Passive Heating & Cooling Design for the 21st Century Passive solar heating, shading, evaporative cooling, natural ventilation, and effective use of offer durable, climate-responsive, socially-in- clusive pathways to and thermal architectural delight. Pas- sive heating and cooling guidelines have changed little in decades, however, despite new insights into solar radiation transmission, fluid mechanics, ma- terials science, and climate modeling, as well as more powerful and efficient field instruments and vastly improved computational tools. With energy con- sumption an inescapable reality of architectural practice, and with passive strategies offering the lowest embodied-energy solutions, educators and researchers must bring passive heating and cooling design into sync with current energy science. This is the goal of my work.

1 Sunspaces in a Land of Fog and Moss ...... 2 2 Oregon Sunspace Redesign / Build ...... 6 3 Thermal Batteries for Buildings ...... 8 4 Hybrid Ventilation in a Chicago Academic Center ...... 12 5 in Everett Community College Offices...... 14 6 Night Cooling of Mass in the Vernonia K-12 School ...... 16 7 3-D Thermal Bridging in Wall Assemblies ...... 16 8 Natural Ventilation in the Lillis Business Complex ...... 17 9 Teaching: Passive Heating and Cooling Design ...... 18 10 Relevant Funding Programs ...... 20 Contents

Pyranometer deployed in a sunspace Alexandra Rempel, Ph.D., M.Arch., 2013 Fig 7

Figure 7. 95 35 a) Gates Measured 90 Modeled 85 30 80 25 75 70 20 Figure 3. Figure 3. Figure 4. Figure 4. 65 60 15 Temperature (ºC) Temperature Temperature (ºF) (ºF) Temperature 55

50 10 45 Figure 4. Figure 4. Figure 4. Figure 4. Fig 7 a) Gatesa) Gates a) Gates a) Gates a) Gatesa) Gates a) Gates a) Gates a) Gates 40 5 Figure 2. 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 Sunspaces in a 0-6a 100-6a 1210 8 12 11 8 11 11 10 11 10 0-6a 100-6a574666 120-6a1017 8574666 120-6a 11 1117 8 16 11 11 11 15 10 16 11 14 15 10 0-6a 14 171069980-6a574666 1117 16106998574666 11 15 16 14 15 14 95hours,106998 confirming106998 that the mass was active in solar per- 35 6a-noon 106a-noon 1210 8 12 11 8 10 11 9 10 9 6a-noon 106a-noon575655 1210 8575655 12 11 8 10 11 9 10 9 575655575655 6a-noon 166a-noon 1016 14 10 12 14 10 126a-noon 10 166a-noon96876 1016 1496876 10 12 14 10 12 10 90formance96876b) Shaw but96876 also, as shown below, losing substantial noon-6p 11noon-6p 1411 12 14 17 12 13 17 13 13 13noon-6p 11noon-6pnoon-6p687977 141117 12noon-6p687977 14 10 1717 12 19 13 10 17 16 13 19 13 12 16 13noon-6p 12 17noon-6p961097687977 1017 19961097687977 10 16 19 12 16 12 961097961097 Land of Fog and Moss 85heat to underlying soil. 30 6p-mid 116p-mid 1211 9 12 13 9 11 13 10 11 10 6p-mid 116p-mid6757656p-mid 121117 96757656p-mid 12 12 1317 9 17 11 12 13 15 10 17 11 12 15 10 6p-mid 12 176p-mid10675765 1217 7 1710675765 1210 15 7 17 8 12 10 15 7 8 12 7 10 710 10 7 8 10 7 8 7 80 b) Shaw b) Shaw b) Shaw b) Shaw Interpretation of passive solar field data with EnergyPlus b) Shaw b) Shaw b) Shaw b) Shaw 25 75 models: Un-conventional wisdom from four sunspaces in 0-6a 6748880-6a 6748880-6a 6748880-6a4424450-6a674888144424450-6a 914 15 9 13 15 13 130-6a 13 140-6a85877442445 914 1585877442445 9 13 15 13 13 13 Models85877 (below)85877 showed close correspondence to mea- 6a-noon 8989986a-noon 8989986a-noon 8989986a-noon45555489899813455554 913 12 9 9 12 8 9 8 1375654455554 913 1275654455554 9 9 12 8 9 8 70 7565475654 Eugene, Oregon. Building and Environment 2013, 60:158-172. 6a-noon 6a-noon 6a-noon 6a-noon sured air temperatures, mass surface temperatures, and 20 noon-6p 13noon-6p 1313 14 13 19 14 14 19 13 14 13noon-6p 13noon-6pnoon-6p7781087 131312 14noon-6p7781087 13 9 1912 14 15 14 9 19 10 13 15 14 8 10 13noon-6p 8 12noon-6p758647781087 912 15758647781087 9 10 15 8 10 8 65heat75864 fluxes,75864 predicting 80-95% of the variability in the 6p-mid 786111096p-mid 786111096p-mid 786111096p-mid4436556p-mid78611109144436556p-mid 1014 15 10 12 15 11 126p-mid 11 146p-mid86876443655 1014 1586876443655 10 12 15 11 12 11 60 8687686876 data and allowing them to be used to gain further in- 15

c) Page c) Page c) Page c) Pagec) Page c) Page c) Page c) Page (ºC) Temperature Temperature (ºF) Temperature 55

