This Old House By: Steve White Ryan Anderson
Thermal Resistance of the House • Denoted by “R Value” • It is the ability of an object or material to resist heat transfer through it. Heat into the house (in the form of natural gas) Heat out of the house
Governing Equation • q=∆T*As/Reqv. • To find the equivalent thermal resistance of the house, solve for Reqv. • Reqv. depends on the materials used to construct the house, the dimensions of the walls and roof, the temperature difference from inside to outside the house, as well as many other factors including the size, shape and quantity of windows.
Data & Calculations Collected Data from monthly bills and Temperatures from Almanac Calculations based on an R Value of 20 Decatherms Used October 3. 5 November 12. 7 December 14. 8 January 13. 9 February 11. 7 March 8. 5 April 6. 3 May 2. 2 October November December January February March April May *Adjusted Watts 0. 41865 0. 74365 0. 99365 1. 04365 0. 86865 0. 61865 0. 44365 0. 19365 * Adjustment based on 78% efficient furnace Watts 1424. 651 5169. 448 6024. 239 5657. 9 4762. 405 3459. 867 2564. 372 895. 495 Watts 0. 536731 0. 953397 1. 27391 1. 338013 1. 113654 0. 793141 0. 568782 0. 248269 *Adjusted Temperature Watts Difference 1111. 228 8. 373 4032. 17 14. 873 4698. 906 19. 873 4413. 162 20. 873 3714. 676 17. 373 2698. 696 12. 373 2000. 21 8. 873 698. 4861 3. 873 Decatherms Used 0. 330757232 0. 587525655 0. 785039827 0. 824542662 0. 686282741 0. 48876857 0. 350508649 0. 152994477 R Value $ Spent 1. 890041 0. 925237 1. 060865 1. 186392 1. 173133 1. 150044 1. 112726 1. 390859 26. 25 95. 25 111 104. 25 87. 75 63. 75 47. 25 16. 5 Total : $552 $ Spent % Savings 2. 48 4. 41 5. 89 6. 18 5. 15 3. 67 2. 63 1. 15 Total : $31. 54 90. 55 95. 37 94. 70 94. 07 94. 13 94. 25 94. 44 93. 05 94. 25
Actual House • Walls constructed of bricks and plaster in the 1950’s • Low quality single pane windows • Cost $552 to heat from October to May
Standard R Value Home • Constructed of newer materials with an overall R value of 20 (which is typical for newly built homes) • Would cost $31. 54 to heat the home from October to May
Application • By raising thermal resistance of a home, the cost of heating can be reduced significantly • In this instance, the heating cost could be lowered by 94. 25% by simply raising thermal resistance to standard levels
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