User:
Moisture Migration
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Bulk water
Vapor movement two forms
- Vapor diffusion
- Air transport
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Stack Effect
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How it works
Why we care
What it will do to you
Where does the moisture come from
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Thermal Voids and Bridges
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Gaps in insulation
Types of thermal bridges
The Passive Haus approach
Thermal imagery
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Conditioned Attic Design
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Either vented ("cold roof") or unvented ("hot roof")
Why vent?
- Cold climates: cold roof surface to control ice dams, vent moisture
- Hot climates: expel solar heated air to reduce cooling
Other considerations:
- Attic needed for living space
- Roof complexity makes venting difficult
- Locating HVAC system components
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Ventilation Strategies
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Geographically dependant
Ventilate for IAQ
Supply vs. exhaust
Balanced ventilation
It's what the "V" stands for
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Precautions
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Where wetting exceeds drying:
BSC says greater than 40 inches of annual rainfall
Type of siding: reservoir claddings need to be separated to prevent thermal drive
Use polypropylene matting between SIP and drain screen with stucco and stone veneer
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