Re: [EnergyPlus_Support] Energy Plus for urban energy plannig

Thanks- Since you like it I have attached some more info-

The calculator titles SRI-calc10 from Berkley labs is what I used for SRI calcs.
The calculator to go back and forth between reflectance and absorbance with copy paste from IDF, and has some figures I researched and input.
The IDF has both SRI and radiant barrier objects I created. The ASHRAE-Min_Roof_SRI-32 is from ASHRAE 90.1 2010 minimum and the Cool-Roof_SRI-81 is a value that is 1 point below title 24 flat roof SRI-82 requirement 2 points above the Enegry Star SRI 79 requirement and 3 points above the LEED SRI 78 requirement so is I think a good average SRI. Keep in mind this is an unaged SRI and that there are requirements for 3 year aged SRI test data.

I wonder--- what anyone thinks of my radiant barrier approach? I used the SRI calc to create the radiant barrier adjacent to a zone or cavity and created an approach for an internal radiant barrier using the movable insulation object with a schedule that turns the resistance off for a 12 hour night.. It seems like a work around but seems better than the recommendation From tips & tricks pages 13 & 14 pasted below.

Modeling Reflective Radiant Barriers

Can EnergyPlus model reflective radiant barriers?

1. For radiant barriers which are exposed to a thermal zone, such as an attic space, specify a reduced thermal absorptance for the innermost material layer.
For example, an attic roof construction might be (outer to inner)

Asphalt shingles, R-30 insulation, Radiant barrier;
The radiant barrier material would be a thin layer with some small resistance with a low thermal absorptance value. This will reduce the radiant heat transfer from the roof surface to other surfaces in the attic zone.

2. If the radiant barrier is within a cavity which is not modeled as a separate thermal zone, then there is not an easy way to model its impact. For example, a wall construction:
Brick,
Radiant barrier,

Air gap,

Gypsum board;

Here, the radiant barrier would reduce the radiant transfer across the air gap. But EnergyPlus air gaps are a fixed thermal resistance, specified in the Material:Airgap object. The user would need to compute an average effective resistance which represents the reduced radiant heat transfer across the air gap due to the radiant barrier. This resistance could then be assigned to the radiant barrier material layer.

Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions

120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951

www.phasechange.com

On Wed, Oct 17, 2012 at 12:11 AM, oscar hernandez <oscarhernandez_81@xxxxxxxxxxx> wrote:

Excelent! thanks for this information Jeremiah!

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jcrossett@xxxxxxxxxxxxxxx
Date: Wed, 17 Oct 2012 00:01:53 -0700
Subject: Re: [EnergyPlus_Support] Energy Plus for urban energy plannig

Possibly I am incorrect, but I recently used a SRI calc to create high SRI materials that should reduce heat island effect, such as the one pasted below;

Name Cool-Roof_SRI-81
Roughness Smooth

Thermal Resistance 0.001
Thermal Absorptance 0.3
Solar Absorptance 0.3

Visible Absorptance 0.3

Then you could also do conceptual massing model green roofs, solar PV, shading from other buildings and much more,

I think E+ could be great for this so long as the modeler minimized the details of the models to high level parameters. Autodesk ecotech or vassarri may do a good job at this "conceptual massing" by making simplified models, so you might want to use a similar approach.

Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions
120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951

www.phasechange.com

On Tue, Oct 16, 2012 at 11:45 PM, oscar hernandez <oscarhernandez_81@xxxxxxxxxxx> wrote:

Hello Alessandro,

Very good question. I've been thinking on. I don"t know maybe the answer its "to try". There are many parameters that e+ doesn't take in count (heat island, wind corridors,etc) but maybe to study the solar influence from others buildings, e+ could be a solution. I don"t know what do you want to do?

Oscar.

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: alexmac_00@xxxxxxxx
Date: Tue, 16 Oct 2012 13:06:06 +0000
Subject: [EnergyPlus_Support] Energy Plus for urban energy plannig

Hello,
do you think Energy Plus could work for energy planning of a whole neighborhood? Would it be only a matter of computing power or there are other issues? Cheers,

Alessandro