[Equest-users] (no subject)

[Bishop, Bill]

Nick,
 
"The "efficiency" of these units ... is going to vary hourly (probably
dramatically) based on the outside-to-interior temperature difference."
Don't think of it as less heat to the space, but more heat to the
exterior. The window U-factor should take care of this.
"apply an ON/OFF/TEMP schedule to an equipment or internal energy load?"
You can apply an equipment power curve as a function of space
temperature (EQUIP-PWR-FT).
"I'm concerned I might be missing something" For the same glazing
properties, the heat loss to the exterior should be the same, EXCEPT
that the interior surface is now warmer, so radiative and convective
losses should be higher. Hopefully the manufacturers account for that in
their rated U-factor. I'm not convinced yet that there is any energy
benefit to this system.
 
Regards,
Bill
 
________________________________

From: Nick Caton [mailto:ncaton at smithboucher.com] 
Sent: Tuesday, August 10, 2010 12:15 PM
To: Sami, Vikram; Sam Mason; Bishop, Bill; Namrata Vora;
equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] (no subject)
 
On further thought, I think the equipment referenced would be
over-simplified if you just modeled an electric baseboard (that was my
intuitive reaction also - a few beat me to the punch)...
 
 
The "efficiency" of these units, meaning the btu/h delivered to the
space for every input kW, is going to vary hourly (probably
dramatically) based on the outside-to-interior temperature difference.
If it's -10F outside and 70F inside, these are going to lose a ton of
the input heat to the exterior for the amount desired heat flowing
inside - heat will flow proportionately to where it's coldest.
 
Time allowing, I'd propose achieving a much higher degree of modeled
accuracy by defining a series of  equipment loads, each with a custom
multiplier schedule (even if the units in reality are under some kind of
thermostatic control) to account for when the units would be turned on.
This would be more work, but then you're able to define a distinct
sensible HG ratio to account for the fraction of heat actually entering
the space (instead of lost to the exterior).  As you can define up to 5
separate equipment load/schedule combinations for one space, you could
come up with a weighted efficiency to apply to the SHG ratio for up to 5
different blocks of time.  Further explanation:  This would involve
creating hourly reports to compare the hourly exterior temps to the
target heating temp for the interior, for the times the units would be
operating, and to use that info to figure out an hourly efficiency for
the system based on how much heat would actually find it's way into the
interior zone.  Those hourly results could be used to come up with
weighted SHG ratio values for 5 blocks of time.
 
On a related note, I've got a question for everyone:  Does anyone know
of any workaround (aside from extensive excel number-crunching) to apply
an ON/OFF/TEMP schedule to an equipment or internal energy load?
 
On another tangent, for my own education, am I wrong to consider heated
glass as an intrinsically inefficient approach to space heating?  It
seems most appropriately applied as a "band-aid" or "patch" solution to
a decision to put too much glazing where drafts will cause discomfort.
One of the previous links has a claim: "When installed as part of a zone
heating strategy, heated windows can actually reduce the overall energy
consumption of a building by decreasing dependence on an inefficient
HVAC system."  Wouldn't this need to be a terribly inefficient heating
system to compare unfavorably to a heating element losing >50% of its
energy to the exterior?  I'm concerned I might be missing something
fundamental for HVAC design here... =/
 
~Nick
 
 
 
 
NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
Check out our new web-site @ www.smithboucher.com 
 
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Sami,
Vikram
Sent: Tuesday, August 10, 2010 11:07 AM
To: Sam Mason; Bishop, Bill; Namrata Vora;
equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] (no subject)
 
I stand corrected - it is a good U-Value :-)
 
Vikram Sami, LEED AP
Sustainable Design Analyst
1382 Peachtree St. NE, Atlanta, GA 30309
t: 404-443-7462    f: 404.892.5823       e: vikram.sami at perkinswill.com
www.perkinswill.com <http://www.perkinswill.com/> 
Perkins+Will.  Ideas + buildings that honor the broader goals of society
 
 
From: Sam Mason [mailto:sam.mason at atelierten.com] 
Sent: Tuesday, August 10, 2010 12:00 PM
To: Sami, Vikram; Bishop, Bill; Namrata Vora;
equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] (no subject)
 
Vikram,
The conversion from W/sq.m.-K to Btu/hr-sq.ft.-F is 5.68. This gives a
U-value of 0.162 Btu/hr-sq.ft.-F.
 
I would like to see a study of the energy consumption of this window
compared to a building with normal low-e IGU and actual radiators. 
 
Sam
 
--
Sam Mason
Atelier Ten
 
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Sami,
Vikram
Sent: Tuesday, August 10, 2010 11:47 AM
To: Bishop, Bill; Namrata Vora; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] (no subject)
 
I'm a little curious - is 0.92 W/m2k a good U-value? Just poking around
on online converters - it looks like the IP version of that is around
0.56 or something in that region - doesn't seem spectacular (you get
0.25 with a lot of double pane low-e IGUs). Unless the 0.922 is for the
entire glazing assembly - in which case its around the same as other
glass types. 
 
I might have got the conversion factor wrong. 
 
Vikram Sami, LEED AP
Sustainable Design Analyst
1382 Peachtree St. NE, Atlanta, GA 30309
t: 404-443-7462    f: 404.892.5823       e: vikram.sami at perkinswill.com
www.perkinswill.com <http://www.perkinswill.com/> 
Perkins+Will.  Ideas + buildings that honor the broader goals of society
 
 
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop,
Bill
Sent: Tuesday, August 10, 2010 11:25 AM
To: Namrata Vora; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] (no subject)
 
Namrata,
 
I would model the heating as electric baseboards and select a glazing
type based on the U-value and SHGC.
 
Regards,
Bill
 
William Bishop, PE, BEMP, LEED(r) AP | Pathfinder Engineers & Architects
LLP
Mechanical Engineer
 
134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
wbishop at pathfinder-ea.com
www.pathfinder-ea.com
P Sustainability - less is more.
________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Namrata
Vora
Sent: Tuesday, August 10, 2010 10:34 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] (no subject)
 
How does one model active heating windows like the ones listed below.
http://www.iqglass.co.uk/p/h/Products/U_Values_%26_Benefits/218/
http://www.thermiquetech.com/about_heated_glass.html
 
Namrata Vora
408-893-3729

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