Deck 5: Properties of the Envelope-I Thermal Properties

Question 1

A wet or moist material provides a higher R- value than if the same material is dry.

Answer 1

False

Question 2

Air is a good thermal insulator, provided that it exists in large volumes.

Answer 2

False

Question 3

Within an air space (cavity), the mode of heat transfer is primarily by

A)conduction.
B)convection.
C)radiation.
D)both A and B.
E)both B and C.

Answer 3

E

Question 4

IECC is an acronym for

A)International Energy Cooperation Council.
B)Institute for Energy Conservation and Codification.
C)Institute for Energy Conversion and Conservation.
D)International Energy Conservation Code.
E)none of the above.

Question 5

Apart from the climate of the location, the other factors that affect energy- conscious building design are

A)building orientation and building shape.
B)building envelope.
C)site conditions.
D)all of the above.
E)A and B.

Question 6

Within a solid, the mode of heat transfer is by

A)convection.
B)radiation.
C)conduction.
D)both A and B.
E)both B and C.

Question 7

The concept of aged R- value is applicable to

A)perlite board insulation.
B)fiberglass insulation.
C)all insulating materials.
D)all building materials.
E)insulating materials that contain HCFC gas.

Question 8

For the same thickness, which of the following materials has the smallest R- value?

A)Gypsum
B)Expanded polystyrene
C)Extruded polystyrene
D)Polyisocyanurate
E)Fiberglass

Question 9

The R- value of a 1- in.- thick extruded polystyrene board is 5.0. If the R- value of a 1- in.- thick brick wall is 0.2, how thick should the brick wall be to equal the R- value of 1- in.- thick extruded polystyrene?

A)50 in.
B)10 in.
C)5 in.
D)2)5 in.
E)None of the above

Question 10

The R- value of a single glass sheet, without considering the film resistances, is approximately

A)4)0.
B)1)0.
C)3)0.
D)0)
E)2)0.

Question 11

The emissivity of a material lies between

A)1 and 2.
B)0 and 100.
C)0 and 1.
D)1 and 10.
E)none of the above.

Question 12

The unit for the measure of energy in the U.S. system of units is

A)Joule.
B)calorie.
C)Watt- hour.
D)Btu.
E)all of the above.

Question 13

The R- value of a building assembly in the SI system is referred to as the

A)SI- value.
B)R- value (SI).
C)RS- value.
D)RSI- value.
E)none of the above.

Question 14

Which of the following insulating materials contain HCFC gas within their voids?

A)Polyurethane
B)Extruded polystyrene
C)Polyisocyanurate
D)All of the above
E)Only B and C

Question 15

One of the main reasons for using HCFC gas in some insulating materials is that it

A)makes the material more economical.
B)makes the material more resistant to decay.
C)makes the material noncombustible.
D)increases the strength of the material.
E)none of the above.

Question 16

The R- value of a 2- in.- thick material is 4.0. What is the R- value of the same material if its thickness is 1 in.?

A)6)0
B)1)0
C)0)5
D)8)0
E)None of the above

Question 17

The R- value of a single glass sheet, including the film resistances, is approximately

A)4)0.
B)0)
C)3)0.
D)2)0.
E)1)0.

Question 18

The unit for the measure of energy in the SI system of units is

A)calorie.
B)Btu.
C)Joule.
D)Watt.

Question 19

For the same thickness, which of the following materials has the highest R- value?

A)Extruded polystyrene
B)Expanded polystyrene
C)Polyisocyanurate
D)Gypsum
E)Fiberglass

Question 20

Insulating materials that contain HCFC gas within their cells have a higher R- value than those that contain air within their cells.

Question 21

The walls of a conditioned basement must be insulated over the entire depth of the wall.

Question 22

In which of the following buildings will heat flow occur unidirectionally?

A)Intermittently heated buildings
B)Intermittently cooled buildings
C)Continuously heated or cooled buildings
D)All of the above
E)None of the above

Question 23

The U.S. Department of Energy's climate zones are based on

A)the exterior air temperature.
B)the exterior humidity.
C)precipitation.
D)A and B.
E)B and C.

Question 24

The use of aluminum foil in attics is more useful in warm climates than in cold climates.

Question 25

The coastal region of the western United States lies in

A)climate zone 2(A).
B)climate zone 3(A).
C)climate zone 1(A).
D)climate zone 4(A).
E)none of the above.