What would it take for passive solar heating to Temperature (°C) 0-6a 80-6a 158 11 15 13 11 12 13 11 12 11 0-6a 80-6a486776 150-6a815 11486776 150-6a 12 1315 11 15 12 12 13 13 11 15 12 15 13 11 0-6a 15 150-6a97878486776 1215 1597878486776 12 13 15 15 13 15 sight97878 into heat97878 gain and loss pathways. Please see publi- perform well in the cloudy, rainy winters of Eugene, 50 10 6a-noon 76a-noon 147 12 14 11 12 7 11 6 7 6 6a-noon 76a-noon6a-noon487643 14714 126a-noon487643 14 10 1114 12 11 7 10 11 7 6 11 7 7 7 6 6a-noon 7 146a-noon86644487643 1014 1186644487643 10 7 11 7 7 7 cation86644 for further86644 details. Oregon? With a West Coast Marine climate (Köp- a)b) Shaw 45 noon-6p 8noon-6p 148 14 14 11 14 7 11 9 7 9 noon-6p 8noon-6pnoon-6p488645 14813 14noon-6p488645 14 10 1113 14 12 7 10 11 5 9 12 7 9 5 9 noon-6p 9 13noon-6p76735488645 1013 1276735488645 10 5 12 9 5 9 Fig 7 7673576735 40 5 pen Cfb) and high latitude, the Pacific Northwest’s 6p-mid 96p-mid 159 12 15 14 12 11 14 10 11 10 6p-mid 96p-mid5878666p-mid 15915 125878666p-mid 15 11 1415 12 15 11 11 14 10 10 15 11 12 10 10 6p-mid 12 156p-mid86857587866 1115 1586857587866 11 10 15 12 10 12Fig 7 8685786857 4.11Agreement 4.12 4.13between 4.14 Measured 4.15 4. and16 Modeled 4.17 4.18 Air Temperatures 4.19 4.20 4.21 overcast skies disguise a solar resource unexpect- d) Cashmand) Cashman d) Cashmand) Cashmand) Cashmand) Cashman d) Cashmand) Cashman 95 35 c) Page 0-6a 9977750-6a 9977750-6a 9977750-6a5544430-6a9977751178785544430-6a 117878Figure0-6a 7. 1178780-6a64444554443117878644445544439590 6444464444 35 edly well-matched to its mild winters and long, cool a) Gates Measured 6a-noon 8878546a-noon 8878546a-noon 8878546a-noon6a-noon4544328878541076316a-noon4544321076316a-noon 1076316a-noon64321454432107631643214544329085 6432164321 30 springs. Yet passive solar heating is rarely practiced (°F) Temperature Modeled noon-6p 81081075noon-6p 81081075noon-6p 81081075noon-6pnoon-6p56554381081075107741noon-6p565543107741noon-6p 107741noon-6p54420565543107741544205655435442054420 30 here, despite widespread enthusiasm for low-energy 8580 6p-mid 91088756p-mid 91088756p-mid 91088756p-mid5654436p-mid91088751288765654436p-mid 1288766p-mid 1288766p-mid64443565443128876644435654436444364443 25 8075 building design. e) Outsidee) Outside e) Outsidee) Outsidee) Outsidee) Outside e) Outsidee) Outside 25 7570 0-6a 380-6a 3538 42 35 41 42 45 41 52 45 52 0-6a 380-6a3265711 350-6a3835 423265711 350-6a 42 4135 42 41 45 42 41 45 52 41 45 52 45 52 0-6a 52 350-6a2657113265711 4235 412657113265711 42 45 41 52 45 52 265711265711 20 7065 6a-noon 406a-noon 3940 46 39 48 46 52 48 60 52 606a-noon 406a-noon6a-noon44891116 394039 466a-noon44891116 39 46 4839 46 48 52 46 48 52 60 48 52 60 52 606a-noon 60 396a-noon444891116 4639 8 48444891116 46 9 52 8 4811 60 9 5216 11 60 16 4 84 9 8 11 9 16 11 16 20 Field work. To investigate Eugene’s passive solar po- 65 47 4447 49 44 53 49 58 53 67 58 67 478 4447 744 498 44 9 49 53 74449 12 53 58 9 4953 14 58 67 12 5358 19 67 14 58 67 19 67 4478 4944 9 7 5378 4912 9 58 9 7 5314 12 67 12 9 5819 14 14 12 67 19 19 1460 7 19 97 12 9 14 12 19 14 19 tential, four sunspaces were instrumented January noon-6p noon-6p noon-6p noon-6pnoon-6p noon-6p noon-6p noon-6p 15 60 (ºC) Temperature 6p-mid 416p-mid 3841 44 38 45 44 49 45 56 49 56 6p-mid 416p-mid53779136p-mid 384138 4453779136p-mid 38 44 4538 44 45 49 44 45 49 56 45 49 56 49 56 6p-mid 56 386p-mid3779135377913 4438 453779135377913 44 49 45 56 49 56 (ºF) Temperature 55 377913377913 15

c) Page (ºC) Temperature

through June 2011, measuring indoor and outdoor air (ºF) Temperature Jan FebJan Mar Feb Apr Mar May Apr Jun May Jun Jan FebJanFeb Mar Feb Mar AprFeb Mar Apr May Mar Apr May Jun Apr May Jun May Jun Jun Feb MarFeb Apr Mar May Apr Jun May Jun 5550 temperature, , mass surface temperatures, 10 5045 10 Air Temperatures (°F and °C) Mass Temperatures Fig 7 surface heat flux, mean radiant temperatures, and in- 45 Fig 740 5 40 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.215 cident solar radiation. The Gates and Shaw sunspac- Sunspace air temperatures (above left) remained many degrees 95 35 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 es were similar, with massive floors and moderate warmer than outside air temperatures throughout the study, 9590 d) Cashman 35 b) Shaw shading, while the Page and Cashman spaces were particularly in the higher-mass Gates and Shaw sunspaces. Air 9085 30 Temperature ( ° F) Temperature 30 highly shaded and the latter had little effective mass. warmth was greatest during afternoons, as expected, and in- 8580 80 25 d) Cashman creased through the season except for March, which was anom- 75 25 Modeling. Each sunspace was then modeled in 7570 alously cool and rainy in 2011. 20 7065 EnergyPlus, a simulation tool well-suited to passive 20 6560 heating and cooling. Models were validated by com- Mass surface temperatures (above right) in the higher-mass 15 Temperature (ºC) Temperature Temperature (ºF) (ºF) Temperature 60 parison to measured field data, showing the ability spaces showed even greater warmth, with nighttime tempera- 55 15 Temperature (ºC) Temperature Temperature (ºF) Temperature 55 to predict about 90% of the variability in these mea- tures frequently 15-17°F higher than outside conditions during 50 10 Temperature (°C) 5045 surements. January, April, and May. Surface heat flux measurements quan- 10 4540 5 Fig 7 tified heat returned from the mass to the space during these 404.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.215 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 Sunspaces 0 15’ 30’ 60’ 95 35 2 c) Page Alexandra Rempel, Ph.D., M.Arch., 2013 90 85 30 Temperature (°F) Temperature 80 25 75 70 20 65 60 15 Temperature (ºC) Temperature Temperature (ºF) (ºF) Temperature 55

