[Strawbale] Forced air

[Robert Tom]

I saw Mark's message just before heading to bed last night (~3:30am) and  
wanted to write a response but well, you know, and this morning, I saw  
that Don beat me to it.

As a sort of corollary to Don's comments about the *significant*  
temperature difference in outside temperatures between the UK and SK, one  
notes that in the significiantly warmer UK winters, the pea-soup-like  
outside air will obviously still hold a significant amount of moisture ...  
whereas in SK which is an arid climate at the best of times, minus 35 deg  
outside air is going to have diddly squat moisture content.

So two identical, not-particularly-air-tight houses in the two locales are  
going to have vastly different interior humidity levels, even if no  
heating were in place.

However once you start heating the SK house, that tosses a humongous  
O/S-I/S temperature differential into the equation as an additional  
driving force behind Ma Nature's propensity to even things out, with the  
result that the interior humidity levels of the SK house would be lowered  
even more, and would probably be best described as "scratchy-throat/crusty  
nose/constant-bad-hair-day/flaky-skin-ish" ... or "exceedingly dry" for  
short.

If the interior humidity levels are extremely low, and moisture is being  
sucked out of one's body as a result, then it's essentially the same  
natural cooling process that our bodies use is summer where excess body  
heat is dumped into moisture which is transpired through our pores and  
then carried away by air moving past our bodies to effect evaporative  
cooling... except that in winter when Old Mark is trying to stay warm, he  
doesn't really appreciate that involuntary evaporative cooling so he kicks  
up the thermostat in an attempt to compensate.

Perhaps what Mark really should be doing is running around the house  
looking for and sealing up air leaks and perhaps considering  
humidification.



On Tue, 08 Jan 2008 00:58:48 -0500, Mark BP / Low Energy Design Ltd  
<mark at lowenergydesign.ca> wrote:


> I'm prepared to believe that forced air doesn't create any more of a
> dust problem.
>
> Re energy consumption, though, the situation doesn't seem to me to be so

> One not-particularly-scientific piece of evidence.  Back in Britain, I
> used to be able to keep daytime thermostat settings (at least when my
> wife wasn't in) down to 16 or 17 deg C.  Here in Saskatchewan, I
> generally find that I need 18.5, 19 or even 20 deg C for my own comfort.
[snip]

On Tue, 08 Jan 2008 09:49:06 -0500, <dfugler at cmhc-schl.gc.ca> wrote:
[mostly <unsnipped> ]
> Mark,
>
> You are probably having to keep the temperature higher in Saskatchewan
> than in England because the walls and windows are colder, not because of
> the change from radiant to forced air heating. The difference between an
> outside temperature of 5°C and - 35°C is substantial. You will have
> increased radiant loss to an outside wall or window when the termperature
> outside is far lower (we could discuss relative wall insulation levels  
> but we won't).
>
> As far as the assertion that radiant heated houses have lower thermostat
> settings, I had heard that frequently as well. So I hired a student in
> Nova Scotia to check a sample of each type of house: radiant flooring and
> forced air. Here is the link to the results:
> http://www.cmhc-schl.gc.ca/odpub/pdf/62675.pdf
>
> Thermostat settings were the same for the forced air and radiant flooring
> houses. The radiant heating industry didn't like the study. They said it
> was not big enough, and that we did not measure comfort created in those
> houses. I challenged them to do their own study, or help us create a
> bigger survey. So far they have not come up with the money to verify  
> their assertions.


-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at chaffY a h o o  dot  c a >
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