62 | Talking Timber: Passivhaus
A WIN-WIN FOR SUSTAINABILITY
Combining a timber-rich building with the certified Passivhaus Standard results in both embodied carbon and in-use energy savings. Additionally, it locks carbon into the fabric and structure of the building for decades, offering the closest approach to net-zero buildings
The Passivhaus Standard is a third party-certified, quality- assured method for designing and constructing buildings of any typology.
With over 30 years of refinement, the Passivhaus Planning Package (PHPP) – a sophisticated Excel-based modelling tool – accounts for all aspects of a building, including site conditions, shading, microclimate, current and future weather data, form factor and
fabrication. Three key principles ensure quality performance: 1. Accurate site-specific modelling in PHPP 2. An integrated approach – balancing energy losses/gains, comfort, and cost
3. Third party quality assurance – ensuring proper construction and commissioning
Additionally, five essential physical characteristics define a Passivhaus building: • A continuous, high-performance thermal envelope and airtight layer
• Consideration of thermal bridging within energy modelling • Solar gains and shading considerations, paired with high- performance glazing and doors
• Quiet and efficient mechanical ventilation with heat recovery (MVHR)
Certified Passivhaus buildings include:
• Residential: detached, semi-detached, terraces, and multi- occupancy housing (mid/high-rise)
• Educational: schools, university buildings, and student accommodations
• Commercial and institutional: offices, factories, hospitals, leisure centres, and more
Embodied carbon considerations are taken seriously. PHribbon, a software plug-in for PHPP, allows designers to evaluate multiple designs by adjusting materials and quantities. Software developer Tim Martel has incorporated all timber products with certified Environmental Product Declarations. Timber and moisture management are critical concerns. Softwood timber must remain below 20% moisture content to prevent rot. To mitigate moisture risks, PH Homes – owners of the PH15 I-joist and LVL system – utilise rain covers during construction, providing a dry assembly environment. Certified Passivhaus buildings are designed with airtight construction, often featuring proprietary airtight timber boards behind interior plasterboard finishes. These boards prevent moisture from interior activities (breathing, cooking, washing,
TTJ | March/April 2025 |
www.ttjonline.com
Tabitha Binding FIMMM, currently works with the
Passivhaus Trust and Coaction
Training CIC, and is a member of the IOM3 Wood Technology Leadership Team. She has previously worked with TDUK, TTF, BM TRADA, TRADA, Woodknowledge
Wales, Coed Cymru, Tir Coed and
Woodland Heritage
drying) from penetrating the timber structure. Instead, moisture is managed through MVHR, which extracts warm, damp air from kitchens and bathrooms, transferring heat to incoming fresh, filtered air supplied to living and sleeping areas. This maintains an indoor relative humidity of around 50% at a comfortable temperature of 21°C, benefiting both occupants and the timber structure. Certified Passivhaus timber-rich homes can incorporate timber materials such as: • CLT, glulam, LVL and I-joists • Solid stud, twin wall, Larson truss systems • OSB, plywood, MDF, particleboards, wood wool boards
• Wood fibre insulation (solid, flexible batts, loose fill)
• Cellulose insulation • Timber-based interior and exterior joinery, cladding, fixtures, and fittings Scotland is moving toward implementing the Scottish Passivhaus Equivalent, while Wales is advancing the ‘Tai ar y Cyd’ project, uniting 23 social housing providers in a timber-framed Passivhaus and AECB- standard pattern book. The Passivhaus Trust offers guidance and a free 4.5-hour online introductory course: How to Build a Passivhaus. https://
passivhaus.uk/. For more in-depth training, Coaction Training CIC provides courses with funding options from CITB and the Welsh government. Learn more at https://coaction.
org.uk/blog ■
Above: Passivhaus PH15 System IMAGE CREDIT: PASSIVHAUS HOMES
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69
