Page 11 - Timber_Log_Buildings.serifbackup

Timber Buildings - thermal mass

The term thermal mass is in widespread use but,
technically, the term refers to a process rather than a
material which is where the misnomer occurs, it’s more
accurate to use:

Figure 10 - Thermal Mass - summer cooling
A building that has good thermal mass is one that has
the ability to absorb, store and release the suns energy.
The material density and thermal capacity of material
used in the building help to keep the temperature in a
building stable - objects that have good thermal capacity
have inherent qualities of heating and cooling.

UK Building Regulations have, over the last 40 years or
more, striven to improve insulation in UK homes. With
mean temperatures on the rise - 0.9 degrees C higher Figure 11 - Thermal Mass - winter heating
2001-2019, overheating in our homes is becoming a
cause for concern. The need for insulation is now under To make effective use of thermal mass first, the home
review with a focus on using passive solar control and should be ideally positioned to take full advantage of
building materials that can work with passive methods. summer and winter sun. Sunlight entering through a
window hits a wall (here we assume a Ritsu log in a
The problem is, all of the modern methods of building) where it excites the electrons in the timber,
construction so far as housing is concerned , many setting them in motion.
cannot be readily adapted to make use of thermal
capacity, except perhaps for concrete, used almost It’s a complex process where atoms make a quantum
exclusively in flats and scores badly with its embodied transition from “electronically excited” to “vibrationally
carbon - meaning that brick and block is going to be excited” meaning the energy causes the whole atom to
around for some time yet, with all of its inherent issues move which we feel as heat, these atoms then collide
concerning global emissions. with other atoms, dissipating their energy in the log -
storing heat. When the sun sets, this heat will be
radiated back into the room.

As we write this, we are looking at a publication online Thermal mass works even in low levels of sunlight as
called “Green Passive Solar Magazine” - it’s about photons are ever present, during the summer it is used
thermal mass and it’s wrong as it gives two examples of to flush warm air out of a home by opening windows -
thermal mass in action - a concrete path and a timber cooling the building.
deck.
In winter months keeping windows and doors closed
The concrete path has melted and obviated the need to allows the heat to radiate back into the room - keeping
shovel snow, a deck to the authors rear garden the building warmer and reducing the need to use
meanwhile is still evenly covered in snow. additional heating.

This is offered as evidence of thermal mass but the “Warm in winter, cooler in summer” - is a term you find
author has confused thermal capacity with thermal used in association with a timber log building and for
mass, demonstrating how difficult this subject is! good reason!