Question 26

The approximate R- value of an air space in a wall with an aluminum foil lining is

A)R- 1.5.
B)R- 2.0.
C)R- 2.5.
D)R- 1.
E)none of the above.

Question 27

A building assembly with a higher U- value is thermally more insulating than one with a lower U- value.

Question 28

The units of measurement of U- value and U- factor are the same.

Question 29

When an aluminum foil is used in attic spaces, it is

A)laminated to fiberglass insulation.
B)laminated to outside- facing surface of roof sheathing.
C)laminated to ceiling gypsum board.
D)laminated to inside- facing surface of roof sheathing.
E)sandwiched between ceiling gypsum board and fiberglass insulation.

Question 30

The approximate R- value of an air space in a wall is

A)R- 2.5.
B)R- 1.
C)R- 2.0.
D)R- 1.5.
E)none of the above.

Question 31

The F- factor relates to heat flow through

A)above- ground opaque wall.
B)a concrete roof slab.
C)a concrete slab- on- ground.
D)basement wall.
E)glazed wall.

Question 32

Aluminum foil is commonly used in building assemblies because it

A)lowers heat transfer due to conduction.
B)lowers heat transfer due to radiation.
C)lowers heat transfer due to convection.
D)lowers heat transfer due to conduction as well as convection.
E)lowers heat transfer due to convection as well as radiation.

Question 33

A wall assembly (total area = 100 ft2)consists of 80 ft2 of opaque wall with an R- value of R- 20 and a 20 ft2 of window whose R- value is R- 2. The effective (overall)R- value of the entire wall assembly is approximately

A)R- 15.
B)R- 7.
C)R- 11.
D)R- 3.
E)none of the above.

Question 34

A concrete slab- on- ground does not require to be insulated in warm climates.

Question 35

In climates where a concrete slab- on- ground must be insulated, it should be insulated under its entire area.

Question 36

Which of the following steel stud wall assemblies gives a higher overall R- value? In both assemblies, the total amount of insulation is R- 15.

A)Assembly B has an exterior insulating sheathing of R- 3 and within- stud insulation of R- 12
B)Assembly A has an exterior insulating sheathing of R- 5 and within- stud insulation of R- 10

Question 37

Like color, emissivity is a property of the surface of the material, not of the entire body of the material.

Question 38

The R- value of a building assembly is influenced by the inside and outside air films. The sum of the R- values of these two films (Rsi + Rso)is approximately equal to

A)10.0.
B)5)0.
C)1)0.
D)0)1.
E)none of the above.

Question 39

The U- value and R- value of an assembly are related to each other by which relationship?

A)U + R = 1
B)(U)(R)= 1.0
C)U = R
D)U2 + R2 = 1.0
E)None of the above

Question 40

Which of the following materials has the smallest value of emissivity?

A)Fiberglass
B)Highly polished metal
C)Metal
D)Highly compressed fiberglass
E)All of the above have the same value of emissivity.

Question 41

Extruded polystyrene (XPS)insulation and polyisocyanurate (ISO)insulation are both closed- cell plastic foams, consisting essentially of the same chemical composition, and both have HCFC gas trapped in cell cavities. Yet their q- values are different. The q- value for ISO = 6.0 and that for XPS = 5.0. Why is that so?

Question 42

Of the two polystyrene foam insulations, one foamed with air and the other foamed with HCFC gas, which one is made by the extrusion process and which one is made by the molding process?

Question 43

Explain why the wetting of an insulating material reduces its R- value. In which situations is this fact is important?

Question 44

In which of the following locations is blown- in insulation most commonly used?

A)Attic spaces
B)Stud wall cavities
C)Top of a flat roof
D)Masonry wall cavities

Question 45

For energy conservation, materials with high thermal mass are effective in climates in which the heat flow through the building envelope is

A)absent during a large part of the year.
B)unidirectional within a 24- h period during a large part of the year.
C)bidirectional within a 24- h period during a large part of the year.

Question 46

Provide the approximate q- value (R- value for 1 in. thick material)for EPS and XPS.

Question 47

The International Energy Conservation Code provides

A)two alternative paths of compliance.
B)four alternative paths of compliance.
C)three alternative paths of compliance.
D)five alternative paths of compliance.
E)none of the above.

