Kohta Ueno Assemblies Building Science Experts' Session ...
Transcript of Kohta Ueno Assemblies Building Science Experts' Session ...
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Building Science Experts' SessionSpecial Use Facilities
Kohta Ueno
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Swimming Pools: Basics & Assemblies
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Swimming Pool Conditions
Typical wintertime interior (30% RH)
Museum 50% RH
Swimming pool
January-Decembermonthly average temperatures
Condensation on any surface colder than ~69° F
Air in swimming pools → dangerous stuff that destroys buildings
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Vapor Diffusion vs. Air Leakage
Vapor Diffusion more to less vapor no air flow flow through tiny pores
Air Convection more to less air pressure flow through visible cracks
and holes vapor is just along for the
ride
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Wall w/o Insulated Sheathing
Air leakage
Vapor Diffusion
Cold = Condensation
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Frosting on Sheathing
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Wall with Insulated Sheathing
30% of R-Value 70% of R-Value
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Wall with Insulated SheathingAir leakage
Vapor Diffusion
Warm = no condensation
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“Perfect Wall”Air leakage
Vapor Diffusion
Warm = no condensation
~100% of R-Value
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The Perfect Wall
Structure (protected) Air-water-vapor barrier
(“Control layers”) Insulation Ventilated gap
(“Rainscreen”) Exterior cladding
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The “Perfect” Wall: Higher Performance
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The Commercial Steel Frame Wall
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Wood Frame Perfect Wall
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Conceptual Pool Enclosure
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Roof-to-Wall Connection
Perfect wall Vented roof All mechanicals
inside shell Thermal bridging at
steel truss Roof-to-wall air/
vapor barrier connection
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Cathedral Vented Roof
“Perfect wall” built on a slope
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Low-Slope (“Flat”) Roof Only works for Climate Zone 4 and warmer
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Low-Slope (“Flat”) Roof
For Climate Zone 5-ish
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Inverted Membrane Roof
Entirely safe: “perfect wall” as roof Top side could be ballast, pavers, “green roof”
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Inverted Membrane Roof
Entirely safe: “perfect wall” as roof Top side could be ballast, pavers, “green roof”
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All-Foam Roof: How Thick?
2015 IECC example (residential R-values) R-49 = 7.8 inches polyisocyanurate
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All-Foam Roof: How Thick?
2015 IECC Table R402.1.4 equivalent U-values U-0.026 = R-38.5 continuous =
6.2 inches polyisocyanurate Walls ~3-4 inches polyisocyanurate typical
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Swimming Pools: Residential Pool Case Study
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Roof-to-Wall Connection
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Roof-to-Wall Air Barrier Connection
Membrane
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Interior & Exterior Air-Vapor Barrier
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Interior & Exterior Air-Vapor Barrier
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Swimming Pools: Closed Cell Spray Foam?
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Failed Pool & Architectural Constraints
“The pool building can’t be a different size than the matching opposite wing.”
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Failed Wall Double wall, fiberglass batts, interior plaster
? ?
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Spray Foam Wall Retrofit ccSPF covered with vapor barrier Steel “buried” in ccSPF Permeable WRB, ventilated rainscreen
Shift stud for access to steel member
Shift stud for access to steel member
Closed cell 2 PCF urethane spray foam
Spray applied vapor barrier (AldoCoat 661)
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Vapor-Permeable Adhered Membrane
Excellent air barrier Ventilated rainscreen—drying of sheathing Continued up cathedral roof assembly
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Interior Vapor Barrier Coating Applied to interior of ccSPF Needed or not? 5.5” ccSPF = 0.3 perms. Class I (under 0.1 perm) recommended
Continuity of coating (air barrier) Problem: compatibility (real or perceived) between
ccSPF & coating Solution: same manufacturer for both
Many Class I materials-VOCs, interior use IAQ
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Thermal Bridging at Steel
Steel for hanging interior finishes or mechanicals “Bury” foam where possible, come inboard Still has risks
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Spray Foam as an Air Barrier
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Spray Foam as an Air Barrier
Spray foam doesn’t air seal where it isn’t there! Wood-to-wood connections
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Spray Foam as an Air Barrier
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Spray Foam as an Air Barrier
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Spray Foam Pool Enclosure: Takeaways Can work if “backed into a corner” Not recommended solution/best practice Risks from air leakage (imperfections in spray
foam if not caught by other layer) Annoyances of vapor barrier coating Risks from thermal bridging
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Swimming Pools: Case Studies & Failures
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Case Study: Roof-Wall Air Barrier Academic pool building stripped, re-insulated,
reclad Climate Zone 6A Efflorescence staining in first winter
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Case Study: Roof-Wall Air Barrier
“Perfect wall”
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Case Study: Roof-Wall Air Barrier
Excellent roof (air-vapor barrier below)
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Case Study: Roof-Wall Air Barrier
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Case Study: Roof-Wall Air Barrier
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Run Pools at Negative Pressure Contains moisture
(outside to inside air leakage)
Contains odors (pool attached to rest of building)
Tighter construction = smaller fan needed
ASHRAE ~ -12 Pa recommended
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Room Pressure Indicator “Ball in the wall” (medical, animal labs, etc.)
