Thermal mass

Ok guys, this burn season my goal is to increase the thermal mass of/around my stove.
In theory this will provide a more even heat throughout the day instead of of temp spikes.
Sometimes I work long hours over the winter, more even heat would lower the wife's workload while I'm gone
My stove is big, but a junk Chinese brand.
With the big firebox I have been able to get 14 hr reload times out of it.
1st thing I'm doing is getting some support jacks for basement so I don't have to worry about to much load on joists.
I need suggestions on what y'all think the best approach is for adding mass.
I've tried solid bricks on top(wife hated the look)
Right now I have a big 1/2" plate of steel in top(in picture)
We have a metal place not to far and I can buy cutoffs like that at scrap price so I'm leaning that direction
How would y'all add mass?

 

I'm gonna add another question.
In running a non epa stove
For longest burn times/ most efficient
Is it better to allow more air intake, while closing off damper farther?
I can visible see flames slow down when I do this. In my head this equals more complete combustion and higher temps.
Or is it better to choke air more and have a less restitched flue?
I've run stove both ways and each has its own pros and cons that I've noticed.
Want to know what more knowledgeable guys think

 

Thermal mass: water. Close to the sides, not on top (boiling).

I don't think the damper or intake will make a difference in burn time; air flow quantity (and thus burn rate) will be the same for restrictions before or after the fire. The flue damper may help shed more heat into the room that choking of the inlet won't.

 

Is water the best heat retainer?
Some form of metal canister on floor by the side?

 

Water retains the most (at least best of materials commonly available) heat energy per pound of material.

I.e. it'll absorb a lot to heat up 1 degree.
And it'll release it slowly, given that the temperature difference between water (with a lot of heat energy but a relatively low temperature) and your room is not that large.

Metal might rust out, so you'd have to keep an eye on that to avoid a mess. But it'll take a while.

Put it where the highest intensity radiative heat is going.

 

Here’s what I did. I went to Menards and purchased 63lb concrete pavers and stacked them around the stove. I think I added about 1500lbs total. I added a bit more after this pic was taken. I also have a 5 gal pot of water on top of the stove. It really does make a difference in evening out the heat. If I burn hot those block can reach 150-160 degrees with one evening fire and are still over 100 the next morning.

you also must have the right kind of stove. If your stove has side shielding the blocks won’t get near as hot as a radiant stove. I filled the sides of my Jotul F45 with pea gravel and removed the rear and bottom heat shields to make it more radiant and it works much better, in fact the stove burns better and lowered my flue temps as well.

 

Is your basement heated? Have you considered a second stove for down there? Are there any insulating or air sealing projects you can do to help reduce heat loss? What kind of temperature spikes are we talking about between high and low? Can a fan move the heat around? I agree that water has the best heat storage capacity but it’s tough to work with. Steel has about the same heat storage capacity per unit volume as water, but you will need literally a ton of it which I would think would be challenging to deal with. In the middle of this, Todd just posted what I would recommend, brick or pavers or stone. But you said your wife doesn’t like the look of brick. I do think that brick (or soapstone as Backwoods Savage mentioned) is the best way to go.

 

Here’s a more recent picture. I’ve done a lot of testing of different burns and I’ve found during the shoulder season a single evening fire with a full load burning at a medium low range will keep my cabin comfy til the next evening better than trying to stretch out two 12 hour reloads or a few small hot fires. As the temp drops this winter I won’t be able to get away with one fire so I’ll go to either a 12 hour reload or 8 hour but the extra mass does help even out the spikes in between.

I have a similar setup in my sauna/bath house. This Nippa stove is a radiant monster and the blocks can reach 350 degrees. One hot fire in this stove in this small 8x16’ cabin will keep it above freezing for over 24 hours even in below zero weather.

 

I like your setup alot

 

Basement unheated,
I've added tonsof insulation to attic, also the entire outside of the house was resheathed last winter
As far as temp swings, last winter we regularly dipped into high 40s inside. With stove ripping it would e 65+ in stove room

 

My wife didn't like the brick because I haphazardly had it on top of stove, but if I made a concrete block wall like above, I think she would be ok

 

This is what I had in mind. Water will store more energy than bricks.

I agree with backwoods it's good to create a thermal gap to the floor. This could simply be an air gap (convection will keep the heat from going to the floor and help.extract the heat from the water).

I have not done this, so can't tell how much noticeable it is.
Having stone (or water) at 100 F hours later may not be giving sufficient heat to notice a different on the other side of the room though.

 

Those blocks also help reflect the radiant heat out into the room heating other objects and the room. As the stove dies down it does seem to help retain some of the heat keeping the up and down spikes less or a more even heat between reloads.

 

Ditto!

 

did my thermal mass project tonight
Got 3 sooport jacks and 24 36 lb cinder blocks.
Just lit up well see how it
In the top picture you can see that I removed side jackets, and as a bonus you can see where I welded patches on to delete secondary burn tubes does

 

added another 200 or so lbs.
Closing in on 1k lbs of thermal mass.
Last night's fire was small and quick (pine)
Upper blocks we're still at 100f for am reload

 

I think your thermal mass would work more as thermal mass (slower in cooling down) if you limit the convection through the core holes. I.e. close those off on the top; they speed up the cooling now.

What is the max temps you see on the inside of the blocks?
If low enough you could fit PVC pipes in the holes, put caps on bot ends, fill them with water and stand them up in there.

 

Maybe a 2" air gap between water and the cap, and a 1/16" venting hole to avoid any pressurization.

 

I agree about the cores letting it cool down faster.
I already had about 1/3rd of the block I needed and Menards didn't stock solids in this size.
Gonna run this setup for a while. May switch to solid upper layers later on, the lowers I'll leave cinder because they don't hardly heat up at all.
Small fires only so far, but saw inner block temps around 200 to 215