Environmental Controls IIG Lecture 9 Heat Flow in

Conductive Heat Flow through opaque materials: Q= U x A x ΔT Q: heat

Transmission Coefficient (U): U= 1/ΣR U: transmission coefficient (Btu/h-ºF-ft 2) ΣR: sum of resistance

Summing R-values Sum of R-values (ΣR): ΣR= 1/h. O+R 1+R 2+R 3+…+1/h. I h.

Air Films Film surface conductance coefficient Outdoor air film: R= 1/h. O Indoor air

Finding h. O and h. I – Emittance(ε): absorption of radiant heat S: p.

Finding h. O and h. I Direction of Heat Flow Film surface conductance coefficient

Finding h. O and h. I – Emittance(ε): absorption of radiant heat Effective Emittance

R-values for Enclosed Air Cavities Air Space Direction of Temperature Film surface conductance coefficient

R-values For Solid Materials Conductance Table 4. 2 Conductivity Thermal Properties of Typical Building

Conductivity and Conductance Conductivity (k) heat flow through a material per unit thickness Conductance

Conductivity and Conductance Example 1 x” Say x=4” Conductivity vs. Conductance 1” 1ºF 1’

Converting to Resistance (R): measure of resistance to the passage of heat (h-ft 2

Converting to Resistance Example 1 (cont. ) x” Say x=4” Conductivity vs. Conductance 1”

Thermal Properties Table 4. 2 Thermal Properties of Typical Building and Insulating Materials S:

U-Value Calculation Wall 1 indoor air film ½” gypsum board 2”x 4” nominal stud

U-Value Calculation Component At Insulation (RI) At Frame (RF) Ref. indoor air film 0.

Finding Indoor Air Film Coefficient –h. I Indoor air film Vertical surface Film surface

Finding Gypsum Board R-value Table 4. 2 Thermal Properties of Typical ½” Gypsum Board

Finding Framing R-value Nominal 2 x 4 Pine stud depth is 3. 5” Ravg=(1.

Thermal Properties Table 3. 5” Insulation Table 4. 2 Thermal Mineral Fiber Properties of

Finding Fiberboard R-value ½” Fiberboard Table 4. 2 Thermal Properties of Typical Building and

Finding Wood Shingle R-value Wood shingles (16”, 12” exposure) Table 4. 2 Thermal Properties

Finding Outdoor Air Film Coefficient--h. O Outdoor air film Winter Wind Film surface conductance

U-Value — Overall Average Component Totals At Insulation (RI) ΣRI 16. 81 UI 0.

Thermal Mass Component indoor air film ½” gypsum board Density #/cf Weight #/sf 0.

Insert Microclimate critiques here Insert Exam results here

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Environmental Controls I/IG Lecture 9 Heat Flow in Opaque Materials Thermal Mass

Conductive Heat Flow through opaque materials: Q= U x A x ΔT Q: heat flow (Btuh) U: transmission coefficient (Btu/h-ºF-ft 2) A: area (ft 2) ΔT: temperature difference (Ti-To)

Transmission Coefficient (U): U= 1/ΣR U: transmission coefficient (Btu/h-ºF-ft 2) ΣR: sum of resistance values (R-values) for layers of a construction assembly

Summing R-values Sum of R-values (ΣR): ΣR= 1/h. O+R 1+R 2+R 3+…+1/h. I h. O, h. I: film surface conductance coefficients R 1, R 2, R 3, …: Resistance values (R-values) for each layer of a construction assembly

Air Films Film surface conductance coefficient Outdoor air film: R= 1/h. O Indoor air film: R=1/h. I

Finding h. O and h. I – Emittance(ε): absorption of radiant heat S: p. 1570, T. E. 3 B

Finding h. O and h. I Direction of Heat Flow Film surface conductance coefficient (S: p. 158, T 4. 3) Position of Surface Air Motion S: p. 1570, T. E. 3 B Emittance

Finding h. O and h. I – Emittance(ε): absorption of radiant heat Effective Emittance (εeff): 1/εeff=1/ε 1+1/ε 2 -1 S: p. 1570, T. E. 3 B

R-values for Enclosed Air Cavities Air Space Direction of Temperature Film surface conductance coefficient Heat Flow (S: p. 161, T 4. 4) Position of Air Space S: p. 1571, T. E. 1 Air Space Width Emittance

R-values For Solid Materials Conductance Table 4. 2 Conductivity Thermal Properties of Typical Building and Insulating Materials Density S: p. 1549, T. E. 1 Resistance

