Table C303.1.3(4)

Default U-Factors for Skylights

		Frame Type
		Aluminum Without Thermal Break	Aluminum With Thermal Break	Reinforced Vinyl/Aluminum- Clad Wood or Vinyl	Wood or Vinyl-Clad Wood/Vinyl Without Reinforcing
Fenestration Type		Aluminum Without Thermal Break	Aluminum With Thermal Break	Reinforced Vinyl/Aluminum- Clad Wood or Vinyl	Wood or Vinyl-Clad Wood/Vinyl Without Reinforcing
Single Glazing
	glass	U-1.58	U-1.51	U-1.40	U-1.18
	acrylic/polycarb	U-1.52	U-1.45	U-1.34	U-1.11
Double Glazing
	air	U-1.05	U-0.89	U-0.84	U-0.67
	argon	U-1.02	U-0.86	U-0.80	U-0.64
Double Glazing, e = 0.20
	air	U-0.96	U-0.80	U-0.75	U-0.59
	argon	U-0.91	U-0.75	U-0.70	U-0.54
Double Glazing, e = 0.10
	air	U-0.94	U-0.79	U-0.74	U-0.58
	argon	U-0.89	U-0.73	U-0.68	U-0.52
Double Glazing, e = 0.05
	air	U-0.93	U-0.78	U-0.73	U-0.56
	argon	U-0.87	U-0.71	U-0.66	U-0.50
Triple Glazing
	air	U-0.90	U-0.70	U-0.67	U-0.51
	argon	U-0.87	U-0.69	U-0.64	U-0.48
Triple Glazing, e = 0.20
	air	U-0.86	U-0.68	U-0.63	U-0.47
	argon	U-0.82	U-0.63	U-0.59	U-0.43
Triple Glazing, e = 0.20 on 2 surfaces
	air	U-0.82	U-0.64	U-0.60	U-0.44
	argon	U-0.79	U-0.60	U-0.56	U-0.40
Triple Glazing, e = 0.10 on 2 surfaces
	air	U-0.81	U-0.62	U-0.58	U-0.42
	argon	U-0.77	U-0.58	U-0.54	U-0.38
Quadruple Glazing, e = 0.10 on 2 surfaces
	air	U-0.78	U-0.59	U-0.55	U-0.39
	argon	U-0.74	U-0.56	U-0.52	U-0.36
	krypton	U-0.70	U-0.52	U-0.48	U-0.32

1	U-factors are applicable to both glass and plastic, flat and domed units, all spacers and gaps.
2	Emissivities shall be less than or equal to the value specified.
3	Gap fill shall be assumed to be air unless there is a minimum of 90 percent argon or krypton.
4	Aluminum frame with thermal break is as defined in footnote 1 to Table C303.1.3(5).