[Bldg-sim] was..Rooftop Snow Cover???
JRR
energy.wwind at cox.net
Thu Dec 3 21:14:09 PST 2009
JRR wrote:
How soon will Energy Plus software support .... PURCHASED SNOW ???
It's great insulation !!! and it changes the albedo of the roof....
You could even
capture rain / snow melt for re-use.... and you could even Snow every
night and
melt it with the Sun to be caught the next day... avoiding peaking
charges.....
Enough viewing into my bag of patent tricks for this evening.........
If you are intrigued by these suggestions you have my email above.
John R Ross III PE
Nick Caton wrote:
>
> Thanks for the response Drury!
>
>
>
> So EnergyPlus will essentially adjust the reflectivity of a roof
> surface hourly based on the albedo TMY data -- that's promising! Can
> we affect the modeled behavior to account for means of preventing
> accumulation, such as snow-melt cable or roof geometries?
>
>
>
> Also, can EnergyPlus (and/or, again, any other energy modeling
> software/engine) take account for the variable insulative effects of
> snow incident on the roof surface? I realize accurately/realistically
> modeling this behavior could be tricky/impossible with the removal of
> snow depth information in TMY3 from TMY2 (from:
> http://www.doe2.com/Download/Weather/TMY3/Users_Manual_for_TMY3_Data_Sets.pdf).
>
>
>
> I'm bringing up and pressing this point because I think we as
> community of energy modelers might want to begin modeling the thermal
> effects of hourly roof snow cover (if we aren't already), both as a
> means of influencing building design for energy-conscious decision
> making and as a means of more accurately modeling real-life thermal
> behavior. I did some quick fact checking -- snow has a fairly
> significant insulative property (approximately R-1 per inch), and I am
> concerned that any energy modeling performed for buildings in
> northerly climates might be significantly off-base without accounting
> for the realities of snow-cover on buildings.
>
>
>
> PS: I had to read up on the term albedo myself. Recommended reading
> for others at: http://en.wikipedia.org/wiki/Albedo
>
>
>
> PPS: It appears snow cover in energy modeling is a pretty deep topic
> in other circles... I found further recommended reading (powerpoint)
> for those interested at:
>
> http://www.google.com/url?sa=t&source=web&ct=res&cd=1&ved=0CAcQFjAA&url=http%3A%2F%2Fwww.nws.noaa.gov%2Fiao%2FInternationalHydrologyCourseCD1%2F1031%2Fhfcourse_snow.ppt&ei=SvEXS5aYLoL0ManeyN8C&usg=AFQjCNEoDwnXD8CynrrptTs5TPgYJ8kbHw&sig2=yXdMijCKnJOu8J-gKEGsxg
> <http://www.google.com/url?sa=t&source=web&ct=res&cd=1&ved=0CAcQFjAA&url=http%3A%2F%2Fwww.nws.noaa.gov%2Fiao%2FInternationalHydrologyCourseCD1%2F1031%2Fhfcourse_snow.ppt&ei=SvEXS5aYLoL0ManeyN8C&usg=AFQjCNEoDwnXD8CynrrptTs5TPgYJ8kbHw&sig2=yXdMijCKnJOu8J-gKEGsxg>
>
>
>
> ~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:* Crawley, Drury [mailto:Drury.Crawley at ee.doe.gov]
> *Sent:* Thursday, December 03, 2009 9:56 AM
> *To:* Nick Caton; muehleisen at iit.edu; Christopher Schaffner
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* RE: [Bldg-sim] Rooftop Snow Cover???
>
>
>
> Yes, EnergyPlus uses the albedo in the TMY3 or snow cover in other
> files to adjust the diffuse radiation.
>
>
>
> ------------------------------------------------------------------------
>
> *From:* bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Nick Caton
> *Sent:* Wednesday, December 02, 2009 5:48 PM
> *To:* muehleisen at iit.edu; Christopher Schaffner
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] Rooftop Snow Cover???
>
> I'm starting a new "thread" as this is a definite tangent from the
> emissivity discussion of the past few days.
>
>
>
> A question occurred to me on reading Ralph / Chris's comments below...
> does _ANY_ energy modeling program/engine today use the snow cover
> data present in TMY2 files? There's obvious implications for things
> like roof surface thermal behavior and hourly photovoltaic array
> performance when you consider the reality of significant snow cover
> presence through the day...
