Thermal mass lessened with overlay over slab?
I have a passive solar off-grid home that works extremely well with a 2 in. concrete slab that is finished with decorative concrete stain/paint. However, the slab and stain/sealer are completely defective and very likely have to be replaced, but one party is proposing a concrete overlay product be put atop the existing slab. The overlay product (ArtCrete Deck Coat, I think it is) consists of two parts–1) Portland cement, aggregate, and a stain, and 2) a modified acrylic latex resin. My belief is this is not good thermal mass (atop the concrete) as the resin component synthetic or at best partly plant material and only earth materials such as stone, clay, water, concrete, provide optimal thermal mass. That in fact the entire slab needs to be removed and the floor rebuilt from scratch to resolve the serious problems and still provide me with optimal thermal mass.
I’ve also been told there’s a table that shows even natural tile atop a slab causes a loss of thermal mass, but I have been unable to find that table. If anyone is aware of this or similar, please let me know.
Note also the slab has severe cracking–cracks at least 3/8 in wide in multiple locations.
Does anyone have experience or knowledge about this? Using or not using a concrete overlay product for the top layer of a floor for thermal mass, vs. a plain darkly stained concrete slab–whether there would be any loss of thermal efficiency.
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