U values of building assemblies

Abstracted from ASHRAE (1989), with permission

Coefficients of transmission U for wood doors (Btu/hr · ft2 · °F)

Thickness

Description

Winter

Summer

15 mi/h wind
70°F inside temperature

7.5 mi/h wind
75°F inside temperature

No storm door

Wood storm door (50% glass)

Metal storm door

No storm door

1 3/8 in

Hollow-core flush door

0.47

0.30

0.32

0.45

1 3/8 in

Solid-core flush door

0.39

0.26

0.28

0.38

1 3/4 in

Solid-core flush door

0.33

0.28

0.25

0.32

1 3/4 in

Solid-core flush door with single glazing (17% glass)

0.46

0.29

0.32

0.44

1 3/4 in

Solid-core flush door with insulating glass (17% glass)

0.37

0.25

0.27

0.36

Coefficients of transmission U for steel doors (Btu/hr · ft2 · °F)

Thickness

Description

No storm door

Metal storm door

1 3/4 in

Fiberglass or mineral fiber core with steel stiffeners, no thermal break

0.60

-

1 3/4 in

Solid urethane foam core with thermal break

0.20

0.16

Overall coefficients of heat transmission U of windows,
sliding patio doors, and skylights (Btu/hr · ft2 · °F)

 

Single Pane

Double Pane

Triple Pane

Plastic domes

No air space

3/16 inch air space

1/4 inch air space

1/2 inch air space

1/4 inch air space

1/2 inch air space

Single wall

Double wall

No low-E coating
e = 0.84

No low-E coating
e = 0.84

No low-E coating
e = 0.84

No low-E coating
e = 0.84

Low-E coating
e = 0.6

Low-E coating
e = 0.4

Low-E coating
e = 0.2

No low-E coating
e = 0.84

No low-E coating
e = 0.84

No storm sash

No shade

Winter

1.1

0.62

0.59

0.49

0.43

0.38

0.32

0.39

0.31

   

Summer

1.04

0.65

0.61

0.56

0.51

0.48

0.38

0.44

0.39

   

Indoor shade

Winter

0.83

0.52

0.48

0.42

0.38

0.36

0.3

0.31

0.26

   

Summer

0.81

0.58

0.55

0.52

0.48

0.43

0.37

0.4

0.36

   

Glass outdoor storm sash with 1 inch airspace

No shade

Winter

0.5

0.37

0.35

0.32

0.3

0.27

0.24

0.27

0.23

   

Summer

0.5

0.4

0.39

0.39

0.36

0.39

0.3

0.32

0.31

   

Indoor shade

Winter

0.44

0.29

0.28

0.25

0.24

0.22

0.2

0.22

0.19

   

Summer

0.49

0.37

0.36

0.3

0.35

0.32

0.28

0.3

0.29

   

Glass indoor storm sash with 1 inch airspace

No shade

Winter

0.5

0.37

0.35

0.31

0.29

0.27

0.25

0.27

0.23

   

Summer

0.5

0.4

0.39

0.38

0.36

0.33

0.29

0.32

0.3

   

Indoor shade

Winter

0.44

0.29

0.28

0.25

0.24

0.22

0.20

0.22

0.19

   

Summer

0.49

0.36

0.36

0.35

0.33

0.31

0.26

0.3

0.28

   

Acrylic indoor storm sash with 1 inch airspace

No shade

Winter

0.48

0.35

0.34

0.3

0.28

0.26

0.24

0.26

0.22

   

Summer

0.48

0.39

0.38

0.37

0.35

0.32

0.28

0.31

0.29

   

Indoor shade

Winter

0.42

0.28

0.27

0.24

0.23

0.22

0.2

0.22

0.18

   

Summer

0.47

0.35

0.34

0.33

0.32

0.3

0.27

0.29

0.28

   

Exterior horizontal panels (skylights)

Winter

1.23

0.7

0.65

0.59

0.48

0.52

0.56

   

1.15

0.7

Summer

0.83

0.57

0.54

0.49

0.36

0.42

0.46

   

0.8

0.46

Notes: