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

Fri Nov 3 06:56:58 PDT 2017

I’ve seen the kind of behavior Jim mentions in some of the DOE Office Prototype models in hot climate zones, like Phoenix, AZ. So, it might not need an unusually high internal load to trigger this kind of behavior.

Given that it’s a hot climate, the U-factor has almost no correlation to cooling, which I presume is your dominant end-use. Look at the SHGC of your 1 Btu/h-ft2-F window and that of your other window. SHGC correlates very well with cooling. Also, check which end-uses are changing as this might give you clues about the source of the changes.

If you are holding SHGC constant, and a file compare does not reveal any other input changes, it might be something with the eQuest internal model itself (I’m not very familiar with eQuest).

From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill via Bldg-sim
Sent: Friday, November 03, 2017 6:34 AM
To: akshay gupta <akshaykg at gmail.com>
Cc: equest-users at lists.onebuilding.org; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] eQuest - Energy consumption increasing on reducing Glass U-Value

Hi Akshay,
If you care to share your model, eQUEST users can take a look at it.
You could email your .pd2, .inp and weather files to equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>.
Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jim Dirkes via Bldg-sim
Sent: Friday, November 03, 2017 9:24 AM
To: akshay gupta <akshaykg at gmail.com<mailto:akshaykg at gmail.com>>
Cc: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: Re: [Bldg-sim] eQuest - Energy consumption increasing on reducing Glass U-Value

That's good to know and rules out my scenario.

I think I can't help more without more details, but I'm also unfamiliar with eQuest.

If you were using EnergyPlus, I'd recommend adding a set of detailed output variables to study the energy use pattern more closely. Perhaps you can do something like that with eQuest....

On Fri, Nov 3, 2017 at 9:18 AM, akshay gupta <akshaykg at gmail.com<mailto:akshaykg at gmail.com>> wrote:
Hi Jim

Thanks for the reply. Actually, the project we are modelling are designed to be energy efficient commercial spaces. So for example, interior LPD is not more than 0.5 W/sqft (LED lights), EPD is around 2.0 - 2.5 W/sqft, Occupant Density is around 50 Sqft /person. So I dont see any area where internal heat gain is unusually higher where the building needs to cool itself off by conducting heat outside (inside hotter than outside).

I think there something else.

Regards

Akshay

On 3 November 2017 at 18:42, Jim Dirkes <jim at buildingperformanceteam.com<mailto:jim at buildingperformanceteam.com>> wrote:
Akshay,
While there are many things that could contribute to this situation, consider:
A smaller U value means that there is less conduction through the construction. With less conduction, a smaller cooling load will normally decrease cooling energy.

An exception to this is when internal loads are higher than normal. In that case, the building needs to get rid of internal heat (provide cooling) most of the year. When the envelope has more insulation (lower U-value), it inhibits heat removal and can increase cooling energy.

Thanks to my friend Javed Iqbal for reminding me of this recently. He is preparing a paper which discusses this phenomenon for buildings in the central European climate.

On Fri, Nov 3, 2017 at 8:37 AM, akshay gupta via Bldg-sim <bldg-sim at lists.onebuilding.org<mailto: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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