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Building Science & Residential Envelopes
 

Building Science & Residential Envelopes

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Rick Roos of George Brown College presents on the topic of building science as it relates to residential building envelopes.

Rick Roos of George Brown College presents on the topic of building science as it relates to residential building envelopes.

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    Building Science & Residential Envelopes Building Science & Residential Envelopes Document Transcript

    • 2013-02-09Building Envelopes Building Science Physics – Risks - Strategies Rick Roos M.A.Sc. Free Powerpoint Templates Rick Roos•  Professor  of  Building  Science  George   Brown  College  •  Principal  of  Integral  Building  Science   –  Savings  By  Design  –  Enbridge  Gas/SBC   –  QA/QC  Evaluations     –  Energy  Analyses   –  Utilities/Governments   –  Architects/Builders     Building Science 1
    • 2013-02-09 Overview of presentation•  Purpose  of  the  envelope  •  Physics  of  Heat,  Air  and  Moisture  •  Control  Layers  •  Risks  of  Inadequate  Envelope  •  Design  Considerations  •  Envelope  Assemblies   New Solutions, New Problems•  Advent of insulation led to moisture problems•  Tighter envelope led to health issues•  Building Science born from the need to KNOW how to build better Roos Building Science 5Building Envelope Requirements•  Control  heat  Klow  •  Control  air  Klow  •  Control  water  vapour  Klow  •  Control  rain  penetration  •  Control  light,  solar    •  Control  noise  •  Control  Kire  •  Provide  strength  and  rigidity  •  Be  durable  •  Be  aesthetically  pleasing  •  Be  economical 2
    • 2013-02-09Physics of the Building Envelope Preparing for the Future•  Increasing demands for energy performance•  Where are we headed?•  What are the influences? Policy to Powerpipe Internaonal   • Kyoto,  Rio   Conference,   Agreements   Earth  Summit     Internal   • Demand  Side   Management;   Policy   Building  Code   Iniaves   Changes   BeCer   • SB-­‐12;  Energy   Performing   Star;  R-­‐2000;   Passive  House   Buildings   3
    • 2013-02-09 Path to Net Zero (Energuide) Divide and Conquer•  Convenient to discuss building science in it’s component parts separately –  Heat Transfer •  Conduction •  Convection •  Radiation –  Moisture •  Bulk Water •  Capillary Transport •  Vapour Diffusion –  Air Leakage Heat  Transfer   4
    • 2013-02-09 Heat transfer•  Conduction•  Convection•  Radiation -20˚C +20˚C Conduction Radiation ConvectionMovement from warmer to colder Fourier’s Law - Conduction q= A/R x ΔT 5
    • 2013-02-09 There are R-values…then there are R-values •  Nominal R-value (OBC) •  Effective Ra-value –  Thermal bridging •  Structural elements that bypass insulation •  ‘Highway’ for heat transfer Accounting For Thermal Bridging 2-dimensional heat Finite Element Analysis transfer •  Realistic modeling of heat flow paths •  Previous accounts did not reflect the actual importance of 2-D heat transfer 17 Effects of Thermal Bridging 10 9 8 7 R-27 R-24 R-22 6RSI (M2K/W) 5 4 3 2 1 0 1a 6b 1b 2a 6a 4d 2b 5b 7 5a 4a 4c 4b 3 8b 8a ii 1a e e e e e e e e e e e as e e e as e e e as as as as as as as as as as as as as as as C C C C C C C C C C C C C C C C C Whole-Wall RSI 6
    • 2013-02-09 Heat & Moisture Inter- relationship  •  Heat and moisture act together•  Difficult to consider one without the other the other Roos Building Science 19 Moisture Transport•  Capillary  Transport  •  Bulk  Water  Transport  •  Vapour  Diffusion   –  Adsorption  •  Air  Leakage 1:10:100 7
