I would like to add thermal mass to my fireplace

Hello everyone,

Finally getting cold on the colorado front range. Ive found myself unemployed again and the idle hands are the work of the devil, according to my wife. This is when I start new projects that make such a mess. A few years ago now I built a RMH in the garage. So much fun. Coinciding with that build, Ive wanted to make the fireplace into a masonry heater...but I dont think Ill ever have the budget to do that properly.

Ive attached a pic of the fireplace. Im assuming that behind that brick veneer is basically stud framing and empty space around the fireplace box? Has anyone ever added mass alongside a fireplace like this, or does anyone know how construction goes around a residential fireplace? For mass possibilities, I have a large supply of 10-20 lb concrete chunks, a mountain of fine grain sandstone block (drywall block) and access to the drop pieces from the granite counter top place in town. As always concrete is cheap. Thanks for any insight, happy halloween

Rich Pasto : I guess about the 1st thing before the weather gets worse, climb up on the roof with a very powerful flashlight a few tools and a measuring
tape, and get a few cell phone pictures if nothing else. We want to count the number of flues and estimate their condition, you may have to remove a
storm hood ! You may be able to find a surviving resident from when your house was built, or go to your local planning board who will probably have a
plot map supped by the Lead contractor, get the contractors name, then you can pin down adage of the build and what kind of 'insert' they were installing
then !

The next step would be a trip online, you probably will get the Specs and minimum clearances, possibly the installation guide supplied with the unit.

Please be aware there is a lot of stinking Crap posted on U-Tube, use a high degree of skepticism regarding the fitness of anything you see on U-Tube !

Good contractors often paced the utility room on the backside of the fireplace, often there were inspection access openings left for the final inspection by
the local code guy !This inspection points are probably long covered with sheet rock,plaster skim coats and paint, but their regular outline, and the fact
that that outline shows a break in what should be Full sheets of drywall will help you find them again !

You really do need to get in there and determine what is in there, if we could successfully Retro-fit an RMH into this area we will greatly increase the safety
factor, due to massive heat storage at lower temps, this area has already experienced temperatures near the boiling point of water. or even higher
depending on the experience and skills of the installation crew.

Time to use your Permies search engine, when you go to the Search page from the Permies Toolbox, your search engine pre-selects a search in the forum
you just left Rocket stoves>rocket stoves /// Ponds > Ponds! Enter RMHs built in Fireplaces in the search field, and select a google search within
Permies you will have lots of 'hits' Good luck and good hunting ! For the good of the craft ! Big AL

to clarify: Im not looking to build a RMH inside the fireplace. I am wondering if there is the fireplace box, so to speak, and then empty space behind that brick veneer. I would simply dry stack bricks or concrete into that space, and reinstall the veneer. Thermal mass.

no way to tell for sure whats there till you look. there should be a lot of space back there though. usually its 24"+ clearance around the insert(if its an insert). you mite be able to get a look from the attic?