Exam 2: MNM Key Topics and Concepts
What are the primary functions of enclosures? - correct answer ✔✔keep water out
Prevent Air Leakage
Control Light
Control the Radiation of Heat
Control the Conduction of Heat
Control Sound
What are the secondary functions of enclosures? - correct answer ✔✔Resist Wind Forces
Control Water Vapor
Accommodate Movement
Thermal Expansion/Contraction
Moisture Expansion/Contraction
Structural Movements
Resist Fire - sometimes a primary function, depending on context
Address Installation Requirements for the Exterior Wall
Allow for Maintenance
Weather Gracefully
Where should glass be used at? - correct answer ✔✔-Glass should be used where it can supply
daylighting and provide views, but also limited to prevent overheating, glare, or excessive heat loss
through the envelope.
-Windows that can be opened and closed by the occupants can help reduce energy costs, in some cases
What areas of the envelope should be air-tight? - correct answer ✔✔The entire envelope should be
detailed for air-tightness. Fresh air to be provided by building ventilation system, not by air leakage
through ext. wall
,How can you maximize heat in the winter? - correct answer ✔✔south-facing walls to let in heat and
sunlight
What 3 conditions must be satisfied for water to penetrate a wall? - correct answer ✔✔-There must be
water present at the outer face of the wall.
-There must be an opening through which the water can move.
-There must be a force to move the water through the opening.
-If any one of these conditions is not satisfied, the wall will not leak
How can you prevent water leakage? - correct answer ✔✔-Keep water away from the wall, if possible via
overhangs or projections.
-Try to seal every opening. This "barrier wall" typically proves unreliable.
-Eliminate or neutralize the forces that move water through a wall.
-Provide strategies for internal drainage or secondary defense, via cavities within the wall assembly that
allow for drainage (pressure equalized design and rainscreen design
What are the 5 forces that move water through a wall? - correct answer ✔✔gravity
momentum
surface tension
capillary action
air currents/pressure differentials
How does water get into the building through gravity? - correct answer ✔✔Is a factor in pulling water
through a wall only if the wall includes an inclined plane that slopes into—rather than out of—the
building
-Sometimes a loose gasket or errant bead of sealant can create this condition even if components are
designed correctly
How does water get into the building through momentum? - correct answer ✔✔-Momentum of falling
raindrops can drive water through a wall only if there is a suitably oriented slot or hole that goes
completely through the wall.
-Neutralized by applying a cover to each joint in the wall or by designing each joint as a simple labyrinth
,How does water get into the building through surface tension? - correct answer ✔✔-Causes water to
adhere to the underside of a cladding component.
-Allows water to be drawn into the building.
-Provision of a drip on any underside surface to which water might adhere will eliminate the problem.
How does water get into the building through capillary action? - correct answer ✔✔-This is the surface
tension effect that pulls water through any opening that can be bridged by a water drop.
-Primary force that draws transports water through the pores of a masonry wall.
-Can be eliminated by making each of the openings larger than a drop of water can bridge.
-Can also/alternatively provide a concealed capillary break somewhere inside the opening
What is pressure-equalized wall design? - correct answer ✔✔Allows wind pressure differences between
inside and outside of exterior wall to neutralize themselves
How does pressure-equalized wall design work? - correct answer ✔✔-Create an airtight plane, called the
air barrier, behind the outer face of the wall.
-Air barrier is protected from direct exposure to the outdoors by an unsealed, labyrinth-jointed layer
known as the rainscreen.
-Between the rainscreen and air barrier is a space known as the pressure equalization chamber (PEC
What are pressure-equalized chambers? - correct answer ✔✔-Pressure-equalized chambers must be
divided into compartments small enough that the volumes of air cannot rush through the joints in
higher-pressure areas of the face and flow across the air chamber to lower-pressure areas, carrying
water with them.
-PECs are normally no taller than one story or wider than one or two column bays. May be much smaller
in some applications
Rainscreen principal vs. Rainscreen cladding - correct answer ✔✔-The term rainscreen principal
originated with the concept of pressure-equalized wall design, and at one time it was used exclusively in
reference to pressure-equalized cladding systems.
, -More recently, the term rainscreen cladding has come to be applied more broadly to any cladding
system with a system of internal drainage, regardless of the extent of compartmentalization of the
drainage space and the degree of pressure equalization that can be achieved.
What are sealant joints? - correct answer ✔✔seams that are closed with rubberlike compounds
What is the purpose of sealant? - correct answer ✔✔Role of sealant is to fill the joints between wall
components, preventing the flow of air and/or water while still allowing reasonable dimensional
tolerances for assembly and reasonable amounts of subsequent movement between the components
What is the typical width of sealant joints? - correct answer ✔✔Sealant joint widths are usually 3/8 to ¾
inch, but can be as small as ¼ inch and sometimes range up to 1 inch or more
What is gunnable sealant? - correct answer ✔✔-Viscous, sticky liquids that are injected into the joints of
a building with a sealant gun.
-They cure within the joint to become rubberlike materials that adhere to the surrounding surfaces and
seal the joint against the passage of air and water
What are low-range sealants? - correct answer ✔✔also called caulks, are materials with very limited
elongation (stretching and squeezing) capabilities, up to +/- 5% of the width of the joint.
What are high-range sealants? - correct answer ✔✔-High-range sealants can safely sustain elongations
of up to +/- 50 to 100% of the width of the joint.
-This category includes polysulfides, polyurethanes, and silicones.
