Assignments' Book - Environmental Tech3

Environmental

Technology 3 ARCH 6A48 - PROF. MILI KYROPOULOU - FALL 2016 - UNIVERSITY OF HOUSTON

Assignments’ Book

TATIANA ZUCCO DA SILVA LUZARDO

1

Dry Bulb Temperature Cooling and Heating Degree Days

Climate

Global Horizontal Radiation Diffuse Horizontal Radiation Psychrometric Chart

Monthly air temperature in the city of Santa Maria, State of Rio Grande do Sul, Brazil. Initially, the intention would be to run all of the present analysis considering the city of Porto Alegre, capital of the state; however, as there is no Macroclimate data of the capital, another city located in the same state and at a very similar latitude was adopted: Santa Maria.

Both cities are under the same Koppen Climate Classification: Humid Subtropical Climate. This climate is characterized by warm, dry summers - average temperatures above 22 °C (71.6 °F) – and cool, wet winters – temperatures between − 5°C and 18 °C. The prevailing winds blow from southeast during summer and fall months and from east during winter and spring, ranging around 6 mph.

Latitude/Longitude: 29.7° South, 53.7° West

http://www.worldatlas.com/sa/br/rs/where-is-santa-maria.html

climate classifications. https://upload.wikimedia.org/wikipedia/commons/ 6/60/World_Koppen_Classification_%28with_authors%29.svg

1

Climate

There is a prevalence of cooling degree days during the year, indicating that passive strategies as good ventilation, windows shading, well sealed buildings, and favorable solar orientation are essential to keep the building from absorbing external higher temperatures. During winter months, strategies as internal heat gain and designing high mass interior surfaces and walls can help the building to keep the warm temperatures inside, even during night, when there is no exposure to sun and the outside temperatures get lower.

1

Climate

The average Global Horizontal Radiation in the region is moderate in most months of the year, especially during summer months (December through March).

Below, graphics demonstrating the hourly average Diffuse Horizontal Radiation during the months of January (summer), June (winter), and October (spring).

The months of January (summer) and October (spring) present a good distribution of Diffuse Horizontal Radiation (DHR) throughout the day; DHR levels start to increase from around 5:00a.m until hitting its maximum amount, around 342.65Wh/m2 in January and 305.71Wh/m2 in October.

Levels decreases until 0 around 8:00 pm.

It is important to notice the drastic reduction in the diffuse horizontal radiation levels during the winter (June). The maximum amount of radiation is 173.1 Wh/m2, observed right after noon; the amount of diffuse radiation is low during the morning (it starts increasing from 7:00am), hits its maximum levels around 2:00pm and decreases rapidly until and 6:00pm. The short span of diffuse radiation during the winter should be considered when designing daylighting strategies for the location, since the size and orientation of windows will have a direct impact in the amount of lux present inside of the building during winter months; insufficient levels of lux in interiors would have to be addressed with the use of artificial lighting, generating an increase in the building’s running costs (increase in expenses with electrical energy).

1

Climate

Passive strategies (outlined in pink) are affective during most of the year. When temperatures range from approximately 13 degree Celsius and 32 degree Celsius (especially mid-season and summer seasons), strategies as internal heat gain, crossed ventilation, northern solar orientation and window overhangs for shading glass surfaces during summer should be enough to maintain internal levels of comfort.

1

Climate

Climate Strategies

2

Wind Rose Wind Profile Total Radiation Rose Diffuse Radiation Rose Direct Radiation Rose

Prevailing winds blowing from southeast and east. The wind speed intensity is low; wind protection would be needed when wind speed goes beyond 8m/s.

Climate Strategies

2

Prevailing winds blowing from southeast and east. The wind speed intensity is low; wind protection would be needed when wind speed goes beyond 8m/s.

Wind roses for summer and spring seasons. Wind direction and intensity was analyzed considering humidity levels above 50%.

This analysis shows that when temperatures go beyond 23 degrees Celsius, there is good opportunity to use natural cross ventilation to minimize the effects of humidity inside of the building, since the wind speed is high when the building has windows oriented to Southeast and East.

Climate Strategies

2

Wind roses for winter and fall seasons. Wind barriers located close to north facades and a well-sealed building will prevent internal heat loss from exposure to winds during these months, keeping elevated humidity levels inside of the building.

