Sustainability and Historic Buildings: An alternative viewpoint on sustainability and the practicalities and options

Andrew Turton 21st February 2012

• Member of the Shape East Design Review panel• Associate Director at AECOM’s sustainable development group

based in Cambridge• Expert in energy and sustainability, working with both government on

policy, and project work

• Existing buildings will remain dominant in the future – pressure to refurbish and upgrade

• Need to make buildings more resilient to climate change and rising energy prices

• “Historic and special buildings” are a small fraction (374,000 listed buildings in UK) overall, but will experience the same pressures

• Conservation status and special designations can be seen as restrictive, but there are many opportunities presented by historic buildings

• How sustainable are historic buildings and how can they be improved further?

Blue Planet Distribution Centre

• First BREEAM ‘Outstanding’ rating. Features include a biomass heating.

Kingspan “Lighthouse”

• Code level 6 ‘Zero Carbon’• Biomass pellet boiler, solar

thermal, and photovoltaic panels.

• High levels of insulation• Good day lighting and natural

ventilation • A “technological” approach to

sustainability

Shorne Wood Visitor Centre, Kent

• AECOM design (structural design and services)• Constructed from locally felled sweet chestnut. Materials informing

structure, similar to many historic timber structures.

Norwich Cathedral Visitor Centre

• AECOM project. New visitors centre with community, exhibition, education, and meeting areas.

• High efficiency combined with sensitive material selection.

• Enhancing and increasing viability of existing historic building.

• Project was awarded the Civic Trust Award and Michael Middleton Special Award 2011.

St Pancras Chambers

• AECOM Project (mechanical, electrical, acoustics, sustainability).

• Novel use of existing services

• Minimal impact on existing fabric and strucutre.

What can we learn?

• Sustainable buildings can take many forms.• There are many different aspects to sustainability: – Historical understanding– Social and community benefits– Impact on the environment– Energy consumption and CO2 emissions– Materials and construction

Sustainability – a definition

Brundtland Report (1987)

“meeting the needs of the present without compromising the ability of future generations to meet their own needs”

Brundtland commission set up by UN in 1983 headed by Gro Harlem Brundtland, former PM of Norway.

UK Government Sustainable Development Strategy (2005): ENVIRONMENTAL

ECONOMIC

SOCIAL

BREEAM: Rating sustainability

• Building Research Establishment Environmental Assessment Methodology

• Rates buildings “Pass” to “Outstanding” taking into account:

• Mostly used on new buildings but refurbishment scheme being introduced. How will historic buildings be included?

• Does this really address sustainability in the round?

Health and wellbeing Management Energy

Water Pollution Materials

Ecology Transport Waste

Two views on sustainable buildings

“The most sustainable building is one which isn’t built”

“The most sustainable building is one which already exists”

Perhaps we should be making better use of our existing valuable assets? How can we help them become more sustainable and adapt to future climates (both environmental and economic!)

Sustainable historic buildings?

• Need to include the history, operation, future, and wider aspects of the building and uses in any assessment.

Important considerations: • Social and historical importance• Existing structures which have worked hard and can be adapted for

future use• Generally designed to operate passively / naturally• Long lasting with inherent quality• Simple, natural materials and construction methods

Why might improvements be required?

• Poor use and occupancy levels – do buildings meet the need of occupiers and are good quality environments offered? Are they suitable for modern uses?

• High maintenance costs – what can be done to limit maintenance costs and improve performance?

• High energy costs – older buildings typically inefficient. Energy efficiency and CO2 reduction is a key challenge to all existing buildings. Need to become more energy secure.

• Marketing – there can be a premium for sustainable buildings which offer tenants and owners benefits. A niche market perhaps for sustainable historic buildings?

Developing a strategy for improvement

Need to consider1. How the building was originally designed to operate.2. What are the current main failings are. Often due to poor

refurbishment or modification. 3. What level of aspiration (and funding!) is available. Have a vision

and plan!4. The significance of the building, and the opportunities and

constraints this may provide.

• Understanding the basic operation and ethos of an historic building is vital....

Understanding the difference between historic and modern buildings

Modern construction• National / international supply chains• Highly processed materials. • Complex components and construction detail

important for performance. • Short lifetimes common (60 years). Traditional construction• Locally sourced natural materials• Inherent quality and durability of materials and

construction. • High cost of labour and labour intensive methods

leads to long life and low maintenance.

• Older buildings designed to breathe: – Removes the need for impermeable materials (they weren't

available!)– Provides a healthy atmosphere– Allows use of natural materials– Reliable – no design detail or operational requirements.

• Majority of problems in older buildings are due to the prevention of breathing. Many common remediation methods make matters worse.

• Need to consider natural materials and historic techniques when repairing and refurbishing.

• BREATHING DIAGRAMS

Cement renderConcrete floorsImpermeable internal finishes (gypsum plaster, tiles, paints)Injected damp proof coursesSealing

Bare brickworkLime mortar re-pointingLime renderSuspended wooden

floorsLime / hemp floorsNatural finishes (lime

plaster, “eco” paints)Good ventilation

Passive operation – daylight and ventilation

• Natural ventilation. Sliding sash windows very effective• Natural light – narrow floor plans combined with tall windows• No cooling required – cross ventilation and high thermal mass

Remove modern internal partitions to allow cross ventilation

Maintain and improve existing sash windows

Inform occupants on how to use windows

Fit high efficiency controlled lighting

Low impact materials

• Historic buildings often characterised by: – Natural materials – clay, stone, timber, lime, metal, straw– Local materials– Long life materials and structures

• Need to ensure renovation is compatible with original techniques • The building already exists! No new materials are required. • Construction waste is about 1/3 of UK annual waste.

