Two years ago I upgraded my attic insulation to R38 --- recently I

was

looking at possibly increasing my attic insulation up to R76 - and I

wanted to know what was the payback (return on investment) - after

much surfing I found the formula below. HTH

The following webpage coves estimating

the payback for adding Insulation to the Attic

http://apps1.eere.energy.gov/consumer/your_home/insulation_airsealing/index=

.cfm/mytopic=11360

(incase the above webpage dissappears ....)

the equation is as follows:

Years to Payback = (C(i) R(1) R(2) E) (C(e) =

[R(2) -

R(1)] HDD 24)

To calculate the payback, you must supply the following information:

C(i) = Cost of insulation in $/square feet.

Collect insulation cost information;

include labor, equipment, and vapor barrier if needed.

C(e) = Cost of energy, expressed in $/Btu.

* To calculate the cost of energy, divide the actual price you pay

per gallon of oil, kilowatt-hour (kWh) of electricity, gallon of

propane, or therm (or per one hundred cubic feet [ccf]) of natural gas

by the Btu content per unit of fuel.

* To figure the price you pay per unit, take the total amount of your

bills (for oil, electricity, propane, or natural gas) during the

heating season, and divide it by the total number of gallons, kWh, or

therms you consumed during those months. Use the following values for

fuel Btu content:

Fuel Oil = 140,000 Btu/gallon

Electricity = 3,413 Btu/kWh

Propane = 91,600 Btu/gallon

Natural Gas = 103,000 Btu/ccf

or 100,000 Btu/therm

E = Efficiency of the heating system. For gas, propane, and fuel oil

systems this is the Annual Fuel Utilization Efficiency or AFUE.

Typical AFUE values are 0.6 to 0.88 for oil or propane furnaces, and

0.7 to 0.95 for natural gas furnaces. Older systems are usually less

efficient. Use E = 1.00 for baseboard electric systems. For heat

pumps, use the Coefficient of Performance or COP for E; where E = 2.1

to 2.5 for conventional heat pumps, and E = 3.2 to 3.5 for geothermal

heat pumps.

( an energy star non-geothermal HVAC is typically going to have an

E=2.5 )

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. This information can usually be

obtained from your local weather station, utility, or oil dealer.

( e.g. for HDD for MD-DC-VA see [1])

24 = Multiplier used to convert heating degree days to heating hours

(24 hours/day).

Example:

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 0.88. You also pay $.87/therm for natural

gas. Let's also suppose that you supply the following values for the

variables in the formula.

C(i) = $.18/square foot

C(e) = ($.87/therm)(100,000 Btu/therm) = $.0000087/Btu

E = 0.88

R(1) = 19

R(2) = 30

R(2) - R(1) = 11

HDD = 7000

By plugging the numbers into the formula, you obtain the years to

payback:

Years to Payback = (C(i) R(1) R(2) E) (C(e) [R(2=

) -

R(1)] HDD 24)

Years to Payback = (0.18 19 30 0.88) ($.0000087 =

11

7000 24)

90.288 16.077 = 5.62 years

[1]HDD

district of columbia

http://www.efficientwindows.org/codes/DC-IECC.pdf

maryland

http://www.efficientwindows.org/codes/MD-IECC.pdf

Virginia

http://www.efficientwindows.org/codes/va-IECC.pdf

*> Two years ago I upgraded my attic insulation to R38 --- recently I*

*> was*

*> looking at possibly increasing my attic insulation up to R76 - and I*

*> wanted to know what was the payback (return on investment) - after*

*> much surfing I found the formula below. HTH*

*> The following webpage coves estimating*

*> the payback for adding Insulation to the Attic*

The infrared thermometer and snow melt pattern show that most of my

remaining attic heat loss is around the edges where I couldn't stuff

in more insulation due to restricted space and protruding roofing

nails. More insulation in the middle wouldn't help much if that isn't

where the larger losses occur.

*> > Two years ago I upgraded my attic insulation to R38 --- recently I*

*> > was*

*> > looking at possibly increasing my attic insulation up to R76 - and I*

*> > wanted to know what was the payback (return on investment) - after*

*> > much surfing I found the formula below. HTH*

*> > The following webpage coves estimating*

*> > the payback for adding Insulation to the Attic*

*> The infrared thermometer and snow melt pattern show that most of my*

*> remaining attic heat loss is around the edges where I couldn't stuff*

*> in more insulation due to restricted space and protruding roofing*

*> nails. More insulation in the middle wouldn't help much if that isn't*

*> where the larger losses occur.*

Sound like a great idea! The farmer's almanac predicts

lotsa of snow this winter for the Mid-Atlanic area so maybe

I'll get a chance to do just that....

