Presentation on theme: "Zero Carbon: Implications and Issues Malcolm Bell Buildings, Energy and Sustainability Group, School of the Built Environment, Leeds Metropolitan University,"— Presentation transcript:
Zero Carbon: Implications and Issues Malcolm Bell Buildings, Energy and Sustainability Group, School of the Built Environment, Leeds Metropolitan University, Leeds, UK. Paper presented to: Towards Zero Carbon Homes 5 July 2007, Milton Keynes, UK.
Towards Zero Carbon
Compliance packages: Zero Carbon 80m 2 Semidetached or end terraced 2 storey house
Base Case - TER
Zero Carbon (TER of -135% to -150%)
Passive House Standards Source: Wall (2006), Photo: Hans Eek Timber frame scheme Göteborg, Sweden (120 m 2 ) Airtightness 1 m/h MVHR – 80% with duct heaters 5m 2 Solar water + resistance top-up
Passive House Standards Source: Wall (2006), Photo: Hans Eek Timber frame scheme Göteborg, Sweden, 120 m 2 Source: Wall (2006), Energy and Buildings. 38, pp TER (kgCO 2 /m 2 ) Design 10.6 Actual 15.3 Under Swedish conditions! 5,868 kWh 6,420 kWh Total energy = 8,160 kWh/a
Implications and issues Lights and appliances represent between 60% and 70% of carbon emissions. Over 5,000 kWh/a may need to be generated by zero carbon sources. (more for larger houses) What chance at the level of the dwelling?
Manufacturers general claims: 1.5 kW (max at 12.5 m/s) Annual energy generated - 2, ,000 kWhs – depending on position and location. Carbon displacement – 1.3 tonnes (30% utilisation) Location: Average wind speed (DTI database) = m Energy – 1,473 kWhs But what about shelter from trees and other buildings?
So what, so far ? Site based generation is problematic. Solar thermal - useful demand reduction Wind is likely to be cheaper and more effective at large scale Biomass may have limited value in CHP but no panacea and an important strategic resource Need to link new building to strategic renewable provision.
So what for the industry? Source: Wall (2006), Photo: Hans Eek Focus attention on as low an energy/carbon demand as possible Deal with generation in a strategic way
But! Does new housing do what it says on the tin?
Notional – v – Real heat loss Plot No. Predicted Fabric Heat Loss (W/K) Predicted Ventilation Heat Loss (W/K) Predicted Total Heat Loss (W/K) Measured Heat Loss (W/K) Measured Heat Loss - Adjusted for Solar Gain (W/K) % +104% The question is: Why?
Thermal bridging & construction Designed performance is almost always degraded
Timber fraction and insulation
Airtightness is improving?
Sequencing and process
A culture of detailed planning?
Build – Destroy – Install – Repair
Understanding complex heat loss paths Party wall heat bypass
Potential CO 2 savings From New Housing built in One Year (~190,000 units) 18,000 tCO 2 /a From Existing Stock (built between 1965 and 2006) 694,000 tCO 2 /a Assumes Party Wall U Value = 0.5 Assumes 10% semi, 20% terrace in stock and new build Calculations for semis and terraces only – no estimate for apartments Fabric heat loss is between 40% and 50% greater than currently estimated. Eliminating the bypass would produce large actual CO 2 savings
We have been rumbled! This time customers will notice! As very low and zero carbon becomes mandatory small things will matter This time building control will notice! We cannot hide behind flawed assumptions
The industry must change! It has been said before But the more it changes the more it remains the same Old problems persist! It is time to retool, to retool cultures and processes as well as technology.
What will change look like? A fully managed process – inception, design, construction and support in use. Performance will have to be guaranteed. A quality control process based on measurement not assumption Re-engineering of processes as well as technology will bring economies! Constant feedback will bring constant improvement.
So what does zero carbon mean?
The world will not be the same! Thomas Kuhn The Structure of Scientific Revolutions We are entering a new paradigm
So what does zero carbon mean? As in science, so in construction: It is time for the industry to Retool!