Design for Comfort. Graham S. Wright, Ph.D. Passive House Ins:tute US

Transcription

1 Design for Comfort Graham S. Wright, Ph.D. Passive House Ins:tute US

2 Passive House Northwest AIA CEU Provider Design for Comfort AIA Course # phnw072 Graham Wright March 27, 2015

3 Credit(s) earned on comple:on of this course will be reported to AIA CES for AIA members. Cer:ficates of Comple:on for both AIA members and non- AIA members are available upon request. for con:nuing professional educa:on. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construc:on or any method or manner of handling, using, distribu:ng, or dealing in any material or product. Ques:ons related to specific materials, methods, and services will be addressed at the conclusion of this presenta:on. This course is registered with AIA CES

4 Copyright Materials This presenta:on is protected by US and Interna:onal Copyright laws. Reproduc:on, distribu:on, display and use of the presenta:on without wriuen permission of the speaker is prohibited. Graham Wright

5 Course Descrip:on This Passive house buildings are characteris:cally designed for low peak or annual hea:ng and cooling loads ("very small furnace size".) One of the selling points is that thermal comfort is improved (and/or that there is less need of distribu:on systems for hea:ng and cooling.) But to the extent that comfort is a primary concern, it would be beuer to design for it directly using human comfort metrics, rather than using energy metrics as proxies.

6 Learning Objec:ves At the end of the this course, par:cipants will be able to: 1. Know the factors affec:ng the human comfort metrics PMV and PPD. 2. Know the differences between the human comfort standards EN ISO 7730, EN 15251, ASHRAE Apply comfort metrics and standards in design, using e.g. WUFI Passive. 4. Know the recent proposed changes to EN

7 Overview Fundamentals & Sohware Factors that affect thermal comfort, and design guidance, according to standards ISO 7730, ASHRAE 55, and EN ASHRAE Comfort Tool, WUFI Passive. Example 1: Thermal comfort check for a residence in Chicago. Passive design vs. old building. Example 2: Thermal comfort and indoor air quality for a sensi:ve client. Geing crea:ve. 3/26/15 7

8 Introduc:on Shelton Group surveys: Frame a ques:on for the head, people say they want energy savings. Frame a ques:on for the heart, people say they want comfort. Source: Comfort is in the eye of the beholder, Lee Ann Head, Shelton Insights, Feb 18, hup://sheltongrp.com/comfort- is- in- the- eye- of- the- beholder 3/26/15 8

9 Introduc:on Caveat: The phrase comfortable home can bring to mind many different things some of which have nothing to do with climate/temperature: A spacious home with high ceilings A home with lots of natural light/big picture windows A home with lots of storage and counter space A home with an open floor plan Some of these comfortable home features can actually make achieving energy efficiency standards more challenging. Source: Comfort is in the eye of the beholder, Lee Ann Head, Shelton Insights, Feb 18, hup://sheltongrp.com/comfort- is- in- the- eye- of- the- beholder 3/26/15 9

10 3 standards in a nutshell ISO Metrics for thermal comfort, how to assess / measure / predict. ASHRAE Agrees with 7730 on basics, more definite about criteria for design, pass/fail thresholds. EN Inputs for energy design, covering the whole indoor environment: thermal, indoor air quality, ligh:ng, acous:cs. 3/26/15 10

11 A state of mind Thermal comfort is that condi:on of mind that expresses sa:sfac:on with the thermal environment. ASHRAE 55, C1; ISO 7730, 7. 3/26/15 11

12 Predicted Mean Vote (PMV) The PMV is an index that predicts the mean value of the votes of a large group of persons on the 7- point thermal sensa:on scale. ISO 7730, 4.1 Healthy adults in moderate thermal environments. Steady- state. Applies for normal building opera:on. Maybe not that useful for survivability studies refers to other standards for extremes ISO 7243:1989 and 7933:2004, for hot ISO 11079:1993 for cold weather clothing 3/26/15 12

13 Six factors found to affect PMV Physical ac:vity WaUs per square meter of skin surface. 1.0 met = 58.2 W/m2. Clothing An R- value, normalized to typical winter:me clothing ensemble. 1.0 clo = m 2 K/W = R h h 2 F/Btu. Air temperature Mean radiant temperature Average of surrounding surface temps accoun:ng for view factor. Air velocity Humidity Each +10% RH felt as about 0.5 F warmer. 3/26/15 13

