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BackgroundBuilding Energy Use Exterior Insulation Retrofits

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					                                                                                                Background/Building Energy Use
                                                                                              • Residential and 
                                                                                                commercial energy use
                                                                                              • 120 million housing units 
Kohta Ueno
                                                                                                (current existing stock); 
Residential Exterior Wall Superinsulation                                                       70% built before energy 
Retrofit Details and Analysis                                                                   codes                                                           45


                                                                                                                                                                40


Thermal Performance of the Exterior Envelopes                                                 • Greatest concentration of                                       35
                                                                                                                                                                                                          2000 to 2005




                                                                                                                                    Millions US Housing Units
of Whole Buildings XI International Conference                                                  oldest housing stock in                                         30                                        1990 to 1999
                                                                                                                                                                                                          1980 to 1989
December 8, 2010                                                                                                                                                25

                                                                                                Northeast/Midwest                                               20
                                                                                                                                                                                                          1970 to 1979
                                                                                                                                                                                                          1960 to 1969
                                                                                                                                                                                                          1950 to 1959

                                                                                                (heating‐dominated)                                             15
                                                                                                                                                                                                          1940 to 1949
                                                                                                                                                                                                          Before 1940

                                                                                                                                                                10


                                                                                                                                                                 5


                                                                                                       Residential Exterior Wall Superinsulation Retrofit Details and Analysis
                                                                                                                                      0                                                                        2
                                                                                                                                                                     Northeast   Midwest   South   West




         Exterior Insulation Retrofits                                                         Previous Work (Exterior Retrofits)
 • Residential wood‐frame walls
                                                                                              • Insulation exterior to structure well‐
 • Going beyond nominal R‐13/R‐19 walls
                                                                                                established technique (Hutcheon, Baker and 
   (R‐8/R‐13 whole‐wall R values)
                                                                                                Makepeace, Lstiburek, CCHRC)
 • Exterior retrofit advantages
     – Insulation outboard of vulnerable structure                                            • Dumont & Orr “Chainsaw Retrofit” 1987 
     – Interior is habitable during retrofit                                                    (R‐40+ enclosure; 3.0 ACH 50→0.3 ACH 50)
     – Retain interior finishes (lose exterior finishes)                                      • ORNL 2007 hot box & airtightness 
     – No loss in interior square footage                                                       measurements of exterior insulation; included 
     – Can inspect condition of enclosure (during                                               foam up to 1” thick (10‐15% energy savings)
       cladding removal)
     – Exterior stairwells (code minimum widths)
               Residential Exterior Wall Superinsulation Retrofit Details and Analysis    3            Residential Exterior Wall Superinsulation Retrofit Details and Analysis                                 4




     Overview of Case Study Houses                                                                   4” Polyisocyanurate Foam



     Concord, MA                    Arlington, MA                     Bedford, MA
    “Four Square”                      “Duplex”                       “Farmhouse”

  Single family house          Duplex (over/under)                Single family house
     2800 + 800 sf            1280 + 1800 + 1280 sf                 1500 + 1060 sf
      circa 1915                   circa 1930                         circa 1850

Local energy-conscious        Local energy-conscious             Habitat for Humanity
  general contractor            general contractor              (volunteers & technical
                                                                     high school)
 All new mechanicals          Retained steam system
                                                                 All new mechanicals
               Residential Exterior Wall Superinsulation Retrofit Details and Analysis    5            Residential Exterior Wall Superinsulation Retrofit Details and Analysis                                 6
           Arlington Duplex Retrofit                                                            Foam Sheathing Cladding Attachment

 REDACT
       ED




REDACTED


                     REDACTED




                   REDACT
                         ED



                                                                                           250 lbs/113 kg load (7.8 psf): <0.003” deflection
                                                                                           Wood siding ~2 psf
                                                                                           Fiber cement 2-3 psf
                                                                                           Stucco 8-10 psf

            Residential Exterior Wall Superinsulation Retrofit Details and Analysis    7                      Residential Exterior Wall Superinsulation Retrofit Details and Analysis    8




 “Innie” and “Outie” Windows                                                                                         “Outie” Window




            Residential Exterior Wall Superinsulation Retrofit Details and Analysis    9                      Residential Exterior Wall Superinsulation Retrofit Details and Analysis   10




                    “Innie” Window                                                                     “Innie” vs. “Outie” Windows
                                                                                            • “Outie” Advantages
                                                                                                 – Simpler drainage plane 
                                                                  Recommend
                                                                  placing drainage                 connections/geometry
                                                                  plane at window
                                                                  location (whichever            – Lower cost (extension 
                                                                  method used—innie                trim is interior material)
                                                                  or outie)!
                                                                                                 – Similar appearance to 
                                                                                                   conventional 
                                                                                                   construction
                                                                                                 – Simpler window 
                                                                                                   replacement

