[Equest-users] (no subject)

Bruce Easterbrook bruce5 at bellnet.ca
Thu Aug 12 17:59:24 PDT 2010


      Nick you understand perfectly and Bill is the one you should be 
listening to.  This is what happens when marketing gets hold of 
something without talking to engineering.  It is all BS.  I looked at 
both sites, basically they are taking a low E thermopane and adding a 
third pane of their heating glass. A real good 2 pane IGU will be about 
R-4.2, add another pane and you could be in the R-7 range or a U value 
of .14, all centre of glass.  There is no way 2 pieces of glass in this 
3 pane unit are the same temperature.  If the middle piece is almost the 
same temperature as the warm inside piece that actually proves you have 
a huge amount of heat moving to outside not to the inside.  There will 
also be radiation, and in this instance it will be significant as well.  
The reflective properties of the low E glass will help, reflecting a 
certain percentage back into the room as the glass should be throwing 
long wavelength radiation but a significant portion will still flow 
through unless the low E coat is thick enough, ie a mirror, which 
doesn't do much for looking outside.  Like you said earlier you have a 
radiator with a 70F room one side and a winter night at -13F on the 
other side, it is not rocket science to know in which direction most of 
the heat will flow.
     Getting to the modelling using baseboards I don't think you can.  A 
baseboard is going to have a R-20 opaque surface behind it and the 
heated glass is going to have a R-4 transparent surface behind it.
     As far as I see it the only real benefit of this glass is you will 
be able to run your humidity higher in the winter without having 
condensation on the edges of the glass but at what I would estimate to 
be a significant energy penalty.  You would get most of these benefits 
just by having the triple low E IGU with low conductivity spacers or by 
having curtains.  You will not heat a room with it and be able to pay 
the hydro bill.  Note all the conformances are for glass.  I don't see 
any insulating window certifications.  Until these are tested no 
jurisdiction in NA will allow you to use them with the numbers they are 
quoting.
Bruce Easterbrook P.Eng.
Abode Engineering


On 12/08/2010 06:50 PM, Nick Caton wrote:
>
> Namrata,
>
> I have patched Bill Bishop's latest response in below in case you 
> missed it.  He's a proven smart cookie, and if he's telling me I've 
> got my head wrapped around the problem the wrong way then I do believe 
> him...
>
> ...but with that caveat, the manufacturer implying zero heat transfer 
> through the entire window assembly (because two of at least 4 surfaces 
> have equal temperature), sounds like flat-out misinformation to me.  
> If two surfaces of a material have equal temperature (say, 100 °F), 
> then yeah, the conduction between them would be zero, but that won't 
> prevent convection/radiation from sweeping a majority of heat away 
> when one side is subject to sub-freezing temperatures!  My car for 
> example has a heated rear window which helps me dislodge nightly 
> glacier-formations in the wintertime.  On a cold day, the heat 
> generated in that glass may help heat the interior air somewhat, but 
> surely a majority is going straight to the literally frozen exterior, 
> especially once the interior air has risen to a temperature in which I 
> can breathe regularly.
>
> I remain skeptical of the concept of using heated windows as a good 
> idea for a space heating source (as opposed to a draft or condensation 
> mitigation strategy -- perhaps to melt snow in a skylight as well?).  
> Still, if these units do put a significant fraction of heat into the 
> space, I think modeling electric baseboard heating will at the least 
> be a good start to emulate the space temperature behavior the actual 
> system may help achieve -- though I'm still stuck wondering how you 
> might account for the amount of energy that is lost to the exterior as 
> the units operate...  hear me out as I think my ducks are in a row 
> here =)!
>
> I'd be cautious that your manufacturer may be, intentionally or not, 
> dumbing down the discussion by framing their "effective U-value" as a 
> material property like "conductivity."  Conductivity is an arbitrary 
> material property that does not change with temperature -- (i.e. steel 
> has a higher conductivity than air).  U-values (and R-values) on the 
> other hand have that tricky little °F (or °C) in their units, because 
> they are tied directly to a heat transfer rate, which requires having 
> a delta-T -- in other words, for a given set of material properties, 
> the rate of heat transfer is dependent on the difference in 
> temperature the assembly is subject to.  That's one reason we come 
> across "summer" and "winter" U-values for window assemblies.
>
> It's my intuition that eQuest (among other variables) uses the hourly 
> exterior temperature from the weather file alongside the hourly 
> calculated interior temperature for the parent zone to determine what 
> temperature difference to use when figuring the hourly heat loss 
> through a window assembly.  A heated window however (when on) should 
> be using a fundamentally different figure for the interior surface 
> temperature than, say, 70°F when determining a temperature difference 
> to find the hourly heat loss for the zone.
>
> I think I'm understanding now what we're all getting at when we speak 
> of "effective U-values:"  If a baseboard heating element in eQuest (or 
> other software) uniformly distributes 100% of its heat to the zone, 
> then we might account for the reality of a significant (?) fraction 
> being lost straight out the window by increasing the window's 
> effective U-value, in turn modeling a realistically higher heat loss 
> through the assembly on account of the higher-than-normal heat 
> temperature difference between the innermost and outermost surfaces of 
> the window, right?
>
> I could certainly be wrong, but an approach defining an electric 
> internal equipment load with an custom equipment power curve (see 
> Bill, below) **might** be easier than an approach defining dynamic 
> window properties (which I do not think is feasible in eQuest).
>
> Again, I am not writing with full confidence that I completely 
> understand exactly how heated windows truly function, but critically 
> thinking this through is helping me get there!  I look forward to 
> anyone stepping up to the plate to affirm or refute my current 
> understanding =).
>
> ~Nick
>
> cid:489575314 at 22072009-0ABB**
>
> * *
>
> *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:* Namrata Vora [mailto:namrata.vora at soladigm.com]
> *Sent:* Thursday, August 12, 2010 2:08 PM
> *To:* Nick Caton; Sami, Vikram; Sam Mason; Bishop, Bill; 
> equest-users at lists.onebuilding.org
> *Subject:* active heating window modeling
>
> All,
>
> Thanks for your prompt responses
>
> The mfg of this technology claim that since the temp difference b/n 
> surface 3 & 4 is zero or minimal, there is no heat transfer out 
> through the windows. In addition the radiant nature of the heat allows 
> the room temperature to be set lower.
>
> This particular company claims a u-value of 0.14 in non-heated state. 
> I tried creating such a low u-value dual pane IGU using WINDOW5 and 
> was unable to get that. So I created it directly in eQuest using 
> simplified glass type method. Now will try adding the radiant heating 
> as electric baseboard as suggested.
>
> http://www.iqglass.com/products_iqglass/products_specs.html
>
> I agree w/ Nick's comment. In addition I wouldn't think the window 
> would be in heating mode all the time. I would need to figure out when 
> to trigger the heating.
>
> Namrata
>
> Cell: 408-893-3729
>
> *From:* Bishop, Bill [mailto:wbishop at pathfinder-ea.com]
> *Sent:* Tuesday, August 10, 2010 1:36 PM
> *To:* Nick Caton; equest-users at lists.onebuilding.org
> *Subject:* RE: [Equest-users] (no subject)
>
> 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
>
> cid:489575314 at 22072009-0ABB**
>
> * *
>
> *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 J
>
> *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^® 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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