OPTIMAL WALLING SOLUTIONS FOR ENERGY EFFICIENT HOMES IN SA

Presented by: Howard Harris, Technical Director, WSP Energy ManagementOctober 2010

Specifying the Minimal ThermalPerformances for External Walling

Prepared by: WSP Energy AfricaAuthors: Prof. D. Holm, H.C. Harris, W. Burton

On Behalf of: ClayBrick.org (Clay Brick Association)

The Development of a Rational Basis for:

The Selection of Thermal Mass and Thermal Insulation in Walling

Deemed-to-Satisfy (DTS) Requirements for Walling in the SANS 204 Standard

Independent Study

FINAL REPORT

Energy Efficiency in Buildings

National Standards and Regulations

Global Energy Efficiency Rules Increased thermal resistance requirements of walling systems

SANS 204 - A World’s First Rational basis for the selection of appropriate thermal capacity or thermal mass to improve energy efficiency of buildings

Energy Efficiency in Buildings

National Standards and Regulations

CR Method Documented building physics assist regulators and designers in achieving energy efficiency

Pioneered by National Building Research Council, early ‘80’s Computer technology used to develop DTS requirements for thermal capacity and thermal resistance

Regulations

SANS 10-400

Part XA standard

First of a series of standards intended to support the recent amendment to national Building Regulations, which are intended to build sustainability into South African building construction.

SANS 204

Specifies the design require-ments for energy efficiency in buildings and of services in buildings with natural environmental control and artificial ventilation or air conditioning systems.

Energy Efficiency in Buildings

Thermal Mass Performs

Empirical Testing in Australia ~ Thermal Lag

Source: Think Brick Australia

Regulations

Amplitude Reduction of Maxima and Minima

Energy Efficiency in Buildings

Regulations

Energy Efficiency in Buildings

Source: Think Brick Australia

Project Methodology

CR Method: Theories used to develop selection of thermal mass

and thermal resistance in walling Results compared with building Energy Simulation

methods and Life Cycle Cost evaluations

Aim: To provide financial justification for specifying amount

of active thermal capacity necessary for optimal occupancy comfort, across varying climatic regions of South Africa.

Project Methodology

DTS Rules Developed in SANS 204 Ensures optimal energy efficiency in walling systems

Active Thermal Capacity Design tool facilitates appropriate selection of thermal mass and thermal resistance

Facilitates reaching national energy reduction targets by 2015

Buildings in RSA classified under Occupancy in SANS 10400 for National Building Regulations

Regional climate classification borrowed from CSIR papers (1970)

Occupancy classes referenced in SANS 204 and initial DTS walling solutions based on Building Code of Australia

SANS 204

Deemed-to-Satisfy Rule for Energy Efficiency in Walling

SANS 204

Minimum Thermal Capacity & Resistance CR Product, in Hours, for External Walling

Occupancy Group / Climate Zone 1 2 3 4 5 6

Residential E1-3,H1-5 100 80 80 100 60 100

Office & Institutional A1-4,C1-2,B1-3,G1 80 80 90 80 80 80

Retail F1-3,J3 80 120 120 90 80 120

Construction Surface Densities less than 180 kg/m2

Minimum Total R-Values

Climatic Zones Minimum Total R-Value

1 & 6 2.2

2, 3, 4 & 5 1.9

Minimum Total R-Value for Surface Densities Greater than 180 kg/m2 = 0.4

SANS 204

External Walls

Complete walling system from outer skin to interior skin excl. glazing. Glazing included in SANS 204-2 and SANS 204-3. Interstitial condensation occurs in walling systems not able to accommodate moisture migration. Vapour barriers and appropriate construction materials, incl. insulation important for thermal efficiency in climate zones with damp and high relative humidity. Thermal resistance added to external walling with high thermal capacity to be placed between layers e.g. in the cavity of a masonry wall. Thermal resistance not be added to internal face of walls with high thermal capacity.

Outlines rational basis for set of rules to be applied for local climatic conditions

Energy efficiency to be acceptable to DME

Proposals to satisfy the National Compulsory Specifications Regulator are set out in SANS 10-400XA

SANS 204 Deemed-to-Satisfy Rule

Energy Efficiency in Walling

Functional Regulations

Hot water to be 50% heated by non-

electrical energy

Buildings designed and constructed to be

energy efficient

National Building Regulations and Standards

Constructed inline with World

Trade Organisation Agreements

Performance based regulations

Nordic structure

Not specific product standards

Effect Constitutional Requirements

Environment notharmful to health

Environment protected for benefit of present

and future generations

Prevention of pollution

Ecological sustainable development

RSA National Building Regulations include requirements for energy efficiency and sustainability

SANS 10-400XA provides for compliance with these regulations

Accepted Routes to Compliance:

- Performance requirements by competent person

- Deemed-to-Satisfy provisions

- Reference building method

Energy Efficiency in Walling

South Africa

Energy Efficiency in Walling

South Africa

The Challenge:

To develop sustainable and energy efficient walling systems

Enable state sponsored housing to meet SANS 204 (or similar level walling) thermal performance

DTS walling solutions in SANS 10-400 XA show minimal movement towards energy efficiency or sustainability

Proposals for SANS 204 are not compulsory

SANS 10-400 XA Rules:

Insufficient to reach 2015 RSA Energy Strategy energy reduction targets

Regulatory Framework

SA National Standard 10-400 X Sustainability Energy subsection XA

Commercial, Retail & Institutional Buildingsby Rational Design bya competent person.