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Case Study: Pressurized Pool
Recently rebuilt NH resort pool
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Case Study: Pressurized Pool
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Case Study: Pressurized Pool
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Case Study: Pressurized Pool Reused existing mechanical system (ventilation-
based dehumidification, not refrigerant-based) Pool running at ~+25 Pascals (up to +40 Pa)
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Case Study: Pressurized Pool Pool conditioning system improperly configured Pressurized pool + greater airtightness →
concentrated air leakage condensation
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Swimming Pool: Pool‐to‐Interior Walls
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Interior-to-Pool Walls Dewpoint of pool air is ~70 F Interior typically at 68-75 F “Cold-weather condensation”
when outdoors is “warm” →relatively low risk
Condensation & moistureresistant assemblies recommended
Double glazed for pool-to-interior windows (eliminates window fogging), or blowing heat
Airtightness—connection to exterior air barrier
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Wine Room Enclosure Assembly XPS on one side of
empty stud frame Taped joints for air barrier
continuity Furring for interior
finishes Challenges at ceiling:
mechanical penetrations & sequencing
ccSPF also an option
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Interior-to-Pool Wall
Perfect Wall exterior
XPS Wall interior
Existing brick walls (~R-3): air barrier coating on pool side
Air barrier detail
Air barrier detail
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Swimming Pool: Takeaways
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Pool Enclosure Takeaways Air inside pool is “dangerous stuff” Perfect wall/roof/slab enclosure ideal Contain with negative pressurization (exhaust) Pool dehumidification system Limit interior to 50-60% RH. Must run 24/7/365 Pool covers will reduce the load
Windows will always condense (unless triple) Detail assuming interior condensation
Air leakage testing at air barrier completion Quality control for air barrier failures Can estimate size of required exhaust fan (~ -12 Pa)
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Museums
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Werner Otto Hall (Harvard)-1991 Was demolished after 19
years of service Pressurized / 50% RH Wintertime condensation,
walls soaked through Icicles from parapets Glass block efflorescence Harvard sued architect & contractor in 1996 Repairs done; still demolished in 2010
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Werner Otto Hall (Harvard)-2008
Metal panel cladding, sealed joints
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Werner Otto Hall (Harvard)-2008
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Museum Storage Building (Insulated Metal Panel)
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Museum Storage Building Constant humidified
50% RH (art storage) Insulated metal panel (IMP)
walls and roofs, simple design Climate Zone 6A Dripping from ceiling during
early fall commissioning Dripping stopped with RH
dropped to 20% Seasonal problems
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IMPs and the Perfect Wall BSI-090: Joseph Haydn
Does The Perfect Wall Perfect air/vapor barriers
on both sides of panel
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IMP Wall Panel Joints Double sealant joint Thermal break at panel
edge Drained and “flashed” joint
(rain has to push uphill at horizontal joints)
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IMP Roof Panel Joints Standing seam w. double sealant
joint, thermally broken Ridge detail (ccSPF) Panel end lap details Dripping coming from end laps
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Minor Thermal Bridging at Roof Clips “Grid of dots” on ceiling Attachment clips bridge
through most of insulation Not the source of dripping
problems
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Depressurization Testing Depressurized to -60 Pa Infrared flow visualization
(warm weather outdoors) Recommended as quality
control during construction
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Depressurization Flow Visualization
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Depressurization Flow Measurement
Some seams airtight, others leaky Airflow 100-300 FPM/feet per minute Not obvious from visual inspections
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Depressurization Flow Visualization
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Roof Dripping Causes Interior-to-exterior air leaks
(from IR visualization) Eave (roof-to-wall) air leaks Interior-to-interior air leaks
also could be contributing (like SIPS panels) Convective looping
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Retrofit Details (Roof Field)
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“Bag and Sag” Roof for Comparison
Fiberglass rolls with polyethylene facer
Steel Z purlins Massive condensation in
winter-unusable at 50%
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Museum Building Takeaways 70F / 50% RH very risky (especially cold climates) Insulated metal panel good solution for high-risk
buildings, BUT Risks are at panel seams & connections Quality control critical Building outdoors in Climate Zone 6A
IMP seams can’t be visually inspected after construction
Air leakage testing as part of commissioning? Or just specify Perfect Wall?
