1. Energy Conservation and Environmental Protection
Home Heating Basics
EGEE 102- S. Pisupati

2. National Average Home Energy Costs
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3. Why do we need Heating?
70 'F
Furnace
30 F
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4. Typical Heat losses- Conventional House
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5. Heat Transfer
Conduction
Convection
Radiation
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6. Conduction Energy is conducted down the rod as the vibrations of
one molecule are passed
to the next, but there
is no movement of energetic
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7. Convection
Energy is carried by the
bulk motion of the fluid
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8. Radiation Energy is carried by electromagnetic waves.
No medium is required
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9. Degree Days
Index of fuel consumption indicating how many degrees the mean temperature fell below 65 degrees for the day
Heating degree days (HDD) are used to estimate the amount of energy required for residential space heating during the cool season.
Cooling degree days (CDD) are used to estimate the amount of air conditioning usage during the warm season
EGEE 102

10. How do we calculate HDD? HDD = Tbase - Ta HDD = 0
if Ta is less than Tbase
HDD = 0
if Ta is greater or equal to Tbase
Where: Tbase = temperature base, usually 65 F Ta = average temperature, Ta = (Tmax + Tmin) / 2
EGEE 102

11. Heating Degree Days
Calculate the number of degree days accumulated in one day in which the average outside temperature is 17ºF.
Degree days = 1 day ( 65 – Tout)
= 1 (65-17)
= 48 degree days
EGEE 102

12. Heating Degree Days in a Heating Season
Calculate the degree days accumulated during a 150-day heating season if the average outside temperature is 17ºF
Solution:
Heating Season Degree days
= 150 days ( 65 – Tout)
= 150 (65-17)
= 7,200 degree days
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13. Degree Days for the Heating Season
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14. EGEE 102

15. Class work
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16. Significance of HDD
Mrs. Young is moving from Anchorage, Alaska (HDD =10,780) to State college, PA (HDD = 6,000). Assuming the cost of energy per million Btu is the same at both places, by what percentage her heating costs will change?
Solution
HDD in Anchorage, Alaska = 10,780
HDD in State College PA = 6,000
Difference = 10, ,000 = 4,780
Saving in fuel costs are
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17. Home Energy Saver
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18. Home Heating Costs in State College
Average House
Energy Efficient
House
Total $1,891
Total $1,019
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19. Home Heating Costs
Related to amount of insulation, material that resists the flow of heat
Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and density.
R-30 better than R-11
EGEE 102

20. Places to Insulate
Attic is usually the easiest ad most cost effective place to add insulation
Floors above unheated basements should be insulated
Heated basements should be insulated around the foundaton
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21. R-values for Building Materials
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22. Thickness of various materials for R-22
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23. R-Value for a Composite Wall
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24. Home Heating Energy Heat loss depends on Surface Area (size)
Temperature Difference
Property of the wall ( R value)
Outside
30¨F
Inside
65¨F
Q (Btus) 1
A (area) x Temperature Diff (Ti – To) =
t (time, h) R
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25. Heat Loss Tcold Thot Q Heat Loss = t Q Id Q/t is in Btu/h Area in ft2
Tin-Tout in °F
Then the thermal resistance is
R-value. The units of R-value are
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26. Wall loss rate in BTUs per hour
For a 10 ft by 10 ft room with an 8 ft ceiling, with all surfaces insulated to R19 as recommended by the U.S. Department of Energy, with inside temperature 68°F and outside temperature 28°F:
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27. Calculation per Day
Heat loss per day = (674 BTU/hr)(24 hr) = 16,168 BTU
Note that this is just through the wall
The loss through the floor and ceiling is a separate calculation, and usually involves different R-values
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28. Calculate loss per "degree day"
This is the loss per day with a one degree
difference between inside and
outside temperature.
If the conditions of case II prevailed all day, you would require 40 degree-days of heating, and therefore require 40 degree-days x 404 BTU/degree day = BTU to keep the inside temperature constant.
EGEE 102

29. Heat Loss for Entire Heating Season.
The typical heating requirement for a Pittsburgh heating season, September to May, is 5960 degree-days (a long-term average).
Heat loss = Q/t = 404 Btu/degree day x 5960 degree days
= 2.4 MM Btus
The typical number of degree-days of heating
or cooling for a given geographical location
can usually be obtained from the weather service.
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30. Numerical Example
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31. Heat loss Calculation
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32. Problem A wall is made up of four elements, as follows ½” wood siding
½” plywood sheathing
3 ½ in of fibber glass
½” of sheet rock
How many Btus per hour per sq.ft. will be lost through the wall when the outside temperature is 50F colder than inside?
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33. Economics of Adding Insulation
Years to Payback  =        C(i) x R(1) x R(2) x E   C(e) x [R(2) - R(1)] x HDD x 24
C(i)  =  Cost of insulation in $/square feet
C(e)  =  Cost of energy, expressed in $/Btu
E  =  Efficiency of the heating system
R(1)  =  Initial R-value of section
R(2)  =  Final R-value of section
R(2) - R(1) =  R-value of additional insulation being considered
HDD  =  Heating degree days/year
24  =  Multiplier used to convert heating degree days to heating hours (24 hours/day).
EGEE 102

