[Bldg-sim] eQuest - Energy consumption increasing on reducing Glass U-Value

[Justin Spencer]

The other thing that could be going on is that a drop in SHGC is driving up
heating loads. That could definitely happen in mild, heating-focused areas,
but does not seem to fit with your case. Are you changing the system sizing
to account for the reduced load or leaving sizing fixed? Do you have reheat
going up because you are pumping too much cold air?

My number one thing when you're seeing something funny is to get into the
hourly output and compare the two cases. Which end uses are going up?
Where? When? Are space temperatures staying in range when they are supposed
to be? Do you have heating and cooling fighting each other?

You might have something else in your model that's messed up that will be
apparent when you look at the hourly output. Plus, there's nothing more fun
in simulation than looking at hourly output, IMHO.

On Fri, Nov 3, 2017 at 2:42 PM, Joe Huang via Bldg-sim <
bldg-sim at lists.onebuilding.org> wrote:

> From my experience, such kinds of counter-intuitive results, e.g., cooling
> energies going up with lower U-values,  are due to overlooked systems/loads
> interactions rather than arcane loads considerations such as spectral
> properties of window glazings.
>
> The three interactions that I would look are:
>
> (1) does the system have an economizer that vents the cooling loads when
> the indoor temperature or enthalpy exceed that outdoor ?
>
> (2) is the system sizing the same for both runs? If not, fix the system
> size to the larger from the two autosized runs.
>
> (3) (this gets rather arcane but explained the anomaly for increased
> heating in mild cooling climates like the Pacific Northwest) change Cooling
> Control from CONSTANT to WARMEST, i.e., control cooling control for the
> warmest zone rather than all zones.
>
> Joe
>
> Joe Huang 	
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 205A
> Moraga CA 94556yjhuang at whiteboxtechnologies.comhttp://weather.whiteboxtechnologies.com for simulation-ready weather datahttp://www.whiteboxtechnologies.com
> (o) (925)388-0265 <(925)%20388-0265>
> (c) (510)928-2683 <(510)%20928-2683>
> "building energy simulations at your fingertips"
>
> On 11/3/2017 7:15 AM, Javed Iqbal via Bldg-sim wrote:
>
> In my past experiences, such problems were resolved by using detailed
> spectral properties      (LBNL window output) in eQuest for an Indian
> composite climate case.
>
>
>
> Sent from mobile, pls excuse typos
>
> On Nov 3, 2017 2:47 PM, "akshay gupta" <akshaykg at gmail.com> wrote:
>
>> Hi Javed
>>
>> Thanks for helping. We were actually modelling using simplified glass
>> inputs. But I can try with detailed glass model as well.
>>
>> Regards
>>
>>
>> On 3 November 2017 at 18:51, Javed Iqbal <javedvit at gmail.com> wrote:
>>
>>> Thank you, Mr. Jim.
>>>
>>> Apart from internal loads, it's worth looking into window spectral
>>> properties. Sometime simple inputs like U value, SHGC and Tvis is not
>>> enough and recommended to use whole assembly window properties generated
>>> through LBNL window software which could be imported directly into the
>>> eQuest.
>>>
>>> It might help!!
>>>
>>> Regards,
>>>
>>> Sent from mobile, pls excuse typos
>>>
>>> On Nov 3, 2017 1:37 PM, "akshay gupta via Bldg-sim" <
>>> bldg-sim at lists.onebuilding.org> wrote:
>>>
>>> Hi There
>>>
>>> I am facing an issue in eQuest in almost all simulation models for most
>>> hot and composite indian climates. Whenever we reduce U-value of glass in
>>> model, from Single Glazing U-Value of 1 Btu/hr Sqft F to 0.32 Btu/hr Sqft F
>>> (or any other U-value lower than 1), we see an increase in energy
>>> consumption.
>>>
>>> Can someone point out principal mistake that may be making in the model.
>>>
>>> Thanks in advance.
>>>
>>> Regards
>>>
>>> Akshay Gupta
>>>
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>>
>
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