# Heat Losses Excel Spreadsheet by agl26257

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Heat Losses Excel Spreadsheet document sample

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Envelope Heat Loss Calculations
Heat Loss Homework Generic Building Template

General Assumptions
Night
Windy
Minimal thermal buffering (no trombe walls)
No latent heat loss (good vapor barriers)

Given Data
Building as described in assignment

Looked-up data
Data                                                                          Source
Tout =                                             oF                         Table 2, p HE-16
Tin =                                              oF                         Given

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Radiative Losses (Sky and Nearby Buildings)
Q = A*E*Gamma*(Tf^4 - Tsky^4) (BTU/hr)
A       = Area of surface (facade or roof)
E      = Emmisivity of surface (per Table 1, p HE 16)
Gamma= Steffan-Boltz constant
= 0.17x10-8 BTU/(hr*ft^2*oR^4)
= 5.7x10-8 W/(m^2*oK^4)
Tf      = Temp of exterior surface of facade (oR = oF + 460; = Tout)
Tsky = Temp of sky (oR = oF + 460; per fig 14 and table 3, p HE 17

Assumptions / Notes
Wall temp inside similar to average interior air temp (losses to inside negligable)
Tf = Tout

Calculations
Object                    Area                 E            Tf         Tsky                Q
(SF)                            (oF)         (oF)            (BTU/hr)

Roof                                                         0                    #VALUE!
Walls                                                        0                    #VALUE!

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Windows                                                 0                   #VALUE!

Qtot

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Conduction
Thru Facade and Roof          Q = A*(Tin-Tout)/Rtot
Rtot = R1+...+Rn (P HE 20 to HE 25)

Through SOG to Soil           Q = A*(Tin-Tout)/Rtot
(Normal to SOG)               Rtot = R1+...+Rn (P HE 20 to HE 25)
Tout for SOG = annual ave temp (Table 2, p HE 16)

Perim of SOG                  Q = L*(Tin-Tout) / R
to atmosphere                 L = perim. length of SOG
(Cooling fin)                 R = perimeter SOG resistance (Table 5, p HE 28)

Assumptions / Notes
None especially

Calculations - Facade, Roof, and SOG to Soil
Location             Area                R       Tout            Tin               Q
(SF)     (ft^2*hr*oF/       (oF)           (oF)           (BTU/hr)
BTU)
Roof                                                    0             0     #VALUE!
Walls                                                   0             0     #VALUE!
Windows                                                 0             0     #VALUE!
SOG                                                                         #VALUE!

Calculations - SOG to atmosphere (cooling fin)
Length               R        Tout            Tin               Q
(ft)   (ft^2*hr*oF/        (oF)           (oF)           (BTU/hr)
BTU)
0             0         #DIV/0!

Qtot

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Air Change

Temperature Induced
Q = C*CFH*(Tin-Tout)
C = Heat capacity of air (0.02 BTU / (ft^3oF)
CFH = cubic ft / hr of air entering the building by infiltration (P HE 9)

Humidity Induced
Q = Cp*CFH*(AHin - AHout)
Cp     = Heat of vaporization of H20 [(0.0113 BTU / Grain) * (Lbs / ft^3)]
CFH = cubic ft / hr of air entering the building by infiltration
AHin, AHout = absolute humidity in and outside (Grains/Lbs; P HE 8)

Assumptions
No inflitration through earth or roof
No ventilation except by infiltration

Calculations - Temperature
Air change rate =                             Air changes per hour
CFH = Building Volume * Air change rate / 2
Building Volume =
CFH =                                       0 Cubic feet per hour

Q    = C*CFH*(Tin-Tout)
Q    =                                                                            0

Calculations - Humidity
CFH =                                          0 Cubic feet per hour
AHin =                                           Grains / Lb
AHout =                                          Grains / Lb

Q=      Cp*CFH*(AHin - AHout)
Q=                                                                                0

Qtot:

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Total Heat Loss (Radiation, Conduction, Infiltration)

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#VALUE!   (BTU/hr)

#VALUE!   (BTU/hr)

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BTU/hr

BTU/hr

0 (BTU/hr)

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#VALUE!   BTU/hr

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