Climate Strategies

2

N

The building is located in a suburban context, in a wooded area. It consists of a 3 stores residential building (10m height). As prevailing winds blow from southeast during summer months, the biggest building’s facades will be north/south oriented, allowing cross ventilation.

Climate Strategies

2

North facades will need additional hangouts and horizontal shading devices during summer seasons.

Climate Strategies

2

Radiation Roses, no context obstructions.

Direct radiation and diffuse radiation is higher along north oriented facades.

Climate Strategies

2

Radiation Roses, projecting two additional buildings (in red in the image on the left) for the future.

1

2

Building number 1 is 40 meters high and building number 2 is 20 meters. The development of these two new constructions will have a huge impact in the solar radiation hitting our projected building (in blue in the left image). This means that during summer and spring months, we would count with the neighbor buildings to provide shading to our building, minimizing heat gain from sun exposure. We would have to assort different strategies to endure passive heat gain during winter and fall seasons, since the direct sun radiation is blocked in the north facade by the future buildings.

Conclusion: The passive design strategies highlighted on the previous assignment were confirmed by the analysis of wind and radiation data. The building would be greatly impacted by the construction of the two new buildings projected for the future. In this context, other strategies like the utilization of mechanical heating and humidification during cold weather will be needed.

Climate Strategies

2

3

Sun Path Diagram 3D Window Location

Solar

Shadow Masks

P2

P1

Window location, Point 1 and Point 2

The sun path diagram on the right demonstrates sun positions for the day 21st. of October, January, and April in Santa Maria, Rio Grande do Sul, Brazil.

As the analyzed location is situated at the South hemisphere (in the south part of Brazil), the sun path is inclined to north. We can notice that during spring (indicated by the upper line of the diagram), the sun altitude is relatively low, offering horizontal sunlight to the interior of the building. Temperatures range between 19 and 31 degree Celsius.

The sun altitude in September (spring) can be considered intermediate. Temperatures range between 15 and 21 degree Celsius.

The summer sun path is characterized for high altitude angle, offering vertical incidence of sunlight into the building’s facade. There is opportunity for the utilization of shading devices along the eastern, northern and western facades, reducing solar heat gain inside of the building.

The proposed building is 226 meters high. The analyzed window is north-west oriented, and it is located at the top 3 floors of the building, configuring a glassed wall that is 15 meters wide and 15 meters high. As these three top floors will be designated to office activity, it is important to control the exposure to sun during the afternoon during these months, avoiding glare and overheating on the interiors of the building, as demonstrated by the diagrams on the right of this page.

Shadow mask - Point 1 - No shading device October to February

Shadow mask - Point 2 - No shading device April to August

Solar

3

Shadow mask - Point 1 - Vertical Shading October to February

Shadow mask - Point 2 - Vertical Shading October to February

The first option of shading device is a series of vertical brises, which shades partially the window during the period of October to February (spring - summer). There are 7 vertical brises between the window’s extremes, spaced 1,30m from each other. 2 additional elements are placed at each window ends. All elements are projected 1.5m from the building’s external surface.

Shadow mask - Point 1 - Vertical and Horiontal Shading October to February

Shadow mask - Point 2 - Vertical and Horizontal Shading October to February

The second option of shading device are rotated vertical planes (45 degrees), together with horizontal brises. The vertical brises are placed within 1.5meters from each other; horizontal brises are spaced 3.75 meters from each other. This solution was the most effective, since it provides shading during most of the afternoon hours. Other measures, as the specification of Low-E glazing can help to mitigate the eventual excessive heat gain during the afternoon hours.

Solar

3

4

Illuminance Levels LEED Daylight Points: Option 2

Daylight

3D Interior Daylighting Simulations

N

5.00

5.00

10.00

5 windows wxh: 1.8m x 1.5m sill hight: 0.8m

north facade

The proposed space is a classroom, located at the city of Santa Maria, Brazil. The room is 10m wide, 5m deep, and 5m high. Five windows were designed along the northern faรงade, the most actively hit by sun radiation during the day in the south hemisphere. Each window is 1.8m wide and 1.5m high; sill window was determined as 0.8m. The glazing utilized in the analysis is the Viracon_VUE_19-50, which offers a nominal light transmittance of 50.

