The Good, The Bad & The Ugly

Transcription

1 The Good, The Bad & The Ugly Green Building, The Law & Competing Products. A 2010 SAHF Presentation by Jean Tresfon

2 Relevance of Green Building to Masonry -New legislation introduced (SANS204 & SANS10400XA) -Introduction of rating systems (GreenStarSA( GreenStarSA) -Buy in of US insurance industry hurt by climate change weather events e and now insisting on green specs -Realisation of green building rental premiums (up to 10% above the t norm) -Increased human productivity levels -Future-proofing of assets against a warming climate -Enhanced property resale values -Post peak oil energy costs can only go up -Removing the dependence on Eskom for all power -Client driven demand (green building movement set to take off exponentially)

3 Obstacles to Green Building Progress -Developing economy versus 1 st world infrastructure -Current economic woes -Social reform mostly takes preference -Incorrect perception of green building cost premium >> Green by design, gizmos not required!

4 So what does the law say? -SANS204 Energy efficiency in buildings -Stipulates minimum R-Values R for walls, dependant on building type and climatic zone. A 230mm Maxi Brick Wall with a 50mm Cavity and plastered on both sides has a R-Value of 0.5m²K/W Latest draft changed to CR Values (hours) Residential Zone 4 requires 100 hours and doubleskin brick wall with 50mm cavity gives 60 hours Requires insulation added

5 So what does the law say? -SANS10400XA Energy usage of buildings -Walling with surface density > 180kg/m² requires min R-Value R = 0.4 -Walling with surface density < 180kg/m² requires min R-Value R = 1,9* * Depends on building type, size and climatic location

6 Green Masonry What is it exactly -Made from recycled materials -Low (measurable) embodied energy -High energy efficiency / good thermal performance -Is fully recyclable

7 The process of using recycled materials -On site demolition & sorting -Transport & dumping -Primary crushing, grading & sieving -Secondary crushing, grading & sieving including removal of contaminants -Stockpiling -Use of materials in manufacture -No downside in terms of quality (non-facing products) -Contaminant removal remains the biggest challenge

8 On site demolition and sorting.

9 Transport to urban quarry

10 Dumping at urban quarry

11 Primary Crushing

12 Reinforcing steel removal belt

13 Reinforcing steel ready for scrap yard

14 Aggregate after primary crushing, grading and sieving

15 Secondary crushing & sieving

16 Brick manufacture

17 The environmental benefits of using recycled materials: -Less virgin aggregates have to be quarried, reducing the mining impact on the environment Due to scarcity of materials quarries are far from factory so less use of virgin aggregates helps to reduce transport energy usage and traffic congestion -Rubble is not dumped thereby easing pressure on landfill sites -Landfill sites are far from demolition sites so less dumping helps to reduce transport energy usage and traffic congestion -Own factory waste can be instantly recycled -One Cape factory saves 3,625,505mJ per month compared with the use u of virgin aggregates (equivalent to 1,007,085kWh or running 1343 medium sized residential houses for the month)

18 Measurement of embodied energy: Embodied Energy - the energy required to acquire the raw materials, manufacture the product and transport it to site Many claims of low embodied energy but what about actual measurements? -Baked clay bricks average 2.5mJ/Kg to 5mJ/Kg -Conventional concrete bricks average 0.95mJ/Kg to 1.5mJ/Kg -Concrete bricks containing 70% recycled material content average 0.39mJ/Kg -International studies vs Local Studies -Problems with comparisons and lack of standard criteria -More research is needed The client can save the equivalent of 100,000kWh of energy emissions ions on an average upmarket house of 60,000 bricks by specifying recycled concrete masonry.

