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P30401 Building Physics & Thermal Comfort. Written report following the construction and run analysis of a working Excel Model calculating the heat/energy gains & losses of a building and the resultant annual heating load. Student: Andrea Luise Schrader. Oxford Brookes University.
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OXFORD BROOKES UNIVERSITY
P30401 – Building Physics & Thermal Comfort. Professor M. G. Hutchins
Assignment 3 – Monday 8th December 2008
Andrea Luise Schrader
CalculationOfAnnualSpaceHeatingRequirement.Atwostoreydetatchedhouseis10mwide,8mdeepwiththelongfacadesfacingNorth/South. Theheight of each storey is 2.75mThe glazed areason theNorth, South, East&West facadesare10m2,15m2,4m2&4m2 respectively.Window framesoccupy15%ofthewindowarea,allwindowshavecleardoubleglazingandallwindowsareunshaded.Theheightoftheatticespaceis2.75mandtheridgeoftheroofarearunsEast/Westandis10mlong.Forallmonthsthereareanaverageof0.5airchangesperhour. Internalgainsamount to 15kWh/day, and the mean internal temperature is required to be 19 oC. A“medium”utilisationfactor(a=1.8)applies.TherespectiveU‐valuesoftheenvelopecomponentsare:WallU‐value=0.35W.m‐2oC‐1FloorU‐value=0.40W.m‐2oC‐1RoofU‐value=0.20W.m‐2oC‐1WindowU‐value=2.7W.m‐2oC‐1(frame&glazing)Windowtotalsolarenergytransmittance,g=0.76The monthly mean daily ambient temperatures and the monthly mean daily solarirradianceoneachverticalplanearegiveninTable1&Table2respectively:
Month JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DECMeanTemp0C
2.9
3.8
7.6
11.0
14.4
18.7
19.6
19.8
14.2
11.7
6.4
1.9
Table1.Monthlymeandailyambienttemperatures.
Month JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DECNorth 0.27 0.49 0.86 1.39 1.87 2.14 1.88 1.45 1.05 0.60 0.34 0.21South 1.24 1.87 1.69 2.23 2.77 2.73 2.78 2.98 2.59 2.33 1.57 1.10East 0.42 0.87 1.37 2.05 2.52 2.75 2.74 2.47 1.65 0.96 0.50 0.32West 0.47 0.87 1.42 2.37 3.03 3.04 3.01 2.78 1.99 1.36 0.72 0.40Table2.Estimatedmonthlymeansofdailyglobalradiationonverticalplanes(kWh/m2day)Additionaldata:No.ofsecondsinoneday=86400Specificheatcapacityofair=1050J/kg.oCDensityofair=1.25kgm‐2MeanDailyGroundTemperature=13oC
FINDTHERESPECTIVEDAILYANDMONTHLY1. HEATLOSSinkWh;SOLARGAINinkWh;TOTALGAINinkWh2. GAIN/LOSSRATIOANDUTILISATIONFACTOR3. USEFULGAINinkWh4. FABRIC/VENTILATIONLOSS5. MONTHLY/ANNUALSPACEHEATINGREQUIREMENT(inkWhandin£)Assumethecost
ofakWhtobe£0.096. INVESTIGATE THE SENSITIVITY OF THE ANNUAL SPACE HEATING REQUIREMENT TO
REPLACINGTHEGLAZINGWITHAWINDOWWITH:
(i) g=0.75,U=1.6W/(m2C);(ii)g=0.34,U=1.1W/m2C7. FOR CASE i) INVESTIGATE THE SENSITIVITY OF THE ANNUAL SPACE HEATING
REQUIREMENTTOTHEWINDOWWALLRATIO.8. FORCASEi)ANDTHEDEFAULTGLAZINGAREASINVESTIGATETHESENSITIVITYOFTHE
ANNUAL SPACE HEATING REQUIREMENT TO THE AIR TIGHTNESS OF THE BUILDING.ASSUMINGANAIDIABETICINTERFACECALCULATEANDCOMPARETHEANNUALSPACEHEATINGREQUIREMENTFORASEMI‐DETATCHEDANDMID‐TERRACEBUILDING.
TotalMonthlyHeatLosses(kWh)
MonthlyHeatLossesDividedBySource(kWh)
TotalMonthlySolarGain.(kWh)
MonthlySolarGainsDividedBySourcingFaçade.(kWh)
TotalMonthlyGain.(kWh)
TotalLosses/TotalUsefulGains/TotalLossesGraphsTobeaddedasoverlayedgraph.
TotalMonthlyGains&Losses.(kWh)
TheGainsToLossesRatio(GLR)&TheUtilisationFactor(UF)Compared.
MonthlyUsefulHeatGain(kWh)
MonthlyVentillationLosses(kWh)
MonthlySpaceHeatingRequirement.(kWh)
AnnualSHR(kWh) 10825.6825
AnnualCost(£0.09) 974.3114251
INVESTIGATE THE SENSITIVITY OF THE ANNUAL SPACE HEATING REQUIREMENT TOREPLACINGTHEGLAZINGWITHAWINDOWWITH:
(i) g=0.75,U=1.6W/(m2C);
AnnualSHR(kWh) 9597.516277
AnnualCost(£0.09) 863.7764649
(ii) g=0.34,U=1.1W/m2C
AnnualSHR(kWh) 9046.125425
AnnualCost(£0.09) 814.1512882
AComparisonOfTheMonthlySHROfOption(i),(ii)&Default.(kWh)
TheaffectofairchangeontheASHRinadetatched,semidetatchedandmidterracehouse.(kWh)
DataForOption(i)Detatched AirChanges/n
AnnualSHR(kWh) Cost(£)
0.1 8026.88 542.420.2 6887.26 619.850.3 7771.00 699.390.4 8675.23 780.770.5 9597.52 863.780.6 10535.81 948.220.7 11488.38 1033.950.8 12453.75 1120.840.9 13430.62 1208.761.0 14417.89 1297.61
DataForOption(i)SemiDetatchedAirChanges/n
AnnualSHR(kWh) Cost(£)
0.1 4384.5 394.610.2 5189.77 467.080.3 6026.12 542.350.4 6889.24 620.030.5 7775.61 699.80.6 8682.31 781.410.7 9606.92 864.62
0.80 10547.41 949.270.90 11502.04 1035.181.00 12469.33 1122.24
DataForOption(i)Mid‐TerraceHouseAirChanges/n
AnnualSHR(kWh) Cost(£)
0.1 2595.75 233.620.2 3305.88 297.530.3 4062.51 365.630.4 4858.13 437.230.5 5686.76 511.810.6 5643.67 588.930.7 7424.95 668.250.8 8327.49 749.470.9 9248.65 832.381 10182.26 916.76
g=0.85TOTALDAILYHEATLOSSES/GAINS/USEFULLGAINSinkWh
MONTHLYHEATLOSSES/GAINS/USEFULLGAINSinkWh
GAIN/LOSSRATIOANDUTILISATIONFACTOR
g=0.75TOTALDAILYHEATLOSSES/GAINS/USEFULLGAINSinkWh
MONTHLYHEATLOSSES/GAINS/USEFULLGAINSinkWh
GAIN/LOSSRATIOANDUTILISATIONFACTOR
g=0.34TOTALDAILYHEATLOSSES/GAINS/USEFULLGAINSinkWh
MONTHLYHEATLOSSES/GAINS/USEFULLGAINSinkWh
GAIN/LOSSRATIOANDUTILISATIONFACTOR
MONTHLYSPACEHEATINGREQUIREMENT(in£)costofakWh‐>£0.09