Illuminance analysis were made in the space, in order to determine levels that could serve as baseline for future improvements in the space configuration. Aiming the compliance with LEED Daylight Requirements, the analysis should result in at least 75% of the occupied space achieving illuminance levels between 300 and 3000lux at 9a.m and 3p.m of one day within 15 days from March 21st and one day within 15 days from September 21st. The achievement of this goal would result in 1 LEED points on daylight parameter.

Daylight

4

Baseline1 - March 21 / 9a.m.

517.52 568.76 540.57 899.55 1267.74 1872.5 3285.02 11397.21 517.68 541.55 601.08 854.03 1233.78 1883.62 3114.48

10369.16 523.27 526.21 575.98 838.17 1254.11 1848.94 2929.01 9825.32 467.56 567.95 655.14 893.62 1277.04 1883.39

2892.18 9916.32 578.14 502.35 665.54 828.12 1232.37 1842.47 2856.31 10080.01 568.99 486.29 629.23 837.3 1206.74

1188.55 1759.1 2825.66 9974.6 525.22 486.96 616.62 854.25 1221.57 1863.88 2801.45 9807.27 494.24 504.02 642.37

1819.62 2776.57 9735.18 501.71 536.83 650.76 877.35 1230.04 1875.41 2842.48 9742.41 542.13 530.18 609.32 849.44

805.32 1198.88 1760.54 2840.76 9562.29 495.38 476.16 583.88 759.59 1084.36 1722.65 2801.58 10013.17 439.81 397.64

489.7 690.63 1068.28 1682.91 2770.46 9899.75 413.2 400.96 476.39 653.57 922.58 1499.3 2590.98 9506.38 369.36

360.59 413.3 546.04 804.97 1326.72 2318.69 9926.77 314.85 326.85 386.97 490.46 680.97 1067.57 1870.66 3728.5

295.93 304.4 368.41 440.61 580.08 810.88 1179.58 2181.4

Percentage of regularly occupied oor area - March 21 9 a.m.

Looking at March 21st illuminance levels at 9a.m., it is possible to observe that 86% of the occupied space has illuminance levels between 300 and 3000 lux; when looking at the distribution diagram, it is possible to notice that the higher illuminance levels are located adjacent to the windows, around the 1920 and 3000lux. This elevated amount of light may result in excessive glare inside of the room and uneven distribution of daylight throughout the space. These facts are directly related to the size of the windows, generating another inconvenient aspects to the comfort inside of the room: excessive heat gain through the glazing.

14%

86%

not compliant

illuminance levels between 300 lux and 3,000 lux

Daylight

4

Baseline - March 21 / 3p.m.

314.97 331.6 390.86 539.63 732.38 1100.84 1796.53 3597.55 373.38 375.54 450.84 643.95 906.74 1528.95 3018.75

7947.27 411.15 409.4 482.32 739.67 1166.5 1961.55 3700.92 8012.72 446.62 446.79 569.58 797.85 1271.74 2091.29

2233.4 3997.44 8060.19 503.48 556.54 625.33 961.57 1436.88 2241.31 3835.61 7195.39 573.88 547.07 641.84 969.03

3803.7 6953.39 503.11 515.94 612.66 896.01 1402.61 2168.93 3839.59 8032.35 487.18 533.19 662.39 913.59 1427.62

1468.59 2239.98 3765.62 7867.29 584.56 560.4 705.46 962.87 1462.79 2255.63 4077.85 8061.72 575.45 622.17 732.14

938.54 1407.95 2307.57 3947.48 7478.38 577.88 589.53 708.17 995.92 1395.9 2248.69 3883.65 7752.41 544.4 544.49

697.46 916.6 1376.28 2297.37 3881.27 8098.93 528.91 497.31 670.05 900.31 1414.35 2272.18 3931.57 7782.83 509.23

506.45 614.6 915.79 1365.12 2314.52 3825.39 5450.13 467.13 535.59 645.4 888.68 1277.41 2124.9 3922.83 8161.78

492.61 489.2 613.22 835.75 1294.34 2061.08 3779.36 8000.52

The numbers at 3p.m., March 21st are pretty similar to the ones at the same day at 9a.m.; the main difference would be the way light penetrates the space. The percentage of area with illuminance levels between 300 and 3000 lux is reduced now to 76%. This decrease is probably due to an increase in the number of Illuminance levels above 3000 lux, since the sun is penetrating more horizontally in the room during the afternoon.

