[Equest-users] Low Heating Consumption

[Scott Parker]

Dan,

I have seen times when the annual heating energy use is relatively low if there is significant internal load most of the time.  However, some items to consider:

*         Are you applying a profile to the plug load that is accurate (i.e. not constant 0.75 W/SF constant)?  Is the plug load too high?  Most times it is not as high as past "rules of thumb".

*         Are you accounting for heating setback during unoccupied times?

*         Are you applying a schedule to the lighting that is reasonable?  Does lighting control align with actual design for lighting control (e.g. are there occupancy sensors that would keep lights off part/most of the time in some spaces; e.g. conference rooms).

*         Check the building envelope wall/window performance for U-value to make sure it is correct.

Beyond the points above, I would say that core spaces don't really have a heating load (except for roof/slab as you mentioned).  An interior conference room does not know if it January or July; it has the same cooling load year-round.

Scott Parker  PE
LEED AP BD+C
Mechanical



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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Daniel Caporizzo
Sent: Thursday, October 23, 2014 1:19 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Low Heating Consumption

I have been working on an energy model for a 5-story, 400,000 SF office building. The ground floor is slightly different in terms of layout (including a kitchen and parking garage) but the other floors are mainly office space with some conference rooms. Currently the system is VAV but I have been toying with doing it as chilled beams, which still has a low heating consumption. The project is in schematic so the zoning does not incorporate the proposed room layout, but rather just perimeter and core zones.

My problem is that the building has very low heating energy consumption. I believe it is due to the core interior zones on 2F-4F have 0 heating load according to my LS-A report (the top and bottom floors only have minimal load due to roof and slab, respectively). The exterior zones have higher heating loads that look in line. This would cause a disproportionate amount of the building is receive no heading, drastically reducing my heating load. Even for a newly constructed building these results look low compared to standard rule-of-thumb numbers.

I noticed that my internal loads (particularly the misc equipment) have a big effect, as I originally had 1 W/sf but had to change it to 0.75 W/sf to get a higher heating load in the building. I have it set to 25 CFM OA/pers at the moment, where in reality it would need much less, but I needed to get the heating load up somehow. The building is a large rectangle for the most part so I don't know if my building just has a low heating load. Currently the boilers are hot water boilers w/ draft, but an option in the project exists to utilize condensing boilers instead. I tried switching them (as well as the loop supply temp) but the heating energy consumption barely changed. Most of the equipment is auto-sized, except for AHU static & CFM, Chiller size, boiler size & efficiency, and pump head, which were calculated separately by the design team.

Thanks,
Dan
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