Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 1
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
(21) Timber External Walls
CI/SfB (21.1) Load-bearing
(21.3) Non Load-bearing
LSBU Tech & Env 2 Lecture
• Domestic, Small & Medium size buildings
• Construction methods, materials, services and systems
• Timber External Walls
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Performance Requirements
Principles of Element Design
20/12/2007 © NGS 2007 (21) Timber External Walls 4
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Wall Actions
• Gravity: downward pull
• Wind: Motive, Destructive, Penetrative
• Rain: Moisture deposition, penetration
• Snow: Moisture deposition, loading
• Moisture vapour: permeation, condensation, insulation impaired, material degredation
• Sun: Temp variation, thermal movement, heat gains, Chemical decomposition
• Dirt and Dust: infiltration, deposition, surface pollution
• Chemicals: corrosion, disintegration, decomposition
• Sound: Noise nuisance, from within and from without
• Attack: Manual, Ballistics, Bomb Blast
• Thermal: heat loss, radiant coolth, condensation, stack effect
Wall Reactions
• Gravity: Support & restraint
• Wind: rigidity, resilience, sealing, air tightness layers and detailing
• Rain: deflection, impervious skin, absorption and drainage, sealing
• Moisture vapour: resistance, hygroscopicity, permability, breathing, moisture mass
• Snow: deflection, impervious skin, absorption and drainage, sealing
• Sun: movement joints, insulation, shielding, invulnerable materials
• Dirt and Dust: repulsion, exclusion, sheilding, cleaning
• Chemicals: invulnerable materials, exclusion,
• Sound: Insulation, absorption, acoustic mass, separation, isolation,
• Attack: toughness, lamination, edge restraint, edge protection
• Insulating: thermal insulation, thermal mass, U value, G value, cold bridge avoidance/minimisation
Principles of Element Design
• Appearance – Interior and exterior materials
and finishes
• Structural strength and stability– Load-bearing
– Wind resistance
• Weather barrier– Rain, snow, wind, sun,
– dirt dust pollution
• Durability – Moisture resistance, frost,
mould
– Moisture Mass & Hygroscopicity
– Ozone and sunlight degradation
• Thermal Performance– Heat Resistance: loss and gain
– Condensation Avoidance
– Airtightness
– Avoidance of Cold Bridges
– Thermal Mass
• Movement– Structural , thermal, moisture,
Frost
– Chemical
Principles of Element Design
• Acoustic Performance– Resistance, absorption
• Fire Performance– Surface spread of flame
– Fire Resistance
• Security
• Inspection and maintenance– Inside & out
• Pest infestation– Termites,
– Termite Barriers
• Rising damp– Barriers
– Capillary Attraction
– Hygroscopic or Hydrophobic
– Frost action
• Health– Moisture Mass
– Low allergy materials
20/12/2007 © NGS 2007 (21) Timber External Walls 9
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Weather Envelope
Absorbent – Repellent – Open Joint Panelled Masonry – Curtain Wall – Rainscreen
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 2
03/10/2007 © NGS 2006 Title 1
www.greenspec.co.uk
ZCD: Other Passive Design
ApproachesBrian Murphy (GreenSpec)
Another GreenSpec CPD to download soon Another GreenSpec CPD to download soon
www.greenspec.co.uk05/10/2006 © NGS 2006 Title 1
Wind
Affects on buildings
03/10/2007 © NGS 2006 Title 1
Airtightness& Testing
A94 on-site testingRegulation, Energy loss, Testing, Sealing,
Construction
Another GreenSpec CPD to download soon
Airtightnesswww.greenspec.co.uk
05/10/2006 © NGS 2006 Title 1
Airtightness & Building Elements
NGS GreenSpec CPD
Another GreenSpec CPD to download soon
www.greenspec.co.uk03/10/2007 © NGS 2006 Title 1
Conduction ConvectionRadiation
Conduction
Another GreenSpec CPD to download soon
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Straw Bale Walls
