Innovation in exterior cladding and its planned maintenance

22 November 2007Ed Suttie, BREGeoff Taylor, Sikkens

Introduction

• Exterior timber cladding• Durability• Innovations to improve durability• System durability• Planned maintenance• Conclude

UK Cladding market : materials

• No direct information on volumes of material used in UK market

Surface (m2) %

Wood 200,000 3

Metal composite 4,800,000 82

Concrete 300,000 5

Fibre cement 300,000 5

uPVC 300,000 5

Sustainability and Life Cycle

Construction

WaterEnergyResourcesWasteEmissions

Maintenance

Demolition

Forestry

Harvest

Manufacture

In service

Energy recovery

Second life...

End of life

Process

• The performance of timber cladding and thus whether service life is met is influenced at all stages

• Need to objectively assess the importance of each component of a system and its contribution to delivery of service life

Raw materials

Manufacture and quality control

Design and specification

Build/install phase

Use phase

Durability

• Capability of a building or its parts to perform its required function over a specified period of time under the influence of the agents anticipated in service

• Material of biological origin - need for protection• Biological durability• Prevent moisture ingress

Delivering durability

• Timber species• Substrate selection• Cladding design• Pre-treatment• End grain protection• Primer or base stain• Top coat• Finishing of the product• Storage, transport• Installation• Planned Maintenance

Cladding design then…..

• Poor substrate selection• Poor design• Non specific fixings• Poor finishing on site• Adequately or poorly

maintained

Met service life??

Cladding design now….

• Substrate selection• Best practice design• Fully factory finished• Just in time delivery• Fitted by qualified installers• Planned maintenance and

care package

Extended service life

Best practice design

Factor method ISO 15686

ESL = RSL x A x B x C x D x E x F x G

A quality of components (durability)

B design level

C work execution level

D indoor environment

E outdoor environment

F usage conditions

G maintenance level

ISO15686 Service Life Prediction

EN335 Use Class

EN350 Natural durability

EN460

BS8417 Preservation

(EN599 and EN351)

Natural durability sufficient?

Substrate quality BS942

INNOVATION: Substrate selection

Durability enhancement

• Upgrade to DC1– Costly, market acceptance?

• Accept that for the chosen design and for timber species of low durability, to maintain the desired appearance, to deliver an acceptable service life then the durability will require enhancing

Enhancing durability

Permanence of characteristic

Planned maintenance

Enhance durability and test

• Wood preservation• Wood modification • Wood coatings• Combinations of the above

ChallengesWood preservation• Restrictions on traditional products

(CCA alternatives)• Registration under Biocidal Products

Directive• Penetration and retentionExterior wood coatings• Low maintenance• Full factory finishing• Low VOC coatings and processesWood modification• Lack of fit with standards• Track record?

INNOVATION: Wood preservation

• Water-borne• Multi functional

– Water repellent

– Colour

• Improved specification• Improved quality of treated products

BS8417 Preservation of timber - Recommendations

WPA Manual

INNOVATION: Wood modification

• The action on wood by chemical, biological or physical means creating a new material - “modified wood” - with a desired property enhancement for the service life of the wood product

• >50 years of wood science• Numerous technologies• Stimulated by the need to consider alternatives to

– Conventional wood protection– Non-sustainable hardwoods

• Exciting commercial reality

Wood Modification

• Modified wood technologies can…– Resist decay organisms (biological durability)– Minimise shrinking and swelling of the wood in changing

moisture conditions (dimensional stability)– Confer hardness and wear resistance– Prolong the life of exterior wood coatings– Compete effectively with less sustainable materials– Improve end of life options

• Thermal modification ThermoWood®

• Acetylation AccoyaTM

• Densification Indurite*

BRE Digest 504 (Nov 07)

Uncoated cladding

• Typically uncoated cladding with non-uniform colour changes can lead to dissatisfaction

• Brush applied maintenance coatings

INNOVATION: Coating system

• Water-borne• Low VOC• Extensibility• Photostability• Improved Environmental Profiles• Full factory finish• Powder coating

Coating of a smooth surface

Coating of a rough sawn

Microscopic view of a rough sawn surface

Microscopic view of a smooth surface

Edge covering

Film build

Coating hardwood – pore filling

Timber cladding behind glass

Full factory finished cladding

INNOVATION: Environmental Profiles

• The Code for Sustainable Homes• The Green Guide to Specification• Presenting the case for timber• Improving product profiles

Code for Sustainable Homes 2007

• Single national standard for England

• EcoHomes in Wales, Scotland, Northern Ireland and for refurbishment

• Industry guide for design and construction for more sustainable new homes

• A step change in sustainable building practice for new homes

Specification tools

INNOVATION: Fire protection

• Multi functional• Fire Safety Design• Fire retardant pre-treatments BS 8414 Part 1 or 2• Wood Protection Association’s (WPA) Fire Retardant

Manual

INNOVATION: Construction

• Off site construction• Full factory finished• Planned maintenance• Site practice and skills

Offsite construction

• Modern methods of construction• Pre-manufacture• Less storage area on site• Quality of workmanship• Improved safety levels• Fast assembly• Reduced costs

– Lower labour costs– Less waste– Less plant hire– Dimensional accuracy– Less disruption

• Enhanced durability

• £1 billion pa maintenance of buildings– Redecoration and maintenance painting of exterior

wood is significant• Demands ‘value for money’

– Reduce unnecessary maintenance activities– Reduce costs of incorrect surveys– Improve process selection– Higher standards of performance and quality– Improve site practices– Minimise waste

• Move away from short-term first costs

INNOVATION: Planned Maintenance

BS6150

Origin of maintenance specifications

In-houseCoating

manufacturer

BS 6150 Other

In-house

Coating manufacturer

Housing stock owner

PDA

BS 6150

BS 8000-12

Other

housing stock owners painting contractors

Partnership and responsibility

• Coatings manufacturer and contractor led with housing stock owners

• Improved product performance• Raising skill levels• Improved maintenance practices• Maximise service life• Extend maintenance intervals

The integrated system?

• The performance of timber cladding and thus whether service life is met is influenced at all stages

• First costs sensitive, quality, consistent• Best practice, control, confidence in supply chain• Skills• Skills, partnership, value• Whole life costs sensitive, partnership, planned

maintenance

Raw materials

Manufacture & Quality Control

Design and specification

Build/install phase

Use phase

• Design, durability and planned maintenance can deliver• Raising standards• Robust technologies fostered• New partnerships to ensure service life• Cladding product accreditation scheme• Holistic approach – durable integrated system

Conclusions

Conclusions

• Great opportunity for exterior timber cladding– fully factory finished

– new substrates

– offsite construction

• Move from a material orientated approach to an integrated product approach

• Use the wood science!• Timber cladding delivered in partnership between the

technology holder, the manufacturer, the specifier, the coating system company, the maintenance contractor and the building user/owner