Our house was foamed by a local company, walls and roof deck, open cell. When the guy was bidding/selling, he said the attic space should be no more than 5 degrees warmer or cooler, depending on the season, than the conditioned living space. So far, that ain't the slightest bit true. Did we get salesman'd or could there be more to the equation? On the warmer days we've had so far I'd say the bonus room (unconditioned but in the same thermal envelope) is 10-15 degrees warmer, it's basically open to the attic space.