comparison of standard comfort ranges in health care settings · 2015. 10. 24. · this paper...

CH-15-C019

Comparison of Standard Comfort Ranges in Health Care Settings

Travis R. English, PE ASHRAE Member

ABSTRACT

This paper compares the comfort compliance requirements of ASHRAE Standard f 70-20f 3 Ventilation for Healthcare Facilities (Sf 70) to the compliance requirements of ASHRAE Standard 55-20f 3 Thermal Comfort (or Human Occupanq (S55), and proposes recommendations to consolidate the two into a common approach. The boc!J text of S55 is ana!Jzed for requirement categories. Those categories are compared to requirements in Sf 70. In general, S55's treatment of comfort is more detailed. To allow users to achieve compliance with both standards, the following are recommended.·

f. Sf 70 could clarijj that designing to its temperature and humidi(y ranges does not assure compliance to S55.

2. Sf 70 could clarijj that thermal comfort requires consideration of all jive factors of S55 (air temperature, radiant, humidi(y, clothing, and metabolic rate.

3. Comfort requirement in Sf 70 should be stated in a wqys so as not to exclude radiant effects. 4. Where Sf 70 requires total air movement (above 24 ACH), local comfort considerations (e.g. air speed, draft) of S55 could be

referenced.

5. A191 space for which Sf 70 has no requirement could be designed to or operated at temperatures indicated l:?J S55. 6. Sf 70 could clarijj which temperature and humidi(y ranges are imposed for irifection prevention, which organisms thry are intended to

protect against, and what the research basis of those ranges are.

BACKGROUND

This paper compares the comfort compliance requirements of ASHRAE Standard f70-20f3 Ventilation for Healthcare Facilities (Sl 70) to the compliance requirements of ASHRAE Standard 55-20f 3 Them1al Comfort for Human Occupanry (SSS), and proposes recommendations for consideration. Both documents cover comfort in their scopes. The two should, ideally, be complementary, since they may both be required for projects. As a practical example, any project seeking LEED certification under the USGBC's LEED-HC system must comply with both Sl 70 and SSS (USGBC 2009). For this to be possible, a minimum coordination between the two documents is advisable:

1. No requirement of Sl 70 should prohibit compliance to SSS, or "trump" a requirement of SSS, without a tacit acknowledgment of doing so.

2. All requirements of SSS should be freely exercisable, within the framework of S 170. 3. No section of Sl 70 should imply compliance to SSS is achieved in a manner inconsistent with SSS.

TEXT ANALYSIS OF S55

The body text of SSS was analyzed for requirement categories, and compared to comparable requirements in Sl 70.

Travis English is the Facilites Planning Engineering Manager and 'Chief Design Engineer' for Kaiser Permanente based in Oakland, CA.

2015 ASHRAE Winter Conference-Papers

CH-15-C019

Both standards address air temperature, humidity, and space air movement. In genera~ SSS's treatment of comfort is more

detailed. There is a significant list of design topics, included in SSS, which are not addressed in Sl 70. The list includes the

following: specific limits of applicability (e.g. §2.3, §S.2.2.3), required documentation of comfort calculations (e.g. §4.1, §4.2, §4.3, §4.S, §S.2), comfort analysis methods (e.g. §S.3, §S.4.1), multiple factor considerations: (e.g. §2.1, §2.2, §2.4), consideration of metabolic rates (e.g. §S.2.1, §4.4), consideration of clothing: (e.g. §S.2.2), interplays between comfort

variables (e.g. §S.3.3.2, §S.4.2.2), local discomfort: (e.g. §S.3.4), air speed and draft (e.g. §S.3.3, §S.3.4.3), temperature asymmetry (e.g. §S.3.4.2, §S.3.4.S), variations of comfort variables with time (e.g. §S.3.S), occupant controls (e.g. §S.2.2.1.2, §S.3.3.1, §S.4.2.2), and evaluation of building comfort, including surveys and field measurements (e.g. §7 .1, §7 .2, §7 .3, §7.4).

