh Napier University was the first to develop thin membrane
vibration isolators (2005) to allow party walls in new attached homes to
be built off raft foundations. This led to the first Proof of Concept for
the construction industry (2008) for perimeter isolators for blockwork
apartments. Several patents have been granted leading to nine products
manufactured by Icopal-Monarfloor, based in Manchester (UK), part of the
Icopal global group. Over 15,000 homes have been built using these
innovative isolators, delivering cost savings to the industry of over £80
million resulting in economic, environmental and quality of life benefits.
A limiting factor for sound insulation performance of cavity party walls
in attached housing is when party wall leafs are bridged by rigid
junctions such as continuous floor slabs, e.g. raft foundations. This
bridging of acoustic and vibration transmission is known as flanking
transmission and reduces insulation performance and quality of life for
occupants. Future increased use of brownfield sites would require greater
use of raft foundations. In 2003 new Part E sound insulation building
standards for England and Wales were the first regulations globally to
incorporate ISO 717 low frequency spectrum (Ctr) for party walls. This
placed significant emphasis on lower sound frequencies, and would not
permit cavity walls to be built off continuous slabs due to flanking sound
and vibration transmission. If no practical solution was found industry
build costs were set to increase by a minimum of 18%.
In 2004 Smith and Wood, both based at Edinburgh Napier
University, started to investigate possible solutions and several house
builders offered test sites. Smith's research on sound and
vibration transmission in complex structures [1,2,3] had identified
limitations of the existing constructions and influence of the ISO
spectrum terms (Ctr) for wall and floor systems. Wood, a
specialist in architectural technology, had previously developed
construction methodologies which led to the Robust Detail Handbook for
Part E . In 2005 following a research of material properties Smith
identified unique vibration and acoustic damping properties of bitumen
compound thin layers (3mm thick) which would reduce acoustic bridging and
flanking transmission. In 2005 Smith and Wood researched
and designed a novel thin membrane system which could be inserted within
existing house designs and not affect the storey heights. In 2005 the
research led to a partnership with Icopal-Monarfloor to develop a patent
application  for acoustic thin membranes for separating walls on raft
foundations called Bridgestop©. Theoretical and parametric studies were
also carried out for complex cellular blocks as found across European
During 2007-08 Smith and Wood also developed new Section
5:Noise design details and performance criteria for the Scottish
Government. These findings led to advancing acoustic thin membrane
research into multi-storey applications. In 2007-08 the team secured the
first ever "proof of concept" funding for construction from Scottish
Enterprise (Project TTAIBA) to extend perimeter isolator research into
apartments, termed Wallcap. This led to a KTP project (2008-11) with
Icopal involving extensive laboratory testing in prototype housing systems
and field tests on sites across the UK. Thermal analysis was included ,
as the membranes could reduce cavity convected heat loss and improve
airtightness within party walls. Research included applications to timber
and steel frame buildings with patent granted in 2012 .
Increasing building standards can lead to compatibility clashes between
the Structure, Energy, Environment and Sound Insulation regulations. Due
to the Napier team knowledge base in addressing such regulatory clashes
they were awarded 3 years funding (£465,000) from the Scottish Funding
Council SPIRIT Awards to support demand led research towards technical
compatibility solutions for the future low carbon housing construction
References to the research
1. R.S. Smith. Implications of Part E Building Regulation
proposals for England and Wales. Submitted to the Building Standards
Advisory Committee (BSAC), Dept of Environment, Transport and Regions. May, 2001.
2. R.S. Smith, J.B. Wood, R.G. Mackenzie and R.K. Mackenzie. "The
Building Regulations 2000 — amendment of the building regulations to
allow robust standard details to be used as an alternative to
pre-completion testing". Public Consultation Document. Office of the
Deputy Prime Minister. August, 2003.
3. R.S. Smith, R.K.T. Mackenzie and T. Waters-Fuller. The
implications of ISO 717 Spectrum adaptation terms for residential
dwellings. Proceedings of the Institute of Acoustics, Vol. 29 (1).
34 - 37. ISSN 0308-437X, 2004.
4. R.S. Smith, J.B. Wood, P. Flynn, D. Parrett and D Bignell. ICOPAL Ltd.
(GB) British. Acoustic Isolator for a Party Wall. (Patent application
2005, Stage A published 2006, Granted 2009,
Patent Published: No. GB 2429719 — product name Bridgestop)
5. R.K.T. Mackenzie, L. Nichols, R.S. Smith, E. Prokofieva. Field-testing
sound insulation results and thermographic analysis of dual purpose party
wall cavity seal and flanking transmission isolator. Internoise 2010,
Lisbon, Portugal. 2010.
6. R.S. Smith and J.B. Wood Granted Patent Published: No. GB 2462037. Acoustic
isolator for building connections, 22 pages. (licensed to
Icopal-Monarfloor, product name WallCap). Publication of notice in the
Patents and Designs Journal, Section 25(1): 15 August 2012.
Key research grants:
2002-04: RSD Project: Investigation into the development of Robust
Standard Details. Home Builders Federation (£500,000). [This project
identified the original issue of raft foundations and sound transmission].
R.K. Mackenzie, R.S. Smith, J.B. Wood and R.G. Mackenzie.
2005: Investigation into thin acoustic membrane for raft
foundations: funded by Edinburgh Napier University (£20,000). J.B. Wood
and R.S. Smith.
2007-08: Project TTAIBA: Proof of Concept for thin acoustic
membrane technologies, Scottish Enterprise, (£141,000), Proof of Concept
Award, March 2008. R.S. Smith and J.B. Wood.
2008-11: Knowledge Transfer Partnership (KTP) Icopal-Monarfloor
and Edinburgh Napier University (£193,000 of which £73,000 from TSB and
£120,000 from Icopal). R.S. Smith, E. Prokofieva and J.B. Wood.
