Reg: Query For DesignBuilder

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Hi,

I am currently modelling a simple HVAC model on DesignBuilder. I need to
run the simulation to obtain annual electricity consumption due to Cooling,
Lighting and Interior Equipment for different construction materials. For
some reason, while all the input is the same apart from the U value for the
external wall, the electricity end-use for lighting and interior equipment
changes as follows:

U value Lighting Equipment
2.04 496.38 885.89
2 494.72 880.84
1.85 487.9 860.3

The LPD and Equipment Power Density remains the same with the same
schedule, why is the annual electricity consumption changing?
--
Thanks and Regards
Kiran K Ghosh
+919582904515
+918152036434
kirankghosh31 at gmail.com

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All lighting and equipment values are within 1% of each other. That's
probably close enough to be considered "the same", considering the complex
E+ calculations and some rounding errors, but it is less close than seems
reasonable. Have you compared inputs and schedules for each of those in
each IDF?

James V Dirkes II, PE's picture
Joined: 2011-10-02
Reputation: 203

Hi Jim,

I have checked each IDF file and the inputs and schedules. It is literally
the same model with only the U values for external walls changed. Could
this possibly affect the equipment and lighting load?

On Thu, 6 Sep 2018 at 01:38, Jim Dirkes
wrote:

--
Thanks and Regards
Kiran K Ghosh
+919582904515
+918152036434
kirankghosh31 at gmail.com

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Hi.
If you modify the U-value, Design Builder modify the insulation
layer thickness to coincide with U-value specified. So, the total wall
thickness can be modified dependent on how you have configured the Geometry
convention template (
https://www.designbuilder.co.uk/helpv5.5/#GeometryAreasAndVolumes.htm%3FTocPath%3DBuilding%2520Models%7CModel%2520Data%7CBuilding%2520Model%2520Data%7CConstruction%2520Data%7CConstructions%7C_____5).
If the Geometry convention template is not "Simple", the wall thickness
will be modify, so the net area is modified too, so for a specified lpd the
total power is different.

*Victor Moreno *

*Green Building & Energy ConsultantLEED AP BD+C
, BREEAM Asesor , CEM
, CMVP
, CxA
gestienergetica at gmail.com
*

El jue., 6 sept. 2018 a las 7:18, Kiran Ghosh via Bldg-sim (<
bldg-sim at lists.onebuilding.org>) escribi?:

gestienergetica's picture
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Hi Kiran,

There isn?t a lot of information here to base a ?diagnosis? on, but I suspect your variation in results is linked to changes in the internal floor area. DesignBuilder uses geometry convention templates which give the modeller the flexibility to either fix the geometric construction thickness or vary it according to the construction type/material layers you specify. With some of the geometry convention templates, when you increase the insulation thickness (presumably that is how you improved the U value) and define the building geometry according to the building?s exterior dimensions, then the increased construction thickness will reduce the available floor area/zone volume. Gains such as lighting and equipment are often specified on a per area basis, so a thicker wall (for example) with less zone floor area will reduce the internal gains. This is consistent with the behaviour you have observed.

Please check the Program Help information on geometry convention templates and make sure you understand them and how the template in your model is working. If this isn?t the reason for change you observed, please raise a support ticket through DesignBuilder?s customer support desk.

Kind regards,

David Cocking MSc CEng MCIBSE MASHRAE
Director I Tel: +44 (0)1453 755500 I david.cocking at designbuilder.co.uk

DesignBuilder Software Ltd, 1st Floor, Clarendon Court, 54-56 London Rd, Stroud, GL5 2AD
www.designbuilder.co.uk

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David Cocking2's picture
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Thank you so much, everyone. As Victor has illustrated, the geometry was
changing and so was the area. Lots of thanks to everyone for pitching in. I
can finally sigh in relief. :)

On Thu, Sep 6, 2018, 2:00 PM V?ctor Moreno Solana
wrote:

Kiran Ghosh's picture
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Hi,

I have modelled an Evaporative Cooler on DesignBuilder usind the Detailed Hvac loop before but is there anyway of simulating an Evaporative Cooler in the simple mode?

Thanking You
Regards

Kiran K Ghosh
Architect | Research Associate
The Energy and Resources Institute
kiran.kghosh at teri.res.in

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