In article , Paul Giverin
writes

Anyway I digress. The greenhouse is erected on a concrete plinth that
was previously used for an aviary. I felt (rightly or wrongly) that I
needed to do something to insulate the concrete because I though it
would be quite cold. I used two or three bags of cheapo compost and
spread it on the floor.

Now I'm wondering if there was a better alternative or whether I need to
use anything at all. I intend to use the greenhouse to over winter a
load of our plants which are in terracotta pots and prone to cracking
with the frost. I've got some bubble wrap and will shortly begin to
lining the greenhouse with it. I've also invested in an electric heater
to keep it frost free but also to help get a head start with next years
seeds.

Mine is concrete - easy to sweep clean. I usually raise plants of the
floor in winter by standing them on something (1) balanced on bricks.
The logic of this is that hot air rises so one might expect a layer of
cold air along the floor (2) - in which case, covering the floor with
compost would merely raise the level of the floor and I'd still want to
raise my plants above it. But there's no guarantee my logic is sound.

(1) old pieces of staging, plastic trays, old polystyrene boxes -
anything that comes to hand

(2) and you can sweep under them
--
Kay
"Do not insult the crocodile until you have crossed the river"