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NC-v4 EAc2:Optimize energy performance

Interior blinds for energy performance

Hi there,

I am performing an energy model with large windows in warm weather. It is proposed to use automatic blinds to improve thermal comfort in the positions close to the facade. Blinds also have a considerable impact in reflecting the heat back, I have estimated about a 20% solar heat gains reduction when the blinds are down and still have acceptable daylight levels in the perimeter. I want to account for this improvement in my proposed model but I am finding ambiguous explanations in ASHRAE 90.1 about this. In appendix G 5.Building Envelope it is specified that automatically controlled fenestration shades or blinds shall be modeled, does this definition includes internal shading devices? I have read in other codes that only can be accounted for if they are external, so I am confused about this. If they can be modeled in the proposed building, should they also be modeled in the baseline building?

Thanks

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Sat, 11/26/2022 - 20:01

This does refer to interior shades/blinds. You could model no shades/blinds or you could model manual shades/blinds in the baseline. Make sure to explain your schedule if modeling manual shades/blinds.

Sat, 11/26/2022 - 20:49

Hi Marcus. I understand that, but i would like to account for interior automatic roller blinds in order to reduce solar heat gains only in the proposed model. Thanks
Profile picture for user sheffer
Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Mon, 11/28/2022 - 13:48

I think techincially you could model no blinds in the baseline as 90.1 G.5 Baseline is silent on the issue. However, I also think that this is not a reasonable or fair comparison unless you can make the case that blinds are not normally installed in similar building in your location. A more reasonable comparison is manual blinds in the baseline vs automatic blinds in the proposed. The dificulty is in determining the schedule for manual blinds. If I was doing this I would research studies that have compared these two options. Such studies are often conducted by the companies that sell automatic blinds. I again would urge you to do what is reasonable and not concentrate on what is technically "allowed".

Mon, 11/28/2022 - 18:40

Hi Marcus. Thank you for your feedback. I believed that similar buildings in the area will not use automatic blinds for solar heat gains but manual blinds for glare. This could be my baseline model in this case. Nevertheless, I will investigate about the most realistic scenario as you suggest.

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