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Term 3 - Load Calculations > Power point > Flashcards

Power point Flashcards

1
Q

What are some cons of installing larger equipment?

A
  1. Cost more
  2. Requires large air distr.
  3. short cycling
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2
Q

Oversized air conditioning equipment will cool faster which decreases the ______________ effect

A

dehumidification

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3
Q

Undersized heating/cooling systems will not be able to ____________ set-point

A

maintain

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4
Q

True or False?

It is more beneficial to have your Heat/AC run all day vs periodically in extreme conditions. Why?

A

True. It will never catch up if extreme set-points are desired in extreme conditions

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5
Q

What is required in order to qualify for many government rebates?

A

Heat gain/loss calculation

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6
Q

Heat flows from hot to cold until?

A

temperatures are equalized

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7
Q

In warmer months, heat leaks ____ the structure

A

in

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8
Q

In colder months, heat leaks ____ the structure

A

out

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9
Q

Rule of thumb load estimate is the first type of load estimate that occurs up front in the design process

it includes

A

sqft
btuh
cfm
gpm

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10
Q

Temperature differential is the difference between the _______ and ______ of the building

A

inside and outside

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11
Q

As the TD increases the _________ _____ increases and rise versa

A

transfer rate

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12
Q

Name three environment effects on a building envelope

A
  1. solar gains (transfer gain tg.)
  2. humidity grains
  3. wind (infiltration gain ig)
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13
Q

True or False?

Daily range is the TD from morning to night

A

True

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14
Q

What is the typical design indoor temperature in heating season?

A

70F

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15
Q

Typical indoor design temperature in cooling season?

A

75F

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16
Q

Name 4 heat loads for heating

A
  1. heat escaping through cracks
  2. poor insulation
  3. heat transferring to colder areas
  4. exposure to wind forcing cold air in
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17
Q

Name 4 heat loads for cooling

A
  1. sun through windows
  2. cracks and openings
  3. sun exposure on outside of building
  4. heat from appliances
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18
Q

What is the R value used for?

A

rate the thermal resistance of insulation materials

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19
Q

The higher the R value, the _______ it is for heat to pass through the material

A

harder

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20
Q

If the wall is made up of different materials, how is the R value calculated?

A

The R value of each material used is added for a total R

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21
Q

Heat ________ is the heat conducted through walls, ceilings, and floors when. temperature difference is present

A

leakage

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22
Q

The amount of heat that will pass through 1ftsq of material 1’’ thick in 1 hour when the temperature difference is 1F is known as ?

A

Thermal conductivity (K value)

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23
Q

High __ values indicate high rate of heat transfer

A

K

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24
Q

Amount of heat that will pass through 1ftsq of material that is NOT 1’’ thick in 1 hour when the temperature difference is 1F is known as?

A

C-value

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25
Q

What is the difference between C and K values?

A

K value is based on material that IS 1’’ thick.

C value is based on material that is NOT 1’’ thick

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26
Q

How to determine thermal conductance?

A

Find on chart and divide K value of each material by its thickness

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27
Q

What is Thermal Resistance (R value)

A

Resistance to heat transfer

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28
Q

Higher R value indicates ________ heat transfer

A

slower

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29
Q

What are some examples of composite building materials?

A

wood, drywall, siding

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30
Q

Formula for calculating homogenous materials R value?

A

R = 1/C (using c factor)

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31
Q

Formula for calculating composite building materials R value?

A

RT = R1 + R2 + R3

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32
Q

What is Thermal transmittance? (U value)

A

Similar to C-value but includes adjustment for boundary air films

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33
Q

Thermal Transmittance (U value)
Formula U = 1/Rof +R1 + R2 + R3 + Rif

What does Rof and Rif mean?

A

Thermal resistance of outside air film and inside air film

34
Q

The U-value describes the thermal _________ of a material

A

conductivity

35
Q

The higher the U value, the _______ it is for heat to pass through a material

A

easier

36
Q

Use construction materials with high __ values and low __ values

A

high r values low u values

37
Q

R and U values are _______ of each other

A

inverse

U= 1/R

38
Q

Summertime indoor design temperature and humidity?

A

75F (24C) @50% relative humidity

39
Q

The rate of heat transfer through a wall is this formula:

Describe each variable

A

Q=U-value x TD x Area

Q = heat in btuh
U-value = U-value of the wall
TD = TD across the wall
Area = Area of the wall

40
Q

Do partition walls require a separate heat loss calculation?

