Enclosure

Question 1

Enclosure Priority Order

Answer 1

In order of importance, enclosures must provide: (1) Support, (2) Rain control, (3) Airflow control, (4) Thermal control, (5) Vapor control.

Question 2

Rain Screen System

Answer 2

A wall assembly that manages water from outside in: mechanical water prevention (e.g. brick), drainage space, insulation, water/air/vapor control layers with flashing, sheathing, structure, and interior finish.

Question 3

Water Barriers

Answer 3

Materials used to prevent water infiltration, including peel-and-stick membranes, liquid-applied systems, housewrap (Tyvek), and tar paper. Seams and penetrations are critical; must be lapped properly and sealed.

Question 4

Blower Door

Answer 4

A device used to measure building airtightness by measuring how many cubic feet of air leave the building under pressure.

Question 5

ACH (Air Changes Per Hour)

Answer 5

A formerly used measure of building airtightness indicating how many times per hour the entire volume of air in a building is replaced.

Question 6

CFM/SF (Cubic Feet per Square Foot)

Answer 6

Current standard measure of building airtightness: cubic feet of air per square foot of skin area, measured at 50-75 pascals of pressure. Allows comparison between buildings of different sizes.

Question 7

Air Tightness Target (Barrier)

Answer 7

Good target for the air barrier itself: <0.004 CFM/SF.

Question 8

Air Tightness Target (Opaque Skin Assembly)

Answer 8

Good target for the overall opaque skin assembly: <0.04 CFM/SF.

Question 9

Air Tightness Target (Whole Building)

Answer 9

Good target for the whole building: <0.4 CFM/SF.

Question 10

Air Pumping

Answer 10

Pressure-driven movement of air in and out of a building assembly due to insufficient airtightness; can cause flutter and moisture problems. Requires very tight construction to avoid.

Question 11

SIPs (Structural Insulated Panels)

Answer 11

Structural insulation panels that eliminate thermal bridging by integrating structure and insulation.

Question 12

Faced Polyisocyanurate / Nailboard

Answer 12

An insulation panel similar to an open-faced SIP; polyisocyanurate foam with a facing. Also called “Polyiso” or “Nailboard.”

Question 13

Expanded Polystyrene (EPS)

Answer 13

Regular styrofoam insulation. Water tolerant, air permeable, cheaper than XPS, flammable, ok below grade. Can serve as water/vapor/air barrier if detailed correctly.

Question 14

Extruded Polystyrene (XPS)

Answer 14

Foam board insulation (styrofoam). Water tolerant, air permeable, better insulator per inch than EPS but more expensive, flammable, ok below grade. Can serve as water/vapor/air barrier if detailed correctly.

Question 15

Closed-Cell Spray Foam (CCSPF)

Answer 15

Hard spray polyurethane foam. Continuous, handles long water exposure, ok below grade, mold resistant. Acts as an effective air and vapor barrier.

Question 16

Open-Cell Spray Foam

Answer 16

Spongy spray foam insulation. Not suitable for wet or below-grade conditions; good for noise insulation; less expensive than closed-cell; mold resistant. Note: some sources debate whether it qualifies as an air barrier at sufficient thickness.

Question 17

Glass Fiber Insulation

Answer 17

Fibrous insulation available in interior and exterior versions. Cannot serve as an air, rain, or vapor barrier. Exterior version can be used as a capillary break drainage plane.

Question 18

Mineral Wool (Rockwool)

Answer 18

Fibrous insulation available in interior and exterior versions. Cannot serve as an air, rain, or vapor barrier. More moisture resistant and more expensive than glass fiber. Exterior version can be used as a capillary break drainage plane.

Question 19

Air Infiltration

Answer 19

Air coming into a building through gaps in the building envelope; more likely to cause condensation than vapor diffusion.

Question 20

Vapor Diffusion

Answer 20

The slow, molecular movement of moisture through permeable materials (as opposed to air infiltration). A separate mechanism from air movement.

Question 21

Perms

Answer 21

Unit of measurement for vapor permeability: 1 grain of water vapor per hour, per square foot, per inch of mercury pressure differential. Higher perm value = more moisture moves through.

Question 22

Classes of Vapor Retarders

Answer 22

Classification of vapor control materials by perm rating: Class I (<0.1 perm), Class II (0.1-1.0 perm), Class III (1-10 perms). Anything over 10 perms is considered vapor permeable.

Question 23

Class I Vapor Retarder

Answer 23

<0.1 perm. Materials include foil, thick polyethylene, plastics, and metals. Considered a Vapor Barrier.

Question 24

Class II Vapor Retarder

Answer 24

0.1-1.0 perm. Materials include some plywoods, kraft paper, and rigid foam insulation (depending on depth and taping). Considered a Vapor Retarder.

Question 25

Class III Vapor Retarder

Answer 25

1-10 perms. Materials include latex paint. Considered a Vapor Retarder.

Question 26

Vapor Barrier

Answer 26

A Class I vapor retarder (<0.1 perm) that is highly effective at stopping moisture movement. Examples: foil and thick polyethylene.

Question 27

Vapor Retarder

Answer 27

A Class II or Class III vapor control material (0.1-10 perms) that slows but does not stop moisture movement.

Question 28

Vapor Control Climate Rule (Zones 1-4)

Answer 28

In southern climate zones 1-4, you can generally use no vapor barrier.

Question 29

Vapor Control Climate Rule (Zones 1-6)

Answer 29

In climate zones 1-6, do not use Class I vapor barriers (summers are too humid). Use a vapor retarder such as drywall with latex paint instead.

Question 30

Vapor Control Climate Rule (Zones 5+)

Answer 30

In northern climate zones 5+, use Class I or II vapor barriers on the warm side of insulation.