F42 Straw Bale Walling Systems
11/12/2007 © NGS 2006 Title 1
www.greenspec.co.uk
F42 Straw Bale Walls
F42 Straw Bale Walling Systems
20/12/2007 © NGS 2007 (21) Timber External Walls 17
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
2 approaches
• Load-bearing bale walls
• Timber framed with bale infill
Straw Bale
• CAT Centre for Alternative Technology
• Published guide
• Amazon Nails: Architect & Builder
• Others: rare experimentation
• Sarah Wigglesworth “any-tech” Architect & Bartlett Lecturer, C4’s Grand Design, small part of own house, architect/client, BCO raises concerns and avoids errors
• Market Share: Few Buildings = Zero +
• NBS published a specification late 2007
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 3
Straw Bales
• Rapidly renewable
• Carbon negative: CO2 Sequestration
• Ideally locally harvested
• Seasonal supply
• High density harvester setting
• Large dimensions
• Designs to respect modular bale size
Construction
• DPC at base of wall: avoid water trap
• Load-bearing or framed structure infill
• External walls
• Thick walls: good U value
• Hygroscopic insulation breathing wall
• Lime or earth renders and plasters
• Weather boarding externally
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
20/12/2007 © NGS 2007 (21) Timber External Walls 22
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Refinements
• Bales trimmed at window openings to create sloping jambs to enable greater light penetration through thick walls
• Softer light and low contrast between outdoor light and dark walls
• Chainsaw and scissors
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Hemp-Lime in timber framed Walls
20/12/2007 © NGS 2007 (21) Timber External Walls 24
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
2 Approaches
• Timber framed wall (wider spacing)– Temporary formwork to walls
– insitu hemp-lime rammed around posts
• Timber cassette panels– Insitu spray into cassette panel onto back
board
– Spray to thickness (greater than posts)
14/04/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Hemp-Lime Construction
On-line CPD topic
Hemp-Lime ‘Cottage Industry’
• Suffolk Housing Association
• Architects Ralf Carpenter of Modece
• Experimental comparison project
• Significantly out performs conventional walls with better U value
• U and k values are not enough to quantify characteristics, next is G values
• Not fully understood outside small circle
• Potentially CO2 negative: Sequestration
DRAFT
FOR YOUR EYES ONLY NOT TO BE CIRCULATED TO ANYONE ELSE
“Hempcrete” Building Construction with Hemp Composites
A Technical and Design Guide
By
Rachel Bevan and Tom Woolley Disclaimer: The author, publisher, DEFRA and NNFCC do not accept any responsibility, nor liability, in any manner whatsoever for any error or omission, nor any loss, damage, injury, or adverse outcome of any kind incurred as a result of the use of the information contained in this report/book, or reliance upon it. Readers are advised to seek specific professional advice relating to their particular house, construction, project and circumstances before embarking on any building work.
DRAFT
FOR YOUR EYES ONLY NOT TO BE CIRCULATED TO ANYONE ELSE
“Hempcrete” Building Construction with Hemp Composites
A Technical and Design Guide
By
Rachel Bevan and Tom Woolley Disclaimer: The author, publisher, DEFRA and NNFCC do not accept any responsibility, nor liability, in any manner whatsoever for any error or omission, nor any loss, damage, injury, or adverse outcome of any kind incurred as a result of the use of the information contained in this report/book, or reliance upon it. Readers are advised to seek specific professional advice relating to their particular house, construction, project and circumstances before embarking on any building work.
