Hi, I have a doubt on how to model unconditioned spaces envelope. As the baseline building meets the requirements of Section 5.5 (ASHRAE 90.1), the baseline building envelope would be modeled according to one of (or both) of the following: - If a building contains a conditioned space, the exterior envelope building envelope shall comply with either the "nonresidential" or "residential" requirements; - If a building contains any semiheated space or unconditioned space, then the semi-exterior envelope shall comply with the requirements for semi-heated space. My case wouldn't be the first one, since the building contains only unconditioned spaces. However, the requirements of the second option refers to semi-exterior building envelope, which does not refer to unconditioned spaces in contact with the exterior. How should I model then? Thanks.

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Wed, 10/02/2013 - 15:16

If the entire building envelope is exposed to the outside (or the ground) and it is not conditioned at all then there are no insulation requirements. If a portion of the building is unconditioned and adjacent to conditioned space then the semi-heated envelope requirements apply.

Luana Bertoletti

Sustentech

LEEDuser Basic Member

24 thumbs up

Wed, 10/02/2013 - 18:18

Hi Marcus, In my case, all the building envelope is exposed to the exterior. So, if the insulation requirements do not apply, how should I model the baseline envelope? Which U values should I adopt? Thanks.

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Wed, 10/02/2013 - 19:13

If it is fully unconditioned you will have some issues. See Table G3.1-10 Proposed (c) and (d). You are required to model a heating and cooling system identical to the Baseline system. This makes the space conditioned so you will therefore need to model the baseline envelope per the Table 5.5-X requirements. The proposed remains uninsulated I would assume for an unconditioned building. Potentially hard to show enough savings under this scenario to submit for LEED.

Luana Bertoletti

Sustentech

LEEDuser Basic Member

24 thumbs up

Thu, 10/03/2013 - 13:04

Hi Marcus, I read many discussions in this forum stating that "You do not have to model heating or cooling in unconditioned spaces", which would be my case. So, why should I model a heating and cooling system?

Jean Marais

b.i.g. Bechtold DesignBuilder Expert

LEEDuser Basic Member

581 thumbs up

Mon, 10/07/2013 - 07:36

As I understand, if the space in the proposed design has either of mechanical heating or mechanical cooling, then you are required to model both, i.e. the missing mechanical system. Else, the space is unconditioned and requires neither.

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Mon, 10/07/2013 - 13:41

There is an acceptable work around related to temperature set points that can render the requirement for a heating or cooling system a moot point. As a result adding such a system is often not enforced. In your case the level of insulation does not matter at all since the space is fully unconditioned. Insulation should have no effect on the results. Since this could go a couple of ways I would recommend that you check the LEED Interpretations for anything applicable and if you cannot find one to address your issue that you submit one.

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