DTS requirements as per SANS 204 for

Residential, Hospital & Other Buildings

Equivalent Performance to Reference building to

SANS 204 for Residential, Hospital etc.

Energy Efficiency in Buildings

National Building Regulations

ACT 106 – Building Standards & Regulations

Routes to Compliance for Walling:

DTS Requirements for Residential and Hospitals Walls have prescriptive requirements Other aspects in terms of SANS 204

Performance Requirements for Energy Usage & Demand Design by Competent Person Offices, Shopping Centres, Institutional Buildings only Table 1 & 2 requirements are met

Reference Building Method an Alternative to SANS 204 DTS Model the deemed-to-satisfy – find the energy usage & demand Develop more energy efficient alternative

National Building Regulations

Compliance with SANS 10-400 XA

SANS 204 & SANS 104 00 PART XA

Overview of Responsibilities

Roles and Responsibilities: Architectural design

Building Services Design

Energy Modelling

Compliance and Verification

Three Compliance Paths:

DTS: Building envelope and components method

Rational Design: Energy usage method

Rational Design: Reference building method

Architect Responsibility

Building Envelope

DTS Provisions Relevant to Building Architecture:

Accounted for in specifications and drawings

Town Planning Site Orientation Building Orientation Shading Building Sealing Building Design

– Floors, Walls, Ceilings and Roofs– External Glazing (Fenestration)– Roof Lights

DTS Provisions Relevant to Building Services Systems:

• DTS provisions accounted for in specifications and drawings

MEP Engineer Responsibilities

Building Services

Lighting

Hot Water Services

Vertical Transportation

Heating, Ventilation & Air Conditioning

Installed Equipment

Modelled Compliance Methods

Building Modelling

Fabric Performance

Operating Hours

Weather (Location)

Occupancy & Internal Heat Gains

Modelled Compliance Methods

Services Modelling

Air & Water-side Design

Heating & Cooling Equipment

Controls

Building TypeEnergy UsekWh/m²/year

Peak demandVA/m²

Entertainment and public assembly

390-440 80-90

Theatrical and indoor sport 390-440 80-90

Places of Instruction 390-440 75-85

Worship 110-125 75-85

Large Shop (incl malls) 240-260 85-95

Offices 185-210 85-95

Hotels 585-650 85-95

Performance Requirements

Buildings within hot interior (climate zone 3) have largest energy use allowance

Buildings in temperate coastal areas (climate zone 4) have lowest energy use allowance

Residential building performance requirements not set out

Scope for rational design uses the reference building

Building Performance Dictated by Climate Zone & Occupancy

SANS 204 in Context

Green Building Markets

Innovators Risk TakersIllegal Practise

Best Practise ~ Green Buildings

Nu

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sBCA Minimum Performance

Typical PracticeThe Majority

75%

Green StarTop 25% of Market

General Principles and Requirements– Dictate date of implementation and responsibilities– Effective 12 months from date of gazetting for projects completed thereafter

Designs within 6 months of Gazetting;– Owners to advise Local Authority– Up to 12 months to complete project

Energy Provisions– Responsibility of Competent Person appointed by building Owner via Forms 1, 2, 3 and 4

Building Inspections – To be performed by Local Authority

Operation of Regulations

SANS 10 - 400XA Timeline

Thermal Design

Influence of Walling

Walling and Elements of Building Shell: Can influence thermal comfort and energy usage of perimeter zone Insignificant influence on interior zone Modeling supports notion that exterior walls are important

determinant of energy efficiency of exterior zone

Important Specification Rules: Specification of walling and building shell not to be influenced by

size of building Shell serves energy efficiency of perimeter zone. Buildings with natural ventilation should comprise of perimeter

zone spaces, i.e rooms with external windows and walling.

Requirements for Energy Efficient Walling Systems

Determinants of Walling Systems in any Climate: Occupancy Type

- Occupation Density

- Levels of Activity

- Heat Generation

Comfort Requirements – as per levels of comfort compliance

e.g. 80% range +/- 3.5K in naturally ventilated buildings

Requirements for an Energy Efficient Walling System

Clusters of Occupancy Groups: Based on Determinants of Walling Systems & Classification

of Buildings in National Building Regulations:

- Residential - Office and Institutional (combined) - Retail

Acceptable Ranges of Human Comfort

Building Type Acceptability Formulae Range

Air Conditioned 90% Tn=18,9+0,225ET*outdoor ±1,2K

Air Conditioned 80%Tn=18,9+0,225ET*outdoor ±2,5K

Naturally Ventilated 90%

Naturally Ventilated 80% Tn=18,9+0,225ET*outdoor ±3,5K

Optimum thermal neutrality temperature - Exists for all climatic regions - Related to mean temperatures of local climate.