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 4
Hemp-lime: Design Guide
• NNFCC National Non-food crops centre
• Funded research project:– Lhoist, Lime Technology Ltd. Hemcrete– Queens University Belfast: Tom Woolley
– NGS GreenSpec: Brian Murphy– Modece: Ralph Carpenter
– Bath Uni: Peter Walker
• Output:– Architects Design Guide– Specification in guide and on GreenSpec site
© reproduced by permission of Lhoist UK
Hemp-lime ‘Industrial scale’
• UK Manufacture
• 3 years of R&D & Marketing
• 50% increase 2006
• 200% increase 2007
• £1.5m turnover
• Growth potential: Exponential
• Market share: minute but growing rapidly
• Many advantages to understand exploit and compete
• Government very interested
Hemp-lime: Violet credentials
• Hemp: CO2 –ve: Sequestration
• Lime: low CO2 (compared to Cement)
• Cement: high CO2
– for fast initial set and long term strength (blockwork standard)
• Aluminium high CO2: add to cement for reaction ‘aircrete’ effect
Hemp-lime
• Green Architects
• Violet Architects with occasional green buildings
Carbon Negative material
• Hemp shiv used as an aggregate and lime as a binder in a limecrete like mix
• Hemp is a rapid growth plant which sequestrates carbon from the atmosphere during photosynthesis whilst growing
• Lime is an adhesive created at lower temperature than cement and is recyclable and reusable
Insitu Constructions
• Light timber frame surrounded by insitu hemp-lime in formwork and rammed
• Backing board with framing, sprayed hemp-lime onto board and built-up to required thickness
• Creates monolithic airtight construction
• Hygroscopic breathing wall
• Ordinary U value with exceptional insulation properties
Blockwork Construction
• Hemp-lime blockwork solid walls
• Hemp-lime blockwork diaphragm walls
• Cavity filled with insitu hemp-lime thermal insulation at a lower density
• Outer skin brickwork for weathering and toughness
• Inner face hemp-lime, lime or clay plaster
• Outer face hemp-lime or lime render
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 5
Proprietary Hemp-lime Blocks
• Hemp-lime blocks not quite yet up to BS for concrete blocks minimum 2.8 kN/mm2
• Manufacturer experimenting with recipe
• Adding cement (high embodied energy) for initial set and ultimate strength
• Also adding aluminium (high embodied energy) to cement in mix matrix to obtain foaming function used in ‘Aircrete’ blocks
• Potentially carbon negative material moves towards carbon neutral or carbon positive 20/12/2007 © NGS 2007 (21) Timber External Walls 39
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Diaphragm Walls
• wide cavity walls
• with diaphragm walls linking inner and outer leaf
• Cavity empty or fully filled with insitu insulation grade hemp-lime mix
• Ideally on eco-concrete foundation
Diaphragm Walls
20/12/2007 © NGS 2007 (21) Timber External Walls 41
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
MMC Hemp-lime
• System with timber picture frame and insitu hemp-lime infill
• Factory production
• Site Assembly
• External walls infill panel to framed building
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Timber Walls
Timber Constructions
FSC Timber suppliers
• 267 UK sources of FSC certified timber
• Chain of Custody
• Importers
• Growers
• Processors
• Makers
• Stockists
• Project Chain of Custody available
Boron
• Timber preservative treatment
• 1980’s unnecessary retro-treatment
• Up to 3 chemical treatments detected in one piece of timber in attic
• 15 years ago to reject CCA= bankruptcy
• Treatment in decline: – was 50%, now 10% of turnover
• ProBor 75%-80% of its 10% turnover
Timber Stud External WallsPlan section
OutsideBreather Membrane, outer lining (plywood)
Timber Studs, Hydrophobic Thermal Insulation
Vapour Barrier, inner lining (plasterboard)Inside
Timber sections: limited depth before uneconomic or unobtainable
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 6
Timber frame walls
Balloon frame Platform Frame
Vapour Barrier/Check
Breather membrane
Eco Concrete Floor
GMV Greenwich Millennium Village Phase 2aTimber stud load-bearing panel walls
GMV Phase 2a 3 storey timber stud panels© NGS
