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Internal Wall Insulation on Solid Wall Buildings Some challenges

Internal Wall Insulation on Solid Wall Buildings Some challenges. Neil May. INTERNAL WALL INSULATION – WHY?. INTERNAL WALL INSULATION – WHY?. ?. INTERNAL WALL INSULATION – WHY?. Any one for EWI ?.

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Internal Wall Insulation on Solid Wall Buildings Some challenges

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  1. Internal Wall Insulation on Solid Wall BuildingsSome challenges Neil May

  2. INTERNAL WALL INSULATION – WHY?

  3. INTERNAL WALL INSULATION – WHY?

  4. ? INTERNAL WALL INSULATION – WHY?

  5. Any one for EWI? Assessing the execution of retrofitted external wall insulation for pre-1919 dwellings in Swansea (UK); Joanne Hopper et al2011

  6. Assessing the execution of retrofitted external wall insulation for pre-1919 dwellings in Swansea (UK); Joanne Hopper et al 2011

  7. Assessing the execution of retrofitted external wall insulation for pre-1919 dwellings in Swansea (UK); Joanne Hopper et al 2011

  8. Background • Government/EU commitment to 80% reduction in GHG by 2050 • All buildings to be near to zero GHG/ Carbon emissions by 2050 • = One building every 50 seconds from now on • Green Deal/ ECO programme starting this autumn (?) with particular emphasis on solid wall buildings • 6 million plus solid wall buildings in UK, most in England, most are brick. • Minimum 2 million expected to use Internal Wall Insulation • Many cavity wall and other buildings to use IWI as well

  9. Research Concerns • Thermal performance • Background issue of U values of traditional walls • Effect of IWI on thermal resistance of masonry • Thermal bridging issues • Overheating issues • Moisture performance • Effect of internal moisture • Effect of driven rain and other liquid moisture sources • Health • Effect of above on occupant health • Interaction with other factors especially ventilation

  10. Thermal issues: Traditional walls • Do not conform to type of wall suited to BR 443 (using BS 9496) – ie discreet layers of known materials • Consequently in –situ testing of traditional wall U values show that most walls perform better than under BR443 (inclRdSAP (2009) default values. Typically traditional walls have U values of 0.9 to 1.6W/m2K for walls over 225mm wide. The thicker the wall the better the U value. • Performance is much affected by moisture. More moisture leads to lower thermal resistance. • U value calculations given for IWI on traditional walls need to take these issues into account.

  11. Thermal Limits (German house)

  12. External Insulation versus Internal Energy loss through external wall in % External insulation Thickness of internal insulation in cm

  13. Practical limits: Thermal Bridges • Refurbishment of a traditional stone wall with 60 mm insulation on the inside • Reveal not insulated • Reveal now insulated with 40 mm insulation

  14. Thermal Bridges: Party Wall Issues Before After 13,1 °C 13,1 °C 12,6 °C 15 °C • Partial fixed internal wall insulation: • Displacement of isotherms, surface temperature sinks on the non-insulated side of the wall • Risk of mould / mildew

  15. Moisture – research background • Experimental work of Tim Padfield, Brian Ridout and others based on material qualities and site testing – no or little modelling used • German work of IBP based on laboratory testing and modelling • Masses of good conservation work and even more bad work on old buildings (no modelling or material testing, just observation) • Everyone agrees that Glaser (ie EN 13788 as per BS5250) is inappropriate for IWI unless walls are absolutely dry and protected. EN 15026 is correct standard at present

  16. Modelling Protocols • BS EN 13788 (BS 5250) versus EN 15026

  17. Driven rain and internal VCLs: Average water content of an external (German) wall Driven rain absorption 100% Variant 1: without VCL water content in kg/m2 Driven rain absorption 50% Variant 2: with VCL Driven rain absorption 0% Insulation thickness (k-value 0.040) in mm Source: Dr. A. Worch: Innendämmung: BauphysikalischeAspekte, Probleme und Grenzen und Lösungswegefür die Praxis (engl: Dr. A. Worch: Internal insulation: structural-physical aspects, problems and limits and solutions for the practice)

  18. Conflicting understanding of risk? • Driven rain is not so important in Germany as UK • IBP sees presence of oxygen as critical • RH limits in IBP • Max RH with air = 85% • Max RH without air = 95% • Part F limits • 1 day 85% • 1 week 75% • 1 month 65%

  19. Some Knowledge Gaps • Material data (thermal and moisture) for traditional buildings • Modelling (thermal and moisture) of traditional buildings • Thermal performance of traditional buildings • Moisture performance of all buildings esp traditional • Weather data – particularly wind driven rain • Mould formation processes and limits • Construction fault modelling? New DIN (68800-2) says 250g/m2 into structure; UK? • Durability of different materials under moisture (ie gypsum plaster) • Consequential effects on whole building performance and occupant health

  20. KTP approach Aim is to find a safe, effective, saleable solution for mainstream application. So focus on 9” to 13” brick buildings in England. Three legged strategy: • Modelling • Case studies, real life monitoring • Laboratory testing Comparative testing of breathable and non-breathable systems