-They do not shrink during curing
What are the 3 types of solid materials used for sealing seams in building exterior walls? - correct answer
✔✔gaskets
preformed cellular tape sealants
preformed solid tape sealants
What are gaskets? - correct answer ✔✔strips of various fully cured elastomeric (rubberlike) materials
What are the primary functions of enclosures? - correct answer ✔✔keep water out
Prevent Air Leakage
Control Light
Control the Radiation of Heat
Control the Conduction of Heat
Control Sound
What are the secondary functions of enclosures? - correct answer ✔✔Resist Wind Forces
Control Water Vapor
Accommodate Movement
Thermal Expansion/Contraction
Moisture Expansion/Contraction
Structural Movements
Resist Fire - sometimes a primary function, depending on context
Address Installation Requirements for the Exterior Wall
Allow for Maintenance
Weather Gracefully
Where should glass be used at? - correct answer ✔✔-Glass should be used where it can supply
daylighting and provide views, but also limited to prevent overheating, glare, or excessive heat loss
through the envelope.
-Windows that can be opened and closed by the occupants can help reduce energy costs, in some cases
What areas of the envelope should be air-tight? - correct answer ✔✔The entire envelope should be
detailed for air-tightness. Fresh air to be provided by building ventilation system, not by air leakage
through ext. wall
,How can you maximize heat in the winter? - correct answer ✔✔south-facing walls to let in heat and
sunlight
What 3 conditions must be satisfied for water to penetrate a wall? - correct answer ✔✔-There must be
water present at the outer face of the wall.
-There must be an opening through which the water can move.
-There must be a force to move the water through the opening.
-If any one of these conditions is not satisfied, the wall will not leak
How can you prevent water leakage? - correct answer ✔✔-Keep water away from the wall, if possible via
overhangs or projections.
-Try to seal every opening. This "barrier wall" typically proves unreliable.
-Eliminate or neutralize the forces that move water through a wall.
-Provide strategies for internal drainage or secondary defense, via cavities within the wall assembly that
allow for drainage (pressure equalized design and rainscreen design
What are the 5 forces that move water through a wall? - correct answer ✔✔gravity
momentum
surface tension
capillary action
air currents/pressure differentials
How does water get into the building through gravity? - correct answer ✔✔Is a factor in pulling water
through a wall only if the wall includes an inclined plane that slopes into—rather than out of—the
building
-Sometimes a loose gasket or errant bead of sealant can create this condition even if components are
designed correctly
How does water get into the building through momentum? - correct answer ✔✔-Momentum of falling
raindrops can drive water through a wall only if there is a suitably oriented slot or hole that goes
completely through the wall.
-Neutralized by applying a cover to each joint in the wall or by designing each joint as a simple labyrinth
,How does water get into the building through surface tension? - correct answer ✔✔-Causes water to
adhere to the underside of a cladding component.
-Allows water to be drawn into the building.
-Provision of a drip on any underside surface to which water might adhere will eliminate the problem.
How does water get into the building through capillary action? - correct answer ✔✔-This is the surface
tension effect that pulls water through any opening that can be bridged by a water drop.
-Primary force that draws transports water through the pores of a masonry wall.
-Can be eliminated by making each of the openings larger than a drop of water can bridge.
-Can also/alternatively provide a concealed capillary break somewhere inside the opening
What is pressure-equalized wall design? - correct answer ✔✔Allows wind pressure differences between
inside and outside of exterior wall to neutralize themselves
How does pressure-equalized wall design work? - correct answer ✔✔-Create an airtight plane, called the
air barrier, behind the outer face of the wall.
-Air barrier is protected from direct exposure to the outdoors by an unsealed, labyrinth-jointed layer
known as the rainscreen.
-Between the rainscreen and air barrier is a space known as the pressure equalization chamber (PEC
What are pressure-equalized chambers? - correct answer ✔✔-Pressure-equalized chambers must be
divided into compartments small enough that the volumes of air cannot rush through the joints in
higher-pressure areas of the face and flow across the air chamber to lower-pressure areas, carrying
water with them.
-PECs are normally no taller than one story or wider than one or two column bays. May be much smaller
in some applications
Rainscreen principal vs. Rainscreen cladding - correct answer ✔✔-The term rainscreen principal
originated with the concept of pressure-equalized wall design, and at one time it was used exclusively in
reference to pressure-equalized cladding systems.
, -More recently, the term rainscreen cladding has come to be applied more broadly to any cladding
system with a system of internal drainage, regardless of the extent of compartmentalization of the
drainage space and the degree of pressure equalization that can be achieved.
What are sealant joints? - correct answer ✔✔seams that are closed with rubberlike compounds
What is the purpose of sealant? - correct answer ✔✔Role of sealant is to fill the joints between wall
components, preventing the flow of air and/or water while still allowing reasonable dimensional
tolerances for assembly and reasonable amounts of subsequent movement between the components
What is the typical width of sealant joints? - correct answer ✔✔Sealant joint widths are usually 3/8 to ¾
inch, but can be as small as ¼ inch and sometimes range up to 1 inch or more
What is gunnable sealant? - correct answer ✔✔-Viscous, sticky liquids that are injected into the joints of
a building with a sealant gun.
-They cure within the joint to become rubberlike materials that adhere to the surrounding surfaces and
seal the joint against the passage of air and water
What are low-range sealants? - correct answer ✔✔also called caulks, are materials with very limited
elongation (stretching and squeezing) capabilities, up to +/- 5% of the width of the joint.
What are high-range sealants? - correct answer ✔✔-High-range sealants can safely sustain elongations
of up to +/- 50 to 100% of the width of the joint.
-This category includes polysulfides, polyurethanes, and silicones.
-They do not shrink during curing
What are the 3 types of solid materials used for sealing seams in building exterior walls? - correct answer
✔✔gaskets
preformed cellular tape sealants
preformed solid tape sealants
What are gaskets? - correct answer ✔✔strips of various fully cured elastomeric (rubberlike) materials
