Identifying the Best of the Walling Alternatives Presented By: Manfred Braune, Technical Executive GBCSA On Behalf of: WSP Green by Design and ClayBrick.org OPTIMAL WALLING SOLUTIONS FOR ENERGY EFFICIENT HOMES IN SA

The 130 m² House Model Derived from CSIR Garsfontein Control House ? 130m² Footprint Hallway, lounge, dining room, kitchen, 3 bedrooms, 2 bathrooms

The 130 m² House Model Example

Insulated brick Johannesburg (CR = 100 h) Insulated brick Durban (CR = 60 h) Walls with Regional CR Specifications

Passive Case Thermal Comfort Single Skin Walling ~ Upington Hourly Predicted Mean Vote (PMV) ~ Values over a Year Zero PMV line represents line of greatest thermal comfort. Deviation from it reflects increasing discomfort. Wall 3.3: 140 mm Concrete Block, Bag and Paint both sides Passive Case reveals nature of the materials alone.

Passive Case Thermal Comfort Comparison

Passive Case Thermal Comfort Daily PMV Amplitude ~ Upington

Passive Case Thermal Comfort

Active Case Heating Energy ~ Upington

Active Case Cooling Fan Energy ~ Upington

Active Case Heating and Cooling Fan Energy ~ Upington

Annual Heating & Cooling Fan Energy 6 Climatic Regions in South Africa (1/2)

Annual Heating & Cooling Fan Energy 6 Climatic Regions in South Africa (2/2)

CR Product Value of a Wall J = Joule (a measure of heat energy) C = Thermal Capacity – the ability to absorb, store and release heat energy, or the heat energy needed to raise the temperature of the material by 1°C. (kJ per °C) R = Thermal Resistance – from thermal conductivity, or the ability to conduct heat energy, or the heat energy lost per second for a difference in temperature on either side of the material. (J per °C.s), C x R = x 0.88 x 1000/3600 = hours, the time constant property of the wall system For every m 2 Wall Type Double Brick (DB) DB with 50mm air cavity DB with R=0.5 Cavity insulation DB with R=1 Cavity insulation DB with R=1 External insulation C act (kJ/m 2.K) CR (hours) CR Product defined

Active Case Energy Heating & Cooling Fan Energy use per Annum vs. External Wall CR Product for 130 m² House as Modelled, Upington

Basis for Costing Total cost comprises: External walling construction External walling maintenance over a 50 year period and Heater and cooling fan energy use over a 50 year period Discount rate for future cash flows 10 % / yr Initial energy cost (start of year 1)83 c / kWh Year 1 energy escalation 25.9 % / yr Year 2 energy escalation 25.9 % / yr Remaining years energy escalation7 % / yr Maintenance expense escalation7 % / yr

Present Value Total Costs for 50 Years (1/2)

Present Value Total Costs for 50 Years (2/2)

High Thermal Capacity Walls: –moderate swings in daily thermal comfort –reduce cooling fan energy (all S.A. climates) Correlation agrees with CR theory: - Heating and cooling fan energy minimised by high CR walling e.g. insulated brick Single Skin Walls (Low C Low R) - Poor choices for envelope walling systems in terms of energy use and thermal comfort. Conclusions for all South African Climates 1/5 (Valid for 130m² house as modelled only)

Conclusions for all South African Climates 2/5 –.. Musina –.. Durban –.. Pretoria –.. Upington –2 nd Cape Town –1 st Johannesburg (Valid for 130m² house as modelled only) Choice of external walling more critical in terms of absolute energy use and energy cost, as one moves through the climates in the following order:

Conclusions for all South African Climates 4/5 (Valid for 130m² house as modelled only) Lightweight walls are not paying back high construction cost with sufficient energy savings in this scenario.

Cost Regulatory or Standards Compliance –SANS 10400, SANS 204, Green Star Thermal Comfort Sound Transmission Local Availability Aesthetics Preference Conclusions for all South African Climates 5/5 (Valid for 130m² house as modelled only) Different Selection Warranted Depending on Actual Goals :

Questions for Further Study? (Valid for 130m² house as modelled only) How does an air conditioning in a house with increased cooling energy use affect energy ranking of walls? How can active thermal capacity be used to gain further insight? What is the sensitivity of the costing to changes in the various parameters such as future electricity tariff escalation?

Low Cost House ~ 40m²

Percentage of Time Occupants Experience Thermal Discomfort ~ Johannesburg LSFB not SANS 517 compliant

Low Cost House 40m²Low Cost House ~ 40m² Monthly Cost of Heating Energy ~ Johannesburg LSFB not SANS 517 compliant 66 c/kWh tariff assumed

Low Cost House ~ 40m² Energy Required to Achieve Comfort on Winter Solstice ~ Johannesburg LSFB not SANS 517 compliant

Low Cost House ~ 40m² Monthly Cost of Heat Energy in the Different Climatic Zones 66 c/kWh tariff assumed

Low Cost House ~ 40m² Monthly Heating Energy in Low Cost House ~ Average of 6 Climate Zones LSFB not SANS 517 compliant

Low Cost House ~ 40m² c Increase in Annual Energy Consumption ~ Light Steel Frame & Clay Brick LSFB not SANS 517 compliant

Low Cost House ~ 40m² In Johannesburg, using two leaf brick as opposed to concrete block saves enough energy yearly to light the household for 55 days. 24 hours a day. Heating Energy per Annum LSFB not SANS 517 compliant

Low Cost House ~ 40m² Carbon Footprint (Construction and Operational Heating Energy) ~ Johannesburg LSFB not SANS 517 compliant

Low Cost House ~ 40m² Construction and Annual Energy Costs ~ Johannesburg LSFB not SANS 517 compliant 66 c/kWh tariff assumed

(Valid for 40m² house as modelled only) Conclusions ~ 40m² Low Cost House Single skin concrete block falls short of conventional clay brick in thermal comfort, electricity cost for heating. Clay brick walls overall best performers. Insulated ceilings should be mandatory ~ significant thermal benefit for reasonable outlay.