50 10 45 Fig 7 40 5 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 95 35 90 d) Cashman 85 30 80 25 75 70 20 65 60 15 Temperature (ºC) Temperature Temperature (ºF) (ºF) Temperature 55

50 10 45 40 5 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 Fig. 10 Figure 8. Solar Heat Gain Paths. Most solar energy entered through Gain (kWh): 450 550 540 760 800 800 Un-Conventional Wisdom. The vener- Roof Solar Gain WINTER SPRING NN NNN tilted roof glazing (orange sectors, left), even in spaces with able work of Balcomb and colleagues Solar Gain 500 500 southeast orientation, countering conventional wisdom that still guides passive solar design educa- 400 400 300 300 only vertical glazing (blue sectors) should be used to take tion, cited by Sun & Light, Heat- kWh kWh 200 200 advantage of low winter sun angles and avoid summer over- ing, Cooling, & Lighting, Mechanical Glazed RoofRoofs a) Gates 100 100 heating. Indeed, the widely-cited sizing tables of Balcomb et and Electrical Engineering for Buildings, W WEW EE Gain (kWh): 460 550 650 980 1030 1040 a) Gates WW EWE EE Glazedal. WallWallslimit consideration of tilted glazing to its “projected verti- and numerous others. In the Pacific J OpaqueInterior Walls Wall F cal area”, greatly diminishing its predicted importance. Northwest, however, these ideas need M substantial revision. A M Since overcast skies are brightest at the top of the sky N N J S SSS b) Shaw 500 SS 800 S dome, however, and tall trees are ubiquitous in the North- 1. Pacific Northwest passive solar heat-

400 600 west, the greatest solar resource was found to exist over- Gain (kWh): 245 325 400 550 600 580 ing potential is far greater than indi- 300 400 head in this climate. (This also greatly diminished orienta- cated by Balcomb’s Solar Savings Frac- 200 200 tion dependence.) Because the Balcomb method neglects tions, which discount gains through 100 b) Shaw W WE E these factors, it vastly underpredicted tilted-glazing solar cloudy skies and tilted glazing. gain for these spaces, estimating only 35-52% of the total in normal months, for example, for the Gates space (below). c) Page 2. Wide deviations from southerly Gain (kWh): 205 250 255 315 350 460 orientation are acceptable, since much TableConventional 3. Contrasting Method Predictions Underestimates of Roof SolarRoof GainSolar Gain N N of the solar resource originates from 500 S 500 S Gates Shaw Page Cashman above and tree shading can be severe. 400 400 Balcomb Methoda percentage of 2011 model values 300 300 % of 2011 actual solar gain predicted January 35b 38 68 45 200 200 d) Cashman 3. Roof glazing is essential since most February42 37 70 43 Jan Feb Mar Apr May June 100 100 winter solar energy enters from above c) Page W EW E March63 43 104 67 and since passive cooling is effective in Heat Loss Pathways as Proportions of Total Solar Gain Glazed Roof April 52 31 93 60 one filled box = 5% of the total summer conditions. Infilt- May 51 34 107 66 ration EnergyPlus / TMY3c Heat Loss Paths. Slab-on-grade floors created significant heat loss 4. Vertical glazing must be site-specif- N N Glazed Wall Glazed 500 S 500 S January 93 94 92 92 pathways in the two spaces (Gates and Shaw) that used them as Floor Opaque Wall ic. On a shady site, it may even be op- 400 400 February 89 93 91 91 thermal mass; and single glazing accounted for most of the tional, contributing primarily to views. 300 300 March 121 122 125 126 remainder. The slab heat loss was unexpected, as it conflicted directly 200 200 April 98 97 98 100 with design guides that advocate only perimeter insulation for slab- 5. Thermal mass must be isolated from 100 100 d) Cashman W EW E May 101 104 102 102 on-grade floors unless they contain radiant heating tubes. In wet envi- wet ground, by insulation or possibly a According to Passive Solar Heating Analysis [22]; Appendix B. ronments with fine-grained soils, however, moisture can be wicked far drainage, to avoid losing a substantial b Text style indicates each value’s relationship to the 2011 model-predicted underneath buildings, and soil moisture greatly increases soil thermal fraction of solar gains. value: plain = lower, bold boxed = ±20%, italics underlined: higher. c Sunspace models simulated with typical, rather than 2011, weather data. conductivity; this apparently caused the patterns found. Please see publication for further details. Sunspaces 4 S S Alexandra Rempel, Ph.D., M.Arch., 2013 kWh 2000 40 Oregon Sunspace Redesign / Build Original mid‐6a 66 69 74 70 86 79

6a‐noon 28 22 17 9 7 7 Temperature ( ° C)

Oregon sunspace redesign/build: New priorities for thermal mass. American Solar Energy Society National Conference, April 2013. ) 1750 30 15 9 10 4 4 5 2 Revising thermal mass design rules for the Pacific Northwest. Building and Environment (submitted August 2013). noon‐6p 6p‐mid 63 69 74 68 70 68 (W/m Redesign. In light of results from the ini- Thermal Mass Slab-on-Grade Surface Temperatures and Heat Loss 1500 20 Gates sunspace model, validated with 2011 and 2012 field data, showing April 2012 averages tial field study (above), builder Ken Gates Redesign mid‐6a 74 92 101 109 133 117

dismantled his sunspace, excavated, and Original Redesign ) 1250 10 6a‐noon 29 28 24 17 14 13 2 (ºC)

added gravel and R-10 insulation beneath a Radiation April 17 17.7 18.1 18.0 18 23 23.2 23.8 23.6 23 noon‐6p 18 16 20 16 26 22 new concrete slab. The new slab held ~30% 6p‐mid 77 97 109 118 135 120 1000 0 (ºC) ° C) 17 18.0 18.3 18.2 18 23 23.7 24.1 24.1 24 Solar more mass, as well, in accord with model

results suggesting that the space could or store more heat. It did not provide as much 18 18.7 18.7 18.5 18 23 24.6 24.6 24.4 24 High Mass mid‐6a 84 93 100 98 119 108 750 ‐10 Temperature (W) mass as suggested by conventional mass 6a‐noon 35 30 24 14 12 12 sizing tables, however. noon‐6p 15 9 10 3 2 2 19 19.4 19.0 18.7 18 24 25.4 24.9 24.6 24 Flux 500 ‐20

