ASHRAE Journal - February 2014 - 31

COLUMN ENGINEER'S NOTEBOOK

Noise transfer may also be a concern if the adjacent space
is anything but a corridor or other non-noise-sensitive
space.
All makeup air is from the adjacent space so the restroom will be warmer based on the exhaust rate and the
lighting load (occupant loads are sufficiently transient,
so they can generally be ignored). If only warmer by 1°F
or 2°F (0.5°C to 1°C), temperatures are generally considered acceptable and are often preferred particularly
at water closets. In the past, lighting loads in restrooms
were high enough that this approach resulted in overly
warm restroom temperatures. But energy codes have
reduced lighting power to 1 W/ft2 (0.1 W/m2) (Standard
90.1) and 0.6 W/ft2 (0.06 W/m2) (California's Title 24
Energy Standards3). At 0.6 W/ft2 and at the exhaust rate
shown in Figure 2, the temperature rise is 1.6°F (1°C)
above adjacent spaces, which is likely to be acceptable.
The undercut or door louver must be sized so that the
differential pressure across the restroom door is not so
high that it will cause whistling or keep the door ajar. A
pressure differential of 0.08 in.w.g.
(20 Pa) is generally acceptable. This
equation can be used to determine
approximate transfer-free area:

FIGURE 4 "Plaster frame" for lay-in grille used for access to balancing damper.

Lay-In Diffuser

Plaster Frame

must be coordinated with the architect to be sure they are
included in door schedules on architectural drawings.
2. Ducted transfer to the ceiling return air plenum (Figure 5b). This option will result in even warmer restroom
temperatures than the previous option if the return air
plenum temperature is above space temperatures due
to the heat from recessed light fixtures. However, the reduced lighting power and the increasing use of pendent
light fixtures in many modern buildings results in little
temperature rise, making this option viable.
Sizing the transfer grille is somewhat tricky because
the return air plenum is also negatively pressurized. If
it is too negative relative to the adjacent space (close to

0.5

A=

Q  C 






4005  DP 

(1)

where A is free area in ft2, Q is
the flow rate in cfm, DP is the pressure drop in in.w.g., and C is the
loss coefficient which varies according to various sources from 1.6 to
2.7.4 Assuming a loss coefficient of
2.5 and 0.08 in.w.g. (20 Pa) pressure drop, door undercut height is
approximately:
H=

0.2 Q
W

(2)

Where H is the height (inches)
and W is the door width (inches). For
the example shown in Figure 2, with a
36 in. (0.9 m) wide door, an undercut
of about 2.5 in. (65 mm) is required.
If more than 3 in. (75 mm) or so is
required, a door louver can be used
instead to improve appearance. Either

