Recommended Levels of Insulation


Walls, attics or floors have different insulation requirements. Likewise, homes in cold, temperate and hot climates involve different insulation needs. And these differences are very important and should be taken into account: recommended insulation levels vary a lot, according to the part of the house and the climate zone.

Climate and recommend Insulation

Climate is an extremely important variable when considering the amounts and the insulation requirements. Even the goals of insulation differ with climate: while the insulation main goal in colder climates is to reduce heat losses, in hot climates the main goal of the insulation is to keep the cool air inside…

Recommended Insulation Levels for the different Parts of the house

Recommended insulation R-values also vary a lot with the part of the house.

Roofs, ceilings, walls, floors and basements have different requirements, according to 1) the extent of their surfaces and their design and position in the home, 2) the way the parts of the house face the sun or wind, or 3) some basic facts like that hot air tends to rise and cold air to descend…

Recommended R-Values in cold and mix climates

The recommended insulation levels considered below (from the American Energy Star) for walls, floors, ceilings and crawl spaces in American climate zones, are obviously applicable to many other states worldwide.

You just have to figure out with which American climate zone your own climate is similar enough. For hotter climates, see: Recommended R-values in hot and tropical climates.

The insulation values in the table are expressed in non-SI units.

Recommended Insulation R-Values for Existing Houses
Ceiling Wood-frame wall Floor Basement/ Crawl space walls d
Warm with cooling and minimal heating requirements (i.e., FL & HI; coastal CA; southeast TX; southern LA, AR, MS, AL & GA). gas/oil or heat pump R-22 to R-38 R-11 to R-13 R-11 to R-13 R-11 to R-19
electric resistance R-38 to R-49 R-13 to R-25 R-13 to R-19 R-11 to R-19
Mixed with moderate heating and cooling requirements (i.e., VA, WV, KY, MO, NE, OK, OR, WA & ID; southern IN, KS, NM & AZ; northern LA, AR, MS, AL & GA; inland CA & western NV). gas/oil or heat pump R-38 R-11 to R-22c R-13 TO R-25 R-11 to R-19
electric resistance R-11 to R-26c R-25 R-11 to R-19
Cold (i.e., PA, NY, New England, northern Midwest, Great Lakes area, mountainous area (e.g., CO, WV, UT, etc.)). gas/oil R-38 to R-49 R-11 to R-22c R-25 R-11 to R-19
heat pump or electric resistance R-49 R-11 to R-28c R-25 R-13 to R-19
b. Insulation is also effective at reducing cooling bills. These levels assume your house has electric air-conditioning.
c. R-values may be achieved through a combination of cavity insulation and rigid board insulation and are for insulation only (not whole wall).
d. Do not insulation crawl space walls if crawl space is wet or ventilated with outdoor air.

Recommended insulation Values for hot, temperate warm and tropical climates

The recommended insulation values listed below (from the Australian Government Greenhouse) for walls and roof/ceilings in Australian climates, are obviously valid for temperate-warm and tropical climates in other countries.

Pay attention to the meaning of the zero value in the table. Zero, in this case, means that insulation may not be needed and be a cause of overheating. In some hot-tropical climates, the insulation isn’t recommended (except reflective insulation and special cases involving the use of air-conditioning. See: Cooling and Insulation).

Pay also attention to the 5,67 element, in each cell. The 5,67 converts the SI-Australian system to the Non-SI units (see, on this issue: non-SI units). In other words: if your country uses the SI system, forget the 5,67. Otherwise…

EXAMPLE OF LOCATIONS (material or system R values)
Cool Temperate & Alpine
Melbourne, Vic 3.0 x 5,67 1.5 x 5,67
Canberra, ACT 3.5 x 5,67 1.5 – 2.0 x 5,67
Hobart, Tas 3.5 x 5,67 1.5 – 2.0 x 5,67
Mt Gambier, SA 3.0 x 5,67 1.5 – 2.0 x 5,67
Ballarat, Vic 3.5 x 5,67 1.5 – 2.0 x 5,67
Thredbo, NSW 4.0 x 5,67 1.5 – 2.0 x 5,67
Hot Humid & Hot Dry
Darwin, NT 0* -4.0 x 5,67 0* – 2,0 x 5,67
Cairns, Qld 0* -3.5 x 5,67 0* – 1,5 x 5,67
Broome, WA 0* -4.0 x 5,67 0* – 2,0 x 5,67
Marble Bar, WA 0* -4.0 x 5,67 0* – 2,0 x 5,67
Mt Isa, QLD 0* -4.0 x 5,67 0* – 2,0x 5,67
Tennant Creek, NT 0* -4.0 x 5,67 0* – 2,0x 5,67
Townsville, QLD 0* -3.5 x 5,67 0* -1,5 x 5,67
Temperate & Warm Humid
Brisbane, QLD 1.5 – 2.5 x 5,67 1.0 x 5,67
Perth, WA 1.5 – 3.0 x 5,67 1.5 x 5,67
Alice Springs, NT 1.5 – 4.0 x 5,67 1.5 – 2.0 x 5,67
Bourke, NSW 1.5 – 4.0 x 5,67 1.5 – 2.0 x 5,67
Sydney, NSW 1.5 – 3.0 x 5,67 1.5 x 5,67
Adelaide, SA 2.0 – 3.0 x 5,67 1.5 x 5,67
Katoomba, NSW 4.0 x 5,67 1.5 – 2.0 x 5,67

Zone Add Insulation to Attic Floor
Uninsulated Attic Existing 3–4 Inches of Insulation
1 R30 to R49 R25 to R30 R13
2 R30 to R60 R25 to R38 R13 to R19
3 R30 to R60 R25 to R38 R19 to R25
4 R38 to R60 R38 R25 to R30
5 to 8 R49 to R60 R38 to R49 R25 to R30
Wall Insulation: Whenever exterior siding is removed on an

Uninsulated wood-frame wall:

  • Drill holes in the sheathing and blow insulation into the empty wall cavity before installing the new siding, and
  • Zones 3–4: Add R5 insulative wall sheathing beneath the new siding
  • Zones 5–8: Add R5 to R6 insulative wall sheathing beneath the new siding.

Insulated wood-frame wall:

  • For Zones 4 to 8: Add R5 insulative sheathing before installing the new siding.


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