Temperature 6p‐mid 75 84 89 83 86 81 Original Temperature ( Temperature 18 18.6 18.4 18.3 18 23 24.3 24.0 23.9 24 Redesign Methods. To evaluate the redesign per- Heat 250 ‐30 High Mass formance and to gain insight into climate- High Water mid‐6a 87 105 112 117 148 132 0.1 0.15 0.16 0.18 0.1 0.03 0.04 0.04 0.04 0.04 High Water responsive priorities for thermal mass, 37 37 29 20 19 19 ) 6a‐noon Heat Flux (W) or Solar Radiation (W/m monitoring resumed from January-June 2 0 ‐40 Solar Radiation ) 2 noon‐6p 14 10 10 4 3 4 2012 with added emphasis on surface heat 0.2 0.16 0.17 0.19 0.2 0.04 0.04 0.04 0.04 0.04 3/07 3/08 3/09 flux measurements. The similar Shaw space 6p‐mid 73 90 95 95 104 97 Original Redesign High Mass High Water (W/m was monitored simultaneously for compari- 0.2 0.17 0.17 0.18 0.2 0.04 0.04 0.04 0.05 0.04 Jan Feb Mar Apr May June Solar Radiation Loss son, and models were again validated with Heat Return to Sunspaces by Thermal Mass Redesign + Models Mass Temperatures and Heat Fluxes of Redesign + Models field data before further interpretation. 0.2 0.19 0.18 0.18 0.2 0.05 0.05 0.04 0.05 0.04 Monthly kWh; High Mass, High Water show design guide recommendations Redesign returns heat earlier, during occupied hours Heat Loss (W/m Heat Results. Mass surface temperatures were 0.2 0.18 0.18 0.19 0.1 0.04 0.04 0.04 0.05 0.04 New Priorities for Thermal Mass. The Gates redesign held much However, the actual redesign showed consistently warmer substantially warmer after the redesign less thermal mass than recommended by Sun Wind & Light, Heat- surface and operative temperatures during occupied evening (upper panels), particularly near the center 1 3.4 5.1 4.4 1 0.3 0.8 1.2 1.1 0.3 ing, Cooling, & Lighting, and Mechanical and Electrical Equipment hours (upper graph), and as a result, much greater heat flux to where solar access was greatest, reflecting for Buildings, suggesting that more mass should have been add- the space when people were actually using it (lower graph). 3 9.8 13.9 12.5 3 0.8 2.4 3.3 3.0 0.8 a reduction in heat loss by about 75% (mid- ed. The field-validated Gates model was therefore used to sim- dle panels). For the heating-season month ulate a “high mass” option, using the textbook consensus on This work therefore supported the priority of separating mass

of April, this diminished slab heat loss from (kWh/mo) 3 9.4 12.6 10.8 3 0.8 2.4 3.2 2.8 0.8 concrete mass, and a “high water” option, using the consensus from wet soil, suggested by the initial field study (above), and about 150 kWh, or 20% of the total gain, to water mass. The three redesign options returned comparable added a new one, explored below: tailoring thermal mass to Loss 4 10.8 13.4 11.3 3 0.9 2.6 3.3 2.8 0.8 about 38 kWh, or about 5% (lower panels). Heat Loss (kWh/mo) total heat to the spaces, all greater than the original (left). the program at hand. Please see the publication for further details. Redesign / Build

