Sweden adopted strict energy
conservation measures after the first
oil crisis in 1973 and has been
strengthening them ever since.
Features like R-33 walls and R-5
windows are now common.
Along with energy-efficiency
standards, however, have come
problems. Sweden experienced a
spate of "sick building syndrome"
claims in the late 1970s.
Government sponsored researchers
have responded by identifying toxins
in building materials and alternative
products. They have also found
correlations between chemical
sensitivity and humidity levels in
buildings. But the majority of their
work has centered on improving
How Much Is Enough?
In this country, ASHRAE
currently recommends ventilating
homes at a rate of .35 air changes
per hour (ACH). Based on their
long experience grappling with airquality
concerns, however, the
Swedes require more ventilation.