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RE: [EnergyPlus_Support] RE: Materials U-Value Calculations in E+





6 in metal studs are very common in commercial construction.  When 3.5 studs are used, R-15 batt is typically used and the metal studs can reduce the effective insulation by about 1/2 .  Construction gets more complex when continuous insulations are added, but bridged by metal components needed to support claddings.  We spend a lot of time with 3D heat transfer software to calculate effective U-values and identify cold spots for potential condensation.

 

Ned Lyon, P.E. (MA, WV)
Staff Consultant

SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct 
617.285.2162 mobile 
781.907.9009 fax
www.sgh.com

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Thursday, February 25, 2016 10:52 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] RE: Materials U-Value Calculations in E+

 

 

I was under the impression that anything besides 3.5" studs  is rarely used in light-frame construction.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 2/25/2016 6:34 PM, 'Edward G. Lyon' eglyon@xxxxxxx [EnergyPlus_Support] wrote:

 

If I recall the ASHRAE numbers correctly, R-19 (6 in. fiberglass) in 6 in. metal stud (uncompressed) 16 in. on center is a 50% reduction.  I usually run my own THERM or HEAT simulation to determine U-Values rather than take the published values because spacing and stud thickness varies a lot and the published values do not always account for head and sill conditions…

 

Ned Lyon, P.E. (MA, WV)
Staff Consultant

SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct 
617.285.2162 mobile 
781.907.9009 fax
www.sgh.com

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Thursday, February 25, 2016 6:42 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] RE: Materials U-Value Calculations in E+

 

 

Ned, others,

There are two effects going on with R-19 insulation between metal studs:
1) compression of R-19 insulation within the 3.5" cavity,  thus reducing its R-value to 18
2) 2-D heat flow due to the metal studs, which is a much bigger effect with the studs acting like radiator fins.

I don't have an exact number in my head, but I recall that the net effect was to degrade the R-value by a huge amount, like 30-40%.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang@xxxxxxxxxxxxxxxxxxxxxxxx
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 2/25/2016 7:39 AM, 'Edward G. Lyon' eglyon@xxxxxxx [EnergyPlus_Support] wrote:

 

One thing to remember is that the assembly and not the materials determine an effective U-value.  R-19 batt insulation between metal studs may be half the R-value, and that is what you should be using for the energy model.  If you select a wall system in design builder that includes thermal bridging elements, it should push the effective insulation value to the energy model.

 

Ned Lyon, P.E. (MA, WV)
Staff Consultant

SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct 
617.285.2162 mobile 
781.907.9009 fax
www.sgh.com

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Thursday, February 25, 2016 8:24 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Materials U-Value Calculations in E+

 

 

Hi everyone, 

 

I need some help to understand how is the calculation of u-value material in energy plus.

 

Someone has a spreadsheet that calculates according to the material specifications?

 

I ask this because I use the design builder to enter the building elements, and saw that the U-value is not the same in EnergyPlus report.

 

I don't know how energyplus calculate this.

 

Thanks for all.

 

Best regards,

 

Ivan Mezzacapa

Cushman & Wakefield

Energy Efficiency and HVAC Coordinator

 

 

 



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Posted by: "Edward G. Lyon" <EGLyon@xxxxxxx>


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