Heat 1 4.3 5.4 4.8 1 0.3 1.0 1.3 1.2 0.3 6 Alexandra Rempel, Ph.D., M.Arch., 2013 Thermal Batteries for Buildings Thickness. Increasing mass thick- Rocks, clays, water, and salts: Highly durable, infinitely recharge- ness, shown for exposed mass walls able, eminently controllable thermal batteries for buildings. characteristically delayed heat de- Special Issue: Geoscience of the Built Environment. Geosciences livery, as expected (right); design 2013, 3: 63-101. guides often recommend increasing the thickness of a thermal mass ele- Design Intent. Passive solar design guides usually ex- ment for this exact purpose. press one of two design intents: (1) minimizing diurnal temperature swings and/or (2) maximizing heat delivery Increased thickness also, however, on an aggregated monthly basis. These may easily miss substantially diminished the mag- the most important goal, however, of delivering heat nitude of the heat delivered, to the (or coolth) when it is most needed. Given the diversity of point that the thickest walls per- thermal behavior among materials, it seems plausible to formed net cooling functions (e.g. match material, configuration, and size to an architec- 24-in adobe). This feature is notably tural program more specifically than is typically discussed. absent from design guides but is Program-responsive heat delivery patterns might include, readily predictable from mass ther- for example, evening heating, afternoon heating, all-night mal properties. heating, and cooling (right). Thermal diffusivity.Granite is denser Method. To determine whether such programmatic ap- and more thermally conductive than plication of thermal mass might be feasible, EnergyPlus concrete, but has a lower specific models were used to simulate performance of exposed heat capacity. To choose between wall, , direct-gain, and sunspace configura- two different materials (apart from Ideal patterns for solar heat gain and delivery to indoor spaces cost), their relative “thermal diffusiv- tions (below) with varying materials and thicknesses. Thermal mass wall sections; yellow = solar gain, blue = delivery ities” are useful, which express the rates at which they equilibrate ther- mally with an environment. Granite, with the highest value, exchanges substantially more heat with the interior space than concrete as a re- sult. Together, these show that both material and thickness may be inten- tionally matched to the timing and intensity of a space’s heating need. Effects of Material and Thickness on Heat Return from Thermal Mass Walls Thermal Batteries 8 a) Exposed mass wall b) Trombe wall c) Direct gain space d) Sunspace Alexandra Rempel, Ph.D., M.Arch., 2013 (a) Exposed(a) mass Exposed(a) wall Exposed mass(a) Exposed wallmass(b) wall Trombe mass wall(b) wall Trombe(b) Trombe wall(b)(c) Trombewall Direct-gain wall(c) Direct-gain space(c) Direct-gain (c)space Direct-gain space space(d) Sunspace(d) Sunspace(d) Sunspace(d) Sunspace Internal Mass. Mass con- Thermal Batteries tained fully within a space for Buildings loses virtually no heat to underlying soil, making it a Internal . Water is good choice in direct-gain widely acknowledged as a good and sunspaces with persis- thermal mass material in the de- tently wet soils. In the form sign literature, but the extraordi- of water drums, it also offers nary potential of internal convec- the warmest possible night- tion to sustain heat delivery over time indoor temperatures for hours seems underappreciated. plants (below left). Evenness of Heat Delivery by Water Trombe Walls Slab-on-Grade Heat Loss over Typical Soil Types In a Trombe wall configuration, for α = soil thermal diffusivities reported in soil science literature Thermal Mass for People and Plants. This work shows example (upper panel), models . Water’s heat-delivery con- stant temperature, avoiding the diminish- Heat Loss to Soil. Previous work suggested stating perimeter insulation is sufficient, but showed that water could combine stancy is rivaled only by phase-change ing returns that occur during solar uptake that thermal mass materials, that heat loss to ground can be high when by climate files and energy models as well. configuration, and size can a strong afternoon heat pulse with materials (PCMs), hydrated salts that as a solid mass heats up. As a result, PCMs soils are moist and fine-grained. Moreover, the Correction of values to those in the soil sci- lower, all-night heat delivery (4-in), absorb heat as they melt and release it as are effective at fractions of the thickness indeed be matched to spe- standard TMY3 weather files use an incorrect ence literature (above) shows that thermal cific design intents. Adobe, while the thickest walls (12-in) fully they solidify. The “latent heats of fusion” of concrete and water, as shown by the default value for soil thermal diffusivity (α). As mass needs minimal separation from low-diffu- absorbed pulses of heat gain and of these materials are quite large, and the 4-in panel of calcium chloride and 2-in brick, granite, concrete, wa- a result, potential heat loss to ground is hid- sivity soils, but that it should be well-protected ter, PCMs, and other materi- delivered heat at a constant rate phase change itself occurs at a near-con- panel of zinc nitrate salts below. den from designers not just by design guides, from moderate-to-high diffusivity soils. to the interior all night. als each have their thermal niches, and once chosen, The explanation for this behavior their thicknesses, volumes, is straightforward: is and separation from soil can limited in part by the surface tem- be calculated to optimize peratures of the entities involved, the timing and amplitude so the ability of warm water to of heat delivery for the pro- rise, leaving the solar collection gram at hand. This provides a surface, and be replaced by cooler program-responsive, climate- water facilitates its solar heat gain. responsive, and material-spe- Similarly, the falling of cool water cific alternative to one-size- on the interior surface and replace- fits-all mass-to-glass ratios. ment by warmer bulk water facili- tates sustained heat delivery. Please see the publication for Evenness of Heat Delivery by Thin PCM Trombe Walls Internal Mass: Complete Protection from Ground Heat Loss further details. Thermal Batteries 10 Alexandra Rempel, Ph.D., M.Arch., 2013 Hybrid Ventilation in the Harm A. Weber Paths. The bowtie was air-condi- Airflow Pathways tioned, and its air was meant to be kept Level 4 Academic Center at Judson College separate from the hybrid-ventilated, mini- mally cooled block by interior . Hybrid Ventilation in the Harm A. Weber Academic Center: A Late-Summer CaseFigure Study. 3. Positions Journal of Hobo of Green dataloggers Building projected 2008, in section3:56-73. (a) and in plan on Levels 3 (b) and 4 (c). Warm block occupants, however, soon a) b) c) discovered that cooling was available by propping these doors open (blue arrows, right). These doors were later restored to IR: Lightwell Air Leak the intended closed positions with signs (below), but air short-circuits persisted: transfer in common walls admitted cool air at high speed (photo 3, left), as did large gaps around interior doors. The lightwell discharged hot air through its Lightwell unsealed as well (top IR photo, right Placement of Temperature Sensors diagram). Center-In,well within theEdge-Out. comfort zone.The WeberConditions Academic on Lev- Centerand near4 within Chicago, the ASHRAE Illinois 55-2004 86comfort zone Level 3 (Alanels 3 and Short 4 changed & Assoc., little compared UK) consists to the noon of a set, “block” during of studios the study. and Deviations library from the zone wereExternal Importance of Field Work. These results connectedhowever, suggesting to a “bowtie” that mechanical of offices cooling had to in- the south.caused In by the high block humidity (above), rather than high84 tempera-SW Lightwell Side IR: Lightwell Warm Glass illustrated the perils of combining day- creased, but was not noticeably affecting conditions ture, however, and bioclimatic evaluation indicatesE Platform Corner ventilation air was taken in actively at ground level (a) and drawn W Platform Corner lighting and cooling intents into a single above Level 2. that airspeeds were also lower than ideal.82 Consis- throughAn alternative a plenum means into of viewing a central thermal lightwell comfort, (photo). tent withAir was these then observations, to flow commentary overheardE Seminar (433) element and assuming that connected upwarddeveloped passively,by Victor Olgyay entering (18), shows occupied the effect space of throughfrom occupants floor-level referred vents primarily to air stillnessW Seminar (425) buildings can act independently (see Lil- andairspeed exiting explicitly through and therefore wall-edge enables vents prediction leading toand terminal stuffi ness, stacks rather (a). than heat. Increased80 potential lis, below). More importantly, however, of airspeeds necessary to provide thermal comfort; for comfort might therefore be achieved with least they show the value of straightforward, 78 Methods.this “bioclimatic” To investigate visualization the is considered system’s es- performance,energy by air approaching temperature humidity and/or airspeed methodical field work in revealing specific pecially useful for design and evaluation of passive values first, perhaps by making greater use of the sensors were placed vertically along the lightwell (a, above), through- reasons that high-performance buildings cooling strategies (4). When dry-bulb temperatures lightwell airfl ow pathway, considered further76 below, out Level 3 (b), and in a transect extending across Level 4 (c) for one IR: Transfer to Bowtie fail to perform as intended.

