Building enclosure design presentation 2

PERFECT WALL

Source: philipluo.com

PERFECT WALL

Source: Building Science Corporation

PERFECT WALL

PERFECT WALL

Source: philipluo.com

INSULATION STRATEGIES

Interior Insulation (wall)

• Advantages • easier to install

• Material costs low

• Disadvantages • Allows dewpoint interior to weather barrier

• May require fire separation from habitable space

• Does not protect weather barrier from thermal movements

• Thermal bridging at framing members reduces effective R-value


Interior Insulation (wall)

• Product Types

• Fiberglass batts (3.1 to 4.3/in)

• Mineral wool (3.7 to 4.5/in)

• Cotton batts (3.5/in)

• Sprayed-in cellulose (3.6 to 3.8/in)

• Sprayed-in fiberglass (3.7 to 4.2/in)

• Closed cell spray foam (6/in)

• Open cell spray foam (3.5/in)


Exterior Insulation (wall)

• Advantages • Mitigates thermal bridging

• Protects weather barrier from thermal movements

• Pushes dewpoint exterior of weather barrier

• Disadvantages • Installation requires more coordination

• Higher material cost

• Drying time of wall may lengthen depending on material choices


Exterior Insulation (wall)

• Product Types

• Extruded polystyrene (XPS) (4.5 to 5.0/in)

• Expanded polystyrene (EPS) (3.6 to 4.0/in)

• Polyisocyanurate (5.6/in)

• Closed cell spray foam (6/in)

• Mineral wool (3.7 to 4.5/in)


Split Insulation (wall) • Advantages

• Mitigates thermal bridging • Protects weather barrier from most thermal

movements • Sometimes cost effective

• Disadvantages • Installation still requires more coordination • Drying time of wall may lengthen depending on

material choices • Weather barrier material choices narrow • Dewpoint will reside in stud cavity….but for how long?


Interior Insulation (roof)

• Advantages • Easier to install

• Material costs low

• Disadvantages • Allows dewpoint interior to roof membrane

• Does not protect roof membrane from thermal movements and weathering

• Susceptible to moisture during construction

• Thermal bridging at fasteners reduces effective R-value mildly


Infrared Scan of EPDM Roof

THERM model w/ fasteners thru all insulation

THERM model w/ fasteners thru first layer of insulation


Exterior Insulation (roof)

• Advantages • Mitigates thermal bridging

• Protects roof membrane from thermal movements

• Pushes dewpoint exterior of roof membrane

• Quicker “dry-in” of building

• Disadvantages • Installation requires more coordination

• Insulation needs to be covered (pavers, ballast, vegetation, etc.) to protect from exposure


Source: Roxul


Source: Roxul

Source: Roxul


Figure source: Roxul

Why is CONTINUITY important?

PORTLAND AIR INFILTRATION

WATER VAPOR DIFFUSION

1” SQUARE HOLE

10000 1000 100 10 1 0.1

# GRAINS PER HOUR

INTERIOR 68°F 50%RH

EXTERIOR 41°F 80%RH

SOURCE: WBDG


MIAMI AIR INFILTRATION

INTERIOR 70°F 50%RH

WATER VAPOR DIFFUSION

1” SQUARE HOLE

EXTERIOR 91°F 56%RH

0.1 1 10 100 1000 10000 # GRAINS PER HOUR

SOURCE: WBDG


Solve the air and water first……..then worry about insulation!

Case Study 1 – Exterior infiltration

Case Study – Exterior infiltration

Case Study 2 – Interior infiltration

• Case Study - Interior


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Temperature = 20°F Relative Humidity = 93%

Vapor Pressure Force = 7.2psf

Temperature = 70°F Relative Humidity = 53%

Vapor Pressure Force = 15.7psf

PENCIL TEST – plans and sections

UNCONDITIONED CONDITIONED


UNCONDITIONED

CONDITIONED

DETAILS

THE OTHER “C” WORD - COMPATIBILITY

COMPATIBILITY

Building enclosure design presentation 2

Environment

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