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Mechanical and Electrical Systems in Architecture, Engineering, and Construction

Joseph B. Wujek, Frank R. Dagostino

Chapter 4

HEATING LOAD COMPUTATIONS FOR BUILDINGS - all with Video Answers

Educators

Chapter Questions

01:20

Problem 1

What is transmission heat loss, and where does it occur in a building?

Ma Ednelyn Lim
Ma Ednelyn Lim
Numerade Educator
01:20

Problem 2

What is infiltration heat loss, and where does it occur in a building?

Ma Ednelyn Lim
Ma Ednelyn Lim
Numerade Educator
01:04

Problem 3

Define and describe the difference between building heat loss and building heat load.

Dading Chen
Dading Chen
Numerade Educator

Problem 4

The transmission heat load is computed by the equation, UA( $\Delta \mathrm{T})$. Describe each term in this equation.

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Problem 5

With respect to a heating load, what is a pick-up allowance?

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01:30

Problem 6

Air infiltration rates (i.e., air change per hour) vary considerably. Describe typical infiltration rates in new and older buildings.

Manik Pulyani
Manik Pulyani
Numerade Educator

Problem 7

How is the outside design temperature determined?

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Problem 8

When are the following winter design conditions used?
a. $99.6 \%$ dry bulb temperature
b. $99.0 \%$ dry bulb temperature

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02:04

Problem 9

Find the outside design temperature for the geographical location at which you reside.

Kayleah Tsai
Kayleah Tsai
Numerade Educator
01:27

Problem 10

Describe the degree-day, and how it will affect the amount of fuel used per year.

Linh Vu
Linh Vu
Numerade Educator
02:02

Problem 11

How does seasonal efficiency of the heating system affect heating costs?

Manik Pulyani
Manik Pulyani
Numerade Educator

Problem 12

List some of the ways in which the heat loss of a building can be controlled.

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02:33

Problem 13

Why is limiting of window area important in keeping the heat loss low?

Jonathan Everett
Jonathan Everett
Numerade Educator

Problem 14

Describe three methods used to estimate energy consumption.

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02:11

Problem 15

Calculate the number of simple degree-days in a day if the high temperature were $40^{\circ} \mathrm{F}$ and the low temperature were $0^{\circ} \mathrm{F}$.
a. For a base temperature of $65^{\circ} \mathrm{F}$.
b. For a base temperature of $60^{\circ} \mathrm{F}$.
c. For a base temperature of $55^{\circ} \mathrm{F}$.

AG
Ankit Gupta
Numerade Educator
01:11

Problem 16

Calculate the number of simple degree-days in a day if the high temperature were $10^{\circ} \mathrm{C}$ and the low temperature were $0^{\circ} \mathrm{C}$.
a. For a base temperature of $18^{\circ} \mathrm{C}$.
b. For a base temperature of $15^{\circ} \mathrm{C}$.
c. For a base temperature of $12^{\circ} \mathrm{C}$.

Allison Knapp
Allison Knapp
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Problem 17

Calculate the number of simple degree-days in a day if the high temperature were $70^{\circ} \mathrm{F}$ and the low temperature were $50^{\circ} \mathrm{F}$.
a. For a base temperature of $65^{\circ} \mathrm{F}$.
b. For a base temperature of $60^{\circ} \mathrm{F}$.
c. For a base temperature of $55^{\circ} \mathrm{F}$.

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02:11

Problem 18

Calculate the number of degree-days in a 30-day month if every day had an average daily temperature of $30^{\circ} \mathrm{F}$.
a. For a base temperature of $65^{\circ} \mathrm{F}$.
b. For a base temperature of $60^{\circ} \mathrm{F}$.
c. For a base temperature of $55^{\circ} \mathrm{F}$.

AG
Ankit Gupta
Numerade Educator
01:54

Problem 19

Calculate the number of degree-days in a 30-day month if every day had an average daily temperature of $10^{\circ} \mathrm{C}$.
a. For a base temperature of $18^{\circ} \mathrm{C}$.
b. For a base temperature of $15^{\circ} \mathrm{C}$.
c. For a base temperature of $12^{\circ} \mathrm{C}$.

AG
Ankit Gupta
Numerade Educator
31:43

Problem 20

Calculate the annual heat loss (in U.S. units) through the following wall assemblies using U -factors from Table 2.9 (in Chapter 2) and the annual heating degreedays over a typical heating season at the geographical location where you reside. Base your analysis on $1000 \mathrm{ft}^2$ of wall area.
a. $2 \times 4$ wood-framed wall with $\mathrm{R}-11$ insulation
b. $2 \times 6$ wood-framed wall with R-19 insulation
c. 8 in concrete uninsulated wall
d. 8 in solid brick uninsulated wall
e. 8 in concrete masonry unit (CMU) wall, with perliteinsulated cores
f. 14 in thick uninsulated adobe wall
g. 16 in solid $\log$ wall
h. 23 in straw bale (R-1.45/inch) wall
i. $31 / 2$ in structural insulated panel (SIP) with EPS core wall