and relative from 8/23, 12:00 noon (for or individually-operable fans. (˚F) Temperature August week, and flow bubbles, infrared (IR) photography, and ane- which operative temperature was plotted in Figure 74 mometers4b) are plotted were on a bioclimaticused to document chart (4), it becomes airflow paths.AIRFLOW ISOLATION clear that positions on Levels 2, 3, and 4 could have WITHIN THE BLOCK 72 Solarbeen brought Gain. intoAlthough the bioclimatic the lightwell comfort zone was with shaded Given internally, the unique it emphasis warmed on center-in, edge-out substantiallyslight decreases eachin relative day, humidity with afternoon combined withpeaks ofairfl ~83 ow°F paths (right). within Heat the radi- block, as well as the con- atedincreases outward in ambient from airspeed: this central a decrease point in dry-bulb (IR photos), ditioned, creating cool, a dry noticeable status of the bowtie70 during the 8/21 12a 8/21 12p 8/22 12a 8/22 12p 8/23 12a 8/23 12p 8/24 12a 8/24 12p cool air (a/c) thermaltemperature gradient would not across have been Levels necessary, 3 and though 4 (right) study,and causing it was expected the studios that airfl ow paths within the ambient-temperature air andit would library have toserved exceed as an thermaleffective alternative comfort (Fig- limits forblock most would occupied be nearly hours. isolated from the bowtie.Temperature At Transect: Lightwell Heating of Level 4 warm air ure 5). the same time, it was expected that airfl ow from the Hybrid Ventilation 12 A second alternative, known as the adaptive lightwell, through the block, to the stack apertures IR: Interior Doors to Bowtie Interior Doors to Bowtie Alexandra Rempel, Ph.D., M.Arch., 2013 model of human thermal comfort, is often used to would proceed as described (10, 11, 20). To investi- establish comfort criteria in unconditioned build- gate these hypotheses, all apertures found between ings and is also incorporated into ASHRAE 55- Levels 3 and 4, the bowtie, the lightwell, and perim- 2004. This approach, which defi nes the acceptable eter stacks were examined with fl utter-strip apparati, range of indoor temperatures on the basis of mean anemometers, and infrared thermography on mul- monthly outdoor temperatures, was considered by tiple occasions each day. the designers but ultimately discarded in favor of the conventional standard (20). Level 3 (Library) Perimeter Hypothesis 1 was therefore proven false: the The library on Levels 2 and 3 is served by 23 pe- HAWAC was, in fact, not operated to keep Levels 3 rimeter stacks embedded within thick walls. Those

Volume 3, Number 1 61

JGB_V3N1_a05_ahmann.indd 61 3/5/08 4:03:35 PM Night Cross Ventilation Pattern: A Warm August Day

Daytime Single-Sided and Nighttime Cross-Ventilation Cooling: August Weekdays 40 90 Daytime Single-Sided Ventilationmaximum and office Cooling:Daytime air temperature August Single Weekdays-Sided Ventilation and Cooling: August Weekdays 85 40 7 40 90 90 30 Cooling Challenge. While80 outdoor air temperatures were ideal for natu- Passive Cooling of Everett, WA 80 6 ral ventilation cooling, reaching the necessary air exchange was not total heat gain F) º 75 30 5 30 80 possible with daytime single-sided80 ventilation alone for any of the test 20 70 Community College Offices ° F) maximum office air temperature maximum office air temperature 70 4 offices (left). At the same time, faculty desired complete acoustic separa- indoor air temp F) total heat gain total heat gain ° F) Natural Ventilation in Everett Community College 65 tion from the atrium, limiting º cross-ventilation options. Night ventilation, 20 3 20 70 70 Offices. Prepared for SRG Architecture, April 2009. 10 60 Temperature ( Temperature 60 2 thermal mass, and ceiling fans were therefore explored in detail. outdoor air temp

Report available upon request. cross vent (1=open) F) F) 55 1 º º Temperature ( Temperature 10 10 60 Solutions. Ultimately, in60 collaboration with the architects, automatic

50 0 Status Vent / Hour per Changes Air 0 50 Temperature ( Temperature vents were developed to allow nighttime cooling of limited thermal mass Temperature ( Temperature by cross-ventilation through the atrium; in combination with daytime Night Cross Vent + Day Single-Sided0 Vent Scheme Heat Gain / Loss (kBtu) 0 50 50 -10 single-sided ventilation and40 ceiling fans, this system predicted accept- Temperature ( Temperature ( Temperature 20 total ventilation cooling total ventilation cooling able comfort in all but a few August hours (below left, and below). Upper Window Heat Gain / Loss (kBtu) Heat Gain / Loss (kBtu) 18 -10 -10 40 40 -20 30 16 Daytimetotal ventilation Single-Sided cooling Ventilation in Large Buildings. As this building, the Weber Cen- Daytime Single-Sided and Nighttime CrossDaytime-Ventilation Single Cooling:-Sided andAugust Nighttime Weekdays Cross-Ventilation Cooling: August Weekdays Cross Ventilation Study Area: Offices and Atrium 14 -2040 -2040 9030 ter, and the Lillis Business9030 Complex (p.17) show, passive ventilation is -30 20 12 quite feasible in large buildings. However, it seems to be explored rarely, Would single-sided natural ven- maximum office air temperature maximum office air temperature 10 apparently because of perceived uncertainty in outcomes. Good model- tilation with restricted awning -3030 -3030 8020 8020 8 ing tools, however, combined with rigorous field work, can remedy this. (section) be sufficient to 6 total heat gain total heat gain cool faculty offices (above) during

average hourly airflow (cfm) rate 4 20 20 70 70 Outside to Inside Day Single-Sided (SS) the warm dry summers of Everett, Airflow Rate (cfm) Hourly Inside to Outside 2 F) F)

Washington? Or would cross ventila- º º ° F) Day Cross Vent (CV) 0 tion be necessary, possibly at night? 20 10 10 60 60 Lower Window 187/01 7/05 7/09 7/14 7/18 7/22 7/27 7/31 8/05 8/09 8/13 8/18 8/22 8/26 8/31 9/04 9/09 9/13 9/17 9/22 9/26 9/30

