Building & insulation values

R-values, U-values, internal gains, solar gain and air leakage.

R-values of materials

Material	R-value
Inside surface (still air)	0.68
Outside surface (15 mph wind)	0.17
Air space	0.97
3/8 in gypsum board	0.32
1/2 in gypsum board	0.5
Face brick	0.39
4 in concrete block	1.11
Wood siding, 1/2 × 8 in	0.85
Building paper	0.06
Wood sheathing	0.98
1 in wood floor	0.98
Linoleum or tile	0.05
Asphalt shingles or plywood	0.95
5 1/2 in fibreglass batt	19

Heat flow (BTU/h) = U × area × temperature difference, where U = 1 ÷ total R. Total R includes the air films (still air inside 0.68, 15 mph wind outside 0.17).

Windows and glass

Glass	U-value	R-value
Single	1.04	0.96
Single with storm	0.56	1.79
Double, 1/2 in space	0.49 to 0.58	1.73 to 2.00
Triple	0.32	3.10
Hollow glass tile	0.60	1.67

Glass loses about three times as much as an ordinary roof or ceiling.

Doors (U-value)

Door	No storm	With storm
Wood, hollow core	0.47	0.30 (wood) / 0.32 (metal)
Wood, solid core	0.39	0.26 / 0.28
Wood, panel	0.54	0.32 / 0.36
Metal, fibreglass core	0.60	0.36
Metal, paper honeycomb core	0.56	0.34
Metal, polystyrene core	0.35	0.21
Metal, polyurethane core	0.29	0.17

Walls, floors and ceilings (U / R)

Construction	U	R
Wood siding, sheathing, studs, 1/2 in gypsum	0.23	4.4
Same plus 1 in polystyrene	0.07	14.4
Same with rock wool fill	0.072	13.9
Stucco, siding, studs, gypsum	0.30	3.3
Brick veneer, sheathing, studs, gypsum	0.25	4.0
Brick veneer plus 1 in polystyrene	0.07	14.4
4 in concrete floor, no finish	0.65	1.54
4 in concrete plus suspended plaster	0.37	2.7
Joists with plaster ceiling, wood floor	0.23	4.4
Joists, no floor, plaster ceiling	0.62	1.6
Same plus 3 5/8 in rock wool	0.079	12.7
Flat metal roof	0.46	2.2

Adjoining unconditioned rooms use half the outdoor temperature difference. An unheated attic or closet sits roughly halfway between indoor and outdoor. A basement is about 60 °F.

Heat from people and equipment

Source	BTU/h
Person sitting	370 sensible + 140 latent (about 510)
Person working	700 to 1500 + 140 latent
Strenuous work	about 2000 + 140 latent
Lights, per kW	3,415
Electric stove, per kW	3,415
Motor inside the space, 1/2 hp or less	4,200 per hp
Motor inside, up to 3 hp	3,700 per hp
Motor inside, up to 20 hp	2,950 per hp
Gas appliance, per ft³ of natural gas	1,100 sensible + 300 latent

Window sun gain (BTU/h per ft², summer)

Direction	Gain
South-west	110
West	100
South	75
East	55
Skylight, single	110
Skylight, double	60
North	1
North-east	2
North-west	3

Heat-absorbing glass cuts solar gain about 30%, double glazing about 15%, awnings or overhangs about 55%. Heat takes 3 to 4 hours to move through a normal wall. A south wall without shade: add 15 °F to the outdoor temperature in a cooling calculation.

Air leakage (air changes per hour), single storey

House	Up to 900 ft²	901 to 1500	1501 to 2000	2001 to 3000	Over 3000
Tight, heating	0.21	0.16	0.14	0.11	0.10
Average, heating	0.61	0.45	0.38	0.32	0.28
Loose, heating	1.29	0.94	0.80	0.66	0.58
Tight, cooling	0.11	0.08	0.07	0.06	0.05
Average, cooling	0.32	0.23	0.20	0.16	0.15
Loose, cooling	0.67	0.49	0.42	0.34	0.30

Infiltration BTU/h (sensible) = 0.018 × ft³ per hour × temperature difference. Slab on grade loses about 18 BTU/h per foot of edge at 0 °F. These are planning figures only; a code-compliant load calculation is required to size equipment.

Take it with you

All of these tables, plus the calculators, are in the HVACopedia app, offline.

Open the app

Calculation aids and reference figures for licensed technicians. Always follow the manufacturer’s data plate and manual for the exact model, and local codes. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Pressures are typical saturation values and change with load and airflow.