Heat from 300w CFL vs 400w HPS

I am currently running a 300w dual spectrum envirolight and would like to upgrade to a 400w HPS. I am a little concerned however as I have heard that the HPS lights kick out a lot more heat than the CFLs. My grow space is around 1.5ft x 3ft x 4.5ft but the ventilation is a little lacking at the moment (1 fan). At the moment my temps vary from 25c to up to 40c on a warm day with the doors closed.

Would a HPS be too hot for my space in its current form?

a watt is a watt is a watt, more energy more heat, however an hid light will always generate more heat because the ballast produces heat as well.

the hps gets hotter, you can get your hand closer on a cfl. the cfl also dissipates heat quicker due to surface area.
i reckon a bit hot if your temps are already that high !

Well, you can keep the ballast outside the growroom. With a 400w and a low powered fan you can expect your temps to be 10f higher than ambient, at least.

Here's a very helpful blog entry on ventilation. CaliGrowers chart is pretty accurate regardless of volume. https://www.rollitup.org/blogs/blog12353-ventilation-chart-calculator.html

You're going to more than double your lumen output with the 400w.