|Number of households by year of construction|
|1990 – 1999||2000 – 2011|
|Dwelling has an attic|
|Dwelling has an insulated attic|
|Yes - on the attic floor||676,020||A||825,535||A|
|Yes - on the attic walls||–||U||–||U|
|Yes - on both the attic floor and walls||114,790||M||234,995||M|
Note:Due to rounding, the numbers may not add up and may differ slightly among tables.
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