Expert: Bruce E. Johnson - 10/5/2010

Question
I am in the process of building a small block building that will sit 15 feet from my home that will house my wood burning heater. My question is what can I insulate the blocks with that will help it hold heat instead of letting it escape? I'm lining the interior walls with iron sheets and firebrick and will apply insulation to the exterior walls along with metal siding. Thanks for any suggestions

Answer
Hi Sharon, it kind of depends on where you are living and how accessible your building is.  Some area insulation contractors offer foam fill for masonry core structures where they drill into the block and fill it with an expanding foam..There is also the old method of filling the block with pearlite or vermiculite granules. You can also line the shed with foil faced dense foam board prior to the iron sheeting installation.  You didn't say how warm the inside of the shed with get at it's peak operating temperature but I believe all of the above have the capability of withstanding a certain amount of high temperatures although prior to using any material you may want to check with the manufacturer's recommendations specifications regarding this subject. Another suggestion would be to fill the entire wall cavity with concrete grout.  The mass of the concrete will absorb the heat and store it.  I hope this information helps, feel free to write again regarding this or other matters, sincerely bruce e johnson