Heat issue

i have a loft grow in a 5m x 7m loft with a sloping roof.

I have a 3250m3 exhaust shooting air into the chimney.

The entire loft is insulated. Wind flows under the tiles into a 4 inch air gap between the rafters and then a layer of kingspan sealing the entire loft followed by an extra layer of space blanket stapled to kingspan for good measure.

I have 5000w of cob led in there and so far with the exhaust on full power my temps rise from 20c when lights come on and slowly creeps up to 28c when lights go off.

I would of thought that due to the size of my exhaust air would be exchanged so far that any heat generated is removed..
I'm concerned as it's currently 0c outside / 32f and in summer it can be 30c outside I guess if my exhaust doesn't work I'll end up hitting 40c in the loft in summer.

Anyone got any ideas what could be causing this?

The volume of the loft 7m x 6m x 2m is a lot larger than it actually is due to sloping roof but if I use those dimensions for the volume the air should be exchanging easily every 2 minutes.

I left the lights on for the last 24 hours and it's weird the temp increases until it hits 28.5c and then stabilises.

Is that normal? Maybe it's just the radiant heat from led increases ambient temp but won't increase it above 28.5 due to the exhaust?

SamWE19 said:

i have a loft grow in a 5m x 7m loft with a sloping roof.

I have a 3250m3 exhaust shooting air into the chimney.

The entire loft is insulated. Wind flows under the tiles into a 4 inch air gap between the rafters and then a layer of kingspan sealing the entire loft followed by an extra layer of space blanket stapled to kingspan for good measure.

I have 5000w of cob led in there and so far with the exhaust on full power my temps rise from 20c when lights come on and slowly creeps up to 28c when lights go off.

I would of thought that due to the size of my exhaust air would be exchanged so far that any heat generated is removed..
I'm concerned as it's currently 0c outside / 32f and in summer it can be 30c outside I guess if my exhaust doesn't work I'll end up hitting 40c in the loft in summer.

Anyone got any ideas what could be causing this?

The volume of the loft 7m x 6m x 2m is a lot larger than it actually is due to sloping roof but if I use those dimensions for the volume the air should be exchanging easily every 2 minutes.

Click to expand...

Fans do not remove heat, only warm air. The source of the heat (the radiating surfaces) stays behind. Only an AC cools.

SamWE19 said:

I left the lights on for the last 24 hours and it's weird the temp increases until it hits 28.5c and then stabilises.

Click to expand...

Ah cool, I was going to suggest an experiment to see if that kind of thing was going on.
Something like, using a heater in the light cycle morning to quickly raise the temps to 28, then seeing what the temps are at lights off.

In this case what would happen in summer when outside temps are 30c?

Would my temp be a problem?

SamWE19 said:

In this case what would happen in summer when outside temps are 30c?

Would my temp be a problem?

Click to expand...

In the summer even with all the insulation I've got the loft basically becomes a clay oven due to clay roof tiles...

I could get dual hose portable AC units but the amount of watts they use would probably overload all my breakers