Ren Jie Tuieng
Ren Jie Tuieng
Numerade Educator
31:43

Problem 21

Calculate the annual heat loss [in metric (SI) units] through the following wall assemblies using U-factors from Table 2.9 (in Chapter 2) and the annual heating degree-days over a typical heating season at the geographical location where you reside. Base your analysis on $100 \mathrm{~m}^2$ of wall area.
a. $38 \mathrm{~mm} \times 88 \mathrm{~mm}$ wood-framed wall with RSI-1.9 insulation
b. $38 \mathrm{~mm} \times 140 \mathrm{~mm}$ wood-framed wall with RSI-3.3 insulation
c. 200 mm standard-weight concrete uninsulated wall
d. 200 mm solid brick uninsulated wall
e. 200 mm CMU wall, with perlite insulated cores
f. 350 mm thick uninsulated adobe wall
g. 400 mm solid $\log$ wall
h. 575 mm straw bale (RSI-0.01/mm) wall
i. 88 mm SIP with EPS core wall

Ren Jie Tuieng
Ren Jie Tuieng
Numerade Educator
31:43

Problem 22

A building has a 9 ft deep basement (foundation) wall that is 160 ft long. The wall has no windows. On average, 8 ft of the wall is below grade (underground). Assume an outside air temperature of $10^{\circ} \mathrm{F}$, an inside temperature of $70^{\circ} \mathrm{F}$, and an average ground temperature of $45^{\circ} \mathrm{F}$.
a. Determine the rate of heat loss through the wall below grade if it is uninsulated.
b. Determine the rate of heat loss through the wall below grade if it is insulated with an R-value of about $12 \mathrm{hr} \cdot{ }^{\circ} \mathrm{F} \cdot \mathrm{ft}^2 / \mathrm{Btu}$.

Ren Jie Tuieng
Ren Jie Tuieng
Numerade Educator
31:43

Problem 23

A building has a 2.4 m deep basement (foundation) wall that is 100 m long. The wall has no windows. On average, 2.1 m of the wall is below grade (underground). Assume the outside air temperature is $-10^{\circ} \mathrm{C}$, the inside temperature is $20^{\circ} \mathrm{C}$, and the average ground temperature is $10^{\circ} \mathrm{C}$.
a. Determine the rate of heat loss through the wall below grade if it is uninsulated.
b. Determine the rate of heat loss through the wall below grade if it is insulated with an R -value of about $2.2^{\circ} \mathrm{C} \cdot \mathrm{m}^2 / \mathrm{W}$.

Ren Jie Tuieng
Ren Jie Tuieng
Numerade Educator
01:02

Problem 24

A commercial building is built on a slab on grade foundation that is a 120 ft by 48 ft rectangular shape. Assume the outside design temperature is $-5^{\circ} \mathrm{F}$. Determine the rate of heat loss through the exterior edge of a concrete slab.
a. For an uninsulated slab edge perimeter.
b. For a slab edge perimeter insulated with 1 in of perimeter insulation (an R-value of about 2.5 ).
c. For a slab edge perimeter insulated with 2 in of perimeter insulation (an R-value of about 5).

Kratika Bhadauria
Kratika Bhadauria
Numerade Educator
01:02

Problem 25

A commercial building is built on a slab on grade foundation that is a 40 m by 18 m rectangular shape. Assume the outside design temperature is $-15^{\circ} \mathrm{C}$. Determine the rate of heat loss through the exterior edge of a concrete slab.
a. For an uninsulated slab edge perimeter.
b. For a slab edge perimeter insulated with 25 mm of perimeter insulation (an RSI-value of about 0.44 ).
c. For a slab edge perimeter insulated with 50 mm of perimeter insulation (an RSI-value of about 0.88 ).

Kratika Bhadauria
Kratika Bhadauria
Numerade Educator
01:30

Problem 26

Calculate the rate of infiltration heat loss of a room with a $380 \mathrm{ft}^2$ floor area and 10 ft high ceilings. Use an inside temperature of $72^{\circ} \mathrm{F}$, an outside ambient temperature of $-5^{\circ} \mathrm{F}$. Assume the heat capacity of air is $0.018 \mathrm{Btu} /$ $\mathrm{ft}^{30} \mathrm{~F}$. Base the analysis on the following hourly air exchange rates:
a. tight, energy efficient construction $(\mathrm{ACH}=0.5)$
b. medium construction $(\mathrm{ACH}=1.0)$
c. loose construction $(\mathrm{ACH}=1.5)$

Manik Pulyani
Manik Pulyani
Numerade Educator
10:23

Problem 27

Calculate the rate of infiltration heat loss of a room with a $42 \mathrm{~m}^2$ floor area and 4 m high ceilings. Use an inside temperature of $21^{\circ} \mathrm{C}$ and an outside ambient temperature of $-15^{\circ} \mathrm{C}$. Assume the heat capacity of air is $0.35 \mathrm{~W} / \mathrm{m}^3$. ${ }^{\circ} \mathrm{C}$. Base the analysis on the following hourly air exchange rates:
a. tight, energy efficient construction $(\mathrm{ACH}=0.5)$
b. medium construction $(\mathrm{ACH}=1.0)$
c. loose construction $(\mathrm{ACH}=1.5)$

Jincy M Saji
Jincy M Saji
Numerade Educator
03:16

Problem 28

A college lecture auditorium is designed for an occupancy of 300 persons. The ASHRAE Standard calls for a minimum outside airflow rate for classrooms of 15 cfm per person. The target inside design temperature is $74^{\circ} \mathrm{F}$ and the outside design temperature is $-5^{\circ} \mathrm{F}$. Determine the sensible heating load from ventilation.

