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Worked calculations for thermal loss example

This page shows the workings associated with calculations of heat loss from a semi-detached house as described on the example page. This example used the imperial quantities of BTU/hr, sq. ft., and °F.

Most of the calculations are fairly straight forward as most of the rooms are of regular shape, the only exception being the hall which extends up the stair well and onto the landing.

Workings of air change losses are at the bottom of this page.

    area
sq. ft
inside
temp
outside temp Temp diff U-value Loss in BTU
Dining Room back wall 72 70 30 40 0.18 518
  window 40 70 30 40 0.51 816
  party wall 136 70 65 5 0.38 258
  ceiling 238 70 65 5 0.29 345
  floor 238 70 30 40 0.12 1142
  Lounge wall 112 70 70 0 0.39 0
  Kitchen wall 112 70 65 5 0.39 218
  Hall wall 24 70 60 10 0.39 94
               
Lounge front wall 72 70 30 40 0.18 518
  window 40 70 30 40 0.51 816
  party wall 120 70 65 5 0.38 228
  ceiling 210 70 65 5 0.29 305
  floor 210 70 30 40 0.12 1008
  Dining wall 112 70 70 0 0.39 0
  Hall wall 120 70 60 10 0.39 468
               
Kitchen back wall 32 65 30 35 0.18 202
  window 16 65 30 35 0.51 286
  side wall 95.75 65 30 35 0.18 603
  back door 16.25 65 30 35 0.42 239
  ceiling 84 65 72 -7 0.25 -147
  floor 84 65 30 35 0.12 353
  Dinning wall 112 65 70 -5 0.39 -218
  Hall wall 48 65 60 5 0.39 94
               
Hall side wall 231.5 60 30 30 0.18 1250
  window 16 60 30 30 0.51 245
  front wall 28.5 60 30 30 0.18 154
  front door 19.5 60 30 30 0.42 246
  ceiling to roof 80 60 30 30 0.05 120
  ceiling to bd 3 48 60 65 -5 0.25 -60
  floor 108 60 30 30 0.12 389
  Lounge/dr wall 144 60 70 -10 0.39 -562
  Kitchen wall 48 60 70 -10 0.39 -187
  Bedroom walls 48 60 65 -5 0.39 -94
               
Bedroom 1 back wall 72 65 30 35 0.18 454
  window 40 65 30 35 0.51 714
  party wall 120 65 60 5 0.38 228
  ceiling 238 65 30 35 0.05 417
  floor 238 65 70 -5 0.29 -345
  Bedroom 2 wall 112 65 65 0 0.39 0
  Bathroom wall 112 65 72 -7 0.39 -306
  Hall wall 24 65 65 0 0.39 0
               
Bedroom 2 front wall 72 65 30 35 0.18 454
  window 40 65 30 35 0.51 714
  party wall 120 65 60 5 0.38 228
  ceiling 210 65 30 35 0.05 368
  floor 210 65 70 -5 0.29 -305
  Bedroom 1 wall 112 65 65 0 0.39 0
  Bedroom 3 wall 64 65 65 0 0.39 0
  Hall wall 56 65 60 5 0.39 109
               
Bedroom 3 side wall 64 65 30 35 0.18 403
  front wall 32 65 30 35 0.18 202
  window 16 65 30 35 0.51 286
  ceiling 48 65 30 35 0.05 84
  floor 48 65 60 5 -0.25 -60
  Bedroom 2 wall 64 65 65 0 0.39 0
  Hall wall 48 65 60 5 0.39 94
               
Bathroom back wall 32 72 30 42 0.18 242
  side wall 112 72 30 42 0.18 847
  window 16 72 30 42 0.51 343
  ceiling 84 72 30 42 0.05 176
  floor 84 72 65 7 0.25 147
  Bedroom 1 wall 112 72 65 7 0.39 306
  Hall 48 72 65 7 0.39 131
               
Air Change   volume       rate  
Dining Room   1904 70 30 40 2 3046
Lounge   1680 70 30 40 1 1344
Kitchen   672 65 30 35 2 941
Hall   240 60 30 30 1.5 216
Bedroom 1   130 65 30 35 0.5 46
Bedroom 2   864 65 30 35 0.5 302
Bedroom 3   256 65 30 35 0.5 90
Bathroom   896 72 30 42 2 1505