>
>
>
> Of note... I'm no expert, but for others' reference I found a nice
> resource this afternoon clarifying the what/why/how of TMY files
> here: http://rredc.nrel.gov/solar/pubs/tmy2/
>
>
>
> ~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:* bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Ralph
> Muehleisen
> *Sent:* Wednesday, December 02, 2009 10:48 AM
> *To:* Christopher Schaffner
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Why should roofs have high emissivity?
>
>
>
> True indeed.
>
> Except when your roofs are not covered with snow.
>
> Here in Chicago, at least the past few years, snow has come in bigger
> chunks with more warmi and cold periods in between. And rooftop snow
> has been melting during the warm periods so rooftops have been bare
> for more of the winter.
>
> It would be an interesting study (maybe I can find an undergrad or
> interested masters student) to actually look at a typical flat roof
> small commercial building and see if the increased summer efficiency
> of cooling equipment from a cool roof offsets the increased winter
> heating load.
>
> Ralph
>
> Ralph Muehleisen, Ph.D., P.E., LEED AP, FASA
> Assistant Professor and Director of the Miller Acoustics Lab
> Civil, Architectural and Environmental Engineering
> Illinois Institute of Technology
> Chicago, IL 60616
> muehleisen at iit.edu <mailto:muehleisen at iit.edu>
> tel: 312-567-3545 fax:312-567-3519
>
> On Wed, Dec 2, 2009 at 5:47 AM, Christopher Schaffner
> <chris at greenengineer.com <mailto:chris at greenengineer.com>> wrote:
>
> Of course, if your roof is well insulated, it will be covered with
> snow. I doubt very much that your "warm" roof will really help much.
> Go with the cool roof.
>
> --
>
> Chris Schaffner, PE, LEED AP, LEED Faculty^(TM)
> Founder and Principal
>
> The Green Engineer, LLP
> Sustainable Design Consulting
> 50 Beharrell Street
> Concord, MA 01742
> T: 978.369.8978
> M:978.844.1464
> chris at greenengineer.com <http://chris@greenengineer.com>
> www.greenengineer.com <http://www.greenengineer.com>
>
>
>
>
> On 12/2/09 12:26 AM, "Ralph Muehleisen" <muehleisen at gmail.com
> <http://muehleisen@gmail.com>> wrote:
>
> Chris makes a good point to consider with cool roofs.
>
> A cool roof will indeed reduce solar heat gain to the roof which
> reduces its temp (good in summer) and reduces cooling requirements
> in summer but will increase heating requirements in the winter.
>
> Until someone develops a material where the emissivity changes
> with temperature (and not just wavelength) a cool roof that is
> good in summer will be bad in winter.
>
> So, in colder climates, a cool roof can indeed increase the
> overall energy use of a building.
>
> Even so, some northern cities like Chicago, mandate cool roofs in
> building code. Why? Because the cool roof will reduce the urban
> heat island effect where the city has increased temperatures
> compared to the surrounding areas.
>
> The thought is that the overall benefits of the reduction in
> urban heat island effect in summer is more important than the
> increased energy use that comes from increased winter cooling load.
>
>
> Ralph
>
> Ralph Muehleisen, Ph.D., P.E., LEED AP, FASA
> Assistant Professor and Director of the Miller Acoustics Lab
> Civil, Architectural and Environmental Engineering
> Illinois Institute of Technology
> Chicago, IL 60616
> muehleisen at iit.edu <http://muehleisen@iit.edu>
> tel: 312-567-3545 fax:312-567-3519
>
>
> On Tue, Dec 1, 2009 at 6:28 PM, Chris Jones <cj at cr-jay.ca
> <http://cj@cr-jay.ca>> wrote:
>
> In some cases it may be counter productive to use a high
> emissivity roof. I have worked on uncooled warehouses where the
> team used an approved roofing product to get that point but the
> heating energy increased enough to lower the savings enough to
> lose an EAc1 point.
>
>
>
>
>
>
> Chris Jones
> 14 Oneida Avenue
> Toronto, ON M5J 2E3.
> Tel. 416-203-7465
> Fax. 416-946-1005
>
>
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