14 Formula for PMV Moderately complex 62 lines of BASIC to code it, needs to iterate on clothing surface temp. Valid ranges: PMV between - 2 and to 4.0 met ASHRAE says met 0 to 2 clo Air temp F Mean radiant F Air speed h/min ASHRAE says 0-40 h/min Vapor pressure Pa (e.g. 85 F, 66%RH) 3/26/15 14

15 1-CLO ZONE. TEMPERATURE LIMITS CORRESPOND TO ~ PMV = 0 ± 0.5. AT 40% RH: F 3/26/15 15

16 Lower humidity limit ASHRAE 55 has no lower humidity limit. EN kind of disagrees... very low humidity, (<15-20%) causes dryness and irrita:on of eyes and air ways. 3/26/15 16

17 Predicted % dissa:sfied (PPD) Used for sugges:ng / seing design criteria. AT LEAST 5% DISSATISFIED, NO MATTER WHAT 3/26/15 17

18 ASHRAE Comfort Tool ~ $100 Example 1 windowless room. At 1.2 met and 1 clo, you really do need 71 F, for a PMV of zero. 3/26/15 18

19 met & clo examples clo (includes chair, ref. ISO 9920) 0.3 T- shirt, shorts, light socks, sandals. 0.5 Short sleeve shirt, light trousers, light socks, shoes. 1.0 Undershirt, shirt, trousers, jacket/sweater, socks, shoes piece suit + overcoat Parka add 0.7. Execu:ve chair add met 0.3 sleeping.* 1.0 seated, relaxed. 1.2 sedentary (office, dwelling, school, lab) 2.0 standing (shop, machine, domes:c) 0.07 About minimum for decency (culture dependent.) *Standards don t apply to sleeping people, they can t answer PMV survey ques:ons. 3/26/15 19

20 Comfort example 2 room with large window Four feet from a 12 h wide x 6 foot high window at 45 F inside surface temp., in a 16x16x8 room. MRT = 66.4 F 3/26/15 20

21 Comfort example 2 room with large window Window shihs PMV cooler by /26/15 21

22 OpHon to use weather- dependent clothing model ASHRAE 55. Also an op:on in EnergyPlus sohware. 3/26/15 22

23 Local discomfort Unwanted hea:ng / cooling of one par:cular part of the body PMV/PPD measure comfort overall. There are four separate effects and criteria for local discomfort, that may need to be considered.* Drah (at the neck) Drah dissa:sfac:on rate DR based on temperature, speed, turbulence. Ver:cal air temp difference (head to ankles). Can t compute this with fully- mixed zone models. Warm and cool floors. Radiant asymmetry. *ASHRAE 55 adds requirements only if clo < 0.7 AND met < 1.3. ISO 7730 says PPD, DR, or PD from other local discomfort should not be added. 3/26/15 23

24 7730 AND 55, SAME CHART. ASHRAE CRITERION, PD < 5. Windows enter into both the overall PPD (through the mean radiant temp) and the radiant asymmetry. Cool- wall asymmetry of itself, up to 18 F ok per ASHRAE. Below 11 F, 99% sa:sfied. 3/26/15 24

25 Temperature varia:ons with :me Cyclic varia:ons Short- term cyclic varia:ons (<15 min period) in opera:ve temperature should be < 2 F peak- to- peak. Drihs or ramps < 4 F per hour, basically. 3/26/15 25

26 So much for metrics. Back to steady state. Design criteria: how good is good enough? ISO 7730 merely suggests three categories that one might choose to design for. 3/26/15 26

27 EN interpreted the categories as follows, and renumbered them I, II, III. (Table 1, A.1) Category ExplanaHon PPD % PMV I II III IV High level of expecta:on and is recommended for spaces occupied by very sensi:ve and fragile persons with special requirements like handicapped, sick, very young children and elderly persons. Normal level of expecta:on and should be used for new buildings and renova:ons. An acceptable, moderate level of expecta:on and may be used for exis:ng buildings. Values outside the criteria for the above categories. This category should only be accepted for a limited part of the year. < 6 ± 0.2 < 10 ± 0.5 < 15 ± 0.7 > 15 > ± 0.7 ASHRAE 55 basically picked Category B / II. 3/26/15 27

28 Revenge of the circula:ng fan In 2010, ASHRAE 55 was revised to allow higher maximum opera:ve temp, at higher air speed (than 40 fpm)*. Up to 157 fpm without local control of fan speed. Up to 236 fpm, with local control. No limit, above 1.3 met. The ceiling fan in my house is good for ~110 fpm at most. *For more info, see Low- Tech Magazine, Sept 10, /26/15 28