Joseph Lentino
Joseph Lentino
Numerade Educator
02:34

Problem 29

A college lecture auditorium is designed for an occupancy of 300 persons. The ASHRAE Standard calls for a minimum outside airflow rate for classrooms of $2 \mathrm{~L} / \mathrm{s}$ per person. The target inside design temperature is $22^{\circ} \mathrm{C}$ and the outside design temperature is $-15^{\circ} \mathrm{C}$. Determine the sensible heating load from ventilation.

Chai Santi
Chai Santi
Numerade Educator
08:54

Problem 30

A building has a heat loss of $100 \mathrm{MB} t \mathrm{u} / \mathrm{hr}$ at design conditions at the geographical location where you reside. Calculate fuel consumed over the heating season at the geographical location where you reside. Base your analysis on the following fuels and efficiencies:
a. Natural gas ( $80 \%$ efficiency)
b. Natural gas ( $92 \%$ efficiency)
c. Liquid petroleum gas/propane ( $80 \%$ efficiency)
d. Fuel oil number 2 ( $78 \%$ efficiency)
e. Electricity, resistance heating ( $100 \%$ efficiency)
f. Wood (pine) ( $50 \%$ efficiency)
g. Coal ( $60 \%$ efficiency)

Aadit Sharma
Aadit Sharma
Numerade Educator
01:30

Problem 31

For the previous exercise: Approximate the fuel cost over the heating season, based on current energy costs. (It will be necessary for you to contact local suppliers to get local costs.)

Manik Pulyani
Manik Pulyani
Numerade Educator
08:54

Problem 32

A building has a heat loss of $100 \mathrm{MJ} / \mathrm{hr}$ at design conditions at the geographical location where you reside. Calculate fuel consumed over the heating season at the geographical location where you reside. Base your analysis on the following fuels and efficiencies:
a. Natural gas ( $80 \%$ efficiency)
b. Natural gas $(92 \%$ efficiency)
c. Liquid petroleum gas/propane ( $80 \%$ efficiency)
d. Fuel oil number 2 ( $78 \%$ efficiency)
e. Electricity, resistance heating ( $100 \%$ efficiency)
f. Wood (pine) ( $50 \%$ efficiency)
g. Coal ( $60 \%$ efficiency)

Aadit Sharma
Aadit Sharma
Numerade Educator
01:30

Problem 33

For the previous exercise: Approximate the fuel cost over the heating season, based on current energy costs. (It will be necessary for you to contact local suppliers to get local costs.)
TABLE CAN'T COPY.

Manik Pulyani
Manik Pulyani
Numerade Educator

Problem 34

For the office building in the preceding table, compute the following for 2006:
a. Monthly natural gas consumption based on $\mathrm{Btu} / \mathrm{ft}^2$ of floor area.
b. Annual natural gas consumption based on $\mathrm{Btu} / \mathrm{ft}^2$ of floor area.
c. Monthly natural gas consumption normalized for weather conditions (degree-days), based on $\mathrm{Btu} / \mathrm{ft}^2$. ( ${ }^{\circ} \mathrm{F} \cdot \mathrm{day}$ ).
d. Annual natural gas consumption normalized for weather conditions (degree-days), based on $\mathrm{Btu} / \mathrm{ft}^2$. ( ${ }^{\circ} \mathrm{F} \cdot \mathrm{day}$ ).

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Problem 35

For the office building in the preceding table, compute the following for 2007:
a. Monthly natural gas consumption based on Btu/ft ${ }^2$ of floor area.
b. Annual natural gas consumption based on $\mathrm{Btu} / \mathrm{ft}^2$ of floor area.
c. Monthly natural gas consumption normalized for weather conditions (degree-days), based on $\mathrm{Btu} / \mathrm{ft}^2$. ( ${ }^{\circ} \mathrm{F} \cdot \mathrm{day}$ ).
d. Annual natural gas consumption normalized for weather conditions (degree-days), based on $\mathrm{Btu} / \mathrm{ft}^2$. ( ${ }^{\circ} \mathrm{F} \cdot$ day).

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Problem 36

Calculate the heat loss for a top-floor apartment and an apartment that is below the top floor, using the apartment building in Appendix A. Assume the apartment will be built at the geographical location where you reside.

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05:15

Problem 37

Calculate the heat loss for the residence in Appendix D on a room-by-room basis. Assume the residence will be built at the geographical location where you reside.
TABLE CAN'T COPY.

Narayan Hari
Narayan Hari
Numerade Educator