TnNV80%=18,9°C+0,225ET*outdoor

Validity limits 17,8°C < Tn < 29,5°C - Tn is the neutrality temperature - ET* is New Effective Temperature. i.e. Considers air temperature and relative humidity.

Unique South African Climate

Thermal Neutrality

Unique South African Climate

Thermal Neutrality

For any regional climate and occupancy group, a range of temperatures satisfies users of buildings.

Fluctuations in daily and seasonal temperature swings acceptable for minimising heating or cooling energy and costs.

Daily fluctuations in temperature within comfort range for many RSA locations much of the year

Unique SA Climate & Thermal Neutrality

Adaptive Indoor Comfort Targets

Building Envelope Effects

Building Envelope contains windows, shading and walls, which can bring comfort or lead to overheating or overcooling.

Overheating in summer to increase in South Africa with global warming aggravated by urban heat islanding.

Building Envelope Effects

Overcooling evident in most small RSA residences.

Building Envelope’s insulation determines conductive,

radiative and convective heat losses or gains.

Denoted by Thermal Resistance - R = m2K/W.

Directly or indirectly exposed indoor air is called Thermal Capacity i.e. C = kJ/kg.K

Indoor thermal mass called active thermal mass interacts with indoor air by heating or cooling.

Air has thermal mass of only 1,2kJ/m3K, whereas; Brickwork = 1360kJ/m3K and Concrete = 1764kJ/m3K.

Such materials have strong impact on indoor air temperatures, which is why much air movement is needed to heat or cool heavy structures.

Air leakage can sometimes annul benefits of C and R.

Building Envelope Effects

Thermal Mass

As house sizes decrease surface-to-volume ratio increases

To retain same indoor climate additional 28% envelope insulation and commensurate thermal mass is required

Thermal performance of freestanding housing poor compared to duplexes or row houses

Design Influences

Building Shell Envelope-to-Volume Ratio

Perimeter to Floor Area Ratio

Reduction of floor area increased perimeter to floor area ratio.

Unwanted heat gains/losses via floor increased with thermal mass effect reduced. Countered with perimeter insulation.

Thermal performance of freestanding housing model compared to multi-story buildings.

Aspect

Deviations in excess of 15° from true North can add 50% to heating energy.

Design Influences

CR product is Thermal Capacity of a wall multiplied by the Thermal Resistance i.e. C x R

Required levels of C and R set out in SANS 204 for climatic regions of RSA

What is the CR Product?

How much?

Optimal Thermal Capacity & Resistance Productby Region and Occupancy (kJ/m2K)

Region 1 2 3 4 5 6

Residential 100 80 80 100 60 90

Office & Institutional 80 80 100 100 80 80

Retail 80 80 120 80 60 100

Correct Level of Thermal Resistance & Capacity of Walling

Rational Design

Basis for rational approach to correct level of thermal resistance and thermal capacity found in application of CR Method

CR Method links degree of modulation and fluctuating internal temperatures with various levels of thermal resistance and thermal capacity

Fluctuation expressed as a ratio of the internal temperature amplitude versus outside diurnal temperature fluctuation

Correct Level of Thermal Resistance & Capacity of Walling

Correct Level of Thermal Resistance & Capacity of Walling

Rational Design

Temperature fluctuations in a building can be reduced by improving thermal efficiency of the shell

Building can then operate at lower energy intensity levels.

CR Method provides CR constant measured in units of time

Indicates minimum required combinations of thermal mass and thermal resistance to maintain temperature fluctuations within the comfort temperature.

Internal Temperature

Effects of Low Mass

Correlation of CR Product to Energy Usage using various walling systems exceeds 90% in most cases.

CR Method used to construct either a Rational Design Tool or a simple DTS rule for walling.

Establishes minimum thermal mass and thermal resistance combination requirements, for use in SANS 204, as means of achieving sustainability in buildings

Guidance to future development of SANS10-400XA in direction of CR Product or Active Thermal Capacity given by research outcomes.

Correlation for CR Product & Energy Usage

Closing Thoughts

Unique RSA climate presents opportunity for using thermal mass in buildings to achieve lower energy usage

Use of high mass building elements traditional in RSA

National Building Regulations references lower standard of thermal performance as indicated by thermal resistance – next 2 years.

Lack of affordability restraining development of energy efficient walling energy in subsidy housing sector

www.claybrick.org.za

Closing Thoughts

No reason why rest of building stock should be given free reign to continue building without sustainable walling systems

Future development of SANS10-400XA in direction of CR Product or Active thermal capacity given by research outcomes.