Research at CWCT
This section gives the details of the research projects in thermal performance that
CWCT have led, or taken part in, over recent years. Current projects are also
included.
The use of BMS to control facades
Status
Starting 1 January 2007
Duration
18 months
Partners
Centre for Window and Cladding Technology (lead)
Council for Aluminium in Building
Carillion
Faber Maunsell
Max Fordham
SE Controls
Velfac
Objectives
There are two objects to this research. One is to identify barriers to the use of BMS
controlled automated facades and to report on the ways that these barriers may be
broken down. The other is to look at additional functionality that will tip the balance in
favour of using BMS controlled automated facades.
This project will;
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Review operable components of facades that are currently available;
Review the limitations of current control strategies for facades, particularly the
control of glare;
Review the current actuator technology including how it interfaces with BMS
and its reliability;
Report on the process of designing buildings with BMS controlled automated
facades, based on interviews with designers;
Report on the construction of buildings that incorporate BMS controlled
facades;
Investigate the additional functionality that can be achieved by using sensors
in different combinations, especially to develop an actuator that can be used
for controlling glare and limiting solar over heating;
Produce two reports. One aimed at clients and architects to show the
benefits of automated facades and how to design/specify them, and the
second for contractors explaining how these systems are integrated with one
another and with the façade and the building.
The use of double facades to facilitate on demand controlled ventilation
Status:
Starting 1 January 2007
Duration:
24 months
Partners:
Allies and Morrison
Bennetts Associates
Centre fro Window and Cladding Technology (lead)
Council for Aluminium in Building
Carillion
Hoare Lea
Sir Robert McAlpine
Objectives:
The objective of this work is to establish virtual precedents of the use
of double facades that will provide a pressure moderated plenum from
which air can be drawn for demand controlled ventilation.
This project will;
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Undertake a desk study of wind events in the UK. This will include a review
of the minimum conditions required to activate ventilation on demand;
Postulate façade geometries for a number of building layouts to optimise the
use of the thermal stack effect;
Model the performance of a pressure moderated plenum of the double façade
using CFD analysis. Different geometries will be looked at;
Study existing building projects to determine the typical demands for
ventilation and other factors controlled by the building envelope including
daylight, solar gain, and heat transfer;
Determine rules for use at the outline design stage using the information
found above;
Produce two reports. One will be written for use by clients and architects and
will present information required to allow the inclusion of an effective double
façade. The other will present an engineering methodology for use by the
cladding and building services engineers.
MODCELL: an innovative straw bale building system
Status:
Starting 1 January 2007
Duration:
24 months
Partners:
Agrifibre Technology Ltd
Centre for Window and Cladding Technology
Eurban Limited
Integral Structural Design
Lime Technology Ltd
University of Bath (lead)
White Design
Objectives:
This project aims to further develop an innovative sustainable building
system using straw bale construction technology. Modcell building
and cladding panels comprise a timber frame in-filled with straw bale
insulation. The bales are compacted and reinforced with steel bars
and protected with lime or cement based plaster coats. The project
seeks to investigate and perfect the manufacturing methods and
develop robust design data. The study will comprise laboratory and
analytical research investigations, design studies, environmental
performance modelling, life cycle assessment, and in-situ monitoring
of prototypes.
CWCT are involved in the thermal analysis and condensation risk assessment of the
constructions. We will be carrying out;
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A literature review of material properties to obtain representative values for
the thermal conductivity and vapour resistivity of straw bales;
One-dimensional static thermal analysis and condensation risk assessment
in order to investigate the effect of bale and render thickness;
One-dimensional dynamic thermal analysis and condensation risk
assessment in order to investigate the effect of bale and render thickness;
Two- or three-dimensional thermal/moisture transfer analysis at the
junctions between the Modcell panels and windows and doors;
Three-dimensional thermal/moisture transfer analysis at localised thermal
bridges.
Hempcrete
Status:
Current
Duration:
Partners:
BSA
BRE
Castle Cement
CWCT
Lhoist
Lime Technology
University of Bath
University of Plymouth
Objectives:
Hemp construction is considered environmentally friendly and highly
sustainable. The hemp can be mixing with lime to form ‘Hempcrete’
and can then be used as a building material in place of
brick/blockwork. A project at Haverhill in Suffolk built two houses out
of Hempcrete and these will be used as the basis of some of the
following work. These houses were identical to some traditionally
constructed houses so comparisons between the two could be made.