To answer these questions, an 16 0 0 50 50 airflow network was created with Node 2 Node 1 14 Temperature ( Temperature Temperature ( Temperature ( Temperature EnergyPlus to simulate bulk airflow (outside) (inside) 12 Heat Heat Gain / Loss (kBtu) Heat Gain / Loss (kBtu) between nodes in offices, outdoors, 10 -10 -10 40 40 and in the atrium under typical 8

weather conditions. Preliminary 6 -20 -20 30 30

modeling showed that stacked aw- average hourly airflow rate (cfm) 4 Outside to Inside total ventilation cooling total ventilation cooling Hourly Airflow Rate (cfm) Hourly ning windows allowed greater ex- 2 Inside to Outside -30 -30 20 20 change than side-by-side windows, 0

allowing air to enter below and exit 7/01 7/05 7/09 7/14 7/18 7/22 7/27 7/31 8/05 8/09 8/13 8/18 8/22 8/26 8/31 9/04 9/09 9/13 9/17 9/22 9/26 9/30 above (right). Airflow Pathways: Single-Sided Natural Ventilation through Stacked Awning Windows (EnergyPlus) Nighttime Cross + Daytime Single-Sided Ventilation August Hourly Adaptive Comfort for Each Ventilation Option Passive Cooling 14 Alexandra Rempel, Ph.D., M.Arch., 2013 DRAFT 4.0 Results Thermal Comfort in Passively-Cooled Zones

4.1 Passively Cooled Spaces Southwest Classroom, Level 2. The west-wing classrooms on the upper level, with southern exposure, present the greatest cooling challenge among the building spaces due to intermittently high occupancy, solar gain through skylights and windows, and minimal losses through the well-insulated envelope. Nevertheless, model-predicted in- door operative temperatures remained well within the ASHRAE 55-2004 adaptive comfort range, with credit taken for elevated air speed (ceiling operation), even on the hottest September days (Fig. 3). Computer Laboratory. Although this space has a northern exposure, high internal loads cause it to experience some warm hours. As for the other classroom, though, these remain within the adaptive comfort range. Administration, Level 2. Offices have the highest sustained internal loads in the building, causing the skylit up- per administration area to be an area of concern. Here, too, operative temperatures remained within the adaptive comfort range. Science Laboratory. The second-floor laboratory, with scientific equipment loads and intermittent high occu- pancy, had the fourth-greatest cooling load and was therefore included in the test zones; however, its operative temperatures remained in the comfort range even without the elevated air speed credit.

Southwest Classroom, Level 2 95 Night Cooling of Mass Occupied Occupied Natural Ventilation in the Lillis 90 in the Vernonia K-12 School 85 Business Complex, Univ. of Oregon 80 Ventilation in the Lillis Business Complex Atrium. ARCH 597: Thermal Comfort in September 75 Comfort Zone Building Case Studies (W. Grondzik), June 2006. Available upon request. (°F)

Passively-Cooled Zones (LEED IAQ Credit 7.1). 70 Prepared for BOORA 65 Architects, June 2011. ATRIUM

Temperature 60 Report available upon 55 request. Outdoor Dry Bulb Temperature 50 Indoor Operative Temperature To achieve low-energy cooling for LEED Platinum and 45 Slab Temperature Net-Zero performance goals, the design team devel- Outdoor Wet Bulb Temperature 40 air velocity (fpm) oped a scheme in which evaporatively-cooled water >100 ∙ Natural Ventilation was pumped through tubes in concrete slabs at night, September 13 September 14 75-99 creating cool mass to take up the following day’s heat Design-Day Adaptive Comfort from Night Cooling of Thermal Mass + Operable 50-74 Air from corridors is intended to flow into Fig.Windows. 3 (above and Academic-year following pages). design Indoor day; operative orange and limits slab temperatures show adaptive during comfort the 48-hour zone. test period, Natural Ventilation Design Intent: 25-49 gains. Teachers controlled operable windows and ceil- compared to outdoor dry-bulb and wet-bulb temperatures. The September comfort zone denotes the September the central atrium, up, and out through rooftop vents (SRG Architecture). <24 ing fans each day, qualifying classrooms for adaptive comfortadaptive comfort standards. threshold (66-78.8 EnergyPlus0F) with the modelingaddition of the 5.4was0F allowance used tofor elevatedunderstand air speed. interac- tions between mechanical and passive systems and to evaluate resulting thermal comfort on the warmest academic-year days. fire doors

Vernonia School District / BOORA Architects 7 Architects intended air from classrooms and offices to 3D Thermal Bridging in Walls SOLARC ARCHITECTURE AND ENGINEERING flow to the central atrium, up, and out through roof vents. Wall Assembly 3D Thermal Modeling for the Lane Communi- Anemometers and flow bubbles showed, however, that air

ty College Downtown Campus. Prepared for SRG Architects, ∙ Thermal Bridging instead flowed rapidly (≥25 fpm) outward from the atrium January 2011. Report available upon request. through corridors and out through open windows, par- Three-dimensional heat transfer is too computation- ticularly those of connected buildings (above). Fire doors ally intensive to be included in whole-building energy (circled) were found open at all times. To determine wheth- simulators, which require users to account for thermal er they were counteracting atrium stack formation, bridging in wall layers. To find composite heat trans- were monitored from atrium bridges with all fire doors fer coefficients for complex assemblies, accounting closed (left). Flow bubbles showed progressively greater for studs, cladding supports, and fasteners, numerical buoyancy over time from blue (time 0) to green (t=30’), yel- methods are required. Here, the finite element solver low (t=1h), orange (t=1.5h), and red (t=2h), supporting this Final Wall Assembly: Steel cladding over Final Wall Performance: Temperatures Stack Restoration Experiment. One warm evening, atrium fire doors were closed hypothesis and showing the value of field work in revealing AnTherm was used to optimize opaque envelope op- horizontal Z-girts + XPS Insulation over verti- from inside (red, 68°F) to outside (blue, and air buoyancy was monitored with flow bubbles from the atrium bridges over tions for a LEED-Platinum college building. cal steel studs + batt insulation 14°F); composite U=0.052 Btu/h SF °F. time. Arrows show bubble paths and clouds show areas of bubble congregation. passive system performance under occupied conditions. Night Cooling of Mass 16 Alexandra Rempel, Ph.D., M.Arch., 2013 1. History Thermal comfort ∙ Vernacular and contemporary case and Context studies ∙ Direct-gain, indirect-gain, and isolated gain solar configurations ∙ Cross and stack ventilation ∙ Introduc- tion to term project ∙ Term project site selection

