Air sealing and insulation can help the overall comfort of a building or home and help prevent some problems from coming in. http://palosantodesigns.com/

1. Air Sealing, Insulation,
& Thermal Bypass

2. How heat flows in a
building:
Air Leakage - need an air
barrier to stop flow.
Transmission - need insulation
to stop flow

3. What is a Building Envelope?
The pressure boundary (air barrier)
AND
The thermal boundary of the house
(insulation)
These must be continuous around the
entire conditioned space

4. What is a Thermal Bypass?
When heat, air and moisture “bypass” the
thermal envelope of a building due to
missing insulation or air barriers.
Insulation must have an air barrier
touching it on all sides. The exception
is at vented ceilings where only a
barrier between the attic and
conditioned space is required.

5. Where is the Building Envelope?
• Basement?
• Enclosed porch?
• Attic?
• Where are the ducts?
• Where is the heating system?
• Potential health and safety
concerns
• NEVER the garage
• Designers should examine the drawings and
determine the location of the envelope.

7. Air Barrier
The Air Barrier:
• Limits air flow between inside and outside
• More difficult to identify
• Not always where you think it is
• Blower door is used to
measure how tight the air
barrier is.
7
BUILDING SCIENCE BASICS

8. The Thermal Boundary:
• Limits heat flow between inside and outside
• Easy to identify by presence of insulation
• The location of insulation in relation to other
building components is critical to its
effectiveness
• Even small areas of
missing insulation are
very important
• Voids of 7% can
reduce effective R-value
by almost 50%

14. What Insulation Does
Primary:
Slows down heat flow
measured by R-value
Secondary:
Control air leakage
Control convective loops
(which is a function of it’s density)
Control water vapor
(measured in perm rating)

15. Cavity Mineral Fiber Batts
Reduce Heat Flow: fair
Control Air Leakage: poor
Control Convective Loops: poor
Control Water Vapor: poor

16. Dirty insulation is
evidence of air
movement.

17. Blown / Spray Mineral Fiber
Reduce Heat Flow: good
Control Air Leakage: fair
Control Convective Loops: fair
Control Water Vapor: poor

18. Blown / Spray Cellulose and Cotton
Reduce Heat Flow: good
Control Air Leakage: good
Control Convective Loops: good
Control Water Vapor: poor

19. Open Cell (1/2 lb.) Spray Polyurethane
Reduce Heat Flow: good
Control Air Leakage: good
Control Convective Loops: great
Control Water Vapor: depends

20. Closed Cell (2 lb.) Spray Polyurethane
Reduce Heat Flow: great
Control Air Leakage: great
Control Convective Loops: great
Control Water Vapor: great

21. Expanded Polystyrene Boards
Reduce Heat Flow: good
Control Air Leakage: great
Control Convective Loops: great
Control Water Vapor: great

22. Extruded Polystyrene
Reduce Heat Flow: good
Control Air Leakage: great
Control Convective Loops: great
Control Water Vapor: great

23. Polyisocyanurate
Reduce Heat Flow: great
Control Air Leakage: great
Control Convective Loops: great
Control Water Vapor: great

24. R-value
is the resistance a material shows to heat flow across
it. Larger numbers show better insulation values.
It must be a tested value from a government lab,
NOT a claimed “effective” value by the manufacturer.
How Is Insulation Measured?

25. R-value
Radiant barrier products claim that R-value only
measures conductive heat flow and ignores convection
and radiation. In fact, R-values include all three.
Making it a useful way to compare products.
How Is Insulation Measured?

26. Typical R-Values
Open Cell Foam R- value 3.6/inch
Closed cell Foam R-value 6.5/inch

27. What Influences the
Performance of Insulation
R value - higher is better
How much air can flow through it
(air impermeability)
Installation - 4% gaps can lead to
30% less effectiveness

31. Convection heat loss
Insulation Problems
Caused By Poor Installation

36. Vented vs. non-vented roofs
• 2006 IRC (not the IECC) section R806.4
• Allows for unvented roofs if “air-
impermeable” insulation can be used in
contact with the roof sheathing.
• “air-impermeable” is defined – but
basically it meets the requirements for
an air barrier.
• Spray foam and rigid foam meet the
standard, but cellulose does not.

37. Vented vs. non-vented roofs
• Section R806.4 allows for a combination
of air-impermeable insulation and air-
permeable insulation as follows:
In climate zones, 5,6, 7 and 8 any air-
impermeable insulation shall be a vapor
retarder, or shall have a vapor retarder
coating or covering in direct contact with
the underside of the insulation.

38. Vented vs. non-vented roofs
 Either items 5.1, 5.2 or 5.3 are met
depending on the air impermeability of
the insulation directly under the
structural roof sheating.
5.1 Air-impermeable insulation only (rigid
or spray foam) shall be applied in direct
contact with the underside of the
structural roof sheathing to the value in
table R806.4

39. Vented vs. non-vented roofs
5.2. Air-permeable insulation only must
also include air-impermeable insulation
(rigid board or spray foam) shall be
installed directly ABOVE the structural
roof sheathing as specified in Table
R806.4
5.3. Air-impermeable and air-permeable
insulation. The Air-impermeable shall be
applied in direct contact with the
underside of the structural roof sheathing

40. Vented vs. non-vented roofs
3. cont….as specified in Table R806.4 for
condensation control. The air-permeable
insulation shall be installed directly under
the air-impermeable insulation.

41. Vented vs. non-vented roofs

42. If you insulate with certain types of foam, thick insulation
puts the planet at greater risk than thin insulation!
Download from www.greenbuildingadvisor.com

43. Choose Palo Santo Designs
for your Custom Home Project
Palo Santo Designs LLC is an Award Winning General
Contractor in Santa Fe, specializing in the design and
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unsurpassed in the design and construction of high
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