[Bldg-sim] ASHRAE 90.1-2007 Fenestration Areas

[Carol Gardner]

Hi Will,*

*I think your answer is here:*

The fenestration area in the baseline building shall be equal to the
fenestration area in the proposed building or 40% of the exterior wall,
whichever is less.*

Based on your table you need to reduce the window area to be 40% of the
overall wall area, making it a band as described, except for the North wall
with 0% glass as it is already less than 40%.

Happy Holidays!

Carol

On Wed, Dec 22, 2010 at 8:39 AM, Will Mak <wmak at epsteinglobal.com> wrote:

> Hi all,
>
>
>
> I am working on a project that has a large amount of glass. ASHRAE
> 90.1-2007 states this about baseline modeling for glass:
>
>
>
> *The fenestration area in the baseline building shall be equal to the
> fenestration area in the proposed building or 40% of the exterior wall,
> whichever is less. If it is necessary to reduce window area in the baseline
> building, then corresponding increases are made in the opaque walls such
> that the gross exterior wall area is unchanged between the proposed building
> and the baseline building.*
>
> * *
>
> *Fenestration area in the baseline building shall be distributed among the
> thermal blocks and around the building in a uniform manner. In each thermal
> block, the fenestration area shall be equal to the window wall ratio for the
> baseline building (the maximum of 40% or the proposed building WWR)
> multiplied times the exterior wall area for the thermal block. If the
> thermal block has more than one exterior wall, window area is placed
> proportionally on each. *
>
> * *
>
> *The window area is positioned in continuous horizontal bands on each
> exterior wall, although the configuration of window area on each wall is not
> significant since neither daylighting or self shading from the building is
> modeled. See Figure G-D. *
>
> * *
>
> *While the prescriptive envelope requirements provide an exception for
> street-level, street-side vertical fenestration (e.g., store display
> windows), the building performance rating method does not. Window area in
> the baseline building is always determined as described above.*
>
> * *
>
> Based on the wordage above, I must develop the baseline model with either
> the same glass areas as the proposed building (essentially copying the
> proposed model and just updating U-values, etc.) or 40% of the exterior
> wall, whichever is smaller. Since I have roughly 60% of glazing, I will have
> to redistribute the glass into continuous horizontal bands on each exterior
> wall, similar to how ASHRAE 90.1-2004. However, as I began to look at the
> glass % of each exterior wall, I ran into a problem:
>
>
>
> *Wall*
>
> *Window SQ FT*
>
> *Wall SQ FT*
>
> *Total SQ FT*
>
> *Window %*
>
> North
>
> 10727.76
>
> 8485.95
>
> 19213.71
>
> 55.83%
>
> North-East
>
> 1812.26
>
> 2272.83
>
> 4085.09
>
> 44.36%
>
> East
>
> 2645.52
>
> 1846.83
>
> 4492.35
>
> 58.89%
>
> South-East
>
> 1683.46
>
> 1222.87
>
> 2906.33
>
> 57.92%
>
> South
>
> 12595.36
>
> 3958.92
>
> 16554.28
>
> 76.09%
>
> South-West
>
> 623.46
>
> 829.56
>
> 1453.02
>
> 42.91%
>
> West
>
> 3282.3
>
> 2924.38
>
> 6206.68
>
> 52.88%
>
> North
>
> 0
>
> 104.26
>
> 104.26
>
> 0.00%
>
> Total
>
> 33370.12
>
> 21645.6
>
> 55015.72
>
> 60.66%
>
>
>
> There is not enough exterior wall space to redistribute glazing to drop the
> percentages for each wall to 40%. Do I just reduce each wall to 40% glazing
> with continuous horizontal bands?
>
>
>
> Thanks!
>
>
>
> *William Mak, LEED Green Associate*
> Mechanical Design Engineer
>
> *EPSTEIN*
> Architecture
> Interiors
> Engineering
> Construction
>
> 600 West Fulton Street
> Chicago, Illinois 60661-1259
>
> D: (312) 429-8116
> F: (312) 559-1217
> E: wmak at epsteinglobal.com
> W: www.epsteinglobal.com
>
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>
>
>
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-- 
Carol Gardner PE
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