[Greenbuilding] skepticism about mass wall values

[Peter Kidd]

I think actually thermal diffusivity is the more relevant parameter.
We are expecting to hit 5C (41F) for the first time since Halloween 
tomorrow, I am not sure thermal mass is so wonderful buried in the wall 
in this climate.
There are several ways that HD Day is calculated. For Code in Canada 
it's based on the mean daily temperature so I suppose that might be seen 
as "hourly computed", but is it /always/ lower?



> On 4/24/2013 12:39 PM, RT wrote:
>> But that doesn't stop me from having an opinion.
> Color me shocked. :-)
>> I also know that the usefulness of a material as beneficial thermal 
>> mass is directly proportional to its density.
> Not quite.  It is proportional to its density times its specific heat 
> (which can vary by material).  But the point is well taken.
>> I can't help but wonder if it might not be better (ie lower cost, 
>> lower embodied-energy, better thermal performance) to simply use a 
>> run-off-the-mill, regular density masonry exposed to the interior and 
>> outsulate it with a good insulation material ?
> Probably.
>
> ...

> I don't see how 'time to heat' can possibly increase annual demand in 
> a more or less continuously occupied building (intermittent is another 
> thing altogether, of course).  Maintaining 68°F 24/365 is just a 
> matter of heat loss * heating degree days.  High mass means that one 
> is computing that on daily or even multi-day average HDD, as opposed 
> to hourly computed HDD.  Which is/always/ going to be lower.
>
> Thank You Kindly,
>
> Corwyn 

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