Wood stove: Insulating above the closure plate, is it common? Good idea?

[billy_wizz]

On 14/12/2023 at 17:00, sime42 said:

With all due respect to your Sweep; I'm certain that he's wrong! Mineral wool will never burn, if indeed it is mineral wool, as it's essentially just glass fibre.

 

I'm interested in the wider question as I have the same set-up. I've never thought about the issue of heat escaping via the closure plate, but my hunch is that it can't be a lot.

 

 

I've had insulation burn it was packed round the flue pipe roughly 12-18 inch above the fire not sure if it was fibreglass or rock wool though!

[Steven P]

So the vermiculite chips around the chimney are to keep the liner hot, the tar won't cool and condense as much and leads to a cleaner chimney (plus fewer nasty chemicals on the liner it could last longer). Often seams to me that the stove industry tells us a lot how to burn wood efficiently and send that heat straight up and out (insulated bricks, heat stays in fire box, insulated chimney, heat stays in that). Insulated chimney doesn't do a lot for house heating.

 

Our master bedroom has the chimney breast and uninsulated chimney it can get nice and warm - never had a problem with that room being cold.

 

I think heat going through the register plate will help heat the chimney brickwork so you get benefit higher up, and noting that I think both ends should be reasonably sealed - so convection currents don't go straight up and out. It is a thought I had before, was going to put a lower plate in nearer the base of the lintel to reduce that void a bit but as above the hot air there is a bit of a heat sink for late evenings, and the fan helps too.

 

Insulation... one test I did once was throw a load into the fire - solid (polystyrene and phenolic type), sheeps wool, rockwool and glass fibre. The Rockwool was fairly stable, then glass fibre which melted quicker, sheeps wool burnt and the solid type burn quite nice. Probably OK to use Rockwool near the liner, might leave a gap though just in case.

 

The reason for burning it? Traditional layout semi- house with 1 stair case, insulating under the suspended floors, and I didn't want anything that would be a raging fire in case of a problem - we still need to escape. We have rock wool under the house, and no solid insulation below the bedroom ceilings height.

 

 

So might be you can pour vermiculite down the chimney if you want some insulation there?