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Sombreuil_mongrel
Re: Paint exterior bare metal door
Nestor wrote:

So, the dust particle causes a tiny droplet of water to form around it out of the humidity in the air.

But, wouldn't you get more of that happening where the air is warmer and has more humidity in it?

That is, why don't you get more dirt accumulation between the studs on the warmer parts of the wall cuz the air is warmer there and can hold more water molecules in suspension?

No,
Because the surface temp has to be below dewpoint. It reaches that temp in winter because of the lack of a thermal break on the joists. In the summer the reverse is true because heat conducted through the wood from the rafters raises the temp far far above any possible dewpoint.
Casey

Nestor
Re: Paint exterior bare metal door
Sombreuil_mongrel wrote:

No,
Because the surface temp has to be below dewpoint. It reaches that temp in winter because of the lack of a thermal break on the joists. In the summer the reverse is true because heat conducted through the wood from the rafters raises the temp far far above any possible dewpoint.
Casey

So, you're saying the wall temperature at the studs gets below the dew point temperature in winter because of a lack of thermal break, whereas the wall temperature between the studs would be warmer.

But, if that were the case, then at night, when the outdoor temperatures got a little cooler, you'd have lots of humidity in the air forming condensation over those studs (just like it does on windows) and I'd wake up to wet walls. But, I've never seen that happen. Not even when I get up at night. The walls are dry everywhere 24/7.

Faron
Re: Paint exterior bare metal door

Pleeeeeze don't take this wrong Nestor, but many things in this thread are getting waaaaayyy too over-analyzed IMO.

I'm pretty certain 98% of people don't really care about tiny details being run thru a wringer. SOME detail yes...but you're burrowing down into details no one really cares about.

It does get a little tiring to read all this "explaining every point" banter.
I'm NOT trying to be at all insulting here, believe it or no!

Now....I'm off to see KISS in MN Lakes country tonight!!!!

Faron

ordjen
Re: Paint exterior bare metal door

Yes, it does occur on a cool evening - on the outside of the wall. On a dewey morning, every stud location can be seen on the outside wall. The studs keep those area warmer and above the dew point.

Sombreuil_mongrel
Re: Paint exterior bare metal door
Nestor wrote:

So, you're saying the wall temperature at the studs gets below the dew point temperature in winter because of a lack of thermal break, whereas the wall temperature between the studs would be warmer.

But, if that were the case, then at night, when the outdoor temperatures got a little cooler, you'd have lots of humidity in the air forming condensation over those studs (just like it does on windows) and I'd wake up to wet walls. But, I've never seen that happen. Not even when I get up at night. The walls are dry everywhere 24/7.

OK, picture this: There are other dynamics at work. Heat cycles on and off. Mini-convection currents are at work all the time. If the dewpoint and air temp are very close, verging on condensation/evaporation, then both could be going on within inches of each other at the same time. I'm talking about minute amounts of condensation bearing dust particles, and in a nonce, the dew evaporates because the heat came up, or a current of air wafted it away, but the dust is left behind. Just because you can't sense the condensation by sight or touch does not mean that it's not there at the molecular level; and that's all that's required to stripe your ceilings with soot between 10 year (or 20?) paint jobs, the relentless and law-conforming cycles of condensation and evaporation all night long through cold months.
Enough said, x3
Casey

Nestor
Re: Paint exterior bare metal door

Faron:

We jammin here.

Ordjen and Sombreuil_mongrel:
I'm afraid we'll just have to agree to disagree. Quantum physics explains the lines on the walls and the dots on the lines without having to rely on condensation for any help.

canuk
Re: Paint exterior bare metal door

Newtonian Physics and Quantum mechanics ?!?!? you might as well include
van der Waals bonds.

I don't believe your illustrations of objects and insects not breaking water surface tension really applies directly when that is liquid water.
Electrostatic attraction with water vapour and dust molecules seems more appropiate in my opinion.

canuk
Re: Paint exterior bare metal door
Nestor wrote:

So, you're saying the wall temperature at the studs gets below the dew point temperature in winter because of a lack of thermal break, whereas the wall temperature between the studs would be warmer.

But, if that were the case, then at night, when the outdoor temperatures got a little cooler, you'd have lots of humidity in the air forming condensation over those studs (just like it does on windows) and I'd wake up to wet walls. But, I've never seen that happen. Not even when I get up at night. The walls are dry everywhere 24/7.

It can and does happen in Winterpeg.
I've seen wet wall surfaces with poor insulation and high indoor RH during cold winters.----to the point where mould and mildew eventually developes.
Ghosting is also not that uncommon as well.

Nestor
Re: Paint exterior bare metal door

Let's just all agree to disagree and let this thread slide down into the quicksand below.

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