We have had numerous wood burners over the years, some with similar problems
to yours. First you must be aware they can generate ALOT of heat, so metal
might not be the best idea. I would go along with first reply. 1-2 inches
loft insulation pinned to brick, then cut a piece of fireboard to size and
cover. Can easily be painted matt black. The burners work best by allowing
air to circulate around them-I don't think once you have it up and burning
you will be worried about reflecting heat back in !

--
Regards,
Stu Devereux.
Fax no. 08701339568
(Outside UK fax 448701339568)
E-mail.
"John Carlyle-Clarke" wrote in message
...
We had a standard 22" square open fire with a clay fireplace. We've now
removed this with precision hammers, and are in the process of getting a
woodburner installed.

I want to put something in behind the woodburner, for two reasons:
firstly,
to tidy up the appearance by hiding the rather unsightly brickwork, and
secondly to reflect heat back out.

I was thinking stainless - basically about 2' x 4', with the sides folded
round to fit the hole.

I've been quoted 90 quid for heavy gauge mild steel, painted in black
stove
enamel, and 180 quid for stainless (apparently it will need to be good
quality to stand the heat, which makes sense).

I'm happy enough with black painted steel from a cosmetic point of view,
but
I'm wondering about heat reflection. My memories of physics lessons
suggest that if the front is painted but the back is left unpainted, it
will tend to absorb heat and re-radiate it back into the room. Is this
correct?