CWCT will be studying the thermal performance of the Hempcrete construction. This
will include;
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Reviewing the construction details and comparing them with those of a
traditional building with the same geometry and usage;
Assessment of all the building elements by either simulation or calculation;
Dynamic heat transfer analysis to compare the temperature variation of
hemp wall over the course of 24 hours with that of a brick-block wall with
identical geometry;
The effect of the surface finish. Different finishes will result in a different
surface emissivity, and affect the therefore the U-value;
Looking at, and comparing, the heat loss due to air leakage through both
houses at Haverhill;
Inputting data obtained previously into whole building energy consumption
software to calculate the overall CO2 emission rate for the hemp house and
the brick-block house at Haverhill.
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New façade technology – removing cold bridges
Status:
Complete (2003 – 2005)
Partners:
Centre for Window and Cladding Technology (lead)
Permasteelisa
Sandberg
Objectives:
The aim of this project is to study existing common construction
details and products and to develop potential solutions to improve
their thermal performance without affecting other aspects of
performance. This will amount to a guidance of production trends in
ten years time. The guidance will cover appropriate calculation
methods for assessing the overall energy loss and condensation risk
of different modern cladding systems and give potential best practice
advice to remove cold bridging.
The construction types to be considered will include:
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Curtain walling
Rainscreen
Punched windows
Insulated panels
The solutions to be considered will include;
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Thicker insulation materials;
Alternative materials;
Removal/reduction of metal components;
Cladding and thermal shielding of components.
Issues to be studied will include;
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Structural integrity;
Thermal and acoustic performance;
Durability;
Buildability.
Thermal performance of a window insert in stick system curtain walling
Status:
Complete (2004 – 2005)
Partners:
Centre for Window and Cladding Technology
Council for Aluminium in Building
Objectives:
This project aimed to specify the methods for calculating U-values of
different types of cladding system. Both simplified and detailed
methods are specified. The project also calculated default values for
the linear thermal transmittance of stick system curtain walls. These
values were found by investigating the most commonly used systems
in the UK and included the -value;
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At a glass edge;
At a panel edge;
Where you have an opening light at one side of mullion/transom;
Where you have opening lights either side of mullion/transom.
Full details are given in the CWCT guide ‘The thermal assessment of window
assemblies, curtain walling and non-traditional building envelopes’ described earlier
(LINK TO PAGE).
Detailing modern non-domestic building envelopes to comply with the new
Approved Document Part L of the Building Regulations
Status:
Complete (2002 – 2004)
Partners:
Centre for Window and Cladding Technology (lead)
Permasteelisa
Sandberg
Objectives:
The aim of this project is to develop and publish advice on detailing
non-domestic building envelopes to comply with the new Approved
Document Part L of the Building Regulations. This will amount to a
'robust detailing' guide that could in future be annexed to Part L.
The guidance will cover appropriate calculation methods for assessing
the overall energy loss and condensation risk of different modern
cladding systems and give best practice advice to avoid cold bridging.
The project will consider junctions and interfaces, fixings and penetrations associated
with;
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Stick system curtain walling;
Insulated panel walls;
Unitised walls;
Slope glazing;
Rainscreen overcladding;
Integral rainscreen.
Assessing the heat loss at the insulating glass sealed unit edge
Status:
Complete (2001 – 2003)
Partners:
Azon
Bostik Findley
British Plastics Federation Windows Group
British Woodworking Federation
Centre for Window and Cladding Technology
Chemetall
Council for Aluminium in Building
Glass and Glazing Federation (lead)
Interpane
National Physical Laboratory
Pilkington
Steel Window Association
Tremco
Objectives:
In recent years glazing technology has made significant progress in improving energy
efficiency, by the introduction of low-E coating of the glass and the filling of the space
between the glass with heavy inert gas. These technologies are approaching
maturity, and are well documented and understood. Warm edge technology, a range
of techniques for replacing the aluminium spacer frame with less conductive metals,
metal composites or other materials, is a more recent development, which has not
been thoroughly researched, or authoritatively appraised. Current warm edge data
resembles inspired market promotion, rather than factual comparisons of
performance, when combined with other technologies, as required for future
fenestration. The combination of technologies should enable the construction
industry to identify routes to better windows, and therefore a significant contribution
to energy conservation. The information developed by this project will enable all
sections of industry to make informed selection of advanced performance
fenestration. In order to meet the national targets for CO2 reduction, it will be
necessary to make energy savings in both new construction and existing property
stock. The adoption of high performance glazing will contribute to proposed and
future targets for pollution control.
This project involves both physical testing and calculation.
NPL will test the thermal conductivities of the various systems available and carry out
a series of hot-box tests, and make comparison between the test data and numerical
modelling.
CWCT will carry out thermal analyses of various combinations of materials and
technologies. These include;
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Six types of window frame;
Six types of glazing spacer;
Three different glazing units.