19 Measurement of embodied energy: -Focus has always been on operational energy & emissions -Embodied energy can account for up to 40% of the total energy component for a residential building -Embodied energy can equal 20 years worth of operational energy for f a new building -Up to 55% of a buildings emissions from embodied energy can be from f masonry alone -As energy costs go up with the resultant required reduction in operational o energy the embodied energy component will become more important -Building lifespans are becoming less resulting in a higher embodied energy component -Correct choice of facade can have a dramatic energy reduction effect fect

20 Energy Efficiency - Operational Energy -What are R-Values R & U-Values U and why do they matter -What is thermal mass and why is it important -The role of passive solar design -Problems with SANS204 and taking corrective action

21 R-Values, U-Values U and why they matter -R-Values are a measure of thermal resistance or a measure of a materials heat loss retardation under specified test conditions -U-Values are a measure of thermal transmittance or measure the rate of heat transfer through a building element over a given area, under standardized conditions -The U-Value U is the inverse of the R-ValueR -SANS204 stipulates minimum CR-Values which for the most part the industry cannot meet without the use of insulation products -Both R-Values R and U-Values U assume a constant difference between the external and internal building temperature which is does not happen pen in the real world -Only focuses on conduction, not convection or radiation -Significant difference in the thermal performance of materials with w similar R-Values -R-Value alone is not a complete indicator of thermal performance and a needs to be considered in the complete context of passive solar design

22 R-Values, U-Values U and why they matter -Important to remember that walling as a complete system is under examination and not masonry products in isolation -Thermal bridging is possible through wall ties etc -R R value enhancement is possible: >> through addition of insulation products in voids >> through addition of cavity insulation >> adding a technical skim plaster >> changing aggregates to include: - fly ash - treated vermiculite

23 What is thermal mass and why is it important -Describes the ability of a material to store heat -Materials should have a high specific heat capacity to maximise the heat that can be stored per kg of material -Materials should be very dense to maximise the weight -Materials should have a moderate thermal conductivity so that heat conduction is in synchronisation with the diurnal flow in and out of the building -Thermal mass only really works where the diurnal temperature difference ference is over 6ºC, 6 i.e. works well in SA where the average is approx 10ºC -Concrete, Brick and Stone all have excellent thermal mass The ability to absorb and release heat enables buildings to respond naturally to changing weather conditions by stabilising the internal temperature and providing a self-regulating environment. This obviates the need for cooling in summer and heating in winter.

24 What is thermal mass and why is it important

25 What is thermal mass and why is it important

26 What is thermal mass and why is it important

27 What is thermal mass and why is it important

28 What is thermal mass and why is it important

29 What is thermal mass and why is it important -Addresses problem of convection and radiation -Reduces energy usage when using artificial heating as heat from internal appliances is captured and later released Steel can store a lot of heat but posses a very high rate of thermal conductivity, so heat is released too quickly to create the required time lag effect. (Architects seem to love glass and steel!)

30 The role of passive solar design -Complete system for energy efficiency -Optimises a building to maximise solar gain in winter and minimise it in summer. At the same time daylight is maximised -Costs very little to implement -Makes a significant contribution to energy reduction Makes use of: >> Orientation >> Shading >> Ventilation >> Insulation >> Thermal Mass To control heat gain & loss through radiation, conduction and convection.

31 The role of passive solar design -Building should be oriented North and non-living areas (garages etc) situated on the opposite side -Majority of windows should face North -Glass type and area (<40% of wall) very important (also spec d in SANS204) -Roof overhang or shading to reduce peak heat from radiation through windows -Some form of insulation required -Night time ventilation in summer -Facade and Floor should have high thermal mass, i.e. brick wall with concrete floor slab -There is nothing new here all these concepts have been known and used since building started!

32 Problems with SANS204 and taking corrective action -Focuses on R-Values R only with regards to walling* -R-Values don t t address convection and radiation -R-Values not based on real world temperature change model -Insulation values can deteriorate over time -Based on passive solar design model but ignores thermal mass* -Developed world legislation now changed to include thermal mass -Low cost housing not included in legislation -Deemed to comply for GreenStar SA Ratings -Historically ignored the brick industry -Huge amount of work done by CBA & Wayne Burton * Latest edition now changed to include the Heat Capacity of the materials in question.