Reduce Waste: Modular design wastes less
• Walter ‘Segal Method’
• Whole component usedfull size no cutting
CAT Centre for Alternative Technology
Robin Hillier ArchitectDiggers Self-build Brighton
Use found materialsBoulders, wild turf roof, gravel margin gutter, rubble wall
Breathing WallsPlan section
OutsideBreather Membrane, Breathing Sheathing Board
Timber Studs, Hygroscopic Thermal Insulation
Vapour permeable Air tightness layer, inner liningInside
Timber sections: limited depth before uneconomic or unobtainable
Brown RoofsCreekside Visitors Centre Deptford London
Timber frame walls
• Balloon frame Platform Frame
Air tightness layer
Breather membrane/sheathing board
Eco Concrete Floor
www.greenspec.co.uk05/10/2006 © NGS 2006 Title 1
On-line CPD topic
Breathing Construction
Another GreenSpec CPD to download soon
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 7
Compound raftersCellulose insulationAcoustic brick floorTimber floor planks
Timber fibre insulationTimber frame wallsTimber batten clad
Construction Resources Showrooms Southwark London
Timber StructureCompound raftersCellulose insulation Acoustic brick floor Timber floor planksTimber fibre insulationTimber frame wallsTimber batten clad
Construction Resources Showrooms Southwark London
Vapour Balanced ConstructionHygroscopic insulationmaintain their performanceeven when wetVapour and water releasedwhen conditions permitNo need for Vapour BarrierUse vapour permeable construction5:1 ratio vr inside:outsideand an air tightness layer
Construction Resources Showrooms Southwark London
EVT Enhanced Vapour Transfer
300-600 mm. deep compoundrafters with Cellulose fibreinsulation High thermal mass cellulosefibre insulation boards inwalls and floors
Construction Resources Showrooms Southwark London
Cellulose FibreWe have a preoccupation withthin walls 300 mm. or lessWhich drives the demand forenergy intensive man-madepetrochemical fossil derivedCFC HCFC HFC HFA foamed plO3 Ozone Depletion Greenhouse Gas Potential300-600 mm. optimuminsulation thickness
Construction Resources Showrooms Southwark London
Thick walls, roofs and floorsThermal mass:High thermal mass cellulosefibre insulation boards inwalls and floors Acoustic unfired clay bricksin floor constructionadds thermal mass
Construction Resources Showrooms Southwark London
Thermal Mass
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 8
Hygroscopic insulationmaintain their performanceeven when wetVapour and water releasedwhen conditions permitNo need for Vapour Barrier VBUse vapour permeable construction5:1 ratio vr inside:outsideAir Tightness Layer ATL
Construction Resources Showrooms Southwark London
EVT Enhanced Vapour TransferThermal mass:High thermal mass cellulosefibre insulation boards inwalls and floors
Construction Resources Showrooms Southwark London
Thermal MassConcrete Frame
Infill panels
Restraint
Restraint
Support
Restraint
Support
Restraint
Support
20/12/2007 © NGS 2007 (21) Timber External Walls 67
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Eco-Concrete
• Ordinary Portland Cement replacement– GGBS and PFA
• Aggregate substitution– Secondary aggregates
– Recycled aggregates
– Recycled concrete aggregates
• Engineers permit or restrict their use
• But do little to encourage it
• Embodied energy is low priority
• Market share: 1% of UK concrete is Eco-concrete GMV Phase 2b 4 storey framed & panel infill Greenwich Millennium Village © NGS
Metal Stud External Walls
Metal C Studs, Thermal Insulation, Breather Membrane, inner lining, Vapour Barrier, outer lining
• Egan initiative implemented: prefabrication off-site, simple assembly on site,reduction of site waste
• later on-sitefactory-production
Greenwich Millennium Village Phase 2a
Factory Prefabrication:
• Conditions ensure no deterioration
• No mud or cement splashes
• No rain to spoil
• Use of all the materials supplied
• Reusing until all is gone
• Virtually no waste
Avoid over design of structure around openingsAvoid lack of design: adding additional studs for luckAvoid creating wide cold bridges through insulation
Avoid Waste: chopping thermal insulation rolls
Strength v U Value in external wall