29 Elevated air speed 3/26/15 29

30 Alternate approach to Summer in naturally- condi7oned spaces Adap:ve comfort: ASHRAE 55 and EN both allow shihing the indoor temperature range up with increasing outdoor temp if: Above 50 F outside. No mechanical cooling (fans ok) met Occupants free to adapt clothing clo or wider. 3/26/15 30

31 EN CHART VERY SIMILAR, BUT RANGE IS WARMER AND LINES ARE STEEPER, SLIGHTLY. 3/26/15 31

32 Design compliance ASHRAE 55 is the most specific / definite about design criteria and procedure. Takes a design condi:ons approach. Design enclosure, mechanicals to maintain indoor comfort at outdoor and indoor design condi:ons. 1. Iden:fy all space types. 2. Determine met and clo for representa:ve occupant. 3. For any space, can use PMV + elevated air speed + local discomfort + :me varia:on criteria. 3/26/15 32

33 Design compliance 4. For summer, naturally condi:oned spaces, can design for climate- dependent opera:ve temperature range. 5. State design condi:ons, e.g. winter & summer outdoor extremes, and indoor loads. 6. Explain why local discomfort won t be a problem, or document calcula:on methods. ISO 7730 makes several sugges:ons for how to evaluate long- term, as in a full- year simula:on or field study. 3/26/15 33

34 Example 1, residence in Chicago Follow the spirit if not the exact leuer of ASHRAE 55. Three spaces cool room, warm room, rest- of- building. Occupants 1.2 met, 1 clo winter, 0.5 clo summer. Has mechanical cooling. R- 45 walls, R- 6 windows, R- 70 ceiling. Main Finding: 68 F / 77 F setpoints were ok, but humidifica:on to 35% was needed for comfort, even with an ERV. 3/26/15 34

35 Example 1, residence in Chicago 68 F / 77 F setpoints were ok, but humidifica:on to 35% was needed for comfort, even with an ERV. Old- building version delivered Category III winter comfort instead of II (15% PPD instead of 10%), using ~10x the hea:ng energy. 3/27/15 35

36 3/27/15 36

37 3/27/15 37

38 Chicago, winter, main zone, inside temps Opera:ve temp and air temp very close together. 3/27/15 38

39 Chicago, winter, main zone, inside RH Humidifier set to 35% RH. 3/27/15 39

40 Chicago, winter, main zone, PMV 68 F air temp with 60 F windows does give almost 68 F opera:ve, which is right at the cool side of the Cat II / ASHRAE 55 comfort limit (- 0.5 PMV / 10% PPD) provided the air was humidified to 35% minimum. 3/27/15 40

41 Chicago, winter, main zone, PPD 68 F air temp with 60 F windows does give almost 68 F opera:ve, which is right at the cool side of the Cat- II / ASHRAE- 55 comfort limit (- 0.5 PMV / 10% PPD) provided the air was humidified to 35% minimum. 3/27/15 41

42 Chicago, winter, main zone, thermal quality All Category I or II achieved yay. 3/27/15 42

43 Chicago, winter, cool zone, inside temps Hardly any sun, temps stay at 68 F. 3/27/15 43

44 Chicago, winter, cool zone, PMV Again, 68 F is barely adequate to maintain PMV - 0.5, if it s not too dry. 3/27/15 44

45 Chicago, winter, cool zone, thermal quality 87% Cat II in the cool room. 3/27/15 45

46 Chicago, winter, warm zone, inside temps. More day:me sun warming than main zone or cool zone. 3/27/15 46

47 Chicago, winter, warm zone, inside temps. In the warm zone the 68 F setpoint gave just enough margin for upside warming. 3/27/15 47

48 SIM STARTUP TRANSIENT INITIAL TEMPERATURE OF EVERYTHING IS 68 F, BUILDING TAKES 4 DAYS TO WARM UP. Chicago, july, main zone, inside temps. Dehumidifica:on to humidity ra:o. Cooling to 77 F. 3/27/15 48

49 Chicago, july, main zone, PMV Dehumidifica:on to humidity ra:o. Cooling to 77 F. 3/27/15 49

50 Chicago, july, main zone, thermal quality 92% Category I yay. Would have been higher without false startup transient. 3/27/15 50