Percentage of regularly occupied oor area - March 21 3p.m.

24%

76%

not compliant

illuminance levels between 300 lux and 3,000 lux

Daylight

4

Baseline- Sept 21 / 9a.m.

130.27 166.56 181.97 261.84 377.92 600.06 1051.3 2008.07 159.48 159.87 203.79 280 426.75 712.96 1252.62

2272.34 185.24 177.39 214.23 299.29 470.26 765.28 1281.37 2181.7 184.02 188.9 221.03 326.39 480.63 780.45

1296.81 2005.95 197.05 198.47 256.95 337.01 497.95 802.99 1357.2 2245.5 211.95 214.17 254.67 351.39 507

811.56 1349.71 2218.38 211.35 224.06 242.05 346.48 511.89 805.45 1302.82 1899.29 199.17 220.31 249.13 364.26

509.28 815.05 1361.46 2233.68 213.03 212.39 269.63 338.53 514.44 806.22 1345.59 2205.59 210.44 217.1 266.68

360.31 506.51 820.4 1309.86 1918.43 203.97 197.91 235.09 341.01 498.62 791.98 1345.36 2219.02 196.33 176.89

228.48 328.69 500.46 802.92 1349.55 2119.62 180.96 182.62 235.44 327.31 478.58 786.86 1300 2015.19 170.09

191.14 201.6 304.97 472.03 742.24 1267.67 2185.58 141.17 168.34 199.23 276.36 424.67 681 1232.7 2234.3

139.62 155.85 194.38 262.59 360.74 592.23 985.43 1755.84

When we change the analysis month to September, it is possible to notice a reduction of the illuminance levels at 9a.m (when comparing the same day and time in March). Illuminance levels during spring season (south hemisphere) are reduced, due to the sun incidence angle in the earth. This time, 59% of the occupied area has illuminance levels between 300 and 3000lux. Looking at the illuminance distribution diagram, it is possible to assume that more area has illuminance levels below 300lux.

Percentage of regularly occupied oor area - Sept 21 9 a.m.

41% 59%

not compliant

illuminance levels between 300 lux and 3,000 lux

Daylight

4

Baseline- Sept 21 / 3p.m.

507.2 478.95 592.03 790.68 1125.55 1720.79 3003.87 6174.99 537.84 558.9 694.51 928.95 1525.2 2484.97 4982.01

18175.97 607.89 609.39 802.75 1090.33 1776.47 3121.75 6139.82 18228.25 631.36 714.62 887.22 1259.86 1924.7 3363.15

6231.26 16553.9 700.75 784.72 948.79 1337.51 2184.73 3510.6 6371.95 18192.29 806.8 794.68 1030.36 1405.81 2176.1

3666.16 6554.22 18352.8 864.53 838.93 989.94 1543.7 2283.56 3702.94 6401.93 16902.74 847.6 898.33 1048.37 1496.71

2193.53 3708.32 6401.55 18066.91 868.4 854.59 1090.67 1515.93 2286.91 3645.59 6606.41 18318.12 841.03 940.79 1132.7

1468.82 2245.83 3780.93 6475.36 17436.32 886.42 785.21 1040.33 1522.49 2237.41 3754.2 6529.41 17782.06 794.01 842.02

1102.69 1470.17 2245.2 3767.36 6751.36 18474.93 742.57 837.05 999.73 1421.1 2228.12 3737.89 6585.65 17970.16 809.3

825.39 970.25 1372.42 2094.05 3670.05 6403.6 9298.9 707.95 782.84 966.47 1304.28 2221.84 3536.23 6508.72 18813.93

Percentage of regularly occupied oor area - Sept 21 3 p.m.

36%

64%

not compliant

illuminance levels between 300 lux and 3,000 lux

731.73 739.95 988.93 1397.55 2037.08 3608.66 6677.31 19124.99

Numbers on September 21st at 3p.m. show an elevated amount of area having illuminance levels above 3000 lux. Only 64% of the area is in compliance with the LEED Requirements.

