9. Home Heating Basics

7/30/2019 9. Home Heating Basics

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EGEE 102 Energy Conservation

And Environmental Protection

Home Heating Basics


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EGEE 102 2

National Average Home

Energy Costs

9%

33%

14%

44%

Heating and Cooling

Refrigrator

Lighting, Cooking and

other Appliances

Water Heating


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EGEE 102 3

Why do we need

Heating?

70 'F

Furnace

30 F


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EGEE 102 4

Typical Heat losses-

Conventional House

5% through ceilings

16%throughwindows

1% throughbasement floor

17% through

frame walls

3% through door

38% through cracksin walls, windows,and doors

20%through

basementwalls


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EGEE 102 5

Heat Transfer

Conduction

Convection

Radiation


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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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Convection

Energy is carried by thebulk motion of the fluid


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Radiation

Energy is carried byelectromagnetic waves.

No medium is required


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Degree Days

Index of fuel consumption indicating howmany degrees the mean temperature fell

below 65 degrees for the day Heating degree days (HDD) are used to

estimate the amount of energy required forresidential space heating during the cool

season. Cooling degree days (CDD) are used to

estimate the amount of air conditioning usage

during the warm season


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How do we calculate

HDD? HDD = Tbase - Ta

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


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Heating Degree Days

Calculate the number of degree daysaccumulated in one day in which the

average outside temperature is 17F.

Degree days = 1 day ( 65 Tout)

= 1 (65-17)

= 48 degree days


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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 17FSolution:

Heating Season Degree days

= 150 days ( 65 Tout)= 150 (65-17)

= 7,200 degree days


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EGEE 102 13

Degree Days for the

Heating SeasonPLACE DEGREE DAYS

Birmingham,

ALABAMA

2,780

Anchorage,

ALASKA

10,780

Barrow, ALASKA 19,994

Tucson, ARIZONA 1,776

Miami, FLORIDA 173

State College ???


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Class work


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EGEE 102 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 whatpercentage her heating costs will change?

Solution

HDD in Anchorage, Alaska = 10,780

HDD in State College PA = 6,000

Difference = 10,780 - 6,000 = 4,780

Saving in fuel costs are %3.44100780,10

780,4


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EGEE 102 17

Home Energy Saver

http://homeenergysaver.lbl.gov/
http://homeenergysaver.lbl.gov/http://homeenergysaver.lbl.gov/


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EGEE 102 18

Home Heating Costs in

State College

$890

$133$227

$305

$232 $106 HeatingCooling

Hot water

Appliances

Misc.

Lighting

Energy Effcient House

$327

$89$114

$205

$232

$52

Total $1,891

Average House

Energy EfficientHouse

Total $1,019


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EGEE 102 19

Home Heating Costs

Related to amount of insulation,material that resists the flow of heat

Insulation is rated in terms ofthermal resistance, called R-value,which indicates the resistance toheat flow. The higher the R-value,

the greater the insulatingeffectiveness. The R-value ofthermal insulation depends on thetype of material, its thickness, anddensity.

R-30 better than R-11


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EGEE 102 20

Places to Insulate

Attic is usually theeasiest ad most costeffective place toadd insulation

Floors aboveunheatedbasements shouldbe insulated

Heated basementsshould be insulatedaround thefoundaton


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EGEE 102 21

R-values for Building

Materials


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Thickness of various

materials for R-22

110"

18"

7"6"

CelluloseFiber

Fiberglass Pine wood Commonbrick


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EGEE 102 23

R-Value for a Composite

Wall

1/2" Plasterboard 0.45

3 1/2" Fiberglass 10.90

3/4" Plywood 0.94

1/2" Wood siding 0.81 RTOTAL = 13.10

ft 2 F hrBTU

R-Value of material


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EGEE 102 24

Home Heating Energy

Heat loss dependson

Surface Area(size)

Temperature

Difference

Property of thewall ( R value)

Inside

65F

Outside

30F

Q (Btus)

t (time, h)= A (area) x Temperature Diff (Ti To)

1

R


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EGEE 102 25

Heat Loss

),tanRe( RWallofthecesisThermal

outsideT

insideTxArea

),tanRe( RWallofthecesisThermal

outsideT

insideTxArea Thot

Tcold

Q

t

Heat Loss =Q

t

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

hrBtu

Fxfto

/

2


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EGEE 102 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 ofEnergy, with inside temperature 68F andoutside temperature 28F:

hrBtu

hBTU

Fxft

FFxft

t

QRateHeatloss /674

/19

286832002

02


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EGEE 102 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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EGEE 102 28

Calculate loss per

"degree day"

If the conditions of case II prevailed all day, youwould require 40 degree-days of heating, andtherefore require 40 degree-days x 404 BTU/degreeday = 16168 BTU to keep the inside temperatureconstant.

