AlbertoArriaga33 is wrestling with plans for a new home in a tropical location. He doesn’t say exactly where, but conditions are certainly challenging: high heat and high humidity, with nighttime temperatures dipping only into the upper 70s and outdoor relative humidity hovering at about 70%.
Exterior walls will be grouted concrete block, what Alberto says is standard construction in the tropics. Outside walls will be finished with a cementitious plaster and then painted. On the inside, light steel framing and stud cavities filled with R-15 mineral wool batts.
“However,” Alberto writes in this Q&A post, “I have many doubts and still not sure if I quite understand how thermal mass works. I’ve read that typically you would want to keep the thermal mass inside in a hot climate in order to keep it from absorbing solar energy, and subsequently heating up your house at night.”
Alberto wonders how the mass of the concrete-block walls will affect interior conditions, and whether the interior insulation will be enough.
“My guess is it would slow down the transfer of thermal energy from the walls to the interior space as it radiates throughout the night. Is the thermal performance of the assembly affected substantially by whether the insulation is on the exterior or interior?”
Those are the questions for this Q&A Spotlight.
Let’s get our terms right
The term “thermal mass” pops up frequently, as it did in Alberto’s post. But, DCContrarian says, it’s not technically correct.
“‘Thermal mass’ is not a term used in science or engineering,” he writes.
Maybe not, says Malcolm Taylor, but in building design the term is commonly understood to mean the “capacity of a high mass material to absorb and store and release energy as heat.”
“And this is why…