Overview
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Introduction to the Weatherization Assistance Program
Communication Skills
House as a System
Building Science Basics
Blower Door Basics
Pressure and Thermal Boundaries
Combustion Safety
Worker Safety
Materials, Tools, & Equipment
Typical Weatherization Measures
Mobile Home Basics
Multifamily Basics
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Learning Objectives
PRESSURE & THERMAL BOUNDARIES
By attending this session, participants will:
• Understand the difference between the thermal boundary
and the air or pressure boundary, and the behavior and
function of each
• Know the proper location of the pressure and
thermal boundaries
• Know common sites for breaks in the pressure and
thermal boundaries
• Understand what is meant by inside and outside in
terms of air barrier, and how a blower door is used to
determine that
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Thermal & Air Barriers
PRESSURE & THERMAL BOUNDARIES
For maximum efficiency and comfort,
the thermal and air barriers must be
continuous and in contact with each other.
WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM
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Thermal & Air Barriers
PRESSURE & THERMAL BOUNDARIES
An uninsulated attic
hatch is a gap in the
attic’s thermal barrier
Air Barrier
Thermal Barrier
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PRESSURE & THERMAL BOUNDARIES
A mechanical chase
containing ducts can
break the attic’s
air barrier
Air Barrier
Thermal Barrier
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Moisture
PRESSURE & THERMAL BOUNDARIES
Moisture flows with warm
air through breaks in the
air barrier, causing damage
when it condenses on
cool surfaces.
Air Barrier
Thermal Barrier
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Blower Door Test
PRESSURE & THERMAL BOUNDARIES
ΔP = -50 Pa
Blower Door
WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM
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Zone Pressure Diagnostics
PRESSURE & THERMAL BOUNDARIES
Pressure difference of
attic with reference to
the house should be
close to -50 Pa
ΔP = -50 Pa
Blower Door
WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM
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Zone Pressure Diagnostics
PRESSURE & THERMAL BOUNDARIES
Pressure difference of
interior wall with reference
to the house should be
close to 0 Pa
ΔP = 0 Pa
Blower Door
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WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM
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Where Is the Air Barrier?
PRESSURE & THERMAL BOUNDARIES
Cape Cod
1½ Story House
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Where Is the Air Barrier?
PRESSURE & THERMAL BOUNDARIES
Pressure difference of the
floor cavity with reference
to the house should be
0 Pa. But, is it?
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Where Is the Air Barrier?
PRESSURE & THERMAL BOUNDARIES
Targeted air sealing
defines air barrier
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Where Is the Air Barrier?
PRESSURE & THERMAL BOUNDARIES
Pressure and thermal
boundaries are
now aligned
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Summary
PRESSURE & THERMAL BOUNDARIES
• For maximum efficiency and comfort, the thermal and
pressure boundaries must be continuous and in contact
with one another
• Electrical and mechanical chases, missing top plates,
knee walls and dropped ceilings are common trouble spots
• Pressure diagnostics determine location and condition
of air barrier
• Zonal pressure readings in conditioned spaces should read
close to 0 WRT inside
• Targeted air sealing defines the pressure boundary
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