Study of the Retrofit of the ground floor of a Victorian Terraced House in Westminster conservation area, London using the Eco-Slab system

1. QueensPark Conservation Area TSB
Retrofit For the Future, London 2011

2. Refurbishment of social housing in
Queens Park, Westminster, London
 2-bedroom, 2-storey Victorian terraced
properties built around1865
 In a Conservation Area of approximately 400
other similar properties
 Client - City West Homes
 Contractor - United House
 Project Manager – Anna Debenham

3. Project Architects: Energy
Conscious Design (ECD)
 Lead Architect - Mark Elton
Associate Director at Energy Conscious Design
On the RIBA ‘sustainable futures’ committee
Special Interest in:
 The potential for reducing carbon emissions through retrofit
of the existing stock
 Refurbishment schemes that combine super-insulated fabric
improvements with integrated renewables

4. Key Improvements to Property
 Internal wall insulated to the exterior solid walls
 Roof insulated
 Doors and windows improved and replaced
 Acoustic insulation fitted to the party walls of bedrooms
 Ground floor suspended timber floors removed and
replaced with an Eco-Slab floor system
 Mechanical ventilation heat recovery (MVHR) installed

5. Thermal image showing heat loss

6. Project funding
 Retrofit for the Future project is funded by
the Technology Strategy Board (TSB) to
find ‘innovative and replicable measures
to make deep cuts in carbon dioxide
emissions from existing properties in the
social housing sector’

7. Driving Innovation in Retrofit
 UK Technology Strategy Board (TSB)
funding was specifically designed to
stimulate the implementation of
innovative cost effective solutions within
the demonstrator houses that can then
be applied across the UK.

8. Evaluation
 SAP tests before and after retrofit
 Used by BRE as a Pilot for their
‘BREEAM Domestic Refurbishment
standard
 Evaluated alongside BRE EcoHomes
XB target criteria and discussed with the
local conservation officer

9. Typical Heat Loss Pattern
Generally agreed that 15% of heat is
lost through the ground floor but it can
be higher in older properties
Heat is lost through draughts in the floor
boards as well as through the fabric

10. Draughts in a typical Victorian
House

11. ‘THERMAL ENVELOPE’
 Insulate the property to keep heat inside
in winter and outside in summer and
maintain a constant internal temperature
 Create an airtight seal to eliminate heat
loss from draughts

12. Thermal Image of Interior of
Victorian Terraced House

13. Retrofitting the Ground Floor
Schedule of Works
 Disconnect Services
 Remove joists and floor timbers
 Fill void
 Reroute and reinstall services
 Lay new floor

14. Challenges of the Site when
Retrofitting the Ground floor
CHALLENGES OF THE BUILDING SITE
Work had to be carried out in a confined space which meant:
 Confined space working Health and Safety Act had to be observed so no petrol
driven machinery
 Materials and installation had to be handled manually
 Labour intensive options not possible
 No room for storing materials in building
 Delivery of materials had to be tailored to the demands of restricted site access
 The original Victorian features had to be protected
 The integrity of the Substructure had to be maintained
 Services had to be re routed
 Void had to be filled and ventilated
 The material effects of retrofit on adjoining properties had to be considered
 Party Wall Act applied
 Security had to be maintained at all times

15. Challenges of the Street When
Retrofitting the Ground floor
New Road and Street Works Act:
Health and Safety conditions Relate to the control of
deliveries
Needed road signs and barriers
Traffic control
Timed deliveries
Make good any damage to road or footpath
Local Council By Laws:
The by laws change depending on the Borough
Not able to start work before 9am
Road had to be cleared and swept by 5pm
No weekend working
Noise and dust restrictions

16. The traditional approach
15 tons of aggregates were
delivered, stored on the road and shoveled
and barrowed in to the house to fill the void
at a rate of a ton a day
Diesel driven whacker plate was used to
create a flat surface putting pressure on
substructure and creating toxic fumes in
confined space violating Health and Safety
laws

17. The Eco-Slab solution
FEATURES OF ECO-SLAB SYSTEM BENEFITS OF ECO-SLAB SYSTEM
‘Just in time engineering’ Minimal materials to store and
organise
Foaming concrete was delivered by a Lorry No complications or concerns with Council
mounted pump, located outside the working Bylaws,
area
Conditions of working in Confined
Foaming concrete used to fill deep void Spaces Health and Safety Act and New
Road and Street Works Act were satisfied
Replaced 15 tons of granular material
Pump set up, filled the void cleaned up
and left within one in an hour with no
manual handling
Minimal Impact on the Street:
Site Activity, Traffic movement, Noise and
Dust all substantially reduced
Minimal supervision to organise delivery

18. Eco-Slab Module

19. Method Statement for Retrofitting
Ground Floor with Eco-Slab
FEATURES OF ECO-SLAB SYSTEM BENEFITS OF ECO-SLAB SYSTEM
‘Just in time engineering’
Eco-Slab was programmed to be delivered Hand off loaded and no storage required
on a light commercial vehicle on day of
installation Unloading and installing completed in one
operation.
Installed by hand by a single semi skilled No machinery required so easily met
operative in one day ‘Confined space working Health and
Safety Act
Eco-Slab was laid directly onto the foam concrete No pressure or penetration of the existing
base walls
Service and ventilation void was provided by Allowed for simple rerouting of services and
100mm legs Under floor ventilation
75mm thick fibre reinforced wearing slab was Reinforcement was in the concrete so delivery and
poured to finished floor level fixing of reinforcement was not needed
All Local Council By Laws and New Road and
Street Works Act easily met as
noise, dust, site activity etc. reduced

20. Insulation Values & Carbon
Reductions
Eco-Slab is made from Carbon Enriched Jablite EPS which has an
A+ rating in the BRE Green Guide
The unique lap & ledge system ensured a continuous 100mm of
insulation throughout the ground floor
200mm Edge beam system gave a U value of zero at the wall/ floor
interface
The Eco-Slab floor provided the base for the thermal envelope
In conjunction with other technologies the energy use for the building was
reduced from 16000 kilo watts per year to 2000 kilo watts without
renewables

21. ECD Architects – Eco-Slab
system ground floor section

22. Conclusions
 Traditional methods of construction cannot meet the demands and
complexities of professional retrofitting on the scale required
 We need to employ new ways of working and new materials
 Modern methods of construction and in particular ‘just in time engineering
can assist in meeting the challenges
 The Eco-Slab system offers a fast and cost effective solution for
retrofitting the ground floor when working in a confined urban environment
 It is particularly cost effective when retrofitting several houses in one area
and the costs of hiring the pump can be shared among several properties
 The Eco-Slab retrofit system using foaming concrete and the Eco-Slab
base significantly reduced the operational and embodied carbon
compared to traditional retrofit methods and combined successfully with
other technologies to create a thermal envelope
www.eco-slab.com