*> Two years ago I upgraded my attic insulation to R38 --- recently I*

*> was*

*> looking at possibly increasing my attic insulation up to R76 - and I*

*> wanted to know what was the payback (return on investment) - after*

*> much surfing I found the formula below. HTH*

*> The following webpage coves estimating*

*> the payback for adding Insulation to the Attic*

*> http://apps1.eere.energy.gov/consumer/your_home/insulation_airsealing ...*

*> (incase the above webpage dissappears ....)*

*> the equation is as follows:*

*> Years to Payback = (C(i) R(1) R(2) E) (C(e) [R(2) -*

*> R(1)] HDD 24)*

*> To calculate the payback, you must supply the following information:*

*> C(i) = Cost of insulation in $/square feet.*

*> Collect insulation cost information;*

*> include labor, equipment, and vapor barrier if needed.*

*> C(e) = Cost of energy, expressed in $/Btu.*

*> * To calculate the cost of energy, divide the actual price you pay*

*> per gallon of oil, kilowatt-hour (kWh) of electricity, gallon of*

*> propane, or therm (or per one hundred cubic feet [ccf]) of natural gas*

*> by the Btu content per unit of fuel.*

*> * To figure the price you pay per unit, take the total amount of your*

*> bills (for oil, electricity, propane, or natural gas) during the*

*> heating season, and divide it by the total number of gallons, kWh, or*

*> therms you consumed during those months. Use the following values for*

*> fuel Btu content:*

*> Fuel Oil = 140,000 Btu/gallon*

*> Electricity = 3,413 Btu/kWh*

*> Propane = 91,600 Btu/gallon*

*> Natural Gas = 103,000 Btu/ccf*

*> or 100,000 Btu/therm*

*> E = Efficiency of the heating system. For gas, propane, and fuel oil*

*> systems this is the Annual Fuel Utilization Efficiency or AFUE.*

*> Typical AFUE values are 0.6 to 0.88 for oil or propane furnaces, and*

*> 0.7 to 0.95 for natural gas furnaces. Older systems are usually less*

*> efficient. Use E = 1.00 for baseboard electric systems. For heat*

*> pumps, use the Coefficient of Performance or COP for E; where E = 2.1*

*> to 2.5 for conventional heat pumps, and E = 3.2 to 3.5 for geothermal*

*> heat pumps.*

*> ( an energy star non-geothermal HVAC is typically going to have an*

*> E=2.5 )*

*> 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. This information can usually be*

*> obtained from your local weather station, utility, or oil dealer.*

*> ( e.g. for HDD for MD-DC-VA see [1])*

*> 24 = Multiplier used to convert heating degree days to heating hours*

*> (24 hours/day).*

*> Example:*

*> 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 0.88. You also pay $.87/therm for natural*

*> gas. Let's also suppose that you supply the following values for the*

*> variables in the formula.*

*> C(i) = $.18/square foot*

*> C(e) = ($.87/therm)(100,000 Btu/therm) = $.0000087/Btu*

*> E = 0.88*

*> R(1) = 19*

*> R(2) = 30*

*> R(2) - R(1) = 11*

*> HDD = 7000*

*> By plugging the numbers into the formula, you obtain the years to*

*> payback:*

*> Years to Payback = (C(i) R(1) R(2) E) (C(e) [R(2) -*

*> R(1)] HDD 24)*

*> Years to Payback = (0.18 19 30 0.88) ($.0000087 11 *

*> 7000 24)*

*> 90.288 16.077 = 5.62 years*

*> [1]HDD*

*> district of columbiahttp://www.efficientwindows.org/codes/DC-IECC.pdf *

*> marylandhttp://www.efficientwindows.org/codes/MD-IECC.pdf *

*> Virginiahttp://www.efficientwindows.org/codes/va-IECC.pdf *

Research how Fiberglass batts loose R value as temps drop. Depending

on where you live and winter lows you can loose 20-30% R value as the

attic gets colder. Also settling. I put in R 100-110 fiberglass batts

and it settled to R 70. Best is Foam. What is your Zone. Settling and

R value loss at -f temps increase payback.

> Two years ago I upgraded my attic insulation to R38 --- recently I> was> looking at possibly increasing my attic insulation up to R76 - and I> wanted to know what was the payback (return on investment) - after> much surfing I found the formula below. HTH> The following webpage coves estimating> the payback for adding Insulation to the Attic