A

yes

41
Q

_________ and ________ are calculated separately in wall heat loss calculations

A

windows and doors

42
Q

What is the net wall area?

A

combined area of windows and doors

43
Q

How to calculate total wall area?

A

perimeter x ceiling height

44
Q

Where to find heat transfer factor (U)

A

from tables

45
Q

How to calculate Transmission gain and loss through a wall?

A

Q= U value x TD x area

46
Q

Heat loss through __________ walls account for a large percentage of total heat loss of a structure

A

exposed walls

47
Q

It is important to know what lumber was framed with and the __ value of the insulation

A

R value

48
Q

Describe heat lag

A

time it takes for heat to travel through a substance heated on one side

49
Q

Normal buildings have _ to _ hours of heat lag

A

3 to 4 hours

50
Q

Well insulated buildings or thick walls have what benefits?

A

Transfer heat into room during the night

Provide warmth after temperature drops

51
Q

Calculate the heat transfer rate using k-values

A

R = 1/K x thickness

52
Q

Calculate the heat transfer rate using C -values

A

Rt= 1/c1 + 1/c2 + 1/c3

53
Q

U is the inverse of R so the formula is?

A

1/Rt

54
Q

Difference between gross and net wall area?

A

gross is before doors or windows net is after

55
Q

How to calculate heat loss through windows and doors?

A

Same method as walls

56
Q

How to calculate heat loss through roofs?

A

Same method as walls but calculating with geometry

57
Q

What is a partition wall?

A

Separates conditioned interior space from an unconditioned interior space

58
Q

TD through partition walls?

A

Indoor design temperature and temperature of unconditioned space

59
Q

The rate of heat loss ______ as the floor gets deeper?

A

decreases

60
Q

Heat loss through floors located above unconditioned spaces is calculated the same as?

A

partition walls

61
Q

Heat loss through slab floors is calculated using the ________ ft of the exposed slab edge not the area of the floor

A

running feet

62
Q

Heat loss through cracks, openings, and deficiencies in structure calculated by;

A

Q-infiltration = 1.08 x cfm x TD

1.08 = constant
com = cubic feet of air entering
TD = design temp diff

63
Q

Duct losses to unconditioned spaces such as attics, ceiling spaces, etc is when?

A

heat is lost passing through an unconditioned space

64
Q

What is one of the major sources for heat gain?

A

windows

65
Q

When calculating heat gain (cooling mode) take into account; (4)

A
  1. envelope contact w outside
  2. occupancy
  3. heat/moisture generating elements
  4. orientation of house
66
Q

Heat gain through exposed exterior walls/Doors is calculated by;

A

Qwall= U value x TDcool x Area
Qdoor = U value x TD cool x Area

Qwall = heat attributed to wall
U value = u value of door
TDcool= two part chart needed
Area = area of the wall

67
Q

Triple glazed glass has a ____ R value and ____ U value

A

high r low u

68
Q

Name 4 types of windows

A
  1. Casement
  2. Double Hung
  3. FIxed
  4. Sliding
69
Q

Infiltration is best described as;

A

air pressure inside is lower than outside due to air leaking in

70
Q

Exfiltration is best described as;

A

air pressure inside is higher than outside due to air leaking out

71
Q

What environmental element causes infiltration and exfiltration?

A

wind

72
Q

Common rule of thumb for building pressure is

A

supply exceeds return + exhaust by 10%

73
Q

Negative pressure is calculated by adding return air cfm and

A

direct exhaust air cfm

74
Q

Balanced pressure means air in =

A

supply air cfm

75
Q

Are internal loads calculated when sizing heat capacity?

A

NO

76
Q

Greatest need for heat is during _________ hours

A

unoccupied hours

77
Q

Warm-up ______ ________ reserve capacity is recommended if set-point setback is used during unoccupied times

A

safety factor

78
Q

Heat is transferred from the body by; (4)

A
  1. Conduction
  2. Convection
  3. Radiation
  4. Evaporation
79
Q

Calculate fluorescent lighting heat gain to space and to return air plenum

A

space = watts x 4.1btuh/watt x 0.60

ra= watts x 4.1btuh/watt x 0.40

80
Q

In a low pressure system, how much static is there and how much cfm is lost?

A

under 2’’ static and 5% cfm lost

81
Q

In a mid pressure system, how much static is there and how much com is lost?

A

2-6’’ static and 2% to 5% cfm is lost

82
Q

In a high pressure system, how much static is there and how much com is lost?

A

over 6’’ static and 1% cfm lost

Term 3 - Load Calculations (4 decks)

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