At this point, it is possible to evaluate the Baseline data for the proposed model. The analysis indicate that the model is not suitable in terms daylighting comfort. During the spring period (September), the illuminance levels are not consistently distributed when comparing the results of 9a.m. and 3p.m, meaning a high number of low illuminance levels during the morning and a high number of high illuminance levels during the afternoon. It is not possible to achieve the LEED Requirements with the baseline model, since the percentage of occupied area with illuminance levels between 300 and 3000 lux is lower than 75% in September 21st at 9am. and at 3p.m.. Also, the illuminance levels in the fall period (March) are proved to be more towards the upper size of the range, close by the 3000 lux; this indicates a higher level of glare inside of the classroom.

Daylight

4

5.00

N

5.00

10.00

6 windows North oriented: wxh: (0.7m x 0.7m) x 5 units South oriented: wxh: (10m x 1.5m) x 1 unit

5.00

north facade

south facade Following the baseline analyses, a change on the design and placement of windows is proposes, aiming more occupied area with appropriate illuminance levels, less glare and even daylight distribution. Five windows are designed on the north faรงade, sizing 0.7 x 0.7m each and placed at 2.6m from the ground. One large window is designed for the south faรงade, measuring 10x 1.5m, and sill height being 2.6m.

Daylight

4

Alternative 1 - March 21 / 9a.m.

214.3 575.6 712.65 807.56 837.95 818.42 1029.73 532.56 297.33 612.58 831.92 891.88 876.39 904.1 830.53

623.89 293.87 672.72 829.23 911.36 900.85 932.86 817 626.16 321.4 662.06 886.05 924.37 951.03 926.31

786.72 605.57 282.82 638.82 838.72 953.71 950.14 919.48 786.48 655.14 299.02 642.98 893.14 936.76 941.38

854.7 791.56 620.87 319.31 653.94 893.42 982.59 933.97 936.4 807.64 622.76 299.48 664.34 875.24 950.56

958.41 895.43 786.41 615.68 276.41 639.28 898.52 959.47 924.56 922.81 821.81 609.32 261.14 599.31 869.07

890.88 916.57 874.6 808.87 592.16 279.74 582.26 790.47 863.42 859.58 843.84 765.15 563.21 252.4 577.23

774.4 809.89 801.96 766.8 716.34 565.73 264.93 532.49 725.21 751.32 757.32 717.31 646.2 519.95 232.42

475.5 629.48 679.49 678 648.11 572.58 482.62 200.29 415.3 530.59 600.38 623.49 574.14 522.84 466.2

153.56 309.54 461 479.13 492.24 473.95 423.47 385.42

The changes in the model have an immediate impact on the Illuminance levels inside of the room. 89% of the occupied area has satisfactory illuminance levels (between 300 and 3000lux). Most of the illuminance levels obtained are between 1110 and 570lux, not requiring any additional means to control glare. Also, the reduction of glazing area in the north façade will result in lower heat gain through that façade.

Percentage of regularly occupied oor area - March 21 9 a.m.

11%

89%

not compliant

illuminance levels between 300 lux and 3,000 lux

Daylight

4

Alternative 1 - March 21 / 3p.m.

171.72 392.21 540.64 596.99 614.9 589.29 535.75 464.15 234.91 522.11 664.76 748.57 743.13 732.73 667.8

521.03 283.81 563.35 737.89 802.67 863.11 851.81 735.75 586.72 292.48 621.01 843.66 885.12 999.4 1055.93

871.31 626.2 310.35 693.53 848.94 942.58 1008.12 1043.56 931.44 631.58 293.69 685.39 990.1 999.15 1052.43

1132.38 879.29 642.7 347.13 757.71 965.33 1072.29 1109.54 1115.08 1028.76 685.07 346.76 708.41 968.59 1108.97

1154.29 1134.07 985.48 678.25 319.5 741.22 954.1 1119.03 1164.53 1195.42 925.14 722.84 351.24 758.62 1014.86

1096.26 1127.57 1103.55 1001.08 702.78 326.9 700.47 906.41 1141.94 1060.18 1122.4 971.63 655.73 325.45 762.49

942.88 1067.61 1150.83 1014.61 903.78 671.92 350.34 723.98 943.85 993.55 1056.84 1125.85 926.95 651.78 314.02

704.87 926.94 1027.06 1090.61 1045.45 911.37 649.01 319.89 647.12 892.64 885.7 1002.9 1053.67 897.9 640.78

253.33 653.94 837.38 891.34 911.09 916.63 820.89 547.16

During the afternoon, the percentage of desirable illuminance levels rises to 95% of the occupied area.