Conductivity and Conductance Conductivity (k) heat flow through a material per unit thickness Conductance (C): heat flow through a material of stated thickness C=k/x where x= unit thickness (in. )

Conductivity and Conductance Example 1 x” Say x=4” Conductivity vs. Conductance 1” 1ºF 1’ Conductance C=k/x=0. 25/4”=0. 0625 Btuh 1’ 1ºF Conductivity k=0. 25 Btuh S: p. 182, F. 7. 8

Converting to Resistance (R): measure of resistance to the passage of heat (h-ft 2 -ºF/Btu) R=1/C or R=x/k

Converting to Resistance Example 1 (cont. ) x” Say x=4” Conductivity vs. Conductance 1” 1ºF 1’ Conductance C=k/x=0. 25/4”=0. 0625 Btuh Resistance R=x/k=4/0. 25=16 1’ 1ºF Conductivity k=0. 25 Btuh Resistance R=1/k=1/0. 25= 4 S: p. 182, F. 7. 8

Thermal Properties Table 4. 2 Thermal Properties of Typical Building and Insulating Materials S: p. 1522 -3, T. E. 1

U-Value Calculation Wall 1 indoor air film ½” gypsum board 2”x 4” nominal stud (pine) w/3. 5” Ins. ½” fiberboard wood shingles (16” long, 12” exposure) outdoor air film Section View

U-Value Calculation Component At Insulation (RI) At Frame (RF) Ref. indoor air film 0. 68 T. E. 3 A ½” gypsum board 0. 45 T. E. 1 2 x 4 stud (3. 5” pine) T. E. 1 3. 5” Insulation n. a. 13. 00 4. 35 n. a. T. E. 1 ½” fiberboard 1. 32 T. E. 1 wood shingles 1. 19 T. E. 1 outdoor air film 0. 17 T. E. 3 A ΣRI 16. 81 ΣRF 8. 16 Totals UI 0. 059 UF 0. 123

Finding Indoor Air Film Coefficient –h. I Indoor air film Vertical surface Film surface conductance coefficient Horizontal heat flow (S: p. 158, T 4. 3) Non-reflective surface h. I=1. 46 R=0. 68 S: p. 1570, T. E. 3 A

Finding Gypsum Board R-value Table 4. 2 Thermal Properties of Typical ½” Gypsum Board Building and Insulating Materials R=0. 45 S: p. 1549, T. E. 1

Finding Framing R-value Nominal 2 x 4 Pine stud depth is 3. 5” Ravg=(1. 35+1. 11)/2=1. 23/inch Table 4. 2 Thermal Properties of Typical Building and Insulating Materials R=3. 5 x 1. 23 =4. 35 S: p. 1567, T. E. 1

Thermal Properties Table 3. 5” Insulation Table 4. 2 Thermal Mineral Fiber Properties of Typical Building and R=13. 00 Insulating Materials S: p. 1522 -3, T. E. 1

Finding Fiberboard R-value ½” Fiberboard Table 4. 2 Thermal Properties of Typical Building and Insulating Materials R=1. 32 S: p. 1549, T. E. 1

Finding Wood Shingle R-value Wood shingles (16”, 12” exposure) Table 4. 2 Thermal Properties of Typical Building and Insulating Materials R=1. 19 S: p. 1567, T. E. 1

Finding Outdoor Air Film Coefficient--h. O Outdoor air film Winter Wind Film surface conductance coefficient Horizontal heat flow (S: p. 158, T 4. 3) Non-reflective surface h. O=6. 0 R=0. 17 S: p. 1570, T. E. 3 A

U-Value — Overall Average Component Totals At Insulation (RI) ΣRI 16. 81 UI 0. 059 At Frame (RF) ΣRF 8. 16 UF 0. 123 15% framing: UAVG=0. 85(0. 059)+0. 15(0. 123)=0. 069

Thermal Mass Component indoor air film ½” gypsum board Density #/cf Weight #/sf 0. 00 50. 0 2. 08 1. 2 0. 35 ½” fiberboard 18. 0 0. 75 wood shingles 26. 6 1. 11 3 -½” insulation outdoor air film 0. 0 4. 29 #/sf 0. 00 Weight (#/sf)=Density (#/cf) x Thickness (ft. ) ½” Gyp. Bd. =50#/cf x 0. 0416’= 2. 08 #/sf

Insert Microclimate critiques here Insert Exam results here