    • 2013-02-09 Vapour Diffusion•  Vapour  moves  from  areas  of  high   concentration  to  low  •  Vapour  pressure  drives  vapour   movement  •  Primary  inKluence:  Temperature   How Does Vapour Move?•  Vapour  moves  from   high  to  low   concentrations  of   vapour  pressure  •  InKluences  relative   humidity  •  Relative  humidity   determines  moisture   content   Permeance Testing Dry Cup Wet Cup Inverted Cup 8
    • 2013-02-09 Which Permeance Value?...When?•  Dry Cup (between 0% and 50% RH) •  When RH levels are expected to be in this region •  E.g. vapour retarder in cold climates•  Wet Cup (between 50% and 100% RH) •  When RH levels are expected to be in this region •  E.g. exterior sheathings in cold climates•  Inverted Wet Cup •  When the material is expected to experience bulk water exposure •  Drainage Plane materials e.g. Housewrap Permeance Data Tables Adsorption15% Relative Humidity 30% Relative Humidity 100% Relative Humidity 9
    • 2013-02-09 Sorption Isotherms Risks of High Levels of R.H. •  Elevated  R.H.  levels   –  For  extended  periods  of  time     •  Increased  Moisture  Content  (building   materials)   •  Risk  of  Biological  Growth   Rule: Each Layer Weaker Than The LastOption A: Option B:•  From interior to exterior •  From interior to exterior during heating season during heating season –  Fibreboard, untreated –  Foamed polystyrene –  Perforated asphalt-coated insulation 25mm (29 kg/m3) sheathing paper –  Cellulose Acetate Film –  Nylon film 0.025mm –  Fibreboard, sheathing grade 10
    • 2013-02-09 Vapour Trap •  Only ONE vapour retarder is allowed in an assembly! •  This must be placed on the warm side of the assembly •  If two are installed, this traps moisture between the two materials creating potential for moisture related damage OBC Vapour Retarder Requirements •  The building code requires vapour retarders on every exterior building envelope component •  The maximum permeance for a vapour retarder in our climatic region is 60 ng/ PaSm2Example: Is This Assembly Acceptable During the Heating Season? Vapour Retarder 11
    • 2013-02-09 Vapour Retarder •  Why  retarder  not  barrier   •  Warm  side  of  the  assembly   •  Need  not  be  continuous   Vapour Retarder •  OBC  –  60  ng/PaŸSŸm2   •  Drying  potential  to  the  interior?   •  Materials:   –  Vapour  retarder  paint   –  “Smart”  vapour  retarders   –  Oriented  Strand  Board   •  Only  ONE  vapour  control  layer  per   assembly!   Sun-­‐Driven  Moisture  36     Roos Building Science 12
    • 2013-02-09Relave  Humidity  at  Condensaon  Plane   100   Risk of Mold 75   #REF!   #REF!   #REF!   #REF!   50   #REF!   #REF!   25   Oct   Nov   Dec   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Roos Building Science 37 Capillary  Transport   Capillary Rise (?) wood cells 13
    • 2013-02-09 Capillary transport-Forces  on   water  molecules   Wetting Hydrophilic  Vs.  Hydrophobic  •  Hydrophilic natural state•  Hydrophobic coating applied 14
    • 2013-02-09 Capillary Rise What Effects Capillary Transport?•  Water rises most in thinnest tube and least in widest tube•  Fluid rises because the adhesive forces of water against capillary material is greater than the cohesive energy between the water molecules Capillary Moisture Transport•  Capillary  breaks  •  Damp-­‐prooKing  •  Gap  size  •  Sponge  video 15
    • 2013-02-09 Rising  Damp  EfflorescenceSubflorescence   16
    • 2013-02-09 Subflorescence Bulk  Water  (Rain  Leakage)   Roos Building Science 50Wall  Classifica*on  System  By  Rain   Penetra*on  Control  Strategy     17
    • 2013-02-09Storage or Mass Construction 52 Perfect  Barriers   •  Joints between elements also designed as perfect barrier: single bead of sealant •  Poor record of performance •  Examples: metal panels, some window frames, EIFS Screened-­‐Drained  Walls   18
    • 2013-02-09 Pressure  Moderated  Air  Space       Drainage  and  Flashing  Concepts   Drying  •  Drying:   –  Evapora*on  from  inside   or  outside  surfaces     –  Vapour  transport  by   diffusion   –  Drainage,  driven  by   gravity   –  Ven*la*on,  if  provided   19