Question 48

In this text, we have used two quantities to specify the insulating value of a material-q- value and R- value. Explain the difference between the two.

Question 49

A wall framed with wood or steel studs is a mass wall.

Question 50

Which of the following insulating materials is available in the form of batts?

A)Expanded perlite
B)Fiberglass
C)Extruded polystyrene
D)Insulating concrete
E)None of the above

Question 51

The composition of an insulating material is such that its solid constituents trap air (or gas)in extremely small volumes. Why does the entrapment of large volumes of air (or gas)reduce the insulating property of the material?

Question 52

Why are insulating materials low- density (light- weight)materials?

Question 53

Name the three modes of heat transfer. Which of these modes is the dominant mode in building assemblies?

Question 54

Which of the following insulating materials is available in the form of rigid boards?

A)Extruded polystyrene
B)Fiberglass
C)Insulating concrete
D)Rock wool
E)None of the above

Question 55

What is the unit of energy in U.S. system of units? In SI system of units?

Question 56

Which of the following insulations is combustible?

A)Perlite board
B)Fiberglass
C)Vermiculite
D)Extruded polystyrene (XPS)board
E)Foamed concrete

Question 57

Which modes of heat transfer occur in gases, such as air?

Question 58

Foamed concrete is generally used as insulation in

A)foundations.
B)walls.
C)steep roofs.
D)all of the above.
E)none of the above.

Question 59

Which of the following plastic foam insulation contains air within its voids?

A)Expanded polystyrene (EPS)board (bead board)
B)Polyisocyanurate board (ISO board)
C)Extruded polystyrene (XPS)board

Question 60

Insulation is most effective if it is placed

A)in the center of the assembly.
B)on the outside face of the assembly.
C)on the inside face of the assembly.

Question 61

Why do we specify LTTR value for some insulating materials?

Question 62

Which modes of heat transfer occur in a vertical air space?

Question 63

What does the acronym LTTR stand for and to which materials is it related?

Question 64

In which climate situations would you consider insulating a concrete slab- on- ground?

Question 65

An 11- in. thick precast concrete curtain wall consists of a 3- in.- thick exterior layer of (normal- weight)concrete, 6- in.- thick interior layer of (normal- weight)concrete and a 2- in- thick XPS insulation sandwiched between the two concrete layers. What is the total R- value of the assembly, considering air- to- air heat transfer? q- value of normal- weight concrete = 0.15; q- value of XPS = 5.0

Question 66

The R- value of an assembly for air- to- air heat transfer is 20. What is its U- value?

Question 67

A concrete slab- on- ground requires to be insulated in cold climates. We generally do not insulate it by placing insulation under the entire slab. Why?

Question 68

Which type of insulation is preferred for below ground insulation (basements and concrete slabs- on- ground)?

Question 69

The R- value of a concrete tilt- up wall is 1.20. What is its R- value considering air- to- air heat transfer through it?

Question 70

What is the R- value of air space in an attic? What is its corresponding R- value if it is lined with aluminum foil (assume warm climate zone so that heat flow is downward)?

Question 71

What is thermal bridging as it relates to building envelope design?

Question 72

What is the difference between: (i)a multilayer assembly in series combination and (ii)a multilayer assembly in parallel combination?

Question 73

Is the effective R- value of the following two walls the same or different? Explain.
(a)A 4- in.- thick metal stud wall with studs spaced 24 in. on center and 4- in- thick fiberglass insulation between studs.
(b)A 4- in.- thick metal stud wall with studs spaced 12 in. on center and 4- in- thick fiberglass insulation between studs.

Question 74

How is aluminum foil lining typically provided in an attic air space?

Question 75

Apart from air and HCFC gas, which other gases are used to provide insulation?

Question 76

If one surface of a vertical air space is lined with aluminum foil, its R- value = 2.5. What will be its R- value if both surfaces of the air space are lined with aluminum foil?

Question 77

Name three insulating materials foamed with HCFC gas and their acronyms.

Question 78

What is the R- value of a vertical air space? What is its R- value if one surface of the air space is lined with aluminum foil?

Question 79

What is the difference between U- factor and F- factor and between U- factor and C- factor?

Question 80

Why do we generally use the R- value of an assembly corresponding to its air- to- air heat transfer?