Reading through Silver Spray's blog one comes across:

http://www.silverspray.co.uk/2011/07/25/wood-vs-other-construction-materials/

Chatting to one developer company, yes wood doesn’t have any thermal mass, but when you are heating (or cooling) the building, you don’t need to also heat (or cool) the physical ‘thermal mass’ structure either.

I think this is, at best, a half truth. The specific heat capacities (i.e., the amount of heat a given mass of material will store for a particular temperature change) for most building materials tends to be pretty similar, around 1 kJ/(kg·K) plus or minus 20% or so. About the only common materials which are well outside this range are water at 4.2 kJ/(kg·K) and phase change materials like wax, etc, over their phase change temperature range.

Of course, the density of wood is less than most other stuff used in building so the volumetric heat capacity is lower. On the other hand, you tend to need more of it.

Also, the thermal conductivity of wood is lower than other non-insulating materials so the volume available to temper the room temperature tends to be less too (see Fostertom's thread on the speed of heat).

Still, it's my view that appropriately designed wood can contribute to the thermal mass of a house. It's why I intend to use a post and beam structure with rafters exposed inside the house - to give a relatively large volume of wood as directly thermally connected to the house air volume as makes structural sense.

I had a thread on that a while ago which concluded that some dense hardwoods have the same (or higher) volumetric heat capacity as concrete or stone and hence are a good choice for for floors (assuming they're from sustainable sources etc.). Wood is made of cellulose which has a lot of hydrogen-bonded -OH groups which contribute to a pretty high specific heat capacity.

Paul in Montreal.

Cross lam buildings with the structure exposed provide quite a decent amount of 'thermal mass' especially when compared to aerated blockwork.

Perhaps the process allows a different species of wood to be used without effecting the durability?

Thanks for the link.

Here's an extract from:-
http://www.fs.fed.us/ccrc/topics/urban-forests/docs/physical%20properties%20and%20moisture%20relations%20of%20wood.pdf

"The heat capacity of wood depends on the temperature
and moisture content of the wood but is practically
independent of density or species.
The heat capacity of wood that contains water is greater than
that of dry wood. Below fiber saturation, it is the sum of the
heat capacity of the dry wood and that of water (cpw) and an
additional adjustment factor Ac that accounts for the additional
energy in the wood–water bond:
cp = (cp0 + 0.01Mcpw)/(1 + 0.01M) + Ac (3–9)
where M is moisture content (%). The heat capacity of water
is about 4.19 kJ/kg·K (1 Btu/lb·°F). The adjustment factor
can be derived from
Ac = M(b1 + b2t + b3M) (3–10)
with b1 = -0.06191, b2 = 2.36 ´ 10-4, and b3 = -1.33 ´ 10-4
with temperature in kelvins (b1 = -4.23 ´ 10-4,
b2 = 3.12 ´ 10-5, and b3 = -3.17 ´ 10-5 with temperature in
°F)."