Fire bricks

The lightweight ones that stop you burning yourself on a oven.  I have a lot!  Are they any use as general insulation?  I'm thinking below grade instead of polystyrene sheets.  
Thanks

Steve Mitchell wrote:The lightweight ones that stop you burning yourself on a oven.  I have a lot!  Are they any use as general insulation?  I'm thinking below grade instead of polystyrene sheets.  
Thanks

You would have to keep them dry. Don't know that it would work below grade. If you're near an industrial kiln, you could glaze them. If not, you could dip them in parafin or tar. As long as they are sealed off on the outside and dry inside I don't see why it wouldn't work. But the cost seems prohibitive. I think you would be better off selling the fire bricks (because they are very expensive) and using a cheaper and less iffy materials.

I've not got the space and access is a problem so selling on isn't an option.  If dry do they compare favourably to polystyrene in performance?  I can only see stats at high temps for these types of bricks.

It's to edge a pit greenhouse, the styrene is expensive!  Any insulation will be covered in poly to keep dry.

Steve Mitchell wrote:I've not got the space and access is a problem so selling on isn't an option.  If dry do they compare favourably to polystyrene in performance?  I can only see stats at high temps for these types of bricks.

It's to edge a pit greenhouse, the styrene is expensive!  Any insulation will be covered in poly to keep dry.

Well, I've got some of these. They do work well at high temps. As long as the pores are full of air and not water you should be good to go.

They will insulate at any temperature as long as they are mostly dry. I would put plastic sheeting between them and the earth, and locate such that they are not getting wet from watering or plants.