    • 2013-02-09 Drying Potential•  Wall, ceiling and floor systems can experience interstitial condensation –  Air leakage –  Bulk water intrusion (rain water) –  Excessive relative humidity•  It’s acceptable, if it is allowed to dry!•  The mechanism for drying is vapour diffusion Drying  (Drainage)  •  Drainage is the most effective means of removing water from wall systems –  Very important mechanism for moisture control•  Even if well drained, there will be water in adsorbed, absorbed states and adhering to surfaces Drying  (Diffusive  Drying)  •  Diffusive drying can occur towards the exterior AND the interior –  Depending on assembly•  Due to solar radiation in cold climates, drying toward the interior can be very important 20
    • 2013-02-09 Drying (Air Movement) •  Air movement can move large amounts of moisture •  While moisture-laden interior air (in cold climates) can cause significant problems –  Dry inward moving exterior air can contribute to drying •  Reliance on uncontrolled air movement is not a reliable or responsible approach Drying  (Ven*la*on)  •  Ventilation of exterior air behind cladding –  Due to wind pressure –  Solar heated rising air•  This can be useful in accelerating drying•  Ventilation bypasses vapour resistant cladding materials thereby allowing drying•  A clear space of 19mm is recommended Air Movement – 3 Requirements •  A Fluid •  A Pressure Difference •  An Opening 21
    • 2013-02-09 Air Flow 64 Buoyancy of Air – Stack Effect SaturationCold Air Warm Air 22
    • 2013-02-09 Psychrometric Chart Air Leakage - Condensation Plane68 Air Air Pressure Pressure Dewpoint Temperature against Condensation Plane Temperature69 35   30   25   20   15   Temperature  (°C)   10   5   0   -­‐5   -­‐10   -­‐15   40087   40118   40148   40179   40210   40238   40269   40299   40330   40360   40391   40422   Roos Building Science #REF!   #REF!   23
    • 2013-02-09 Condensing Plane Temperatures Air Leakage – Vapour Diffusion71 Air Air Pressure Pressure Vapour Pressure Vapour Pressure Roos Building Science Mold 24
    • 2013-02-09 Substrate  Classes  •  Substrate  class  0:   Opmal  culture  medium  (e.g.  full  medium).  This  isopleth  system   represents  the  maximum  growth  possible  for  any  mold  found  in  buildings.        •  Substrate  class  I:   Bio-­‐ulizable  substrates,  such  as  wall  paper,  plaster  board,  building   products  made  of  biologically  degradable  materials,  materials  for   permanently  elasc  joints,  strongly  contaminated  surfaces.        •  Substrate  class  II:   Less  bio-­‐ulizable  substrates  with  porous  structure,  such  as  plasters,   mineral  building  materials,  certain  woods,  insulang  materials  not   belonging  to  group  I.       Mold  Germinaon  &  Growth   Isopleths   Spore Germination Mold Spore Spore contents (moisture storage Exterior consideration) Wall Spore wall (vapour diffusion resistance) 25
    • 2013-02-09Moisture  Isopleths  (With  VR)   Moisture  Isopleths  (No  VR)   Control Layers 26
    • 2013-02-09 Control layers•  What  do  we  need  to  control?   –  Heat  transfer  –  Thermal  Control  Layer   –  Bulk  water  intrusion  –  Rain  Control  Layer   –  Air  leakage  –  Air  Control  Layer   –  Vapour  diffusion  –  Vapour  Control  Layer  •  Some*mes  Control  layers  are  combined  into   a  single  material  or  membrane   Thermal Control Layer•  Continuity  •  Thermal  bridging   Strategies to Address Thermal Bridging •  Exterior Insulation –  Increase ratio of outboard to inboard insulation –  Towards 100% exterior insulation •  Reduce area occupied by structural components 27
    • 2013-02-09 Thermal Bridging Effects  of  Thermal  Bridging      Roos Building Science 84 28
