naturally vented cavity

elena · Posts: 25

hi!
i need to simulate the changes in the air temperature that occur if i add an exterior naturally vented cavity in the external wall but i'm not sure about how to simulate it..
i tryed creating a small zone close to the wall and adding a hole up and down..
but i get an error output..
i attach the file..
can you help me somehow?
thanks,
elena.

Andy Tindale · Posts: 1111 Location: Stroud

Dear Elena,

I have a couple of suggestions for improving your model:

1. Check that the constructions used in your model correctly represent reality. From a quick look at your model it appears that you may have included too many layers in your floor slab material. Take a look at the on-line help topic Construction Locations for details on the meaning of each of the construction types (external wall, floor slab etc). When your floor slab construction is simplified the model runs without errors.

2. You might consider changing the zone type on the activity tab to '3-Glazed cavity' which uses an algorithm to calculate the convection coefficients for a narrow sealed vertical cavity based on the ISO 15099 standard. This may (or may not) be better for your vented cavity than the standard zone convective heat transfer coefficients. Your cavity is not glazed, but this option also includes non-glazed cavity spaces and its name will be changed to '3-Cavity' in the next release.

Regards,

Andy

elena · Posts: 25

hi Andy..
i tryed to do what you suggested me and now the file is simulating correctly.
but, taking a look to the results i've noticed that the air temperature in the room that has a "common wall" is lower than the one with glazed cavity all around.
this shouldn't be true..infact in july i was monitoring the building with some instruments and i found out the opposite results..
i get a good output if i change glazed cavity in semi exterior unconditioned in the zone type (activity template).
do you think it is a correct way of simulating a vented cavity?
moreover, what do you think is better to simulate a vented cavity to add holes or to add fans in the cavity?
thanks.
kind regards,
ele.

elena · Posts: 25

i think i solved the problem by myself..
i did "glazed cavity" with vents in the wall and not in the ceiling and roof because it was not possible..
now the air temperatures coincide with the real ones i obtained with monitoring.
bye bye!
ele.

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