www.info.hotims.com/49801-27
FEBRUARY 2014

ashrae.org

ashraE JourNal

31



ASHRAE Journal - February 2014

Table of Contents for the Digital Edition of ASHRAE Journal - February 2014

ASHRAE Journal - February 2014
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Understanding Salaries in the A/E Industry
Improving Operating Room Contamination Control
Standing Columns
Engineer's Notebook
Saving Energy with Cooling Towers
Building Sciences
ACREX India 2014 Show Guide
HVAC Applications
Technical vs. Process Commissioning: Design Phase Commissioning
Data Centers
IAQ Applications
Energy Modeling
InfoCenter
Refrigeration Applications
Products
Classified Advertising
Advertisers Index
ASHRAE Journal - February 2014 - ASHRAE Journal - February 2014
ASHRAE Journal - February 2014 - Cover2
ASHRAE Journal - February 2014 - 1
ASHRAE Journal - February 2014 - 2
ASHRAE Journal - February 2014 - Contents
ASHRAE Journal - February 2014 - Commentary
ASHRAE Journal - February 2014 - 5
ASHRAE Journal - February 2014 - Industry News
ASHRAE Journal - February 2014 - 7
ASHRAE Journal - February 2014 - 8
ASHRAE Journal - February 2014 - Letters
ASHRAE Journal - February 2014 - Meetings and Shows
ASHRAE Journal - February 2014 - 11
ASHRAE Journal - February 2014 - Understanding Salaries in the A/E Industry
ASHRAE Journal - February 2014 - 13
ASHRAE Journal - February 2014 - 14
ASHRAE Journal - February 2014 - 15
ASHRAE Journal - February 2014 - 16
ASHRAE Journal - February 2014 - 17
ASHRAE Journal - February 2014 - Improving Operating Room Contamination Control
ASHRAE Journal - February 2014 - 19
ASHRAE Journal - February 2014 - 20
ASHRAE Journal - February 2014 - 21
ASHRAE Journal - February 2014 - 22
ASHRAE Journal - February 2014 - 23
ASHRAE Journal - February 2014 - 24
ASHRAE Journal - February 2014 - 25
ASHRAE Journal - February 2014 - 26
ASHRAE Journal - February 2014 - 27
ASHRAE Journal - February 2014 - Engineer's Notebook
ASHRAE Journal - February 2014 - 29
ASHRAE Journal - February 2014 - 30
ASHRAE Journal - February 2014 - 31
ASHRAE Journal - February 2014 - 32
ASHRAE Journal - February 2014 - 33
ASHRAE Journal - February 2014 - Saving Energy with Cooling Towers
ASHRAE Journal - February 2014 - 35
ASHRAE Journal - February 2014 - 36
ASHRAE Journal - February 2014 - 37
ASHRAE Journal - February 2014 - 38
ASHRAE Journal - February 2014 - 39
ASHRAE Journal - February 2014 - 40
ASHRAE Journal - February 2014 - 41
ASHRAE Journal - February 2014 - Building Sciences
ASHRAE Journal - February 2014 - 43
ASHRAE Journal - February 2014 - 44
ASHRAE Journal - February 2014 - 45
ASHRAE Journal - February 2014 - 46
ASHRAE Journal - February 2014 - 47
ASHRAE Journal - February 2014 - 48
ASHRAE Journal - February 2014 - ACREX India 2014 Show Guide
ASHRAE Journal - February 2014 - SCover2
ASHRAE Journal - February 2014 - S1
ASHRAE Journal - February 2014 - S2
ASHRAE Journal - February 2014 - S3
ASHRAE Journal - February 2014 - S4
ASHRAE Journal - February 2014 - S5
ASHRAE Journal - February 2014 - S6
ASHRAE Journal - February 2014 - S7
ASHRAE Journal - February 2014 - S8
ASHRAE Journal - February 2014 - S9
ASHRAE Journal - February 2014 - S10
ASHRAE Journal - February 2014 - S11
ASHRAE Journal - February 2014 - S12
ASHRAE Journal - February 2014 - S13
ASHRAE Journal - February 2014 - S14
ASHRAE Journal - February 2014 - S15
ASHRAE Journal - February 2014 - S16
ASHRAE Journal - February 2014 - S17
ASHRAE Journal - February 2014 - S18
ASHRAE Journal - February 2014 - S19
ASHRAE Journal - February 2014 - S20
ASHRAE Journal - February 2014 - S21
ASHRAE Journal - February 2014 - SCover4
ASHRAE Journal - February 2014 - HVAC Applications
ASHRAE Journal - February 2014 - 50
ASHRAE Journal - February 2014 - 51
ASHRAE Journal - February 2014 - Technical vs. Process Commissioning: Design Phase Commissioning
ASHRAE Journal - February 2014 - 53
ASHRAE Journal - February 2014 - 54
ASHRAE Journal - February 2014 - 55
ASHRAE Journal - February 2014 - 56
ASHRAE Journal - February 2014 - 57
ASHRAE Journal - February 2014 - Data Centers
ASHRAE Journal - February 2014 - 59
ASHRAE Journal - February 2014 - 60
ASHRAE Journal - February 2014 - 61
ASHRAE Journal - February 2014 - IAQ Applications
ASHRAE Journal - February 2014 - 63
ASHRAE Journal - February 2014 - 64
ASHRAE Journal - February 2014 - 65
ASHRAE Journal - February 2014 - 66
ASHRAE Journal - February 2014 - 67
ASHRAE Journal - February 2014 - Energy Modeling
ASHRAE Journal - February 2014 - 69
ASHRAE Journal - February 2014 - InfoCenter
ASHRAE Journal - February 2014 - 71
ASHRAE Journal - February 2014 - 72
ASHRAE Journal - February 2014 - 73
ASHRAE Journal - February 2014 - Refrigeration Applications
ASHRAE Journal - February 2014 - 75
ASHRAE Journal - February 2014 - Products
ASHRAE Journal - February 2014 - 77
ASHRAE Journal - February 2014 - 78
ASHRAE Journal - February 2014 - Classified Advertising
ASHRAE Journal - February 2014 - Advertisers Index
ASHRAE Journal - February 2014 - Cover3
ASHRAE Journal - February 2014 - Cover4
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