OPTIMAL WALLING SOLUTIONS FOR ENERGY EFFICIENT HOMES IN SA Presented by: Howard Harris, Technical Director, WSP Energy Management October 2010 Specifying the Minimal Thermal Performances for External Walling

Prepared by: WSP Energy Africa Authors: 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 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 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 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 Residential E1-3,H Office & Institutional A1-4,C1-2,B1-3,G Retail F1-3,J Construction Surface Densities less than 180 kg/m2 Minimum Total R-Values Climatic ZonesMinimum Total R-Value 1 & , 3, 4 & 51.9 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 and SANS 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 XA 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 in line with World Trade Organisation Agreements Performance based regulations Nordic structure Not specific product standards Effect Constitutional Requirements Environment not harmful 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 XA 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 XA show minimal movement towards energy efficiency or sustainability Proposals for SANS 204 are not compulsory SANS XA Rules: Insufficient to reach 2015 RSA Energy Strategy energy reduction targets

Regulatory Framework SA National Standard X Sustainability Energy subsection XA Commercial, Retail & Institutional Buildings by Rational Design by a 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 XA

SANS 204 & SANS 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 Type Energy Use kWh/m²/year Peak demand VA/m² Entertainment and public assembly Theatrical and indoor sport Places of Instruction Worship Large Shop (incl malls) Offices Hotels 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 Number of Buildings BCA Minimum Performance Typical Practice The Majority 75% Green Star Top 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 XA 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 TypeAcceptabilityFormulaeRange 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. Tn NV80% =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 = m 2 K/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/m 3 K, whereas; Brickwork = 1360kJ/m 3 K and Concrete = 1764kJ/m 3 K. 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 Product by Region and Occupancy (kJ/m 2 K) Region Residential Office & Institutional Retail

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

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

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.