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

Towards Zero Carbon

Compliance packages: Zero Carbon 80m2 Semidetached or end terraced 2 storey house

Base Case - TER

Zero Carbon (TER of -135% to -150%)

Zero Carbon (TER of -135% to -150%)

Passive House Standards Timber frame scheme Göteborg, Sweden (120 m2) Airtightness 1 m/h Source: Wall (2006), Photo: Hans Eek MVHR – 80% with duct heaters 5m2 Solar water + resistance top-up

Passive House Standards Timber frame scheme Göteborg, Sweden, 120 m2 5,868 kWh 6,420 kWh Source: Wall (2006), Photo: Hans Eek TER (kgCO2/m2) Design ≈ 10.6 Actual ≈ 15.3 Under Swedish conditions! Total energy = 8,160 kWh/a Source: Wall (2006), Energy and Buildings. 38, pp 627-634

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?

Solar thermal?

Solar thermal?

Micro wind?

Micro wind?

Micro wind? Manufacturer’s general claims: 1.5 kW (max at 12.5 m/s) Annual energy generated - 2,000 - 3,000 kWhs – depending on position and location. Carbon displacement – 1.3 tonnes (30% utilisation) Location: Average wind speed (DTI database) = 5.1 m/s @ 10m Energy – 1,473 kWhs But what about shelter from trees and other buildings?

Micro wind? 5.1 m/s 4 m/s 3 m/s

Photovoltaic panels

Cost and scale

Cost and scale Wind PV Solar thermal small scale – 17 p/kWh large scale – 4 p/kWh PV Small scale – 55 p/kWh large scale – 23 p/kWh Solar thermal small scale – 9 p/kWh large scale – 7 p/kWh preliminary calculations – Barrett 2007

Biomass? Biomass in a 2006 dwelling!

Biomass? Biomass in a 2016 dwelling

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

Does new housing do what it says on the tin? 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) 13 50.6 13.2 63.8 105.4 111.7 402 54.9 20.3 75.2 136.3 153.4 +75% +104% The question is: Why?

Thermal bridges

Thermal bridging & construction Designed performance is almost always degraded

Timber fraction and insulation

Airtightness is improving?

Sequencing and process

Hidden leakage

A culture of detailed planning?

A culture of detailed planning? Build – Destroy – Install – Repair

Understanding complex heat loss paths Party wall heat bypass

Potential CO2 savings 18,000 tCO2/a Fabric heat loss is between 40% and 50% greater than currently estimated. Eliminating the bypass would produce large actual CO2 savings From New Housing built in One Year (~190,000 units) 18,000 tCO2/a From Existing Stock (built between 1965 and 2006) 694,000 tCO2/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

We have been rumbled! As very low and zero carbon becomes mandatory small things will matter This time customers will notice! 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!