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<div class="moz-cite-prefix"><font face="Helvetica, Arial,
sans-serif">Yes, you can distinguish sensible from latent
(humidity) energy in the lab or carefully instrumented houses.<br>
No, it is not easy to measure in normal homes, but you can if
you are careful and have numerous instruments.<br>
<br>
Systems that ventilate buildings with cool outdoor air are
called "economizers" in commercial buildings. They are used on
many many modern buildings. As they were being deployed it was
noticed that you could not use temperature as a trigger for when
to ventilate, because ventilation often brought in significant
amounts of humidity which was adsorbed and stored in materials
and furnishings. When the AC turned on during warmer hours, it
had to work much harder to remove this stored moisture, and
comfort was compromised. So they invented "enthalpy control"
which only ventilates when the air outside has less energy in
it, eg some combination of temperature and humidity. Dont
ventilate when it is 65F and raining, do ventilate when it is
70F and 40%RH. <br>
<br>
The folks at Florida Solar Energy Center and my colleague at
BSC, Armin Rudd, have studied this effect in hot-humid climate
housing and it is a really big deal. Often the energy saved by
window opening during summer is almost zero.<br>
<br>
As we get to super insulated homes, more and more of the AC
energy required is to remove latent energy (control humidity).
This is a topic of active and intense research as normal AC
systems dont do this: their ratio of sensible to latent heat is
pretty much fixed. We see lots of problem buildings with poor
summer humidity control now that many new buildings have an
enclosure is insulated and good window solar control is added.
Many solve this with energy consuming dehumidifiers.<br>
<br>
In my own super insulated house, I have no over heating issues
at all and I try to operate the windows very carefully, but
humidity becomes a problem after 3 or 4 days of warm (over 80)
humid weather. I am using a dehumidifier to limit RH peaks.
Next year I will be installing a variable capacity mini-split to
do this more efficiently.<br>
<br>
And, I tried the getting a cold beer as a solution, but this was
not quite good enough :)<br>
<br>
</font>
<div class="moz-signature">Dr John Straube, P.Eng. <br>
<a class="moz-txt-link-abbreviated" href="http://www.BuildingScience.com">www.BuildingScience.com</a></div>
On 12-08-16 10:57 AM, Alan Abrams wrote:<br>
</div>
<blockquote
cite="mid:CADj3_s65nBZK=zwtL40gWVFd0YzVVj7=L6TqR6FWVcXcOE_V=w@mail.gmail.com"
type="cite">this leads to a question...in a refrigerated system,
can you effectively distinguish the energy required for reducing
sensible heat from the energy to reduce latent heat? The question
arose on a project I am consulting on, in which the supposedly
leading edge mechanical contractor designed an AC system that uses
the dank, dark, and dismal 120 yr old basement as a return
plenum. </blockquote>
<br>
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