Zone heights and DB

Pilch · Posts: 51

I was just flicking through the iSBEM manual for clarification on some zone height information and wondered if DB automatically deals correctly with zone heights or if perhaps I should be making manual adjustments.

Example would be an industrial building with a pitched roof and no ceiling. The iSBEM technical manual confirms the zone height is floor to soffit, effectively ignoring the space above the level of the soffit. If I draw the building as it is, open up to the roof pitch, does DB correctly assess the zone height or will it take the additional space into account?

Pilch · Posts: 51

Any clarification on this please from Andy or Andrew?

Thanks.

Andrew Bairstow · Site Admin Posts: 247 Location: Birmingham, UK

Alistair
DB calculates the zone volume and divides by the zone area to determine the zone height.
Apologies for the delay.
Andrew

Pilch · Posts: 51

Thanks Andrew. Is this technically not quite accurate then? If for example an industrial unit has a pitched roof with no internal ceiling, according to the iSBEM manual, the zone height should be floor to soffit and the 'roof space' therefore ignored - if I model the building as it is with the pitched roof then dividing volume by floor area will result in a zone height that is slightly higher than floor to soffit.

Andrew Bairstow · Site Admin Posts: 247 Location: Birmingham, UK

Alistair
Unfortunately the uses and definitions of the parameter "zone height" are ambiguous. For example SBEM calculates Building volume by summing the zone height x zone area for each zone. This is why we define it this way. If zone height is set as the floor to soffit distance in the case of a pitched roof or a dropped ceiling then the Building Volume is incorrectly calculated in iSBEM.
Regards
Andrew Smile

Pilch · Posts: 51

Thanks Andrew. I appreciate that iSBEM is technically getting the volume wrong by using floor to soffit on a pitched roof with no ceiling, however the guidelines say you should use floor to soffit and ignore the roof space. If the pitched roof is modelled in DB then the extra volume is included in the calculations.

Although the extra volume calculation is more accurate in terms of what is actually present, does it not mean that using DB for this sort of building is going against zone measurement guidance (even if it is producing the result of what is representative of the building) and could produce a different result compared to using iSBEM? I presume if the volume of the building is bigger a larger heat demand may then be assumed, worsening the rating?

Andrew Bairstow · Site Admin Posts: 247 Location: Birmingham, UK

Alistair
Sorry, thought I'd got back to you last week. We have discussed this and decided to allow users to override the default zone height. This should only be necessary in a few situations (so generally reset at zone height for specific zones).
Regards
Andrew

Pilch · Posts: 51

Great stuff. Is that available now or a future version (don't think I'm running the latest beta)?

Thanks

Andrew Bairstow · Site Admin Posts: 247 Location: Birmingham, UK

Sorry but it hasn't been implemented yet.
Andrew

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