SBEM doesn't compliance

VE-SBEM for compliance and EPC generation.
mcbni
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SBEM doesn't compliance

Postby mcbni » Mon Jun 15, 2015 1:38 pm

Hi,

I am looking for an answer to the fact that SBEM doesn't compliance in a project that used to compliance after a change in the system.

I took one project, I changed the systems and it doesn't compliance because the U-value in one of the walls is higher than it is accepted.

If I only changed the systems (I did it twice to confirm), how can the problem be in the U-value?

I think I am becoming crazy.

Thanks

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PCully
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Re: SBEM doesn't compliance

Postby PCully » Mon Jun 15, 2015 4:49 pm

Hi,

Only reason I could think this would happen is if you changed a system to or from 'not set' and thus mark a space as unconditioned when previously it was conditioned.

Phil
IES Worldwide Technical Support

mcbni
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Re: SBEM doesn't compliance

Postby mcbni » Tue Jun 16, 2015 7:40 am

Thank you for your answer. The spaces that I changed are a lobby and a plant room. They have no heating and only the lobby will have natural ventilation. I set the system as "none" and I got U-values higher than they should be. That happened when I first posted.

Then I created a system which type is "not set" and allocated it to these spaces. Now I get the pass.

If "none" and "not set" are the same, how can I get so different results?

Thanks

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PCully
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Re: SBEM doesn't compliance

Postby PCully » Thu Jun 18, 2015 8:45 am

Hi,

Sorry I didn't mean not set I meant 'none'

not set would be a system with no NCM type which isn't allowed for Compliance. An apache system will always have heating and potentially cooling properties associated to it regardless of whether it has an NCM type or not so that won't make a difference regards space conditioning but there is an NCM rule that the type has to be set for each one so aux energy calcs and notional equivalents can be created etc.

When you set the system for a room to none so effectively marked it as not heated then this changes how the room is seen for SBEM. At this stage SBEM considers it to be outside building thermal envelope and walls between this room and adjacent conditioned rooms are then considered on the u-value criteria 2 checks. The BRE guidelines suggest that for such spaces within the building they should be treated as indirectly conditioned by the dominant adjacent conditioned room so you can either connect them or assign the same system to these rooms as is assigned to the adjacent room.

This is because SBEM isn't a dynamic simulation and so can't properly treat internal voids which are not directly conditioned. If you are using ApacheSim for example then the calculations are equipped to model this air volume and the conduction through internal surfaces from heated rooms and so you can fully model internal voids and as such set system to none or use the internal void room type.

Phil
IES Worldwide Technical Support


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