Okay, sick of this discussion, so I did the math. Go ahead and carry on arguing with it, without
Repeating my earlier point, the average bedroom measures a mere 86ft^2, or roughly 600ft^3, Meaning a 2400CFM box fan will completely remove the air from the room every 15 seconds. Two will then do the job every 7.5 seconds.
1 BTU will heat 55 ft^3 of air (at STP and H) by 1F. 20KW = 68290BTU/hr.
20KW will therefore heat 3755950 ft^3 per hour, or 62600 ft^3 per minute, or 7825 ft^3 per 7.5 seconds, by a single Fahrenheit degree. Or, put more usefully, it will heat 600ft^3 by 13F every 7.5 seconds; At 4800CFM (one full air-exchange per 7.5 seconds), that gives us a mean-over-time rise of 6.5F - Pretty damned close to my "feels 5F warmer" estimate from the woodstove. Funny, that
For the rest of this, I will refer to the Radeon 6990, the hottest single card (AFAIK) in common use. Your "preferences" of running cooler than spec aside, a Radeon HD 6970 (and the 6990 just contains two downclocked 6970 Cayman chips) has a tMax of 194F.
Now we have an interesting result here - With the stock cooler and under full load, a 6990 will violate its own spec
at ANY ambient over 73F. This would make the naysayers appear correct...
But! We've also demonstrated that two box fans will
clear 20KW of heat from a room, with a 6.5F steady-state rise. That reduces the problem to airflow at the ambient/heatsink interface.
Since we've limited this discussion to airflow, I'll limit the following to fan/heatsink combos only. Using a halfway decent aftermarket cooler, you can drop the under-load temperature to below 160F (you can find similar numbers in dozens of articles on Tom's Hardware or AnandTech, if you like - For my exact source, I found http://www.kitguru.net/components/graphic-cards/zardon/arctic-cooling-accelero-twin-turbo-6990-cooler-review/5/
helpful in that it described the test conditions sufficiently well to extrapolate from them), for a plausible under-load delta-T of a mere 87F.
This, then, gives us a "feasibility" result of 107F at the intake, or a raw outside temperature of 100.5F.
Call that a win or a lose, as you like. Where I live (if I didn't pay a fortune for electricity), it would put me over my "thermal budget" for two days in the past decade (no, DeathAndTaxes
, not talking about winter, nor did I ever). And I don't live in Sweden.