[Greenbuilding] Passive House Overheating

[Don Lush]

John- Perhaps you should have supplied a reference for your "cold beer" in
the palm of your  hand solution. There was an excellent article in the new e
Journal of Disruptive Science and Technology. 

 

 http://online.liebertpub.com/loi/DST 

that addresses this issue. It is in the premier issue entitled Enhancing
Thermal Exchange in Humans and Practical Applications Description: free
accessH. Craig Heller, Dennis A. Grahn 

Disruptive Science and Technology. 2012, 1(1): 11-19.

 

 

In summary it says that "The intermittent application of vacuum cooling to
the palms of individuals exercising in a hot environment had the effects of
lowering the rate of rise of core temperature and enhancing performance".
What we need is a beer holder that applies an intermittent vacuum to the
hand that holds it. Less spillage and a cooler feeling environment. 

 

Don

 

 

From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of John
Straube
Sent: Thursday, August 16, 2012 11:16 AM
To: Alan Abrams
Cc: Green Building
Subject: Re: [Greenbuilding] Passive House Overheating

 

Yes, you can distinguish sensible from latent (humidity) energy in the lab
or carefully instrumented houses.
No, it is not easy to measure in normal homes, but you can if you are
careful and have numerous instruments.

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. 

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.

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.

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.

And, I tried the getting a cold beer as a solution, but this was not quite
good enough :)

Dr John Straube, P.Eng. 
www.BuildingScience.com

On 12-08-16 10:57 AM, Alan Abrams wrote:

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.  

 

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