            Residential Exterior Wall Superinsulation Retrofit Details and Analysis   11                      Residential Exterior Wall Superinsulation Retrofit Details and Analysis   12
         “Innie” vs. “Outie” Windows                                                             Retrofitting Exterior Air Barriers
• “Innie” Advantages
  – Window supported by 
    lumber frame (foam 
    install)
  – Greater protection from 
    wind‐driven rain (inset)
                                                                                                    Concord, MA                 Arlington, MA                    Bedford, MA
  – Less condensation risk (?)                                                                     “Four Square”                   “Duplex”                      “Farmhouse”
  – Thermal performance (?)
                                                                                                    3.1 ACH 50                    5.0 ACH 50                     6.2 ACH 50
  – Can use existing window 
    trim                                                                                      Mechanical penetrations,           Basement                 No secondary air barrier
                                                                                                porch attachments,           compartmentalized?               (housewrap w.
  – Solar shading (advantage                                                                     replacement sash          (1000 CFM 50 vs. 2129          connections); mediocre
    or disadvantage)                                                                                  windows                  CFM 50 total)               roof-wall connections

               Residential Exterior Wall Superinsulation Retrofit Details and Analysis   13                Residential Exterior Wall Superinsulation Retrofit Details and Analysis   14




     Retrofitting Exterior Air Barriers                                                          Retrofitting Exterior Air Barriers
                                                                                              • Roof‐wall connections
                                                                                              • Wall‐foundation 
                                                                                                connections
                                                                                              • Wall‐window connections
    St. Agatha, ON             Utica, NY (NYSERDA)                    Belmont, MA             • Windows 
      ~1 ACH 50                      2.3 ACH 50                        0.9 ACH 50               (actual units)—
Spray foam on exterior;         Rigid air barrier layer        Rigid foam as air barrier,       installation 
 all windows well air          under foam/over board           “chainsaw” retrofit of roof
  sealed; casement/            sheathing; spray foam               overhangs/eaves,             flaws?
    awning typical            roof-wall & bsmt rim joist         meticulous air barrier,
                                  (non-”chainsaw”)                blower door tests in
                                                                       progress
               Residential Exterior Wall Superinsulation Retrofit Details and Analysis   15                Residential Exterior Wall Superinsulation Retrofit Details and Analysis   16




     Retrofitting Exterior Air Barriers                                                             Retrofits and Water Intrusion
 • Structural attachments                                                                     • Generally improves wall durability
                                                                                                  – Rebuilt drainage plane; redundant layers
 • Mechanical system 
                                                                                                  – Ventilated drainage gap (3/4” cavity)
   penetrations
                                                                                                  – Reduced risk of interstitial condensation
 • Trades knowledge?                                                                          • Reduced vapor permeability due to foam
                                                                                                  – Reduced drying to exterior of bulk water events
                                                                                                  – Reduced airflow → reduced drying?
                                                                                              • Hygrothermal simulations of “survivable” leak 
                                                                                                in pre‐ & post‐retrofit walls
                                                                                                  – Limited applicability—”bounding exercise”

               Residential Exterior Wall Superinsulation Retrofit Details and Analysis   17                Residential Exterior Wall Superinsulation Retrofit Details and Analysis   18
  “Survivable” leak (Existing Wall)                                                                                                                                                                                          0.5% Leak in Retrofit Wall
                                        35%                                                                                                30                                                                          35%                                                                                       30

                                                                                                                                           25                                                                                                                                                                    25
                                        30%                                                                                                                                                                            30%
                                                                                                                                           20                                                                                                                                                                    20




                                                                                                                                                                                           Wood Moisture Content (%)
   Wood Moisture Content (%)




                                        25%                                                                                                                                                                            25%                                                                                       15
                                                                                                                                           15
                                                                                                                                                                                                                                                                                                       N
                                                                                                                                                                                                                                                                            N




                                                                                                                                                                                                                                                                                                                       Exterior T (C)
                                                                                                                                                                                                                                                                                                                 10




                                                                                                                                                    Exterior T (C)
                                                                                                                                           10                                                                          20%
                                        20%
                                                                    N                            N                            N                                                                                                              N                                                                   5
                                                                                                                                           5
                                        15%                                                                                                                                                                            15%
                                                                                                                                           0                                                                                                                                                                     0
                                                                    N                            N                            N                                                                                                              S
                                                                                                                                                                                                                                                                           S                           S
                                                                                                                                           -5                                                                          10%                                                                                       -5
                                        10%
                                                                    S                            S                           S             -10                                                                                                                                                                   -10
                                              5%                                                                                                                                                                       5%
                                                                                                                                           -15                                                                                                                                                                   -15