Percentage of regularly occupied oor area - March 21 3 p.m.

5%

95%

not compliant

illuminance levels between 300 lux and 3,000 lux

Daylight

4

Alternative 1 - Sept 21 / 9a.m.

139.18 350.68 526.06 510.91 494.6 460.03 401.54 316.01 169.91 448.87 588.39 619.87 602.83 504.41 476.51

369.73 179.67 487.88 633.44 688.6 649.03 573.29 496.91 388.42 178.72 530.16 719.07 703.64 709.9 596.02

654.62 511.03 446.34 187.78 550.76 770.81 772.87 774.6 680.73 568.69 459.44 178.85 572.41 801.63 798.26

501.71 405.62 193.34 551.31 728.48 732.59 709.07 652.35 529.87 431.14 194.01 540.33 771.57 759.67 754.36

798.99 690.72 587.12 443.04 185.29 549.42 781.94 794.43 745.75 642.78 603.85 458.6 194.52 562.67 775.87

774.21 773.49 673.66 557.77 440.17 164.8 554.28 735.14 779.5 708.98 654.06 577.59 431.92 174.9 544.64

756.9 739.6 683.98 631.22 511.04 427.96 181.37 536.82 711.38 708.87 686.93 633.57 512.84 414.52 179.79

474.32 661.11 675.74 579.96 561.33 493.87 375.31 158.89 436.54 605.56 586.83 553.05 522.33 437.3 345.68

132.95 352.39 475.38 507.41 463.24 431.99 396.56 286.93

Illuminance levels in September at 9:00 are adequate for 87% of the space. The majority of illuminance levels range from the 570 lux to 1100 lux, being adequate for the classroom environment.

Percentage of regularly occupied oor area - Sept 21 9 a.m.

13%

87%

not compliant

illuminance levels between 300 lux and 3,000 lux

Daylight

4

Alternative 1 - Sept 21 / 3p.m.

329.23 734.92 981.89 1055.79 1086.62 1005.75 890.61 656.81 429.28 939.74 1244.09 1290.31 1330.84 1182.23 1046.63

789.46 497.16 1098.93 1435.72 1523.59 1541.32 1432.98 1286.8 917.8 534.44 1257.74 1553.72 1684.64 1784.52 1719.5

1467.25 1008.26 619.19 1356.22 1715.34 1805.55 1829.25 1767.71 1521.36 1024.63 594.57 1351.58 1782.2 1910.86 1753.84

1726.4 1419.72 1074.36 530.77 1518.42 1791.8 1896.93 2016.66 2045.02 1702.02 1102.73 632.3 1400.18 1792.75 1974.1

2124.17 2009.75 1581.72 1104.29 615.45 1485.62 1968.5 1936.6 2064.64 1995.46 1571 1129.15 630.98 1448.93 1902.21

1925.8 2163.23 1971.55 1563.89 1117.54 578.14 1417.08 1857.9 2003.72 2100.76 1907.48 1615.17 1080.1 668.46 1381.06

1855.77 1974.2 2002.32 1920.87 1569.93 1130.05 598.2 1396.56 1807.08 1826.92 2032.45 1913.55 1569.94 1135.21 609.39

Percentage of regularly occupied floor area - Sept 21 3 p.m.

0%

100%

not compliant

illuminance levels between 300 lux and 3,000 lux

1380.88 1786.75 1908.24 1926.58 1801.45 1529.76 1015.7 554.38 1323.77 1648.83 1804.04 1756.38 1677.71 1542.3 1000.25

503.34 1107.4 1479.58 1549.64 1565.04 1578.31 1339.59 896.01

Illuminance levels between 300 and 3000lux can be found in 100% of the occupied area in september 21st at 3p.m.

The majority of levels range from 1380lux to 2190lux. Blinds or shades may be used along northern windows in order to control excessive glare from those windows.

Conclusion: The analysis indicate that the window’s design has and definitive impact in the illuminance levels and distribution.

