Download Heating a house with gas

ERIE COMMUNITY COLLEGE
TITLE III GRANT
Heat a house with gas
Interdisciplinary Course Materials
Architectural Technology
Course:
Course Outline Topic:
Project Title:
Project description:
Author:
Curriculum Expert:
Semester Created:
A.
MT001 or MT003
Decimals and basic Geometry
How much gas is needed to heat a house?
In this project students will be expected to design a small cabin 24 feet by 24 feet
with rooms 8 feet high. To determine how much heat is needed to maintain a
steady temperature of 72o inside the building. The student must calculate the
British thermal unit per hour (Btu/hr)
Mary Beth Orrange
Timothy Schnaufer, Architectural Technology
Fall 2009
Essential Question: How much gas is needed to heat a house? What is the cost?
B.
Introduction:
In this project you will work with a small cabin, 24 feet by 24 feet and determine
how much gas is needed to heat it at a constant 72o temperature. Then you will calculate the cost to heat it each
year and month.
C.
Basic Directions: In this project you will find the R and U values for walls and ceilings, the areas of the
same walls and ceilings, averages, and heat loss. You will perform several calculations and determine the cost
of heating your house for the year.
D.
Things to Learn before Starting the Project: You will need to know a few basics about heating and
cooling systems.
R value is the thermal resistance of a material; that is how much is slows down the heat loss.
U value is the reciprocal of the R value. U values cannot be added but R values can.
The higher the R value the better, the lower the U value the better.
The design temperature is the optimal temperature inside your building; the outside design temperature is the
cold value of the outside temperature (winter average.)
BTU/hr is the British thermal unit or heat loss per hour. A more official definition is a unit of heat equal to the
amount of heat required to raise one pound of water one degree Fahrenheit at one atmosphere pressure.
You must also be able to substitute values into given formulas, calculate the area of a rectangle, find the
reciprocal of a number, convert feet and inches to decimal feet, and follow directions.
Rounding to the hundredths place is appropriate for this type of calculations.
Erie Community College
Title III Grant
E.
The Project Assignment: follows the grading section
F. and G. Student and Faculty Resources: Search the internet for the terms used in this project. Use a search
engine and enter the terms gas heat costs, R and U – values of insulation, heat loss, and British thermal
Unit.
H.
Grading Rubric: 35% of the point value should be awarded for steps 1 and 2. 10% for questions 3, 4,
and 6.
Erie Community College
Title III Grant
Name ________________________________________ Heating a building
Step 1: Building Materials - find the R and U values for the walls and ceilings.
Wall type 1: (75% of the walls are constructed using these materials)
Material:
R-value
Outside air film
0.17
Vinyl siding
0.61
¼" rigid (bead) insulation
1.25
TYVEC house wrap
½" plywood
0.62
5 ½" Batt instulation
19.00
Vapor barrier
½" G.W.B.
0.45
Inside air film
0.68
TOTAL R value for wall 1
_____ (sum the R-values for wall 1)
U-value for wall 1
________ (reciprocal of the R value)
Wall type 2: (25% of the walls are constructed using these materials)
Material:
R-value
Outside air film
0.17
Vinyl siding
0.61
¼" rigid (bead) insulation
1.25
TYVEC house wrap
½" plywood
0.62
5 ½" STUD (Doug fir = 1.06/")
5.83
Vapor barrier
½" G.W.B.
0.45
Inside air film
0.68
TOTAL R value for wall 2
_____ (sum the R-values for wall 2)
U-value for wall 2
________ (reciprocal of the R value)
Ceiling type 1: (95% of the ceilings are constructed using these materials)
Material:
R-value
Outside air film
0.17
10" Batt instulation
30.00
Vapor barrier
½" G.W.B.
0.45
Inside air film
0.68
TOTAL R value for ceiling 1
_____ (sum the R-values for ceiling 1)
U-value for ceiling 1
Erie Community College
Title III Grant
________ (reciprocal of the R value)
Ceiling type 2: (5% of the ceilings are constructed using these materials)
Material:
R-value
Outside air film
0.17
3 1/2 " STUD (Doug fir = 1.06/")
3.71
Vapor barrier
½" G.W.B.
0.45
Inside air film
0.68
TOTAL R value for ceiling 2
_____ (sum the R-values for ceiling 2)
U-value for ceiling 2
________ (reciprocal of the R value)
There is one door and four windows in the cabin. The U values for them are:
Window
Door
U = 0.23 from Pella Catalog for double hung
U = 0.20 from chart
Foundation is constructed of 1 ½" rigid insulation and 10" concrete.
U value is 0.13
A value called the F2 factor is used in calculating the heat loss through the foundation.
F2 factor for the 1 ½ rigid insulation is 0.44
Step 2: Find the areas of the walls and ceilings as well as the perimeter of the foundation
wall.
The building is 24' square and 9' high.
The area of the four walls together is:
_____________________________________
There are four windows with 12.5 square feet each. The area of the four windows taken together is:
___________________________________________
There is one door 3'0" by 6'8". Find the area ___________________________________
The area of the walls without the windows and door is ____________________________
75% of the wall area for wall type 1 is _______________________________________
25% of the wall area for wall type 2 is _______________________________________
The area of the ceiling is ______________________________ (remember, it's a 24' square room)
95% of the ceiling area for ceiling type 1 is ________________________________________________
5% of the ceiling area for ceiling type 2 is ________________________________________________
The perimeter of the foundation wall is ____________________ (it's still a 24' square room)
Erie Community College
Title III Grant
Step 3: Calculate the U0 Average.
The formula for the Average is: (w represents wall 1, Aw1 represents Area of wall one, c1 represents
area of ceiling 1, etc.)
U0 is the value calculated above.
Step 4: Calculate the Heat loss given a formula.
The heat loss is represented by q(c) using the U0 calculated above, the area of the four sides and the ceiling, and
the change of temperature. The change of temperature is found by subtracting the outside winter design
temperature, in our case we use 6o, below the desired inside temperature, 72o. We will use 66o
q(c) = U0A066
Calculate q(c) _______________________________________________
This value is in Btu/h or British thermal unit per hour.
Doing similar calculations the heat loss for the slab edge foundation, q(se), and the amount of heat loss due to
air changes per hour (infiltration / exhilaration), q(i), comes to:
q(se) = 2787.84 Btu/h
and
q(i) = 4105.73 Btu/h
The total heat loss is the sum of the three values.
What is it?
______________________
Step 5: Calculate the yearly heating energy.
Utilizing similar formulas the Energy use of this building is 36,621.9 cubic feet per year.
Step 6: Calculate the fuel cost.
At the time of this writing, Natural gas costs = $2.335 per hundred cubic feet.
What's the cost of fuel for this house per year?
_________________________
What the cost of fuel for this house per month on the average?
Erie Community College
Title III Grant
_______________