51 Chicago, july, warm zone, inside temperatures Almost iden:cal to main zone. 3/27/15 51

52 Chicago, july, warm zone, PMV Almost iden:cal to main zone. 3/27/15 52

53 Chicago, july, warm zone, PMV Almost iden:cal to main zone. 3/27/15 53

54 Chicago, april, outside temp Goes from 30 to 90 in two weeks. 3/27/15 54

55 Chicago, april, main zone, inside temps Ten days or so of neither hea:ng nor cooling required, daily fluctua:on of 5 F or less. 3/27/15 55

56 Chicago, april, main zone, inside temps Using weather- dependent clothing func:on per ASHRAE 55 Figure That was a bad idea for winter or summer, but helped a lot in the swing season. 3/27/15 56

57 Chicago, april, main zone, inside temps 78% Category I or II. 3/27/15 57

58 Compare to old building More even window distribu:on. Single pane windows. R- 13 wall, R- 20 ceiling. Tightness 7 ACH 50. Humidifica:on to 25% RH. 3/27/15 58

59 3/27/15 59

60 Chicago, old house, winter, warm zone, inside temps Window inside surface temps are off scale low, but the opera:ve temp is only dragged down a degree or so. 3/27/15 60

61 Chicago, old house, winter, warm zone, inside temps Window inside surface temps are off scale low, but the opera:ve temp is only dragged down a degree or so. Humidifica:on to 25%. 3/27/15 61

62 Chicago, old house, winter, warm zone, PMV Lower opera:ve temp and lower humidity are making people feel a liule colder even though the air temp is s:ll 68 F. 3/27/15 62

63 Chicago, old house, winter, warm zone, PPD Dissa:sfac:on is more than 10% but mostly less than 15%. 3/27/15 63

64 Chicago, old house, winter, warm zone, quality. Mostly category III, ok for old building. 3/27/15 64

65 Example 2. Small 4- bdrm house, sensi:ve occupant 0.3 ACH ven:la:on was not enough if 5 people are there all the :me. 18 cfm/person = 0.58 ACH, even this was not enough to keep CO2 under 1000 ppm. Doubling ven:la:on to 1.2 ACH fixes the CO2, but then it gets too dry in winter even with an ERV. Those measures plus humidifica:on to 40% gave 90% category I thermal comfort and 75% category I air quality, per EN /27/15 65

66 Staten Island / Newark, small house facing SE. 3/27/15 66

67 Staten Island, outside temp, Jan /27/15 67

68 Staten Island, inside temp, Jan /27/15 68

69 Staten Island, inside RH, Jan 1-2. Humidifier ran steadily. 3/27/15 69

70 Staten Island, inside CO2, Jan ACH ven:la:on needed to keep CO2 down with five full- :me occupants (2 adult 3 child). 3/27/15 70

71 Staten Island, PMV, Jan 1-2. Nice narrow range. Q: But why did PMV go down when temperature went up? A: Humidity effect? RH was being held constant but PMV is driven by vapor pressure. 3/27/15 71

72 Staten Island, environment quality, Jan 1-2. PreUy good, 90% Category I thermal comfort and 75% Category I air quality, but that humidifica:on energy at high ven:la:on rate drove the energy use way up. 3/27/15 72

73 Conclusions 68 F opera:ve really is the lower limit for PPD < 10%. Humidity below 35% or so will kick it over that. Probably should plan on humidifying to 25% RH or more. The trick of keeping the surface temperatures up so that the air temp can be lowered to 68 F does work (takes back some of the comfort improvement to save energy.) ASHRAE Comfort tool and WUFI Passive (dynamic) can help design for comfort, especially in case of risky or stringent situa:ons. We re not taking full advantage of circula:ng fans for cooling in our planning. 3/27/15 73

74 Geing crea:ve Low- tech magazine did a good series of ar:cles recently on combining old and modern comfort technology. The Revenge of the Circula:ng fan, Sep 10, Restoring the old way of warming: hea:ng people, not places, Feb 11, How to keep warm in a cool house, Mar 11, Radiant and Conduc:ve hea:ng systems, Mar 11, /27/15 74

75 Fan cooling without blowing paper around Hybrid system: AC cools to 84 F, add fans. Adap:ve Thermal Comfort: Principles and Prac:ce, Fergus Nicol, Michael Humphreys & Susan Roaf, /27/15 75

76 Vintage hooded chairs 3/27/15 76

77 Modern hooded chair 3/27/15 77

78 Electric Kotatsu 3/27/15 78

79 This concludes The American Ins:tute of Architects Con:nuing Educa:on Systems Course Passive House Northwest 3/26/15 79