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OPTIMAL WALLING SOLUTIONS FOR ENERGY EFFICIENT HOMES IN SA

OPTIMAL WALLING SOLUTIONS FOR ENERGY EFFICIENT HOMES IN SA. Specifying the Minimal Thermal Performances for External Walling. Presented by: Howard Harris, Technical Director, WSP Energy Management October 2010. FINAL REPORT. Independent Study. The Development of a Rational Basis for:

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OPTIMAL WALLING SOLUTIONS FOR ENERGY EFFICIENT HOMES IN SA

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

  2. FINAL REPORT Independent Study • 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 Prepared by: WSP Energy Africa Authors: Prof. D. Holm, H.C. Harris, W. Burton On Behalf of: ClayBrick.org (Clay Brick Association)

  3. National Standards and Regulations Energy Efficiency in Buildings • 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

  4. National Standards and Regulations Energy Efficiency in Buildings • 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

  5. Regulations Energy Efficiency in Buildings 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.

  6. Thermal Mass Performs Empirical Testing in Australia ~ Thermal Lag Source: Think Brick Australia

  7. Regulations Energy Efficiency in Buildings Amplitude Reduction of Maxima and Minima

  8. Regulations Energy Efficiency in Buildings Source: Think Brick Australia

  9. 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.

  10. 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

  11. SANS 204 Deemed-to-Satisfy Rule for Energy Efficiency in Walling • 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

  12. SANS 204 Minimum Total R-Values Construction Surface Densities less than 180 kg/m2 Minimum Total R-Value for Surface Densities Greater than 180 kg/m2 = 0.4

  13. 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.

  14. SANS 204 Deemed-to-Satisfy Rule Energy Efficiency in Walling • 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

  15. National Building Regulations and Standards Constructed in line with World Trade Organisation Agreements Performance based regulations Nordic structure Not specific product standards Functional Regulations Hot water to be 50% heated by non-electrical energy Buildings designed and constructed to be energy efficient Effect Constitutional Requirements Environment not harmful to health Environment protected for benefit of present and future generations Prevention of pollution Ecological sustainable development

  16. Energy Efficiency in Walling South Africa • 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

  17. Energy Efficiency in Walling South Africa • DTS walling solutions in SANS 10-400 XA show minimal movement towards energy efficiency or sustainability • Proposals for SANS 204 are not compulsory • The Challenge: • To develop sustainable and energy efficient walling systems • Enable state sponsored housing to meet SANS 204 (or similar level walling) thermal performance • SANS 10-400 XA Rules: • Insufficient to reach 2015 RSA Energy Strategy energy reduction • targets

  18. Regulatory Framework Energy Efficiency in Buildings ACT 106 – Building Standards & Regulations National Building Regulations SA National Standard 10-400 X Sustainability Energy subsection XA Equivalent Performance to Reference building to SANS 204 for Residential, Hospital etc. Commercial, Retail & Institutional Buildings by Rational Design by a competent person. DTS requirements as per SANS 204 for Residential, Hospital & Other Buildings

  19. National Building Regulations Compliance with SANS 10-400 XA • 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

  20. 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

  21. Architect Responsibility Building Envelope DTS Provisions Relevant to Building Architecture: • Town Planning • Site Orientation • Building Orientation • Shading • Building Sealing • Building Design • Floors, Walls, Ceilings and Roofs • External Glazing (Fenestration) • Roof Lights • Accounted for in specifications and drawings

  22. MEP Engineer Responsibilities Building Services DTS Provisions Relevant to Building Services Systems: • Lighting • Hot Water Services • Vertical Transportation • Heating, Ventilation & Air Conditioning • Installed Equipment • DTS provisions accounted for in specifications and drawings

  23. Modelled Compliance Methods • Building Modelling • Fabric Performance • Operating Hours • Weather (Location) • Occupancy & Internal Heat Gains

  24. Modelled Compliance Methods • Services Modelling • Air & Water-side Design • Heating & Cooling Equipment • Controls

  25. Performance Requirements Building Performance Dictated by Climate Zone & Occupancy • 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

  26. SANS 204 in Context Green Building Markets BCA Minimum Performance Number of Buildings Typical Practice The Majority 75% Green Star Top 25% of Market Illegal Practise Innovators Risk Takers Best Practise ~ Green Buildings

  27. Operation of Regulations SANS 10 - 400XA Timeline • 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

  28. 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.

  29. 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

  30. 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

  31. Acceptable Ranges of Human Comfort

  32. Unique South African Climate Thermal Neutrality • 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.

  33. 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

  34. Unique SA Climate & Thermal Neutrality Adaptive Indoor Comfort Targets

  35. Building Envelope Effects • Building Envelopecontains 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.

  36. Building Envelope Effects • Overcooling evident in most small RSA residences. • Building Envelope’sinsulation determines conductive, radiative and convective heat losses or gains. • Denoted by Thermal Resistance - R = m2K/W.

  37. Building Envelope Effects Thermal Mass • Directly or indirectly exposed indoor air is called Thermal Capacity i.e. C = kJ/kg.K • Indoor thermal mass called active thermal massinteracts 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.

  38. Design Influences Building Shell Envelope-to-Volume Ratio • 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

  39. Design Influences • 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.

  40. What is the CR Product? How much? • 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

  41. Rational Design Correct Level of Thermal Resistance & Capacity of Walling Correct Level of Thermal Resistance & Capacity of Walling • 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

  42. Rational Design Correct Level of Thermal Resistance & Capacity of Walling • 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.

  43. Internal Temperature Effects of Low Mass

  44. Correlation for CR Product & Energy Usage • 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.

  45. 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

  46. 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. www.claybrick.org.za

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