Bricks on top of stove to increase thermal mass?

A fan would be more effective.

mark cline said:

A fan would be more effective.

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x2

You want heat transfer from in the box to the room.
Let the house be the heat sink.

OP did not ask about transfering heat instead the question was how to store some of the heat and reclame it later. My opinion you will need alot of brick to be able to see any difference better if you get peace of soapstone placed on top it would looks better too.

If you can find someone near you that cuts soapstone kitchen countertops, ask if they will sell the sink cutout from one. It should be very cheap and will look much nicer. Soapstone will hold a lot more heat than a brick lb for lb.

Funnily enough I was wondering today about the possibility of putting a slab of soapstone on my stove top in order to store some heat overnight. My stove is too small to hold heat that makes a difference for more than five hours after a full load, but I notice that the stone wall behind the stove holds ALOT of warmth overnight that the room benefits from in the morning - it's warm then, even when the stove is cold... So was wondering about ways to add more stone = more heat store.

No problem having a full slab on top, I have a rear flue exit (Esprit, i guess you do too?) So what sort of thickness of soapstone slab would be best?

DougA said:

Soapstone will hold a lot more heat than a brick lb for lb.

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The heat capacity of brick and soapstone are actually very similar (0.9 to 1 J/gK). Soapstone is more dense so at the same volume it holds more heat. Nevertheless, gypsum is even slightly better at 1.1 J/gK so your drywall actually retains quite a bit of heat. I would rather look for ways to keep the heat in the house by weathersealing and insulation. That will be a better investment and make a larger difference in heat retention than piling rocks on the stove. Don't forget that those also act as an insulator for the stove top so you may lose more heat up the flue.

I put a slab of soapstone on top of my stove with a small air gap ... I haven't noticed any significant improvement ... but it does look nice.

I prefer a few large pots of water... adds thermal mass AND a little humidity.

Consider that you can add thermal mass to your living space by having some mass near the stove, not just on it. Obviously a brick or stone fireplace or wall holds a lot of heat, but anything else in the room (large potted plants, stone coffee table or sculpture, etc.) will absorb some heat and re-radiate it.

Grisu said:

.Don't forget that those also act as an insulator for the stove top so you may lose more heat up the flue.

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I'd wondered about that part....

I think Ill just stay content with the amazing storage heater I have in that sandstone wall behind my stove. An added bonus that never even occurred to me when the stove first went in.

Like the pots of water on stove tops - if not mostly for looks it is mostly a waste of time. Not in a bad way - just not valued per gained BTU in the house way. Just like the increase in relative humidity in your home cannot be measured in a way that justifies the pot on the stove. It is cosmetic and we all like our stove enough to dress them up from time to time.

Most stoves of any quality are designed to perform there best so all that heat the bricks would be absorbing would be in the room anyway. Yes, they will likely hold onto it as stove goes into the back end of a burn cycle and slowly release it into the home but by no means at a measurable rate that you could physically notice.

I even went so far as to think of a radiator system that I would create in the welding/blacksmith shop. Something fancy with fins and such that would truly move heat from the stove to the room but.... upon further review, help from many here and some conversations with stove manufacturers, it became obvious that I would be robbing Peter to pay Paul so to speak. ie. stealing heat that is needed inside the stove that allows it to work properly. This in turn would rob secondary burn and cool flue gas potentially to the point of creo and diminished return.

I still love the idea of removable radiator plates on a stove but realize its futility.

Grisu said:

The heat capacity of brick and soapstone are actually very similar (0.9 to 1 J/gK). Soapstone is more dense so at the same volume it holds more heat. Nevertheless, gypsum is even slightly better at 1.1 J/gK so your drywall actually retains quite a bit of heat. I would rather look for ways to keep the heat in the house by weathersealing and insulation. That will be a better investment and make a larger difference in heat retention than piling rocks on the stove. Don't forget that those also act as an insulator for the stove top so you may lose more heat up the flue.

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Someone who gets it. Cheers!

Grisu said:

The heat capacity of brick and soapstone are actually very similar (0.9 to 1 J/gK). Soapstone is more dense so at the same volume it holds more heat. Nevertheless, gypsum is even slightly better at 1.1 J/gK so your drywall actually retains quite a bit of heat. I would rather look for ways to keep the heat in the house by weathersealing and insulation. That will be a better investment and make a larger difference in heat retention than piling rocks on the stove. Don't forget that those also act as an insulator for the stove top so you may lose more heat up the flue.

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True, but then compare the heat capacity of a few bricks or a coupl'a pounds of soapstone to the net mass of every object within the insulated envelope of your house. To the op: the mass and heat capacity of the stove is not a substantial factor in extending the time a given load of wood will heat your home. BTU in = BTU out, divided by efficiency, after all.

The reason you want mass in the stove is to help even out relatively short (eg. < 30 minute) spikes and dips in firebox temperature.

For years i had 4 or 5 of those 3 inch cement blocks on my old wood stove. It never helped from what i could tell. By the time the stove cooled the cement blocks were cool as well.