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Timber Buildings - thermal mass, technical

But this ignores several key factors:
1. The thinking is narrow and confined to small
sections of timber as might be used in timber frame
- logs used in Ritsu buildings are upwards of 195
mm.

2. Brick, concrete, concrete blocks all have high
densities but poorer thermal conductivity, meaning
they all lose heat more quickly

3. Of all of the commonly used building materials,
timber is actually the top performer in terms of its
thermal conductivity, that is, it loses heat more
slowly
Figure 13 - Thermal Mass - thermal gain/loss daily cycle
4. Thermal mass on a daily cycle sees the most
The effects of Thermal Mass on a home (Figure 13) built effective depth of material as being the first 50 mm,
using suitable materials, essentially you are “capping” between 50 - 100 mm the efficiency declines and
the fluctuations and maintaining temperatures within a beyond 100 mm the mass becomes
comfort zone. inconsequential

This reduces the need for winter heating and summer
cooling.

Factors determining Thermal Mass

Specific heat capacity refers to a material's capacity to
store heat for every kilogram of mass. A material of
'high' thermal mass has a high specific heat capacity.
Specific heat capacity is measured in J/kg.K

Figure 13 - Thermal Mass - thermal efficiency v thickness
The density refers to the mass (or 'weight') per unit
volume of a material and is measured in kg/m3. A high This is why UK brick sizes are set at 65 mm as standard
density material maximises the overall weight and is an and similarly, concrete blocks are set at 100 mm in
aspect of 'high' thermal mass. depth. Ritsu use larger log sizes of greater than 195
mm in homes - this is mainly for structural reasons but
the mass also has positive benefits.
Thermal conductivity measures the ease with which
heat can travel through a material. For 'high' thermal A material's thermal conductivity is the number of
mass, thermal conductivity usually needs to be Watts conducted per metre thickness of the material,
moderate so that the absorption and release of heat per degree of temperature difference between one side
synchronises with the building's heating and cooling and the other (W/mK). As a rule of thumb, the lower the
cycle. Thermal conductivity is measured in units of thermal conductivity the better, because the material
W/m.K conducts less heat energy.
Timbers thermal conductivity is 0.14 W/mK, for brick
Timber is often rated as having “low effectiveness” in
terms of its thermal mass against materials like brick, 0.73 and concrete 1.13.