This is the loss per day with a one degreedifference between inside andoutside temperature.


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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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Numerical Example


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Heat loss Calculation

dayhdaysreeAnnualofNumberAR

Qtotal /24deg1


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Problem

A wall is made up of four elements, as follows

wood siding

plywood sheathing 3 in of fibber glass

of sheet rock

How many Btus per hour per sq.ft. will be lostthrough the wall when the outsidetemperature is 50F colder than inside?


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EGEE 102 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 (24hours/day).


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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 additionalinsulation in your attic. You are planning to increase

the level of insulation from R-19 (6 inch fiberglassbatts with moisture barrier on the warm side) to R-30by adding R-11 (3.5 inch unfaced fiberglass batts).You have a gas furnace with an AFUE of 0.88. 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) = $0.000007/Btu; E = 0.88; R(1) = 19; R(2) = 30;R(2) - R(1) = 11; HDD = 7000


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EGEE 102 35

Household Heating Fuel

56%

26.00%

11.00% 10.00%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Natural

Gas

Electricity Fuel Oil Other

Heating Fuel


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EGEE 102 36

Average Heating Value

of Common FuelsFuel Type No. of Btu/Unit (Kilocalories/Unit)

Kerosene (No. 1 Fuel Oil) 135,000/gallon (8,988/liter)

No. 2 Fuel Oil 140,000/gallon (9,320/liter)

Electricity 3,412/kWh (859/kWh)Natural Gas 1,028,000/thousand cubic feet (7,336/cubic meter)

Propane 91,333/gallon (6,081/liter)

Bituminous Coal 23,000,000/ton (6,400,000/tonne)

Anthracite Coal 24,800,000/ton (5,670,000/tonne)

Hardwood (20% moisture)* 24,000,000/cord (1,687,500/cubic meter)Pine (20% moisture)* 18,000,000/cord (1,265,625/cubic meter)

Pellets (for pellet stoves; premium) 16,500,000/ton (4,584,200/tonne)


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Fuel Type - Heating Equipment Efficiency (%)Coal (bituminous)

Central heating, hand-fired 45

Central heating, stoker-fired 60

Water heating, pot stove (50 gal.[227.3 liter]) 14.5

Oil

High efficiency central heating 89

Typical central heating 78

Water heater (50 gal.[2227.3 liter]) 59.5

Gas

High efficiency central heating 92

Typical central heating 82

Room heater, unvented 91

Room heater, vented 78

Water heater (50 gal.[227.3 liter]) 62

ElectricityCentral heating, resistance 97

Central heating, heat pump 200+

Ground source heat pump 300+

Water heaters (50 gal.[227.3 liter]) 97

Wood & Pellets

Franklin stoves 30.0 - 40.0

Stoves with circulating fans 40.0 - 70.0

Catalytic stoves 65.0 - 75.0

Pellet stoves 85.0 - 95.0

Typical Heating Furnace

Efficiencies


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Comparing the Fuel

Costs

EfficiencyunitoffuelMMBtuueHeatingValofFuelperUnitCost

CostEnergy

)/(


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Fuel Costs

Electric resistance heat cost =$0.082 (price per kWh) / [ 0.003413 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) / [ 0.0913 x 0.80 (efficiency)]= $10.65 per million Btu.


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Heating Systems


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Heating Systems

Some hot watersystems circulate

water throughplastic tubing in thefloor, called radiantfloor heating.


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Electric Heating

Systems1. Resistance heating systems

Converts electric current directly intoheat

1. usually the most expensive2. Inefficient way to heat a building

2. Heat pumpsUse electricity to move heat rather than

to generate it, they can deliver moreenergy to a home than they consume1. Most heat pumps have a COP of 1.5 to 3.5.