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 9
Compound section reduces amount of materials used, weight, cold-bridging
Layering: Services Zone simplify installation & avoid penetrations
Compound Studs ‘I Studs’ to accommodate more thermal insulation
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
MMC Modern Methods of
Construction
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Insulated Structural Floor, wall & roof
PanelsTimber Constructions
Prefabricated external wall panel
Compound Studs ‘I Studs’, inner and outer boards and thermal insulation
Prefabricated external wall panels
Compound studs ‘I studs’, inner and outer boards and thermal insulation
Insulated structural Panels
Roof panels create
Habitable Roof Space
Platform Frame
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Structural Insulated Load-bearing panel roof, wall & floors
Timber ConstructionsPrefabricated external wall panel
SIP Structural Insulated Panel
Prefabricated external wall panel
SIP Structural Insulated Panel
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 10
Structural Insulated Panels
Roof panels create
Habitable Roof Space
Platform Frame
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Load-bearing Laminated Timber roof, wall & floors
Timber Constructions
20/12/2007 © NGS 2007 (21) Timber External Walls 85
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Load bearing solid timber panel
• Egan Report
• Lean thinking, offsite fabrication
• Carbon sequestration
• CR and EUrban import
• KLM & LinoTec from EU
• Design & Build Contractor
• Established 2002
• £1m turnover 2006/7
• www.eurban.co.uk
Prefabricated external wall panelsoftwood lamina or plywood core option
Load-bearing Structural Timber Panel
20/12/2007 © NGS 2007 (21) Timber External Walls 87
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
20/12/2007 © NGS 2007 (21) Timber External Walls 88
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Laminated timbershear walls floors and roofs
Laminated timbershear walls floors and roofs Laminated timber
shear walls floors and roofs
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 11
Roof panels create
Habitable Roof Space
Platform Frame
Laminated structural timber Panels23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Load-bearing Timber blockwork
Opaque Timber WallsTimber Constructions
Load bearing timber blockwork
• Swiss made
• Radically different construction
• Ideal for DIY and Self-build
• 1 or 2 UK projects
• Tried to include in GMV Greenwich Millennium Village (1300 homes) but not suitable
• CR tried to interest UK manufacture
• CR imported it but no longer
• UK Market share: Zero
Steko “Lego for Self-builders”• Waste from forest thinning
• Low carbon, carbon neutral
• Carbon sequestration
• Dry Construction
• Self-build unskilled construction
• Fast construction (3 day house)
• No waste on site (designed)
• Accommodates services
• Accommodates thermal or acoustic insulation
• Lightweight 6kg (children too)
• Load-bearing (designed to 7 stories)
• Internal and external walls
• 160 mm. modules
STEKOLoad-bearing timber blockworkConstruction Resources Showrooms Southwark London
STEKO
Load-bearing timber blockwork
Attic spaces
Party walls between
flats and terraced or
semi-detached houses
Acoustic details in
Party walls make
heat loss prevention difficult
Party Walls act as heat stacks
(21) Timber External Walls 20/12/2007
© NGS 2007 Brian Murphy 12
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Resource Efficiency
23/11/2007 12:06 © NGS 2002-2006 Waste At Design Diagrams 1
15/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Design to help Reduce Waste
Easy steps to reduce your shareof the 90 m tonnes of construction and
demolition and excavation waste each year
Another GreenSpec CPD to download soon
23/11/2007 © NGS 2006 Title 1
www.greenspec.co.uk
Resource Efficiency:
Timber
Reused wood better than newBedZED Beddington Sutton Architect: Dr Bill Dunster, Reclaim: BioRegional ReCLAIMED © NGS
Reduce Demand
• Don’t cut section from solid if compound is possible
• Reduce solid sections to compound to reduce weight and materials used