The baseline model is the most usual configuration used in classrooms: big windows located close to the desks surfaces levels. This configuration generates excessive exposure to daylight in areas close to the windows, resulting in a high contrast of illuminance levels throughout the room. It also has implications in other factors not considered in this analysis, like the excessive heat gain along the northern façade. On the other hand, diminishing the size of glazing on the north façade and adding a window to the southern façade contributes to a more homogeneous distribution of light, resulting also in lower ranges of illuminance levels, more adequate to a classroom space.

Although the results of the alternative option are satisfying to the accomplishment of 1 point on LEED Daylight Requirements, it is important to consider that this could not be the best approach for the classroom proposed. The configuration of the windows on the baseline model generated excessive daylighting, but it also provided views to the outside. The alternative option is more confined, maybe not that stimulating to the process of learning. The student’s productivity and attention can be largely affected by light levels, but also by the access to exterior views.

We believe that a third option would need to be tested, but this analysis lead us to one solid conclusion: the applications of the LEED metrics alone will not guarantee a satisfactory project. The critical analysis of data allied with good architectural design is paramount to the achievement of projects that would attend technical but also human demands.

Daylight

4

Envelope calculations

5

U-Value R- Value Thermal Loads Calculations

U-Factor A) Calculate the U-value of the wall in the example used in class if instead of expanded polystyrene insulation the wall had an unventilated air cavity with a thermal resistance of 12 °F ft2h / Btu (U-Factor= 0.038 Btu/h ft2) .

The wall on the class example was made of materials as listed below: 4” concrete block 0.8” inner layer with gypsum 4” external brickwork 4” thermal insulation in cavity

As the exercise asks for a change in materials, the main objective is to substitute the expanded polystyrene resistance value in the U-Factor calculation, changing the resistance from 20.00 oF ft2/Btu to 12 °F ft2h / Btu, as shown below: U=1(Rsi+ R1+ R2+ … + Ra+ … + Rn+ Rso) => U-value (conductive and convective barriers to transfer heat) U=1(0.06+0.66+4+12+1.11+0.026) U=1/17.85 U=0.056 Btu/h ft2

Notice that the wall’s final U-factor value was increased, from U=0.038 Btu/h ft2 to U=0.056 Btu/h ft2. This means that the total transmittance of the wall increased, resulting in a less efficient barrier against heat transfer. The utilization of an unventilated air cavity within the wall is proved to be less efficient than the utilization of expanded polystyrene in terms of energy savings.

B) What thickness of thermal insulation of thermal conductivity 0.2 Btu-in./h ft2°F would be required to give the same wall a U-value of 0.02 Btu-in/ ft2 oF? Extended polystyrene U=1/ΣR 0.02=1/(0.06+.66+4+X+1.11+0.026) 0.02=1/(5.85+x) X=0.89/0.02 X=44.5 oF ft2/Btu R=d/k 44.5=d/0.2 d=8.9”

C) How thick should this wall be in order to have a U-value of 0.02 Btu-in./h ft2°F, if entirely made of brickwork of thermal conductivity 0.25 Btu-in./h ft2°F, or of dense concrete of thermal conductivity 0.8 Btu-in./h ft2°F, or of stone of thermal conductivity of 1.44 Btu-in./h ft2°F? Brickwork Thermal Conductivity= 0.25 Btu-in/ ft2 oF U=1/ΣR 0.02=1/ ΣR ΣR= 50 R=d/k 50=d/0.25 d=12.5” Concrete Thermal Conductivity= 0.8 Btu-in/ ft2 oF ΣR= 50 R=d/k 50=d/0.8 d=40” Stone Thermal Conductivity= 1.44 Btu-in/ ft2 oF ΣR= 50 R=d/k 50=d/1.44 d=72”

In comparisson with the wall proposed on the previous exercises, a wall made entirelly of oconcrete or stone would present large and inappropriate measurements in order to keep the U-factor of 0.02 Btu-in./h ft2°F ( 40” and 72” respectivelly).

The total thickness of the wall suggested on the previous exercise would be 17.7’ (utilizing expanded polystyrene as insulation). Therefore, the same wall made of Brickwork offers low thermal conductivity, being able to mantain the U-fAactor suggested but reducing the final thickness of the wall to 12.5”.

In order to achieve the U-factor of 0.02 Btu-in/ ft2 oF utilizing a thermal insulation (in this case, expanded polystyrene), the thickness required would be of 8.9”, more than twice the thickness of the wall on the first exercise.