2. All air-source heat pumps (those thatexchange heat with outdoor air, as opposed

to bodies of water or the ground) are ratedwith a "heating season performance factor"


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Geothermal Heat Pumps

They use the Earthas a heat sink in the

summer and a heatsource in the winter,and therefore relyon the relative

warmth of the earthfor their heating andcooling production.

Additional reading

http://www.eren.doe.gov/erec/factsheets/geo_heatpumps.html#sidebar


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EGEE 102 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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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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Passive Solar

A passive solar system uses no externalenergy, 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)


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EGEE 102 47

Passive Solar

Deciduous trees on the south side tocool the house in summer, let light in in

the winter. Insulating drapes (closed at night and inthe summer)

Greenhouse addition

Indirect gain systems also such as largeconcrete walls to transfer heat inside


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Passive Solar Heating


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Passive Heating


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Dire c t Gain The rmal St o rag e

W a l l

S u n s p a c e

g

Passive CoolingS ha d ing Ve n t ila t io n Earth Cont ac t


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Active Solar Heating

Flat plate collectors are usually placedon the roof or ground in the sunlight.

The sunny side has a glass or plasticcover.

The inside space is a black absorbingmaterial.

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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Active Solar

Heating


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Flat Plate Collector

Solar Collectorsheat fluid and theheated fluid heatsthe space eitherdirectly or indirectly


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Efficiency of Furnace

The "combustion efficiency" gives you asnapshot in time of how efficient the heatingsystem is while it is operating continuously

The "annual fuel utilization efficiency" (AFUE)tells you how efficient the system isthroughout 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 possibleto compare heating systems.


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EGEE 102 55

Efficiencies of Home

Heating.

U.S. stock

1975-1976 building practice(NAHB)

LBL standard(medium infiltration)

LBL standard(low inf iltration)

Brownell Saskatoon

Pasqua

Saskatche-wan house

IvanhoeMastin

Leger

BalcombPhelps

1 Btu/ft 2 per degree day

Annualfuelinputfor

spaceheat

(10

6Btu/100

0ft

2)

Btu/ft2perdegreed

ay

Degree days (base 65F)

110

100

90

80

70

60

50

40

30

20

10

00 2000 4000 6000 8000 10,000

9

7

5

3

1


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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 blockedby furniture, carpeting, or drapes.

Bleed trapped air from hot-water radiators once ortwice a season; if in doubt about how to perform thistask, call a professional.

Place heat-resistant radiator reflectors betweenexterior walls and the radiators.
http://www.eren.doe.gov/consumerinfo/energy_savers/filters.htmlhttp://www.eren.doe.gov/consumerinfo/energy_savers/filters.html


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Use kitchen, bath, and other ventilating fans wisely;in just 1 hour, these fans can pull out a houseful ofwarmed or cooled air. Turn fans off as soon as they

have done the job. During the heating season, keep the draperies and

shades on yoursouth-facing windows open duringthe day to allow sunlight to enter your home and

closed at night to reduce the chill you may feel fromcold windows. During the cooling season, keep thewindow coverings closed during the day to preventsolar gain.
http://www.eren.doe.gov/consumerinfo/energy_savers/south_facing.htmlhttp://www.eren.doe.gov/consumerinfo/energy_savers/south_facing.htmlhttp://www.eren.doe.gov/consumerinfo/energy_savers/south_facing.htmlhttp://www.eren.doe.gov/consumerinfo/energy_savers/south_facing.html


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Close an unoccupied room that is isolated from therest of the house, such as in a corner, and turn downthe thermostat or turn off the heating for that room or

zone. However, do not turn the heating off if itadversely affects the rest of your system. Forexample, if you heat your house with a heat pump, donot close the ventsclosing the vents could harm theheat pump.

Select energy-efficient equipment when you buy newheating and cooling equipment. Your contractorshould be able to give you energy fact sheets fordifferent types, models, and designs to help youcompare energy usage. Look for high Annual Fuel
http://www.eren.doe.gov/consumerinfo/energy_savers/glossary.htmlhttp://www.eren.doe.gov/consumerinfo/energy_savers/glossary.html

9. Home Heating Basics

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