In my opinion you can follow this approach
a)
Concerning repetitive thermal
bridges (as studs or rafters in a wall) the best option is to use “equivalent”
layers including the effect of thermal bridges
b)
Concerning linear thermal bridges
(as intersections between wall and floors or…) the best option is to
introduce a small opaque surface (=door) with the equivalent thermal transmittance
than the previously obtained following 2D calculations. The principle is to
introduce a “fictitious door” having similar thermal transmission
than the thermal bridging effect.
It will be easier if Energy plus could accept “linear
elements” (one line instated surfaces) characterized by its linear
thermal transmittance Y expressed in W/m·K but I don’t know if this improvement
will be included in some newer releases ¿can someone inform us?
Josep
Solé
URSA Insulation S.A-
URALITA
European Sustainibility & Technical Manager
Móvil +34 606 42 32 14
P
URALITA / URSA se compromete con el ahorro de energía. Antes de
imprimir este mensaje asegúrese de que es necesario.
De: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] En nombre de Pedro Peixeiro
Enviado el: jueves, 06 de octubre de 2011 16:53
Para: EnergyPlus_Support@xxxxxxxxxxxxxxx
Asunto: Re: [EnergyPlus_Support] modelling thermal bridging in energy
plus
point taken. thanks. though i dont see how one can be more
carefull about thermal bridges in E+ other than modelling the building as
accurately as possible, i'm not aware of specific inputs for this issue.
Pedro.
On 06-10-2011 15:36, josep.sole@xxxxxxxxxxx
wrote:
Concerning thermal bridges in
buildings I’m not fully agree.
If thermal bridges are not
avoided they will a big issue specially in Passive Houses or Nearly Zero Energy
houses then you need to take care before to say “…you
shouldn’t worried very much….”-
For your specific case have a
look on “Composite wall constructions” in IO reference document
probably will help you
For linear thermal bridges
due to intersection between building elements some special care is needed when
modeling in Energy +
Josep Solé
URSA Insulation S.A- URALITA
European Sustainibility & Technical Manager
Móvil +34 606 42 32 14
P
URALITA / URSA se
compromete con el ahorro de energía. Antes de imprimir este mensaje asegúrese
de que es necesario.
De: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
En nombre de Pedro Peixeiro
Enviado el: jueves, 06 de octubre de 2011 16:05
Para: EnergyPlus_Support@xxxxxxxxxxxxxxx
Asunto: Re: [EnergyPlus_Support] modelling thermal bridging in energy
plus
If you model your house accurately (surface geometry, surface layers and
materials) you shouldn't be worried too much about thermal bridging, the
software takes care of properly simulating heat transfer through the surfaces.
When dealing with windows, however, there are two fields related to thermal
bridging due to window frames in the WindowProperty:FrameAndDivider object:
"Ratio of Frame-Edge Glass Conductance to Center-Of-Glass
Conductance" and "Ratio of Divider-Edge Glass Conductance to
Center-Of-Glass Conductance". Look them up in the I/O Reference document,
and see for yourself if they are of any use to you (they will only be usefull
for window frames, as mentioned).
Infiltration rates can be obtained using the zone infiltration objects (in the
IDF, they are under the zone airflow group). Again, take a look at the
documents to see how they work.
As for natural ventilation, things might get a bit more tricky. For this, you
have to use the AirflowNetwork:Multizone objects. These are a bit more complex,
and you should expect the need to spend a bit more time around this to learn
how it works. The documentation provides much information on the AN setup (look
first in the I/O ref document) and you can also take a look at the example file
AirflowNetwork3zvent, for starters. Any further questions/problems you
encounter, feel free to ask.
Note: you wont be able to use the zone infiltration objects at the same time
you use the airflow network (simply because its the way the software works).
The first ones are there for a more general approach on zone infiltration,
whereas the airflow network is for detailed natural ventilation prediction and
zone infiltration.
Pedro.
On 06-10-2011 12:31, tichaona wrote:
Dear Collegues
I am just beginning using Energy Plus. I am creating geometry using Open Studio and then importing it to Energy Plus. I have modelled a light steel frame house, which has glasswool in combination with light steel, hence there is going to be thermal bridging. How can i input this in the energy plus IDF editor. How can i also input infiltration rates in the energy plus IDF editor? How can I also do natural ventilation analysis using the IDF editor. I will be very gratefull for any help in this regard.
Kind Regards
T. K
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