                                              0%                                                                                           -20                                                                         0%                                                                                        -20
                                               9-2008          4-2009         11-2009          5-2010          12-2010        6-2011                                                                                    9-2008         4-2009         11-2009          5-2010           12-2010      6-2011

                                                          Case 1 North Existing
                                                         Case 1b North Existing        Case 2bSouth Existing
                                                                                       Case 2 South Existing        Boston Temperature
                                                                                                                    Boston Temperature                                                                                             Case 3 North Retrofit        Case 4 South Retrofit       Boston Temperature


                                               0.5% incident rain penetration ≈ 20-25% peak north MCs                                                                                                                    0.5% incident rain penetration → upwards “ratcheting” wood MCs
                                               1% incident rain penetration ≈ 35-40% peak north MCs →                                                                                                                    Previously survivable leak becomes “unsurvivable”
                                               “unsurvivable” leak Wall Superinsulation Retrofit Details and Analysis
                                                   Residential Exterior                                                                                                       19                                                 Residential Exterior Wall Superinsulation Retrofit Details and Analysis                                20




                                               0.25% Leak in Retrofit Wall                                                                                                                                                            Economic Analysis
                                              35%                                                                                              30

                                                                                                                                               25
                                                                                                                                                                                      • Diminishing returns at greater insulation levels
                                              30%
                                                                                                                                               20                                     • Original analysis $4/gallon → $2.50‐$3.50/gal
                  Wood Moisture Content (%)




                                              25%                                                                                              15

                                                                                                                                                                                      • $4/sf incremental cost of opaque wall upgrade 
                                                                                                                                                             Exterior T (C)




                                                                                                                                               10
                                              20%


                                              15%
                                                                                                                                               5
                                                                                                                                                                                        not including recladding costs
                                                                        N                            N                            N            0

                                              10%
                                                                     S
                                                                                                     S                            S
                                                                                                                                               -5                                     • Airtightness as part of calculated energy benefit
                                                                                                                                               -10
                                                                                                                                                                                                                                                                            Annual                 Simple Payback w/o
                                               5%
                                                                                                                                               -15
                                                                                                                                                                                   Oil $                                                    Install cost                   Savings                Payback     airtight
                                                                                                                                                                                   $2.50                               Inner 2"                  $8,200                       $510                    16            25
                                               0%                                                                                              -20
                                                9-2008          4-2009            11-2009       5-2010           12-2010       6-2011                                              $2.50                               Outer 2"                  $4,100                       $118                    35            59
                                                          Case 3a North Retrofit        Case 4a South Retrofit        Boston Temperature
                                                                                                                                                                                   $4.00                               Inner 2"                     $8,200                       $816                      10                                15
                                               Reducing rain leakage to half (0.5% → 0.25%) keeps wood MCs stable;                                                                 $4.00                               Outer 2"                     $4,100                       $188                      22                                37
                                               same range as existing wall. Rain control critical for retrofits.
                                                    permeable exterior rigid insulation? XPS→ minimal.
                                               MoreResidential Exterior Wall Superinsulation Retrofit Details and Analysis 21                                                                                                    Residential Exterior Wall Superinsulation Retrofit Details and Analysis                                22
                                               EPS → Improvement




                                                                            Conclusions
• Excellent opportunity for retrofit during 
  periodic exterior cladding replacement
• Air barrier detailing and technology can use 
                                                                                                                                                                                      Questions?
  improvement; examine more options
  – Fully adhered membrane
  – Exterior spray foam
• Impermeable exterior insulation reduces 
  available drying
                                                                                                                                                                                     kohta@buildingscience.com


                                                         Residential Exterior Wall Superinsulation Retrofit Details and Analysis                                              23                                                 Residential Exterior Wall Superinsulation Retrofit Details and Analysis                                24
4‐½” High Density Spray Foam




   Residential Exterior Wall Superinsulation Retrofit Details and Analysis   25                 Residential Exterior Wall Superinsulation Retrofit Details and Analysis   26




Cladding Support over Foam                                                                Cladding Support over Foam




   Residential Exterior Wall Superinsulation Retrofit Details and Analysis   27                 Residential Exterior Wall Superinsulation Retrofit Details and Analysis   28




 Nominal vs. Actual R Value                                                                Taped Sheathing Air Barrier




                                                                                  New England Region Modular PassiveHaus: 0.7 ACH 50



   Residential Exterior Wall Superinsulation Retrofit Details and Analysis   29                 Residential Exterior Wall Superinsulation Retrofit Details and Analysis   30
Arlington Duplex Retrofit                                                       Exterior Retrofit Complications




 Residential Exterior Wall Superinsulation Retrofit Details and Analysis   31       Residential Exterior Wall Superinsulation Retrofit Details and Analysis   32

				
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