Tom Dollard Head of Sustainability Pollard SME Builder’s Book Consultation

How to reduce the performance gap? The Builder’s Book Question / Answer session Complete feedback form = drink!

Performance Gap The performance gap - what? The difference between the design and the completed performance of the building There are many reasons for this, stemming across design, procurement and construction The Zero Carbon Hub has produced several reports and in depth research on this subject Design, Procurement, Construction Site issues Site examples

Zero Carbon Hub – Performance Gap The government has challenged industry to reduce the gap between the design and the completed performance of buildings Many independent studies have shown this gap to be from 60%-120% more energy use than predicted. The Zero Carbon Hub has been researching this throughout , with evidence gathered from 22 sites in the UK. The end of term report was issued in July 2014, and work continues......

The evidence gathering stage A team of 4 people assessed each of the 22 sites across the UK including small, medium and large developers 5 days of evidence gathering for each site: Interviews Design Review Construction walk-through

What did we find out? There is a significant performance gap – 15% - 50% higher than asbuilt SAP No sites had the same window specification as SAP Unaccounted thermal bridging is prevalent Overheating is not considered Part L accredited details not used correctly – knowledge Gap, not robust The performance gap can be attributed to a large number of small errors throughout the design and construction process

Common issues on site Windows set too far forward with no overlap to cavity = thermal bridge Windows – incorrect specification U value and G value worse than design Gaps in insulation – poor installation of rigid board and injected insulation

LACK OF SITE TEAM ENERGY PERFORMANCE RELATED KNOWLEDGE AND SKILLS AND/OR CARE Example Windows pulled forward from their design positions Overlap with the cavity closer well below the minimum requirements Mastic or foam fill interrupted by metal fixing straps

Common issues on site Dense Blocks instead of aircrete blocks No insulation below DPC Beam and block floors - approx 20% unaccounted thermal bridges and gaps in installation

POOR INSTALLATION OF FABRIC Example Incorrectly fitted insulation Detail when constructed deviates from the design

Common issues on site Standard cavity closer on site but hi- performance insulated closer specified Cavities not consistent width so closer does not fit tightly to block Soffit not insulated – heat loss Flat roof leaves 2 bricks thermal bridge Lintels different to design

LACK IF ADEQUATE QUALITY ASSURANCE ON SITE Example Cavity insulation board stopping short of cavity closers at openings Gaps between boards leading to increased heat loss

Performance Gap(on site) Products / Materials Installation Thermal Bridging Thermal Bypass Airtightness Damp Tolerance Product checklist Design vs Site findings Linked to SAP categories Builder’s book - Installation guide How/what to check? Sequenced diagrams/photos Windows/ Doors Blocks Cavity closers/Lintels Insulation Services incorrect/damaged / substituted

Introduction (1 page) House Section drawing and sequencing (1 page) Common themes on site – top performance gap issues and how to improve (2 pages) Site Posters – Fabric and Services - 18 sheets on specific areas/ junctions (18 pages) Summary Checklist (1 page) Fabric 1.Foundation/Ground Detail 2.Beam and Block Floor 3.Solid Floor 4.Door Thresholds 5.Cavity Wall – partial fill 6.Cavity wall – full fill 7.Floor Joists – intermediate floor 8.Party wall 9.Window cavity closer, cill and lintel 10.Window installation 11.Openings – Bay, oriel windows 12.External Doors 13.Eaves 14.Roof 15.Dryline/plaster 16.Finals Builder’s Book Contents Services/Renewables 1.First fix 2.Second Fix

Improved Process on site? Copy of latest drawings/specification accessible on site Check all elements are in line with the design drawings and specification Site Manager/builder must have adequate communication with design team SAP assessor and Architect on site Hold regular toolbox talks with trades Any others??

Any questions?

Feedback Consultation sessions on site? How useful? How to improve? Please complete form and scribble comments on posters

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