Defining Thermal Mass and alternative Design

This forum is to discuss the pros and cons of thermal mass in building design and construction.  What works and what does not work.  Consider ways of gathering or making thermal mass without it costing an arm and a leg.
Seek advice and offer solutions.  Good thermal mass is one way of keeping the home warm in winter and cool in summer, and minimising the requirements to go to extremes for heating and cooling.

This is a research paper on the effects of thermal mass in homes in a temperate climate
https://www.sciencedirect.com/science/article/pii/S0360544220300918
It has interesting points about the benefit of replacing thin timber walls with thermal mass, even with lower differences of temperature.

I think this so called “thermal mass” phenomena is not just about mass and not just about insulation, but about the combined effect of both mass and insulation properties in one single material.

So, in that paper what they are using for “thermal mass” is “Cellular concrete blocks”.  This is aerated concrete or foamed concrete.  The material is both insulating and has some heft to it.
Take a look at Table 3 in that paper. The material properties are within 10%-20% that of OSB!  
Did you think of OSB as “thermal mass”?  I hadn’t been.  Yet by their numbers, OSB (and pine beam!) actually have 1/3 lower thermal diffusivity than the Cellular concrete blocks!  Guess the log cabin folks are doin’ alright!

My take on thermal mass is that it is mass as in quantity and thermal in that it delays the transmission of heat or cold through it.  So anything with enough mass can delay the transmission of temperature change or can retain a constant temperature.  Our home is constructed with 300 mm (1') compressed earth blocks so the temperature transmission delay is, according to what I have read, 10 hours.  What we have effectively is a heat pump.  With good management, our house is between 16 deg C and 27 deg C  all year round.  We have a wood fire (A rmh/ stove is in the planning) and ceiling fans.  In a 12 month period, we never have a living space is too cold and if we don't get it right, a couple of days that are too hot (over 30 deg C)  The construction is post and beam to prevent the engineering and stabilisation of the bricks.  They are 100% dirt from our block of land.  An air gap is also a great form of thermoregulation.  We have a metal foil, a bit like double layer bubble wrap under our glass wool fibre mats. This gives us about an R10 so we lose little heat through the ceiling.

I live in a house that is solid brick on the first floor,  and stud framed on the second.
The western wall gets a huge amount of solar gain , it boarders a driveway and it has no porch, trees or neiboring houses to protect it from the afternoon sun.
I was inclined  to cover it in reflective mylar, but I suspected that would be frowned upon.
Instead, it is shaded by a grape vine that grows down a guy wire  trellis.
Between the shade and the aspiration of the leaves, I think it is cooler  on average.


I am fascinated by liquid thermal mass,because it is movable.
In conjunction with an insulation barrier it can allow the active gathering and storage  of thermal energy.
While passive thermal storage might be more efficient,  I think active thermal storage is easier to retrofit to existing buildings.