4.2 - FOUNDATION
  Number of households by year of construction
1970 – 1979 1980 – 1989 1990 – 1999 2000 – 2011
Dwelling has a basement for foundation
Yes 1,458,776 A 1,208,227 A 948,455 A 1,272,615 A
No 240,406 A 246,433 A 266,066 M 320,798 M
Don't know U U U U
Not stated 97,604 M U U U
Dwelling has a crawl space for foundation
Yes 161,287 A 131,484 A 87,996 M 134,274 M
No 1,537,896 A 1,323,175 A 1,126,525 A 1,459,140 A
Don't know U U U U
Not stated 97,604 M U U U
Dwelling has concret slabs for foundation
Yes 124,143 M 162,635 M 218,638 M U
No 1,575,040 A 1,292,024 A 995,883 A 1,409,808 A
Don't know U U U U
Not stated 97,604 M U U U
Dwelling has pillars for foundation
Yes U U U U
No 1,681,325 A 1,433,095 A 1,192,235 A 1,569,142 A
Don't know U U U U
Not stated 97,604 M U U U
Other type of dwelling foundation
Yes U U U U
No 1,661,086 A 1,443,269 A 1,203,362 A 1,559,072 A
Don't know U U U U
Not stated 97,604 M U U U
Dwelling has no foundation
Yes U U U U
No 1,676,760 A 1,425,428 A 1,210,308 A 1,574,379 A
Don't know U U U U
Not stated 97,604 M U U U
Basement / crawl space is heated
Yes 1,463,245 A 1,180,237 A 922,570 A 1,235,642 A
No 98,108 A 111,646 M 69,852 M 126,503 M
Don't know U U U U
Not stated 109,384 M 73,115 M U U
Insulation of any outside basement / crawl space walls
Yes 1,271,802 A 1,066,085 A 873,316 A 1,186,304 A
No 102,935 M U U U
Don't know 106,776 M U U U
Not stated 126,526 M 99,509 M 126,547 M 102,397 M
Percentage of outside basement / crawl space walls insulated
25 percent or less U U U U
26 to 50 percent 57,238 M 53,008 M U U
51 to 75 percent 111,852 M 56,598 M U U
76 to 100 percent 810,095 A 703,707 A 576,179 A 909,059 A
Don't know 360,278 A 258,924 A 248,013 A 208,562 M
Not stated 152,115 M 129,289 M 154,415 M 112,953 M

Note:

Due to rounding, the numbers may not add up and may differ slightly among tables.

Legend:

The letter beside each estimate classifies its quality as follows: A–Acceptable, M–Use with caution, U–Too unreliable to be published.

Source:

2011 Survey of Household Energy Use