The dining room/parlour of my 1928 house has a log-burning stove set into the old fireplace. This means there is one leaf of bricks between me and the outside world. Three questions:
a. Can I put some insulation on the wall? There's a 4" gap behind the stove but it gets hot - what should I use?
b. Is it worth doing?
c. There's a similar arrangement in the lounge but with a coal-effect gas stove - I assume the same answers apply?
Another Dave
For a quick and easy test, try lining the back of the recess with aluminium foil. If it helps noticeably, then replace the foil with a sheet of unpainted metal with an air gap behind it. The heat there is mostly radiation, so the foil/ metal will reflect this back.
Yes, I like the idea of a curtain of foil, open top and bottom, to reflect heat plus allow a convection path, the back wall still needs a non combustible insulation though and watch the distances comply with part J.
AJH
The only things I can thick of that would stand the heat are asbestos, glass(etc)wool and vermiculite.
Ignoring the first one, one option might be to make up a false back out of shiny metal (eg stainless sheet) then, leaving as much of a gap as possible between that and the bricks, fill the gap with glass wool or vermiculite.
Watch that you leave the required space between the back of the stove and the new wall surface (my stove wants >=2")
So you might manage 2" insulation if your stove is happy - roughly equivalent to a cavity wall.
Obviously use nothing remotely combustible back there - no wood battens
- all mountings done in metal etc etc. Rawlbolts could be a decent method and mount the sheet on studs with nuts both sides to achieve the required standoff.
It might be worth doing as that section of the wall could run really really hot during use so the power loss will be significant. Does that part of the wall outside get hot to the touch?
Fibrefrax sheet with a metal panel in front of it
Masterboard will take heat up to dull red. Its a glass/cement board I think.
I used it when soldering plumbing, and to make up stove surrounds
Expesnive, but works.
Insulating properties similar to plsterboard.
Foil covering is possible, but not that much use id say.
It's hard to do this in such a small gap. There are also regulatory limits on how close you can get.
One of the best ways (and cheap) is just a sheet of steel, with a large air gap on its cold side and enough gap above and below to allow air circulation. This acts as a radiation barrier between stove and wall, and becomes a convection heater in its own right. Most modern box stoves are double-walled for just this reason. You can also mount this on the rear of your stove (useful for regulatory gap measurements), although it's useful if it's also shielding the flue outlet (using two plates can be useful, one notched to clear the flue, the other covering this gap from the back). The reason it works is because of the Stefan-Boltzman law - radiation is proportional to the fourth power of the absolute temperature. So a hot stove radiates a lot of power (into the cold wall), but this cooler plate will radiate far less of it into that wall. Your lossy wall now has less valuable energy hitting it for it to lose - this reduces the waste at source, also reduces the wall temperature and thus the difficulty of insulating it.
I have a similar problem in the near future, and I'm planning on adding insulation to that wall over a fireplace-sized patch, but doing it on the outside rather than the inside.
Taking this one step further, why not fit a single rad with fins on the wall. Does the same job as a plain sheet of metal, plus the fins will give you much better heat transfer and you have the stand off from the wall.
Whether you plumb it into anything or leave it open ended is a good experiment.
Dave.
I'm the OP.
I didn't make myself clear, sorry. I'm not interested in retaining the heat of the log stove - the room gets so hot when it's running we have to open the door to let the heat circulate through the rest of the house ;-) I only run the stove when the temperature gets below 5C i.e. every day for the last month.
However, the single leaf of bricks (1.5 M square) must lose a lot of heat at other times when I rely on the central heating. Thanks for all the suggestions - I'll report back when I've done something about it.
Another Dave
cant you put insulation on the outside of the wall? [g]
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