    • 2013-02-09 Strategy #1 Strategy #2 •  Exterior Insulation •  Blunts the effects of thermal bridgingStrategies to Address Thermal Bridging •  Exterior Insulation (‘Outsulation’) –  Increase ratio of outboard to inboard insulation –  Towards 100% exterior insulation •  Reduce area occupied by structural components 29
    • 2013-02-09 Calculating Effective R-ValuesParallel Planes In Series Effective Thermal Resistance•  RSIeff = RSIseries + RSIparallel Exterior Insulation•  Building  code  •  Thermal  bridging  •  Convenient  balance   30
    • 2013-02-09 Rain Control Layer - Drainage Plane •  Resists  liquid  water   penetration   •  Vapour  permeable   •  Eliminate  capillary   transport   predominantly   Drainage Plane92 Roos Building Science Bulk water leakage •  Drainage Plane –  Assume water will get past 1st line of defence •  Contiguous overlapping system 31
    • 2013-02-09Water Damage - Mold Flashing Sealing 32
    • 2013-02-09 Window Sill Pan Air Control Layer•  Must be continuous•  Detailing in drawings•  Detailing on site•  Specify responsible on-site person Location of Air Barrier 33
    • 2013-02-09 Common  Air  Leakage  Locations   Attics & Roofs•  Main  areas  of  roof  and  attic  air  leakage:   –  Plumbing  stacks   –  ASc  hatch   –  Recessed  fixtures   –  Par**on  walls   –  Chimneys  •  Stack  Effect   34
    • 2013-02-09 Ceiling & Attic Air LeaksAir Leakage Related Mold Growth Air Leakage – Plumbing Stack 35
    • 2013-02-09 Air Leakage - Building Envelope•  Common  areas  of  air  leakage  in  new  homes   –  Rooms  over  garages   –  Behind  tubs  and  stairs   –  Behind  back  framing   –  Recessed  fixtures   –  Exhaust  fans   –  Headers  and  sills   –  Electrical  and  cable  boxes   –  Window  framing Rooms  over  garages  Exposed  Kloors  and  cantilevers   36
    • 2013-02-09  Back  Framing     Pot  lights  Headers  and  cantilevers   37
    • 2013-02-09 Sill PlatesElectrical  and  cable  boxes   Windows 38
    • 2013-02-09 Air Barrier Strategies Exterior Air Barrier SystemsAir Leakage Control Summary•  Key  areas  on  which  to  focus:   –  Know  the  main  air  leakage  loca*ons   –  Provide  adequate  training  to  subtrades   –  Perform  air  barrier  inspec*on –  Perform  air  leakage  tests  early  in  the   construc*on  phase   –  Facilitate  explora*on  of  new  air  barrier   techniques   39
    • 2013-02-09 Air leakage of building envelopes  Blower-­‐door  test    (fan   pressurizaon  test)  –   measures  enclosure   integrity   Roos Building Science 119 Wall Assemblies 40
    • 2013-02-09 Standard 2006 OBC (R20)2006 OBC Wall Typical Approach to R27 Double Stud FramingExterior Insulated Finish SystemNext Generation Reason for Improvement 41
    • 2013-02-09 Insulated Concrete Form Insulated Concrete FormStructural Insulated Panels 42
    • 2013-02-09 Cross-Laminated Timber The Perfect Wall•  All control layers on the exterior of the structure –  Thermal –  Rain –  Vapour –  Air•  Protect the structure•  Eliminate thermal bridging•  Eliminate risks of moisture damage! Risks of inadequate building envelope•  Moisture  Related  Risks  •  Air  Leakage  •  Bulk  water  leakage  •  EfKlorescence  •  SubKlorescence  •  Vapour   –  Outward   –  Inward  •  Thermal  losses  •  Architectural  detailing   –  Old  EIFS  system   –  Window  flashing  •  WorkKlow  management   –  Who’s  job  is  it  to  detail  the  air  barrier? 43
    • 2013-02-09 Design Considerations•  Increased  ratio  of  ‘out’sulation  to  insulation   –  Blunt  or  eliminate  thermal  bridging   –  Reduce  moisture  related  problems  •  Flashing,  Klashing,  Klashing!  •  Air  barrier  continuity!  •  Capillary  breaks  •  Vapour  retarders  bi-­‐directional  drying  potential  •  Toward  the  perfect  wall Build better buildings 44