Aymeric,
If you mount a shading device in your DSF and you dont ventilate it, it will heat up considerably. this is a problem that can occur even during the winter if the climate is predominantly hot. I would point out initially for a ventilated façade, even if its just to prevent it from heating up too much and cause an adittional heating load into the main zone. Run some tests and check surface temperatures (note: if you report the surface inside temperature for the outer pane of the DSF, you'll get the shading temperature) and overall heating loads. It will all depend mostly on climate, and make sure you use reliable data on wind speed and direction, it will influence a lot DSF natural ventilation (i'm assuming you'll use Airflow Network).
As for the blind simulation: if you want to check the difference with slat width, don't forget to change the slat separation accordingly. if you don't, E+ will proportionaly increase the number of slats according to the change you make in the slat width, in order to occupy the entire glazing area.
As for light shelves is concerned: unfortunately i'm not a daylight expert, can't give you any special advice on how to model them other than to follow instructions on the I/O reference. but i would guess that, depending on the blinds, you could benefit from the shelves since daylighting would normally be reduced when the shading is on. I would also suggest using DElight objects, they seem to be able to handle inter-reflections better (Eng. Reference, pag 183).
Pedro
On 02-03-2011 3:36, aymericnovel wrote:
Hi Pedro,
From what I read at p.444, E+ can handle daylight through the DSF but won't manage all inter reflexions, especially those going out on the other side of the zone. But that can be surely considered as a small fraction.
As for the DSF, it is a summer dominated climate so the main use if ventilated cavity. However, the whole simulation study is broader and aims at determining if the DSF should be tightly closed and vented in summer to allow a double use and act as a buffer in winter of if we should just let it not tight and therefore design it like a giant external shading only used for summer protection. Given the low degree days in this location I believe we are likely to go for option 2. It is also of course a question of cost and fire safety considerations.
For the blinds I was trying to understand what the model was actually doing so I have been varying the slat width, separations and visible reflectance. Separation and reflectance variations showed logical results and sensitivity but slat width variation, as I said before, when getting close to 0, should give results closer and closer to the "unshaded" simulation. But it is not, and far from that. So I assume the whole blind model for daylight works only in a typical range of blind geometrical properties because I don't observe continuity of results.
I don't think it is very useful to be used as a light shelve anyway because it is so glazed, but lighting requirements are high too and take a major part of the bill so it deserves a triple check to know if I can or cannot bring more light deeper in the space.
but if you have another idea to model a light shelve in the DSF cavity and correctly determine its solar shading and light shelve combined effect, I'll take any advise because this is typically a case where it is difficult to know where the program is reliable or not...
Regards,
Aymeric
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Pedro Peixeiro <ppeixeiro@...> wrote:
>
> Hi Aymeric.
>
> The calculation method for daylight takes into consideration the
> presence of a DSF when one exists (I/O reference, pag. 444). As for the
> construction being fully glazed, its an interesting case scenario. Can't
> provide you with an answer, but i'm also curious as to know if E+ can
> handle all the transmissions/reflections that occurs in such a zone.
>
> Some questions: do you have some kind of ventilation on your DSF or is
> it acting like a buffer? And what parameter or parameters of the blind
> are you actually using to reduse its size?
>
> Pedro.
>
>
> On 01-03-2011 9:56, aymericnovel wrote:
> >
> > Dear all,
> >
> > I am facing a quite challenging design right now and I a m not sure if
> > the current Eplus can do it. the software isn't bugging but I am
> > worrying about the validity of the model.
> >
> > Rough description is:
> > Fully glazed double skin open space for sport activity
> > 10m floor to height ceiling and 64m side lenght (it's a square)
> > Double skin design (double pane for internal skin and simple pane for
> > external skin)
> >
> > So far I have not even tempted to read results obtained from the real
> > architecture that includes some details that makes it not exactly a
> > square geometry. I want to validate the simple square model.
> >
> > I am not sure of:
> > 1) Is the geometry not compatible with energy plus daylighting
> > calculation capabilities (flux split method is said to be limited to
> > cases where room depth is less than 3 times floor to height ceiling):
> > Here it is not the case but the space is fully glazed.
> >
> > 2) Is the daylighting model capable of properly handling the daylight
> > distribution in the sport area with a double skin zone between it and
> > outside?
> >
> > 3) If 2) is possible, what happens if I put a blind in the double skin
> > zone? I have tried many simulations and I believe this is not working
> > well. When one tries to reduce the blind dimensions to almost nothing
> > to get close to the case where there is no blind, results don't get close.
> >
> > It is a very tricky design and the architect counts on these
> > simulations to be sure of his facade design. Of course it is a hot and
> > sunny climate so the guy came and said "hey, can you help me doing an
> > energy efficient glass cube under the sun?".
> >
> > Any help on the above questions and/or about a proper methodology to
> > assess such a case would be immensely appreciated!
> >
> > Thanks a lot!
> > Aymeric
> >
> >
>
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