Lessons from UK Passivhaus projects - a certifiers view peter warm CEng BSc MCIBSE MIE WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546
What is a Passivhaus? Examples of UK Passivhauses Common failures Rules for Success WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546
What is a Passivhaus? Examples of UK Passivhauses Common failures Rules for Success WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546
Definition of a PassivHaus Definition of a Passivhaus without reference to physics: A Passivhaus is a building, in which thermal comfort can be provided solely by heating or cooling of the fresh air flow* which is required for good indoor air quality (Passipedia) In practice A building with space heating requirement designed close to the theoretical minimum Using Passive principles to their full extent before active insulation before heating system, With low energy design included in all the services: heating, hot water, lighting and appliances Note: Heating not necessarily achieved through air heating *without using recirculation WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546 4 4
Passivhaus standard Air-tightness Surface temp (windows) Summer overheating 0.6 ach @ 50Pa (n50) >17 C Max 10% >25 C Comfort Comfort Comfort Ventilation Heating Primary Energy ~30 m 3 /hr.person 15 kwh/m 2 yr @20 C Or 10 W/m 2 Heating Load 120 kwh/m 2 yr Comfort Energy Energy WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546 5
Why bother with Passivhaus? Avg UK House 17 C 20,000 kwh 700 Cold and expensive Go for comfort 22 C 40,000 kwh 1400 Mild and very expensive Add cavity wall, loft insulation, draughtproofing 22 C 20,000 kwh 700 Mild and expensive. Note: No fuel or carbon savings over start point Passivhaus 20 C 2,000 kwh 70 Warm and Wise! WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546 6
What is a Passivhaus Examples of UK Passivhauses Common failures Rules for Success WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546
1 house; one of first Passivhauses in UK; 300mm cavity wall; conservatory Denby Dale, Green Building Store
20 houses; one of first Passivhaus schemes in UK; Simple thermal geometry, Well monitored Ford Close, St Ive Sarsen HA
~30 homes; 4blocks, 2 to PH, 2 same construction Not designed as PH Sulgrave Gardens, London Octavia HA
Chester Balmore, London Camden Council 53 homes 3 blocks, all PH Not designed as PH
Massive 10,000 m2. 2 stage tender Designed as PH Curtain walling Medical building, Leicester University
Hereford Archive, Herford Council Truly Novel Airtightness and Thermal mass, not close control a/con
Multi residential with Central Services All Electric Nokes, Dacorum Borough Council
Woodside Towers, Glasgow Passivhaus EnerPHit project All Electric Novel ventilation
What is a Passivhaus Examples of UK Passivhauses Common failures Rules for Success WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546
Common Failures Airtightness Major reason for cost overruns Covering up work before testing = massive cost and time overrun Design the program to allow early testing whilst airtight layer is still accessible. Thermal Bridges Make sure details are worked out by the structural engineer before you start to build. Choosing a construction system that is not sympathetic to super insulation will likely cause problems brick finish especially an issue Ventilation The most problematic of all. Standards of ventilation systems very poor in UK, probably due to lack of experience. Noise a key indicator of poor design and execution. Commissioning seems to be a tick box affair. WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546
Issues moving to large scale Passivhaus Passivhaus = Higher Quality than normal Airtightness and Thermal continuity standards are different - Works fine on small projects, needs communication and site leadership on larger projects. Larger projects also have a lot more people to tell to do things differently, and a larger churn of subcontractors How to communicate the basic information for: 1. Thermal continuity 2. Airtightness 3. Ventilation? Wilmott Dixon had a solution (at least for the first two): WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546
Examples of Large Scale Passivhaus in the UK Issues moving to larger scale Common failures Rules for Success WARM: Low Energy Building Practice www.peterwarm.co.uk PLYMOUTH (01752) 542546
Design the job before you get to site You are trying to better than the norm, so standard details wont work! Communicate with your workforce about insulation, airtightness and general higher quality build The Willmott Dixon example worked Allow for more oversight and checking. Plan for early air testing change the construction sequence to make sure no air tight layer is covered up before it is tested. Recognise that the Ventilation is the weak link in the UK. Quiet systems are not the norm, but are a requirement for Passivhaus. They require Rules larger for ducts, success silencers, in large and experience projects at the design and installation stage. Use Passivhaus experienced designers and installers. Thanks for listening. info@peterwarm.co.uk WARM: Low Energy Building Practice