Hi Linda,

Funny you ask, I am currently experimenting with modeling UFAD systems in
eQuest (and would appreciate feedback on my methods from the bldg sim
group).

The application I'm working on is for core zones only, so the loads are
people, lighting, equipment (cooling loads) and outdoor air ventilation.

A few notes on UFAD systems in general:

Supply air for UFAD (under floor air distribution systems) is supplied
through diffusers in floor panels. Correct design results in stratification
(see http://www.hpac.com/Issue/Article/38686/38686#f1 for explanation).

Cooling supply air temperature is usually around 63-65 F

The thermostat is usually located at 48"

In cooling mode, air is supplied low at a relatively high temperature and
returned high at a higher temperature, this allows a greater dT across the
cooling coil.

In order to model this system, the stratification of the space and higher
return air temperatures must be taken into account. To achieve this, I
split each room into an upper and lower section at about 5'. The upper
space is designated as a return air plenum and contains all lighting loads
(except for task lighting loads). The lower section contains the people
loads and the equipment loads. Any exterior windows or doors should be
distributed across the elevation of both spaces representing actual building
design. The upper and lower sections are split with a horizontal partition
of type "air barrier." I then run the model to determine the difference in
space temperature between upper and lower room sections, during hours when
the building is conditioned (fan "on" hours). I look for a difference of
about 2 degrees F for times when the space is in cooling mode. For the
systems I have tried, I usually end up the yearly average for "fan-on" hours
to be about 1 degree F. This number can be changed by adjusting the U-value
of the partition, and adjusting the internal loads (within reason), if
necessary.

I set the thermostat for the space to be 1 degree cooler than the baseline
case.

Supply air temperature is 63-65 degrees, depending on design. The supply
fan may also have a lower pressure drop than the base case.

I have modeled the system as Packaged Multizone with heating locked out
above 65 degrees, and cooling locked out below 65 degrees to simulate bypass
(this method is documented in the DOE2.2 help file).

So far with this method, I have come up with energy savings of 15-20% for
both cooling and fan energy, which is consistent with the range given by
UFAD documentation.

If anyone has information regarding UFAD systems and heating energy use, I'm
interested.

~karen~