Non-applicability of Natural Ventilation

SSS also includes a treatment of natural ventilation (e.g. §S.4, §7.2.2.2), based on the adaptive model of human comfort. Sl 70 effectively prohibits natural ventilation in healthcare spaces by virtue of its filter requirements. As such, the remainder of this paper will treat all healthcare spaces as mechanically ventilated, heated, and cooled.

COMFORT CONDITIONS SUGGESTED BY S55

Proposed Occupant Types for Consideration in Healthcare Spaces

Table 1 lists typical occupant types likely in healthcare spaces. For each occupant type, a clothing insulation level (do) and metabolic rate (met) is proposed.

Table 1: Occupant, Clo, And Met Assumptions For Healthcare Occupants

Occupant Type Clo Met Gowned Healthcare Workers 1.4 1.4

Healthcare workers O.S 1.4

Healthcare workers 1 1.4

Patients t 0.31 0.7

Workers, patients, or guests o.s 1 Workers, patients, or guests 1.0 1

t- occupants in beds, with access to sheets can control their Clo level. Please consider in the following analysis that sheet control can reduces the need for very warm temperatures.

For each occupant type, assume compliant air speed and a negligible difference between radiant and air temperatures (an assumption which requires design validation per application). Table 2 lists the highest and lowest temperatures which could achieve SSS compliance, at the low and high humidity levels. Figuire 1 shows these outputs graphically.

Table 2: Broadest Acceptable PMV And PPD Extremes Using 555 Methodology

Occupant Type Clo Met Op T (°F (0 C)) Max RH PMV PPD

Gowned Healthcare Workers 1.4 1.4 S9.0 (1S.O) 20 -0.5 10.23

Gowned Healthcare Workers 1.4 1.4 57.5 (14.1) 60 -0.5 10.22

Gowned Healthcare Workers 1.4 1.4 70.8 (21 .6) 20 0.5 10.22

Gowned Healthcare Workers 1.4 1.4 68.6 (20.3) 60 0.5 10.22

Healthcare workers 0.5 1.4 72.8 (22.7) 2 -0.5 10.22

Healthcare workers 0.5 1.4 70.7 (21.S) 60 -0.5 10.22

Healthcare workers 0.5 1.4 79.9 (26.6) 2 0.5 10.11

Healthcare workers 0.5 1.4 77.3 (25.2) 60 0.5 10.22

Healthcare workers 1.4 65.S (18.6) 2 -0.5 10.22

Healthcare workers 1 1.4 63.2 (17.4) 60 -0.5 10.22

Healthcare workers 1 1.4 75.5 (24.1) 2 0.5 10.23

Healthcare workers 1 1.4 72.4 (22.4) 60 0.5 10.22

2015 ASHRAE Winter Conference-Papers 2

CH-15-C019

Table 2: Broadest Acceptable PMV And PPD Extremes Using 555 Methodology

Occupant Type Clo Met Op T (°F(0 C)) Max RH PMV PPD

Patients 0.31 t 0.7 84.7 (29.3) 2 -0.5 10.21

Patients 0.31 t 0.7 82.4 (28.0) 60 -0.5 10.22 Patients 0.31 t 0.7 87.4 (30.8) 2 0.5 10.23 Patients 0.31 t 0.7 85.0 (29.4) 60 0.5 10.22

Workers, patients, or guests 0.5 78.7 (26.0) 2 -0.5 10.22 Workers, patients, or guests 0.5 76.4 (24.7) 60 -0.5 10.22

Workers, patients, or guests 0.5 1 83.6 (28.7) 2 0.5 10.23 Workers, patients, or guests 0.5 1 80.9 (27.1) 60 0.5 10.22 Workers, patients, or guests 73.3 (22.9) 2 -0.5 10.22

Workers, patients, or guests 70.6 (21.4) 60 -0.5 10.23 Workers, patients, or guests 1 80.1 (26.7) 2 0.5 10.23

Workers, patients, or guests 76.7 (24.9) 60 0.5 10.22

t - occupants in beds, with access to sheets can control their Clo level. Please consider in the following analysis that sheet control can reduces the need for very warm temperatures.