2010-2013: SPIRIT Project: Technical compatibility for future low
carbon housing — for structural, energy and acoustic building standards.
Scottish Funding Council (£465,000). R.S. Smith, J.B. Wood, J. Currie and
Details of the impact
Introduction: Icopal were chosen as industry partner due to their
global lead in geo-membranes and crucially the UK Manchester plant could
manufacture the alumite-bitumen compounds required for the thin membrane
technology. This impact case study outlines the substantial benefits to
the company, industry sector, environment and home occupants quality of
life as a result of this original research. The Napier team also developed
animations to assist installation training for both Bridestop© and Wallcap
series of products which can be viewed via reference [5.1].
Impact period 2008-2013: In 2008 brownfield sites accounted for
over 70% of new housing sites and raft foundations were increasingly
common. In 2008 the Napier team assisted Icopal-Monarfloor to commence
application for Robust Detail status for Bridgestop©. This would allow
entry into the Robust Detail Handbook, which is used by over 8,000
specifiers and designers across the new build housing sector. Bridgestop©
achieved on site field trials with an average sound insulation performance
of 10 dB (decibels) better than building standards, providing the highest
levels of sound insulation for new housing. The Bridgestop© isolator
system for raft foundations was awarded Robust Detail status and published
in October 2008 (reference E-WM-19) [5.2]. The sustainable construction
benefits [5.2] which when applied over the 15,000 homes built during the
REF impact period has avoided using 1,080 tonnes of additional gypsum
lining (72 kg per attached home) to achieve the equivalent sound
insulation performance. Thus also delivering resource efficiencies in
materials, transport and carbon. In 2010 Bridgestop© was the first wall
structure to receive the maximum four credits under the Code for
Sustainable Homes under Health and Wellbeing for sound insulation [5.3].
Many supply chain partners benefited from the system including Wimpey
Homes and Roger Bullivant Ltd [5.2, 5.3]. In 2010 Bridgestop© was
shortlisted by industry peers for UK Housing Innovation Product of the
The extension of thin membranes to apartment upper wall-floor junctions
(termed Wallcap) was supported by the first ever Scottish Enterprise Proof
of Concept Award for construction sector in March 2008 — illustrated by
reference code 8-CON-001. Wallcap was licensed to Icopal-Monarfloor in
2009 and was shortlisted for UK Housing Innovation Product of the Year in
2012 [5.5]. Wallcap also complies with the `effective edge seal'
requirements for the Part L thermal regulations to tackle cavity thermal
bypass [5.6] which can reduce heat loss by 20% in attached housing. The
Napier design of the isolators was such that the Manchester production
line produces zero waste. The cavity wall base is also lined with an
acoustic isolator involving recycled foam to prevent any mortar drops
bridging the cavity party walls. Due to the resilience of the
alumite-bitumen compound within the Bridgestop© dpc material it can also
act as a methane and radon barrier and also protect such barriers which
may be placed below the Bridgestop preventing them being damaged or torn
[5.7]. This benefits home occupants and benefits the intended full life
cycle of the construction.
Enhancement of Icopal's existing thin membrane patented technology was
strengthened as a result of the work with Edinburgh Napier [5.8]. These
products are now used by aggregate block, aircrete, timber frame and steel
frame industry sectors. The KTP project with Icopal-Monarfloor delivered
more than three times the estimated turnover and led to over 50% of
company profits stemming from these Napier designed products. In May 2013
the KTP was classified by the Technology Strategy Board as "outstanding"
and nominated for national KTP awards 2013. [5.9]
Icopal-Monarfloor (UK) is working with the Icopal global group to develop
similar isolator solutions for wider international markets. 9 new products
have emerged from the Napier research with a further 4 planned for launch
in 2014. New industry supply chain partnerships and joint ventures between
Icopal-Monarfloor and other companies have since been formed including UK
and other multinational companies (e.g. Knauf).
The research team have presented their findings to over 200 companies at
industry seminars and exhibited at Ecobuild, Futurebuild and the Edinburgh
Science Festival. Finally one of the most powerful statements of the
benefits from the original research is provided from the company: "The
average cost saving on substructure costs, by using Bridgestop and not
having to undertake expensive alternative build systems is 18%. This has
since been used in over 15,000 homes across the UK saving £80 million in
build costs by not having to build alternative constructions involving
deeper foundations, secondary suspended floors or additional gypsum
linings which has also resulted in substantial sustainability benefits."
Lee Nichols, Product Development Manager, Icopal Monarfloor.
Sources to corroborate the impact
[5.1] Icopal website showing Bridgestop and Wallcap products and
product animations designed and developed by Napier team.
[5.2] The Bridgestop © isolator system for raft foundations was
awarded Robust Detail status and in October 2008 (Robust Detail reference
[5.3] Bridestop is ranked for the highest level of sound
insulation under Code for Sustainable Homes and is awarded maximum 4
credits and benefits to Roger Bullivant foundation systems. http://www.architectsjournal.co.uk/specification/product-anatomy/icopals-bridgestop-is-first-to-four-
[5.4] Bridgestop shortlisted by industry peers for UK Housing
Innovation Product of the Year in 2010
[5.5] Wallcap shortlisted by industry peers for UK Housing
Innovation Product of the Year in 2012 http://www.house-builder.co.uk/awards/?awards_id=23
[5.6] Thermal benefits of Wallcap and Part L regulations
[5.7] Benefits of application of system to protect radon barriers
and gas protection barriers by use of the bridgestop system preventing
[5.8] Strengthening of Icopal group's existing product patent
portfolio (Last Paragraph)
[5.9] Rating by Technology Strategy Board on the KTP partnership
between Icopal and Napier developing perimeter isolators