34. Pay Back Period Calculation
Suppose that you want to know how many years it will take to recover the cost of installing additional insulation in your attic. You are planning to increase the level of insulation from R-19 (6 inch fiberglass batts with moisture barrier on the warm side) to R-30 by adding R-11 (3.5 inch unfaced fiberglass batts). You have a gas furnace with an AFUE of You also pay $0.70/therm for natural gas.
Given
C(i) = $0.18/square foot; C(e) = ($0.70/therm)/(100,000 Btu/therm) = $ /Btu; E = 0.88; R(1) = 19; R(2) = 30; R(2) - R(1) = 11; HDD = 7000
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35. Household Heating Fuel
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36. Average Heating Value of Common Fuels
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37. Typical Heating Furnace Efficiencies
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38. Comparing the Fuel Costs
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39. Fuel Costs
Electric resistance heat cost = $0.082 (price per kWh) / [ x 0.97 (efficiency)] = $24.77 per million Btu.
Natural gas (in central heating system) cost = $6.60 (per thousand cubic feet) / [ 1.0 x 0.80 (efficiency)] = $8.25 per million Btu.
Oil (in central heating system) cost = $0.88 (price per gallon) / [ 0.14 x 0.80 (efficiency)] = $7.86 per million Btu.
Propane (in central heating system) cost = $0.778 (price per gallon) / [ x 0.80 (efficiency)] = $10.65 per million Btu.
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40. Heating Systems
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41. Energy Conservation and Environmental Protection
Heating Systems
Some hot water systems circulate water through plastic tubing in the floor, called radiant floor heating.
notes
EGEE 102
EGEE 102- S. Pisupati

42. Electric Heating Systems
Resistance heating systems
Converts electric current directly into heat
usually the most expensive
Inefficient way to heat a building
Heat pumps
Use electricity to move heat rather than to generate it, they can deliver more energy to a home than they consume
Most heat pumps have a COP of 1.5 to 3.5.
All air-source heat pumps (those that exchange heat with outdoor air, as opposed to bodies of water or the ground) are rated with a "heating season performance factor" (HSPF)
EGEE 102

43. Geothermal Heat Pumps
They use the Earth as a heat sink in the summer and a heat source in the winter, and therefore rely on the relative warmth of the earth for their heating and cooling production.
Additional reading
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44. Benefits of a GHP System
Low Energy Use
Free or Reduced-Cost Hot Water
Year-Round Comfort
Low Environmental Impact
Durability
Reduced Vandalism
Zone Heating and Cooling
Low Maintenance
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45. Solar Heating and Cooling
Most American houses receive enough solar energy on their roof to provide all their heating needs all year!
Active Solar
Passive Solar
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46. Passive Solar
A passive solar system uses no external energy, its key element is good design:
House faces south
South facing side has maximum window area (double or triple glazed)
Roof overhangs to reduce cooling costs
Thermal mass inside the house (brick, stones or dark tile)
EGEE 102

47. Passive Solar
Deciduous trees on the south side to cool the house in summer, let light in in the winter.
Insulating drapes (closed at night and in the summer)
Greenhouse addition
Indirect gain systems also such as large concrete walls to transfer heat inside
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48. Passive Solar Heating
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49. Source: Global Science, Energy Resources Environment
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Source: Global Science, Energy Resources Environment

50. EGEE 102

51. Active Solar Heating
Flat plate collectors are usually placed on the roof or ground in the sunlight.
The sunny side has a glass or plastic cover.
The inside space is a black absorbing material.
Air or water is pumped (hence active) through the space to collect the heat.
Fans or pumps deliver the heat to the house
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52. Active Solar Heating
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53. Flat Plate Collector
Solar Collectors heat fluid and the heated fluid heats the space either directly or indirectly
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54. Efficiency of Furnace
The "combustion efficiency" gives you a snapshot in time of how efficient the heating system is while it is operating continuously
The "annual fuel utilization efficiency" (AFUE) tells you how efficient the system is throughout the year, taking into account start-up, cool-down, and other operating losses that occur in real operating conditions.
AFUE is a more accurate measure of efficiency and should be used if possible to compare heating systems.
EGEE 102

55. Efficiencies of Home Heating
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56. Tips (Individual) to Save Energy and Environment
Set your thermostat as low as is comfortable in the winter and as high as is comfortable in the summer.
Clean or replace filters on furnaces once a month or as needed.
Clean warm-air registers, baseboard heaters, and radiators as needed; make sure they're not blocked by furniture, carpeting, or drapes.
Bleed trapped air from hot-water radiators once or twice a season; if in doubt about how to perform this task, call a professional.
Place heat-resistant radiator reflectors between exterior walls and the radiators.
EGEE 102

57. Use kitchen, bath, and other ventilating fans wisely; in just 1 hour, these fans can pull out a houseful of warmed or cooled air. Turn fans off as soon as they have done the job.
During the heating season, keep the draperies and shades on your south-facing windows open during the day to allow sunlight to enter your home and closed at night to reduce the chill you may feel from cold windows. During the cooling season, keep the window coverings closed during the day to prevent solar gain.
EGEE 102

58. Close an unoccupied room that is isolated from the rest of the house, such as in a corner, and turn down the thermostat or turn off the heating for that room or zone. However, do not turn the heating off if it adversely affects the rest of your system. For example, if you heat your house with a heat pump, do not close the vents—closing the vents could harm the heat pump.
Select energy-efficient equipment when you buy new heating and cooling equipment. Your contractor should be able to give you energy fact sheets for different types, models, and designs to help you compare energy usage. Look for high Annual Fuel Utilization Efficiency (AFUE) ratings and the Seasonal Energy Efficiency Ratio (SEER). The national minimums are 78% AFUE and 10 SEER.
EGEE 102