-Gowned HCWorlcer

-He Wor<er [QS ck>)

- HCWorl<er {l.Ock>)

-worker, Guest, P.atient [1.0do)

Fig ure 1: Comfort ranges indicated by SSS for Health Care Occupants

COMFORT COMPLIANCE REQUIRMENTS OF 5170

Temperature and Humidity Requirements


CH-15-C019

The comfort requirements in Sl 70 are the temperature and humidity ranges presented in its space-by-space

requirement table. There are fifteen unique temperature and humidity critera in this table. The ranges, and a sample space for each, are listed in Table 3 below.

Table 3: Unique Temperature And Humidity Requirements Of 5170

Temp, °F(0 C) Humidity Range (No of Spaces), e.g. Space RH

A 68 - 73 (20 - 23) 20 - 60 (1) e.g. Gastrointestinal Endoscopy procedure room

B 68 - 75 (20 - 24) 20-60 (3) e.g. Classes B&C operating rooms c 70 - 75 (21 - 24) 20 - 60 (5) e.g. Recovery Room D 70 - 75 (21 - 24) 30 - 60 (2) e.g. Critical and intensive care E 72 - 78 (22 - 26) 30 - 60 (1) e.g. Newborn intensive care F 70 - 75 (21 - 24) 40 - 60 (1) e.g. Wound intensive care G 70 - 75 (21 - 24) Max60 (14) e.g. Intermediate care H 72 - 78 (22 - 26) Max 60 (3) e.g. X-ray, diagnostic and treatment I 72 - 80 (22 - 27) NR (1) e.g. Physical therapy

J 70 - 75 (21 - 24) Max65 (1) e.g. ER Waiting Rooms K 68 - 73 (20 - 23) NR (1) e.g. Bronscoscopy, sputum collection and

pentamidine administration L 70 - 75 (21 - 24) NR (19) e.g. Resident Room M 72 - 78 (22 - 26) NR (9) e.g. Dialysis treatment room N 72 - 80 (22 - 27) NR (1) e.g. Hydrotherapy 0 NR NR (28) e.g. Substerile service area

Minimum Room Air Movement Requirements

Most spaces in Sl 70 also require total air movement minimums. This requirement is umque to Sl 70; No such

requirements are apparent in SSS.

Cross-Checking S170 Requirements Using the S55 Method

Conditions A through 0 of Table 3 were analyzed using the SSS methodology. Table 4 below summarizes the

comfort compliance at the high and low ends of the prescribed ranges, using the upper and lower limits of occupant

assumptions. Many of the ranges are non-compliant at the extremes, suggesting a more detailed comfort analysis might

benefit space outcomes.

Table 4: 555 Anal~sis Of HiSh And Lows Limits Of 5170 Tem~rature And Humidit~ Ranses

Condition T op!oc~ RH. Clo Met Air S£ eed PMV PPD S55 Result

Min. 68 (21 ) 20 0.5 1.0 30 -2.59 95.2 Does not comply A

Max. 73 (23) 60 1.0 1.4 30 0.57 11.8 Does not comply

Min. 68 (20) 20 0.5 1.0 30 -2.59 95.2 Does not comply B


Min. 70 (21) 20 0.5 1.0 30 -2.17 83.9 Does not comply c Max. 75 (24) 60 1.0 1.4 30 0.79 18.3 D oes not comply

Min. 70 (21) 30 0.5 1.0 30 -2. 11 81.3 Does not comply D


Min. 72 (22) 30 0.5 1.0 30 -1.68 60.8 Does not comply E


F Min. 70 (21) 40 0.5 1.0 30 -2.04 78.5 Does not comply


CH-15-C019

Table 4: 555 Analys is Of High And Lows Limits Of 5 170 Temperature And Humidity Ranges