Embodied carbon• A measure of how much energy is used in creating

a building. • Modern house: – Typically 50 tonnes embodied carbon to build– Saves 3 tonnes per year over existing house– 17 year payback

• Modern efficient buildings have a significant carbon footprint upfront.

• How can we reduce operational emissions from historic buildings? Possibly the biggest challenge!

Improving the sustainability of historic buildings

• Maintain natural and passive performance. Back to basics. • Improve energy efficiency• Reduce operation and maintenance costs• Provide a good internal environment for users• Sustainable long lasting maintenance

• Remember – there is much that can be done before touching the building fabric. Management, waste, transport, procurement, food, water, etc... Many of these are free or low cost options!

• But energy efficiency is possibly one of the biggest challenges for the building.

The energy hierarchy

1. Improving energy efficiency

2. Using energy efficiently

3. Renewable and low carbon energy supply

Increasing cost and smaller returns

Building regulations – Part L

• Conservation for fuel and power• Exemptions for:

– Listed– Conservation areas– Scheduled ancient monuments

where alterations would unacceptably alter character or appearance.

Important to understand the significance of the building and the limitations and opportunities this may pose.

Energy efficiency - Insulation

• Generally poor in old buildings – external walls the biggest problem. • Some modern materials may be suitable (eg glass wool). • Natural alternatives include Hemp, sheep's wool, straw, flax.

Becoming increasingly available.

Insulation - walls

• External insulation: Need to consider visual appearance. Could be possible with existing rendering or cladding.

• Internal: Consider impact on existing finishes such as plasterwork. Can potentially cause serious problems with condensation and thermal bridging.

• Generally very difficult and needs careful consideration. • Most opportunities presented at major renovation.

Insulation – floors and roofs

• Floors– Suspended – can insulate but need to

consider ventilation– Solid – need to use breathable materials

such as limecrete and hempcrete.

• Roofs– Relatively simple using a range of materials.

Ventilation of roof timbers vital.– Can be incorporated under new coverings –

consider vapour control and prevention of condensation (particularly for metal coverings)

Hemp and lime (an aside)

• Two complimentary materials• Low embodied carbon• Structural, insulation, render, infill.

And what happens when you don’t use lime...

• Cement – inflexible and impermeable. • Causes frost damage, damp, and cracking

• Otherwise known as draught proofing - not to be confused with breathability

• Can be a considerable source of heat loss in older buildings (although not as bad as some newer buildings!)

• Can control loss though windows, doors, chimneys, floors by around half.

• Very low cost and effective. • Reduces energy demand and improves

perceived comfort.

Glazing• Windows – often a significant architectural

feature. • Options available for double glazing retrofit

(eg ‘slimlite) but not always practical. • Heat loss through glazing can be large, but

savings may be relatively small compared with other inefficiencies.

• Drivers for glazing replacement are more often maintenance, condensation, draughts, down-draughts. Solve these first!

GlazingTry not to replace entire windows for efficiency purposesuPVC....NO!

Provide adequate controlled ventilation to reduce condensation

Maintain and improve existing windowsUse replacement double glazed units

where possible and no adverse impact (but respect historic quality of old glass)

Install secondary glazingReplacement – most traditional types

available.

Controls and management

• Significant potential for savings through good controls and management (>10% should be achievable)

• Link the control strategy to building type and use – consider occupancy patterns. Who needs heat and when?

• Monitor energy consumption before and after making changes. Don’t forget water too!

• Heating controls – zoning, internal temperature control, weather and load compensation, distribution temperatures, dual systems.

• Make someone responsible! • Provide simple instructions and educate building users!

• First target – good controls and high efficiency condensing gas boiler• Low carbon technologies:– Combined heat and power (suited to high heat loads)– Community heating schemes (district heating). Talk to others!

• Renewable technologies– Biomass boilers. Suited to high temperature and constant heat

demands. Consider space and operation requirements. – Heat pumps (air source and ground source). Require low

temperature systems (eg underfloor). Operate best in highly efficient buildings (and so probably not many historic buildings!)

Installing services

• What are the opportunities provided by the building: – Chimneys (services routing, stack ventilation)– Service tunnels. Can these be refurbished? Need to consider

asbestos. • External services – consider how these can be carefully routed.

What is the visual impact of pipework and cabling. • Is surface mounting less destructive than routing though fabric?

Consider historic flooring and ceilings. • Retrofit can be challenging – existing systems modified and extended

over time. Potentially many systems in one building.

Renewable systems

• Make sure efficiency is addressed first!

• Photovoltaic and solar thermal prime options.

• Significance – balance between integrated solutions for visual reasons vs non-integrated for limiting impact on fabric

• Potential for reducing visual impact – installation on flat roofs, behind parapets, in valleys.

• Free standing installations? • May be “permitted development”

• Think carefully about the opportunities and constraints. • If in doubt, ask! – Local conservation officer– Architects specialising in historic buildings– Engineers with historic expertise

• Engage early with conservation officers and building control, and planning.

• Always make use of contractors with suitable experience. Be careful of hi-tech quick fixes.

• Think long term – consider the lifecycle costs and future maintenance.• Research and think carefully before making a decision.

Useful websites

• http://www.helm.org.uk/

• www.greenspec.co.uk

• www.buildingconservation.com

• http://www.brebookshop.com/