  21. Modelling • Use of WUFI Pro 5 1D • Also use of Build Desk Modelling can tell you a lot, however…..

  22. Problems with Modelling • Human error • Manipulation • Data errors/ unknowns (ie OSB µ = 30/175) • Simplification of complex structures • Problems at junctions/ bits you can’t model • Issue of how to model bad application • False certainty

  23. Swansea, SW London, SW Pavadentro on 9” solid brick, 1%DR

  24. Swansea, SW Swansea, N Pavadentro on 9” solid brick, 1%DR

  25. London, N London, SW Pavadentro on 9” solid brick, 1%DR

  26. 100mm Pavaflex on 9”solid brick, 0 DR

  27. Impact of density On 9”solid brick Swansea 1% DR

  28. Case Studies • Very few available • 2 year KTP, but problems may take 10 or 20 years to develop • So many variables between each case study Neil May, February 2012

  29. Case Studies • Solid brick and Pavadentro • 1 with external render • 1 without render • Solid brick and Celotex, without render, but brick impregnated • LEAF funded project • 2 solid stone terraces with Pavadentro system & one new breathable system (not started) • Trinity College Cambridge (not directly linked to KTP) • ERDF Aim High 10 solid wall brick houses in Birmingham

  30. Trinity College • WUFI modelling with 3 different companies in 4 iterations, giving very different results • Material Property Testing (GCU) • Site survey (blower door, in situ U-value, RH monitoring, core samples for density and initial MC) 2 times with very different results • Extensive monitoring planned after application Neil May, February 2012

  31. Laboratory testing • Test methodology • Laboratory test update • Proposals for future tests • Investigate the dry-out potential • Liquid moisture ingress – wind driven rain

  32. Test methodology • 8 different internal insulation systems • 4 conventional systems – the most common IWI systems in the UK market • 4 breathable systems from NBT – development of two new systems

  33. MOISTURE TRANSFER Moisture convection: leaks Liquid transport: Wind driven rain Vapour diffusion Construction moisture summer winter

  34. MOISTURE TRANSFER – TEST 1 Moisture convection: leaks Liquid transport: Wind driven rain Vapour diffusion Construction moisture

  35. T [ºC] T [ºC] INTERNAL WALL INSULATION – LIMITS EXT INT EXT INT Low temperature at the wall-insulation interface Risk of interstitial condensation and mould growth

  36. INTERNAL WALL INSULATION – LIMITS Low temperature at the wall-insulation interface Risk of interstitial condensation and mould growth

  37. To what extent breathable materials can reduce the risk of interstitial condensation?

  38. TEST METHODOLOGY

  39. TEST METHODOLOGY • Monitoring interstitial condensation by measuring the RH at the wall-insulation interface • 6 RH capacitance sensors each section • Additional test: comparison between monitoring and hygrothermal modelling (WUFI Pro)

  40. Settings: • Driving force: vapour pressure differential • External conditions: Manchester TRY file from CIBSE, diurnal temperature variation into account • Internal conditions: WarmFront data (UCL), 80th percentile bedroom RH • Rain is not simulated TEST 1 Δ VP ΔVP ΔVP

  41. TEST 1 The wall is exposed to: • November, December – winter: vapour adsorption due to diffusion • May, June – spring: vapour desorption due to diffusion

  42. TEST 1 – COMPARISON OF RELATIVE HUMIDITY Breathable materials: 22% average RH reduction Non-breathable materials: 8% average RH reduction Higher speed of desorption in breathable materials

  43. TEST 1 Higher speed of desorption in breathable materials (measured at the wall-insulation interface) • Possible reasons: • Low vapour permeability (vapour movement on both sides) • The capillary suction moves the moisture away from the critical interface • Breathable materials can store moisture • (hygroscopicity) ΔVP ΔVP

  44. Settings: • WUFI Pro 1D • Climate file from chamber • Only diffusion (rain is off) • Initial conditions from chamber (trends comparison) COMPARISON OF MONITORING AND MODELLING

  45. RH - simulated RH - monitored COMPARISON OF MONITORING AND MODELLING Dry-fit Pavadentro Wetting well simulated – drying underestimated

  46. RH - simulated COMPARISON OF MONITORING AND MODELLING RH - monitored Pavaclay and Pavaflex

  47. RH - simulated RH - monitored COMPARISON OF MONITORING AND MODELLING PIR

  48. WUFI calculations agree with the measured data during vapour adsorption (“winter”) • The simulation underestimates the dry-out potential of the materials • Possible reason: • Underestimation of liquid transport coefficient in clay blocks and insulation materials • Incorrect algorithms in model COMPARISON OF MONITORING AND MODELLING Do we know the properties of materials in traditional buildings?

  49. Some Specific Problems in Practice • Rising damp. • Different moisture levels at different parts of walls (ie corners). • Joist ends • Window reveals • Partition/ party walls • Uneven walls • Gypsum plaster • Knowing what walls are made of • Quality of workmanship/ bad application • Services • Application in wet areas (bathroom, below DPC,…) • What are extreme conditions/ limits? Human behaviour issues • Long term maintenance of fabric and building services

  50. Some interactions to be considered • Internal Wall Insulation and thermal performance due to changing moisture levels • Overheating • Indoor air quality • Ventilation requirements and systems • Heating systems • Occupant behaviour

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