Getting More Heat From Your Wood Stove By Adding A Heat Sink

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A wood stove is a great thing to have…toasty toes and a warmth that is psychologically comforting, so much better than central heating, the problem is though, they go out.

If you are relying on a solid fuel stove this is a major drawback because you get up in the morning and the house is freezing, and unlike a flick a switch system, with radiators in every room, it takes quite a while to heat the place up again.

The answer to this problem is quite simple and although it’s a little time intensive it’s well with the effort. You need to create a heat sink, a storage heater that passively takes in heat and then gives it back when the air in the room cools down – usually when the fire has gone out.

Anything that passively absorbs heat and is not combustible will work just fine. Many people use metal but that confuses me because it cools down fast, stone on the other hand does not.

Medium to large stones, bricks, breeze blocks and rocks hold heat well and pose far less of a burn risk than metals. You simply stack them up either side of the stove, and at the back if you have the space and as the stove throws out heat the rocks heat up – it really is that simple.

Think of a brick wall that has had the sun on it for a few hours, it stays warm for a good while after the sun has gone down. That’s exactly the same principle as a heat sink around a solid fuel stove.

Now rock can shatter if it goes from cold to hot too fast so make sure that the rocks aren’t touching your stove. Take the time to stack them so they’re not a collapse hazard, rocks are better in this respect because they kind of ‘lock’ into each other if you twist and turn them to find the best fit.

Not only do the stones give out heat into the room when the stove goes out, you use less fuel because the stones are heating up and putting heat out into the room all the time the stone is burning.

The top of the sink, which will be about the height of the top of the stove give or take a couple of inches, is warm enough to air up clothes and gently dry a pair of boots but not hot enough to burn them.

As a kid my grandparents would take a couple of stones they kept at the back of the range and put them in the beds to warm them up in winter, kind of poor mans water bottles…without the water and without the bottle!

They also kept a metal box at the back of the heat sink and dropped fruit peel into it to gently dry, this would then be grated and stored in jars to add to her version of yogurt, which she made in a big bowl, covered with a towel up in the corner, she’d removed a stone so the bowl rested securely and there it sat for two days…us kids watching and waiting with spoons in hand. Whilst I’m off down memory lane I recall she kept some smaller stones to drop into boots to assist with the drying process…she was a very practical woman was gran.

Now don’t get me wrong, heat sinks are great but they are not miracle workers, you are not going to get up the next morning and find the lounge is snug and cosy, but it will be warmer than it would have been by quite a stretch.

Add thick well lined curtains and a few draught dodgers and you can improve your lot no end, especially if the winters are harsh where you are

I may have mentioned it just once or twice before but I hate the cold, this is another way that helps me ‘trap’ heat that would otherwise have been wasted.

Take care,

Liz

7 thoughts on “Getting More Heat From Your Wood Stove By Adding A Heat Sink”

  1. The same principal as adding thermal mass for passive solar homes. Stores the heat generated from the wood stove (or the sun) and it gets released when the air temp falls below the temp of the mass (rocks). It really helps stabilize the indoor temperature if you add enough thermal mass, but requires additional energy to warm it initially and pulls a lot of heat out of the air if it’s allowed to cool considerably. No free lunches in the laws of thermodynamics after all 🙂

    We built a passive solar home about a decade ago, 2 story ICF, with a raised concrete slab for the upper level floor to provide most of the thermal mass. Wood stove on the lower level. Very energy efficient, and the inside temp remains very stable even hours after the fire goes out. At the time we built I really wanted to incorporate phase change drywall/gypsum board into the design and not need the raised concrete slab, but PCM drywall was too new at the time (and not even sure it’s available for the residential market yet). If space doesn’t allow for a rock wall, might check out National Gypsum’s “ThermalCore” or BASF “SmartBoard” drywall/gypsum boards with embedded phase change materials though. A 5/8″ sheet of drywall can store as much heat (at a specific temp) as a brick wall of the same surface area.

    Alternately, while probably still expensive (haven’t priced any recently), buy the raw “macro encapsulated phase change material” product and incorporate it into your home yourself. Fill an internal wall, between the studs, with it maybe. I thought about filling a bean bag chair with PCMs, a lightweight and movable piece of furniture that stores as much heat as a boulder of the same size might have some advantages 🙂

    1. Hiya Ron,

      Thank you so much for reading and taking the time to leave such a great comment. Very good information that I’m sure will be useful for other readers.
      regards
      Liz

  2. Hi Liz

    Read this post when it first hit the net. What a brilliant idea! Our woodstove is down in the basement to allow the heat to rise up to the main floor. Also handy for keeping the pipes from freezing in a power outage. Never thought about creating a heat sink around it before. It would certainly keep thing warmer. Have already been downstairs to check how best to set something up. Hubby would be hard to convince but since it doesn’t require masonry skills, even I could do it. Now my brain cells are madly working overtime trying how to create a heat sink in the living room. Usually keep a container of water by the fireplace so we have warm water for bathing in case of power outages.

    Had always wanted to have a masonry heater installed in a new house. Guess I better win the lottery!

    kk

    1. Evening KK,

      Tell you what it really does work. Gran used to air laundry, dry boots and even prove the bread dough on top of hers. I have seen some that are bricked in place but the loose stacked ones allow for bed warming, cleaning and stove repairs without expense or damage. Did you read about the floor grills the same gran had? Literally holes in the floor that let heat go into the room above, a little grille, like a sliding air brick cover went over the hole and the grille was metal but you could stand in the bedroom and feel the warm air coming through it from downstairs.

      No mains utilities, a range with an eight inch fire box and never were we cold…amazing.

      I have no idea what a masonry heater is if I am honest…enlighten me lol.

      Love to the family

      Liz

      1. A masonry heater is a bulky fireplace like they use in the Scandinavian countries. Has baffles inside to retain the heat and the walls of the unit are made with thick masonry or some other material. If you google it, there’s lots of info about them. 🙂

        Had already figured out the floor grille trick years ago when I lived with my first husband. We had a coal/wood stove in the basement where the kids played. Since we constantly had power outages in winter, thanks to the snow and ice build-up, I figured out how to disconnect the furnace ducts from the grilles to allow the heat to rise. Plan on doing the same thing here.

        Have a good evening. Hope Shortie is enjoying school.

        kk

    2. Oh, off topic I finally made the subscribe button work…sorting out the gremlins one by one lol. Oh and howard made a comment that was just so brilliant I put it on the site.

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