[maryz]

The answer is as simple as the houses we grew up in. Insulation was unknown until the 50's.

Geez -- you'd better let all those researchers who are stymied by the dramatic rise in asthma know that you've figured it out! They're still theorizing about and investigating things like cockroach droppings (true) and overvaccination preventing proper development of the immune system (true), and probably lots of other things.

[hotshot]

Maybe no has asked about the effect of closed(non-recirculating) air in a energy efficient house. It is no different than the kids trapped in the car. (check family court docs. to find out how many kids have been taken for exposure to smoke).
It would require a thought process, not a closed mind. I bought an energy house in which brown water stains would run down the walls when the humidity in the house was up due to cooking or showers.(guess what the brown running down the walls was?)

[Gabz]

Good grief - don't get me started about roach droppings and associated problems!!!!

Believe me I am more than happy to have an occasional mouse in a trap now that I live in the country than ever again deal with the roach problem of "city" living!!!!