2. Climate; Graphing direct and diffuse solar radiation on sun path Solar and Wind diagrams ∙ Cloud scattering of solar radiation ∙ Graphing Resources heating and cooling degree-days ∙ Buoyancy ∙ Wind roses ∙ Microclimates ∙ Estimating solar glazing angle and tilt Recent Publicity Solar Site Surveying Overhang Shade Analysis Solar Pathfinder DView: Hourly Sky Cover 3. EnergyPlus Why model? ∙ Program setup ∙ Opening, viewing, and ed- Passive Heating and Cooling Design: iting input files ∙ Viewing variables in xEsoView ∙ Export- Teaching SUS 4043. Boston Architectural College. ing results in *.csv files ∙ Term project program selection Materials available upon request. 4. Solar Site Magnetic declination ∙ Tree shapes & identification ∙ Evidence-based. Teaching architecture students not only Surveying Measuring tree & building height with inclinometers ∙ Drawing shading masks ∙ Modifying optimal solar glazing conceptual schematic design, but also design development Wind Rose skills, for passive heating and cooling is essential. When angle and tilt ∙ Urban tree canopy debate Field-validated. Instruments for measuring dry- clients and consultants question the ability of a passive 5. Windows, Solar spectrum ∙ Window glass composition ∙ Visible and bulb, wet-bulb, surface, and soil temperatures; system to work, the architect must be able to provide solid Shading, and IR transmission ∙ Emissivity and coatings ∙ Multi-glazed air speed and direction; incident solar radiation, il- site, climatic, and thermal evidence for making decisions. Movable windows ∙ Choosing solar glass ∙ Sizing solar glazing lumination, and relative humidity are durable and Insulation by hand ∙ Scheduling shading and movable insulation ∙ Climate-responsive. Most current textbooks and design Modeling windows in WINDOW 6 for EnergyPlus inexpensive, and their value in building students’ guides base the critical sizing and positioning of glass and intuition for outdoor microclimates and indoor mass on tables and calculations developed in sunny dry cli- 6. Thermal Heat capacity ∙ Thermal conductivity and diffusivity ∙ passive system performance is enormous. They mates; these fail to work in numerous other climates. With Mass Convection ∙ Radiation ∙ Adobe, concrete, stone, water, are also essential for model validation. PCMs ∙ Matching material to program ∙ Conceptual sizing strong climate analysis skills, however, architects can esti- ∙ Ground heat transfer ∙ Internal mass ∙ Modeling mate optimal parameters for passive systems quite well. Ready to go. Fortunately, we can equip students 7. Natural Airflow and thermal comfort ∙ Evaporative cooling ∙ Site with a full set of tools for passive design using Model-savvy. Long-term performance analysis is greatly fa- Ventilation wind paths ∙ Cross ventilation aperture positioning and a combination of field measurements, climate cilitated by models if good site work has been performed. sizing ∙ Stack ventilation aperture positioning and sizing ∙ data, and appropriate modeling tools. The course Passive heating and cooling are not usually taught to me- Wind site survey ∙ Indoor ventilation survey ∙ Modeling outline at left describes a course I’ve developed chanical engineers or building energy consultants, howev- for the Boston Architectural College’s Sustainable Presentation and quantitative performance evaluation er, and their typical modeling software cannot simulate the 8. Synthesis Design Institute, described further in a recent In- of the term-project site and passively conditioned space hours-long patterns of mass-based systems. The architect habitat article (far left; http://inhabitat.com/learn- must therefore understand the modeling tools available. Course Outline: Passive Heating and Cooling Design, Boston Arch. College 2013 the-core-concepts-of-passive-design/). Teaching 18 Alexandra Rempel, Ph.D., M.Arch., 2013 Relevant Funding Programs Passive building design work is fundable through sustainability, , and greenhouse-focused agriculture programs at the federal level. A number of the most promising are listed below. In addition, this work is eligible for funding through the Northwest Energy Efficiency Alliance, covering Montana in addition to Oregon, Washington, and Idaho, as well as state Department of Energy initiatives. Please see my curriculum vitae for a summary of past research funding.

National Science Foundation mission. All proposed technologies or approaches must have Contact: Bruce Hamilton, Engineering Directorate the potential to reduce building energy consumption, energy costs, or GHG emissions. Annual. 1. Sustainable Energy Pathways (SEP). Awards: Up to $2M, 3 years. Topics include: Energy Harvesting & Conversion from Renewable Resources; Sustainable Energy Storage Solutions; U.S. Department of Agriculture Critical Elements & Materials for Sustainable Energy; Nature- Contact: Bradley Rein, USDA Inspired Processes for Sustainable Energy Solutions; Reduc- 6. Sustainable Development: Sustainable Agriculture Research ing Carbon Intensity from Energy Conversion & Use. Annual; and Education Program (SARE). Awards: $60K-$150K; Re- FY2014 announcement planned in June 2013. gional; Renewable. Goal: Promote good stewardship of 2. Environmental Sustainability. Topic 3: Green Engineering. Re- the nation’s natural resources by providing site specific and search to advance the sustainability of ... green buildings ... profitable sustainable farming and ranching methods that ... taking a systems or holistic approach to green buildings. In- conserve soil, water, energy, and natural resources. Annual; novations in green engineering techniques to support sustain- FY2014 announcement planned April 15, 2013. able construction projects. Proposals due January 15, 2014. 7. Agricultural & Food Research Initiative (AFRI): Agricultural 3. Science in Energy and Environmental Design (SEED). Topics and Natural Resources Science for Climate Variability and focus on low-energy building design. Annual, but topics vary; Change. Goal Area 1. Adaptation: Maximize resiliency and re- FY2014 announcement date pending. duce the impact of climate variability and change on the sus- tainability and productivity of agricultural ecosystems under changing climates by providing producers and decision-mak- U.S. Department of Energy ers with new and sustainable management methods and tech- Contact: Greg Stark, National Renewable Energy Laboratory nologies. Annual; FY2014 announcement planned October 13, 4. Energy Savings through Improved Mechanical Systems and 2013. Building Envelope Technologies. Topic 1: Energy Saving Heat- ing, Ventilation and (HVAC) systems, Subtopic Northwest Energy Efficiency Alliance 1.2: Alternative Space-Heating Systems. Awards: $10K-$1.5M, 3 Contact: John Jennings, Charles Stephens years. Annual. 8. Emerging Energy-Efficient Technologies. Projects must pro- 5. Building Technologies Innovations Program. Awards: $250K- mote energy savings in the Northwest and face clear market $750K, ≤2 years. All building energy topics are eligible for sub- barriers. Awards: $1-50K. Rolling submissions. This page intentionally left blank. Funding 20 Alexandra Rempel, Ph.D., M.Arch., 2013