[Equest-users] Huge envelope changes having small affect on energy savings

David Eldridge DEldridge at grummanbutkus.com
Wed Aug 22 10:01:42 PDT 2012


Take a look at the energy end-use breakdown between the two runs to see which specific areas resulted in savings. For instance if the building has a lot of lighting and plug loads, the percentage improvement from envelope improvements will be less.

Also the LV report that gives you the design load on the space doesn't include the "system" and ventilation loads, so if your building has a lot of outside air or high minimum airflows that require reheat energy, both of these could make the impact from envelope upgrades become a smaller percentage.

If the form of the building has a lot of interior areas relative to perimeter zones, the percentage reduction from envelope upgrades will be less.

You should also confirm the unmet hours were similar between the two cases.

Last idea - confirm that you modeled the building with perimeter zones and not one-per-floor configuration.

David


David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Project Manager

Direct: (847) 316-9224 | Fax: (847) 328-4550

Grumman/Butkus Associates | 820 Davis Street, Suite 300 | Evanston, IL 60201
Energy Efficiency Consultants and Sustainable Design Engineers



From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Lee Chorney
Sent: Wednesday, August 22, 2012 11:48 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Huge envelope changes having small affect on energy savings

Hi All,


I recently did a model where I had the same system in both base and proposed but I changed the R-Value from 4 (base) to 20 (proposed). I also changed the window U-value from .80 (base) to .35 (proposed). After I did the run, I saw only a 5% savings between the heating and cooling use in the model. When I looked at the loads I saw the base had twice as much cooling and heating load than the proposed. Does any know why the energy savings would only be 5% when you have a huge difference between the cooling and heating loads?

Thanks,

Lee
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