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Beyond Zero Carbon Housing - Peter Conboy


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A one day symposium on zero/low carbon sustainable homes took place at The University of Nottingham on the 24th October, 2012. The event offered professionals within the construction industry a unique opportunity to gain added and significant insight into the innovations, policies and legislation which are driving the construction of zero/low carbon energy efficient homes both here in the UK and elsewhere in Europe. It explored solutions to sustainability issues “beyond” the zero carbon agenda. BZCH followed on from the successful ‘Towards Zero Carbon Housing’ symposium the University hosted in 2007. This event is part of the Europe Wide Ten Act10n project which is supported by the European Commission Intelligent Energy Europe.

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Beyond Zero Carbon Housing - Peter Conboy

  1. 1. Beyond ZeroCarbon Housingexploring solutions to sustainability issues beyond the zero carbon agenda2 4 th O c t o b e r 2 0 1 2 a t T h e U n i v e r s i t y o f N o t t i n g h a mDepartment of Architecture and Built Environment
  2. 2. © Copyright Notice A l l t h e m a te r i a l i n t h e s e s l i d e sm ay n o t b e u s e d o r re p ro d u c e d w i t h o u t t h e ex p re s s p e r m i s s i o n o f t h e a u t h o rs
  3. 3. The Challenge of DeliveringEnergy Efficient Housing for Market Sale Green Street Nottingham Peter Conboy, Blueprint
  4. 4. Green Street – Project Context• Former primary school site owned by NCC• Close to the River Trent and riverside Memorial Gardens;• Adjoins the Meadows priority housing regeneration area;• NCC ambition to raise housing quality standards and salesvalues• Use this to enhance viability and delivery for wider scalehousing regeneration in Meadows• Market crash in 2008 caused some delay and renegotiation ofterms• Planning approval secured 2009 and start on site Jan 2010 Green Street
  5. 5. Green Street - Scheme Description• 38 No. Family Houses in a mix of 3 and 4 bed;• 15 no. of the homes are low-cost home ownership (shared low-equity);• Code for sustainable homes level 4;• EPC A or high B depending on roof space for PV panels;• Fabric first approach - highly insulated and air-tight structural air-solution with mechanical ventilation and heat recovery;• Scheme completed in July 2012 and is fully occupied. Green Street
  6. 6. Site Location
  7. 7. Ground Floor First Floor Second Floor
  8. 8. First Floor Second FloorGround Floor
  9. 9. First Floor Second Floor
  10. 10. First Floor Second FloorGround Floor
  11. 11. First Floor Second FloorGround Floor
  12. 12. First Floor Second FloorGround Floor
  13. 13. Green st Costs• Total building contract value £5.5 million• JCT 2005 Design and Build• Headline cost - £125 psf• Excluding PV and flood abnormals - £110 psf.• Average sales values £158 psf• Meadows average values circa £135spf• Peak value achieved at Green Street £174 psf – 3 bed £186k and 4 bed £230k
  14. 14. Green St – Fabric Design Performance• Considered Passivhaus at planning stage• Timescale for grant expenditure very tight and delivery risk considered too great• Fabric first approach plus efficient condensing boilers and heat recovery. Element u-Value / 2013 Build 1960s w(m2.k) Regs FEES External 0.13 0.18 1.7 Walls Roof 0.11 0.13 1.42 Floor 0.15 0.13 N/A Windows 1.20 1.40 5.7 / doors
  15. 15. Green St – Other Features• Solar PV array – typically 1.4 to 1.6 kW peak to achieve EPC A rating overall;• Phase 1 of Green Street – timber frame, phases 2 and 3 traditional masonry construction;• External blinds to prevent overheating in phase 1• Phases 2 and 3 internal wet plastered masonry walls to enhance thermal mass;
  16. 16. Actual v Design Performance DEVIL Ψ IS IN THE DETAILING•Blueprint working with Nottm University to test actual thermalperformance of occupied homes via the TSB study•Design air permeability for Green Street - 3 cu metres per hr / sqmetre at 50 pascal;•2013 Building Regs suggestion - 5 cu. metres per hour / sq metres?•Previous testing regime requires only a sample of homes within ascheme to be tested;•Some homes can perform significantly worse than the design levelwhich means energy efficiency is way off target – a 1 mm gap 1 metrelong changes the 1 sq metres u-value from 0.3 to 1.44 u-•To deliver very air tight homes need both careful detailing of fabricdesign and monitoring on site to ensure workmanship is up to scratch– with additional costs resulting?
  17. 17. Actual v Design Performance DEVIL Ψ IS IN THE DETAILING•As dwellings become better insulated (fabric u-values fall) the relative u-importance of thermal bridging in conduction heat loss increases –could account for 30% of heat loss post 2013;
  18. 18. Actual v Design Performance SOME KEY QUESTIONS•Research shows actual energy performance from 10% to 120% worsethan predicted design performance with the average (in the research)at circa 40%•How can the gap between actual and design performance be closedeffectively and at an affordable cost?•Can housebuilding industry supply-chains actually deliver the higher supply-performing homes required in the numbers that are required – circa200k homes per annum?•Are the skill levels present in the house building industry at present tobuild energy efficient homes that actually perform as designed?•How can quality control and inspection be managed on site acrosslarge scale developments?