Fire back for woodburner
 

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?

Fire back for woodburner
 

"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?


Silver will reflect heat, black will absorb and when the fireback has heated
up enough, reradiate. The cheapest option IMO is to go for a black painted
fireback, with a bit of rockwool behind it. You can make space for an inch
or two of rockwool presumably?

Andy.

Fire back for woodburner
 

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?

Fire back for woodburner
 

Stewart Devereux wrote:

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 !


Thanks for the reply, and to Andy too.

This one is a tiddler, and only 4kW. Nonetheless, I agree it should put out
a lot of heat.

One installer told me they could not put it in without enlarging the
aperture, because all the heat would get absorbed by the brickwork and none
would come out into the room.

Another installer (the one I want to use) said that was true, but he
proposed to use a 90 degree elbow from the back rather than the top, and
put the unit 3/4 way out of the hole, so only 1/4 of it is inside the
aperture.

That is really why I was thinking about the reflective qualities of the
backing, but I guess with a stove obscuring most of the opening,
re-radiated or reflected heat from the backing is not going to make much
difference.

Fire back for woodburner
 

"John Carlyle-Clarke" wrote in message
...
Stewart Devereux wrote:

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 !


Thanks for the reply, and to Andy too.

This one is a tiddler, and only 4kW. Nonetheless, I agree it should put
out
a lot of heat.

One installer told me they could not put it in without enlarging the
aperture, because all the heat would get absorbed by the brickwork and
none
would come out into the room.



I think you may be missing here one the greatest benefits of woodburners.
Whilst the stove is burning the room is heated by radiant energy whilst the
mass of the brickwork around the stove warms up and stores the heat. That
heat is then released slowly over time even when the stove is out. Of course
if the wall behind is an exterior wall then it's going to be a lot less
efficient.

Our front room , which besides having a woodburner has an inadequate
radiator, is a much nicer place to be for at least a couple of days after
having had the woodburner running.

Some woodburners are designed to use the thermal mass of the brickwork
around the stove to store energy and increase efficiency. Google for
"russian stove" to see examples.

H

Fire back for woodburner
 

Andy wrote:
"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?


Silver will reflect heat, black will absorb and when the fireback has heated
up enough, reradiate. The cheapest option IMO is to go for a black painted
fireback, with a bit of rockwool behind it. You can make space for an inch
or two of rockwool presumably?

Andy.



cheapest is to render the whole fireplace frankly..I've got a rendered
behind the stove back. It works well

Stoves don't put out fierce heat to the fireplace, unlike an open fire.
They radiate a far more even heat - the high temps are all inside, as
you will discover when firebricks disintegrate and grates buckle and
bend. And finally oxidise and fail ;-)

When you operate solid fuel devices, you get to understand how primitive
man discovered how to smelt metals..

Also bonfires on clay soil make quite GOOD lumps of brick..

Fire back for woodburner
 

John Carlyle-Clarke wrote:
Stewart Devereux wrote:

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 !


Thanks for the reply, and to Andy too.

This one is a tiddler, and only 4kW. Nonetheless, I agree it should put out
a lot of heat.

One installer told me they could not put it in without enlarging the
aperture, because all the heat would get absorbed by the brickwork and none
would come out into the room.

And where does he think the heat will go when the brickwork has absorbed it?

I'd say that was a plus. My massive open fire chimneys and masonry
surrounds may take three hours to warm up, but they keep the temperature
up all night afterwards..and in summer, down all day too.

The aga flue heats the bedroom upstairs as ell.



Another installer (the one I want to use) said that was true, but he
proposed to use a 90 degree elbow from the back rather than the top, and
put the unit 3/4 way out of the hole, so only 1/4 of it is inside the
aperture.

Hmm.

That is really why I was thinking about the reflective qualities of the
backing, but I guess with a stove obscuring most of the opening,
re-radiated or reflected heat from the backing is not going to make much
difference.

Nope. Render it. All you really need is an air gap around it to allow
convection off it to come out to the room, A couple of inches is fine.

The actual stove temps are not that great. Couple of hundred C at the
most outside. OK too much for wood, and maybe plaster, but fine on
masonry and render.

Or as John says, use some fireproof board painted black. Thats quick and
simple. and will let less heat into the structure than render. But I
think render - with sharp sand and white cement - looks nicer.


4KW is a powerful fire. The UFH in my house is rated at 100w/sq meter.
Thats 3KW in a 6x5 sq meter room. I get a rate of rise of about 1 deg C
per hour with that..the open fires do about three times that once the
brickwork is warm.

I think you are going to love that stove.

Fire back for woodburner
 

HLAH wrote:
"John Carlyle-Clarke" wrote in message
...
Stewart Devereux wrote:

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 !

Thanks for the reply, and to Andy too.

This one is a tiddler, and only 4kW. Nonetheless, I agree it should put
out
a lot of heat.

One installer told me they could not put it in without enlarging the
aperture, because all the heat would get absorbed by the brickwork and
none
would come out into the room.



I think you may be missing here one the greatest benefits of woodburners.
Whilst the stove is burning the room is heated by radiant energy whilst the
mass of the brickwork around the stove warms up and stores the heat. That
heat is then released slowly over time even when the stove is out. Of course
if the wall behind is an exterior wall then it's going to be a lot less
efficient.

Our front room , which besides having a woodburner has an inadequate
radiator, is a much nicer place to be for at least a couple of days after
having had the woodburner running.

Some woodburners are designed to use the thermal mass of the brickwork
around the stove to store energy and increase efficiency. Google for
"russian stove" to see examples.


Mmm. My sister had one of those things installed in a house in Germany.
Its basically a stove built into a vast brick and concrete block
structure with convection vents and double skins.

It certainly made a great space heater, till they got too old to faff
around carting fuel for it. Also a great room COOLER in summer, when unlit.

Agas are the same. A quirky and indifferent cooker, but the best and
most efficient space heater I have ever used. The flue is cool to the
touch..all the heat goes into the room. FAR better efficiency than any
pumped boiler. Even the heat that DOES go up the flue ends up in the
room above.

Also useful in summer when unlit to keep daytime temps down.






H

Fire back for woodburner
 

The Natural Philosopher wrote:

John Carlyle-Clarke wrote:
That is really why I was thinking about the reflective qualities of the
backing, but I guess with a stove obscuring most of the opening,
re-radiated or reflected heat from the backing is not going to make much
difference.

Nope. Render it. All you really need is an air gap around it to allow
convection off it to come out to the room, A couple of inches is fine.

The actual stove temps are not that great. Couple of hundred C at the
most outside. OK too much for wood, and maybe plaster, but fine on
masonry and render.

Or as John says, use some fireproof board painted black. Thats quick and
simple. and will let less heat into the structure than render. But I
think render - with sharp sand and white cement - looks nicer.


4KW is a powerful fire. The UFH in my house is rated at 100w/sq meter.
Thats 3KW in a 6x5 sq meter room. I get a rate of rise of about 1 deg C
per hour with that..the open fires do about three times that once the
brickwork is warm.

I think you are going to love that stove.

Thanks for all your comments. I thought the same thing about the brickwork,
but the HETAS registered installer that I spoke to first was so firm about
it being a problem that I assumed he must be right and I must be wrong. It
is an internal wall.

Rendering I suppose is a good solution, and cheaper than the £90 for painted
steel.

I'm hoping we're going to love the stove too :) This room is also about 6m
x 5m.

Here is the little beauty.

http://www.aarrowfires.com/which_multi_acorn.php