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Refrigerated Warehouses
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Refrigerated Warehouses Multiple investigations Refrigerated food distribution
centers/warehouses Entire space running 0-30 F Typical walls IMP or IMP
inboard of existing CMU Typical roofs metal deck,
insulation, single-ply membrane
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Drips from Ceiling
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Icicles from Ceiling
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Infrared Visualization of Air Leaks
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Infrared Visualization of Air Leaks
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Infrared Visualization of Air Leaks
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Airflow Measurement
Airflow below measurements limits (40 FPM) But no other explanation: moisture-laden air into
cold spaces
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Mechanical Penthouses
Cooling equipment in rooftop penthouse Penthouse acts as return plenum open to
warehouse below
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Mechanical Penthouses
Penthouses operate at negative pressures Penthouses are taller than rest of warehouse
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Mechanical Penthouses
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Refrigerated Warehouses and Stack Effect
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Driving Forces
Wind Effect Stack Effect Combustion and Ventilation
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Stack Effect (Winter & Summer)
Theoretical open tube NPP = neutral pressure plane
Winter Conditions Summer Conditions
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Stack Effect Stack calculated based on: Temperature difference Height of open “stack” (taller buildings = more stack)
Typically a problem in cold climates/winters Assume ~70F indoors Cold winter @ 0F, ∆T = 70F Hot summer @ 100F, ∆T = 30F
Freezer warehouses are different! Assume ~10F indoors Hot summer @ 100F, ∆T = 90F
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Stack Effect Calculation
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Refrigerated Warehouses Details & Solutions
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Detailing: Roof Edge
Relies on spray foam for air seal Source of moisture = exterior air Roof membrane should be air/vapor barrier here
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Roof Edge Air Leak (CMU + IMP Wall)
Was roof membrane detailed as air barrier? Reliance on ccSPF “blind” for air seal Problems worst at corners & transitions
Roof membrane; drawings show detailing as air barrier, but not confirmed with disassembly
Air leakage pathway from exterior; assumes roof membrane-to-CMU joint not effectively sealed
Air leakage pathway from CMU-to-IMP gap. Inward vapor drives can increase dewpoint at gap substantially
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Roof Edge Detailing (IMP Only)
Change termination bar to “lipped” termination bar, with fillet sealant joint below
Add self-adhered membrane tape at panel seams below roof membrane line
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Demising Walls (Cold-to-Warm)
Calls for spray foam above & below metal deck Condensation problems
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Demising Walls (Cold-to-Warm)
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Air Leakage Through Roof “Sandwich”
Air leakage deck-to-insulation Air leakage at polyiso layers Air leakage through “blind” ccSPF detail
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Demising Walls (Cold-to-Warm)
“Zig-zag” membrane through roof layers Termination bar to metal deck
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Demising Walls (Roof Dam Detail)
“Dam” detail within roof assembly Sealant from dam to roof membrane
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Demising Walls (Roof Dam Detail)
Self-adhered or fluid-applied membrane Has to conform to deck flutes Has to be applied to low temperature surfaces
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Refrigerated Warehouses Takeaways Leakage of warm humid outdoor air can cause
major problems Huge air pressure pulling outdoor air in at top of
building, worst in summer (high ∆T, high DP) Can’t neutralize with pressurization Relying on spray foam detailing problematic Membranes and sealants, termination bars Air leakage testing as quality control tool
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Questions?Kohta Uenokohta (at sign) buildingscience dot com
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