FFS no way? I've just bought this spec as I couldn't use my Antminer lol. What about cooling it down with something? I think the 580 I bought has a lot of cooling with it?
It doesn't matter how good the GPU cooler is. If the GPU consumes 150W with a good cooler, it is going to put as much heat in the room as another 150W GPU with a bad cooler. The GPU with a good cooler will do it while keeping the GPU components at lower temps (i.e. keeping the core at 50º instead 70º), but both will output the same amount of heat to the room (power consumption = heat generated).
The good thing is that you can configure the GPUs to run at lower speeds to consume less power. This would result in lower hashrate, but at least you won't have issues with the wood in your garage.
Think about it this way - your garage is a sealed box, and you're putting a 1/1.5kw heater in it.
It's going to heat it up a lot, so you need to move that heat out of the box - an extractor fan up high and some holes covered in mesh low down will be surprisingly effective.