[Greenbuilding] Condensation on windows

[John Salmen]

Ironically I just tested two glazed units with an ir and also with some odd
unit that identifies glass coatings, etc. Both are over a bathtub and
basically identical. The owner complained that one was continually showing
condensation and the other wasn't. No obvious signs (or industry standard
indicators) of failure in the questionable unit and the glass readings were
correct (glazing thickness, type, gas, film orientations, etc.) but the ir
readings were definitely off in comparison to a comparable unit - so it was
a failed unit (though the manuf. does not recognize that). Like anything you
take enough readings within similar conditions to create a sample and then
compare. That gives you information - it doesn't give you solutions.

So I would say an ir is definitely useful if you have a control unit or
something to compare to (apples to oranges or even better having nick on
site). In a building I use IR, hammers, drills, cigars - whatever tools I
have on hand to either identify or provoke signs and symptoms. IR is so
cheap and such a useful tool - but the precision is similar to hammers,
drills and cigars - which is about the same level of precision you get from
the medical community for basic diagnosis or emergency medical. 


-----Original Message-----
From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org]
On Behalf Of nick pine
Sent: October-29-12 6:58 PM
To: greenbuilding at lists.bioenergylists.org
Subject: Re: [Greenbuilding] Condensation on windows

Bob klahn <Home-NRG at dnaco.net> wrote:

>> IR thermometers do not read accurately on glass...

> They read close enough, even without adjusting for a 0.88 vs 0.95 
> emissivity.

Well, maybe not. If they expect a 0.95 emissivity and read 60 F (520 R) for
glass with a 0.88 emissivity, 0.88sTg^4 = 0.95s520^4 makes the actual glass
temp Tg = (0.95/0.88)^0.25x520 = 530 R, ie 70 F, correcting with a
calculator.

Nick 


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