Condition T op(oC) RH. Clo Met Air Speed PMV PPD S55 Result


Min. 70 (21) 2 0.5 1.0 30 -2.29 88.0 Does not comply G


Min. 72 (22) 2 0.5 1.0 30 -1.88 71.1 Does not comply H


l\1in. 70 (21 ) 2 0.5 1.0 30 -1.88 71.1 Does not comply


Min. 70 (21) 2 0.5 1.0 30 -2.29 88.0 Does not comply


Min. 68 (20) 2 0.5 1.0 30 -2.70 96.8 Does not comply K


Min. 70 (21) 2 0.5 1.0 30 -2.29 88.0 Does not comply L


Min. 72 (22) 2 0.5 1.0 30 -1.88 71.1 Does not comply M


Min. 72 (22) 2 0.5 1.0 30 -1.88 71.1 Does not comply N


CONCLUSION

To allow or encourage compliance with both standards, the following are recommended

1. S 170 should make it clear that compliance to the temperature and humidity ranges in it does not assure

compliance to SSS. Considerations of comfort could be referenced to SSS. Air temperature and humidity should not be considered as a complete comfort assessment, without a corresponding consideration of clothing, metabolic rate, and radiant temperature.

2. Sl 70 should clearly state that design for thermal comfort requires consideration of all five factors of SSS (air temperature, radiant temperature, humidity, clothing, and metabolic rate), or directly reference compliance to SSS.

3. In Table 7, the temperature requirement could be stated as operative temperature guidelines - not air temperatures - to allow the inclusion of radiant effects. Alternately, the temperature requirements could be removed from Table 7 altogether if they are intended for comfort only (see additional recommendations 1-3 below).

4. Where total air movement is required (above 2-4 ACH), air speed may be high. Local comfort considerations

(e.g. air speed, draft) of SSS could be referenced in S170, similar to the reference in S170 §7.2.2.c.1. Alternately, compliance to SSS could be required for all spaces.

S. Any space for which tl1ere is "NR" for temperature or humidity could be referenced to SSS. 6. A patient in a hospital gown is very lightly clothed, and liable to feel cool. SSS specifically excludes both

sleeping people and occupants in beds (who have control over their level of sheets and blankets) . If Sl 70 is to make an assertion of comfort for such lightly clothed occupants in beds with access to sheets, specific research should be conducted.


CH-15-C019

Additional recommendations are here listed for consideration regarding asepsis and infection control. The temperature and humidity ranges of Sl 70 have sometimes been associated to asepsis and infection control. Since there is no explanation of this in the text, it may be assumed by readers that the temperature and humidity ranges in the table are not boundaries of comfort, but boundaries set by infection prevention.

1. The text could make clear which temperature and humidity ranges are imposed for asepsis, which organisms they are intended to protect against, and what the research basis of those ranges are.

2. Since there is a substantial variation in the research reporting, specific temperature and humidity ranges may not directly follow from research. To avoid misinterpretation, a literature-review based treatment on the topic would be helpful as an Informative Appendix. For example, such a treatment is given in Memarzadeh (2011) pages 30-36.

3. When temperature and humidity are dictated by asepsis or infection controL those boundaries should either be included in, or override, the comfort analysis. Design guidance should be provided such that spaces with substantially different needs (comfort versus asepsis) not be grouped on the same system.

REFERENCES

ASHRAE. 2013. ANSI / ASHRAE Standard 55-2013 Thermal Environmental Conditions for Human Occupancy. American Society of Heating Ventilation and Air Conditioning Engineers, Atlanta, GA.

ASHRAE. 2013a. ANSI/ ASHRAE/ ASHE Standard 170-2013 Ventilation of Health Care Facilities. American Society of Heating Ventilation and Air Conditioning Engineers, Atlanta, GA.

ASHRAE. 2013. ANSI/ASHRAE Standard 62.1-2013 Ventilation for Acceptable Indoor Air Quality. American Society of Heating Ventilation and Air Conditioning Engineers, Atlanta, GA.

Memarzadeh, F. 2011. The environment of care and health care-associated infections: an engineering perspective. American Society for Healthcare Engineering, Chicago, IL.

USGBC. 2009. LEED for Healthcare v2009. US Green Building Council. Accessed 5/ 5/ 2013.


comparison of standard comfort ranges in health care settings · 2015. 10. 24. · this paper...

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