Envelope calculations

5

Thermal Gains Based on the example used in class (table below), find a combination of three realistic strategies to reduce the load to or around 36000 Btu/hr(3 ton).

Test 1 - Will Orientation will impact gains through walls/roofs and windows (glazing)? q= U x A x DETD Before –west, north, and east walls. q=0.085 x (240+240+480) x 19 q=1.550 btu/hr Proposal – west, south, and east walls. q=0.085 x (240+240+480) x 21 q=1.713 btu/hr Result: increase of 200 btu/hr when we change the glazing area orientation. This action may be an advantage if the relocation of the glassed façade results in a significant heat gain reduction through glass.

Test 2 - Changing the glazing orientation and area. q= A x DCLF

or 45.093/12.000 = 4 tons

Before : south oriented glazing wall q= 480 x 24 q= 11.520 btu/hr

walls

glazing

New Goal: 36000 Btu/hr(3 ton) Reduction of at least 9093 Btu/hr

Proposal : north oriented glazing wall and reduction of glazing area, from 480sf to 240sf. Is proposed also to add some draperies or venetian blinds to the windows in order to reduce the load factor through glass from 24 to 14. q= 240 x 14 q=3.360 btu/hr Also, recalculation of the heat gains through walls due to the reduction of the windows size.

}

Proposal – west, south, and east walls. q=0.085 x (240+240+480+240) x 21 q=2.142 btu/hr

Strategies Tested

Envelope calculations

5

Proposal:

glazing

south

Scanned by CamScanner

Scanned by CamScanner

Before:

glazing

north

Results: Heat gain through walls + windows: Before: 13.070 btu/hr Proposal: 5.502 btu/hr TOTAL REDUCTION OF 7568 btu/hr => good oprion, but still 1.525 btu/hr over budget (the goal is to achieve a reduction of 9093 btu/hr.

Test 3 - Reduce gains through Before: q= 28 people x 255btu/person (working seated) q=7.140 btu/hr

New Thermal Loads - Proposal: Walls Roof Windows - glazing infiltration ventilation people light equipment sensible heat (25% of total)

2142 3360 1325 2160 5500 6375 3819 2400 6770.25

TOTAL THERMAL LOAD:

33851.25

Goal Achieved: New thermal load = 33 851.25 btu/hr (2.82 ton)

Proposal: reducing the number of people inside of the room by 10%, from 28 to 25 people. q=25 x 255 btu/hr q=6.375 btu/hr Results: reduction of 765 btu/hr => moving towards the final goal.

Test 4 – Reduce gains through Ventilation, due to the reduction of the number of people inside of the room.

Before: q= (28x10) x 22 q= 6.160 btu/hr

Conclusion: The reduction of the total heat gain in the building was possible by changing some aspects of the building design, as orientation of walls, glazing orientation and size, and number of people utilizing the space (impacting heat gain by ventilation and number of occupants). We opted for designing proposals that wouldn’t interfere on the building’s general dimensions and type of usage (activities), imagining that the project could have dimension restrictions regarding the site and local regulations (as setbacks, height, or zoning).

It is important to observe how design decisions can have a significant impact on the building’s life. The reduction of heat gain loads mean a significant reduction on the dimensioning of HVAC systems, resulting on less operational and maintenance costs through the building’s life span). Additionally, these savings impact the society as a whole, as it results in the reduction of the building’s carbon footprint.

Proposal: q= (25x10) x 22 q= 5.500 btu/hr Results: reduction of 660 btu/hr of gains through ventilation. => moving towards the final goal.

Envelope calculations

5

Envelope analysis

6

Envelope Analysis Materials Selection COMcheck Evaluation Envelope Compliance Certificate

Baseline Building

PERSPECTIVE: NORTH AND WEST FACADES BASELINE MODEL

PERSPECTIVE: SOUTH AND EAST FACADES BASELINE MODEL

The proposed building was originally designed for a site located in the city of Porto Alegre, south of Brazil.

The building is classified as a mixed use building (commercial activity on the first floor and 8 residential floors above it). The original site was located at a corner, having its main façade oriented to North (favorable orientation for building located in the south hemisphere). As the tool we are using to run this study doesn’t support cities outside the U.S., we are considering Houston as an adaptation to the building’s site.

This choice was made considering the similarity between the latitude of the two cities; Porto Alegre, is situated at a latitude of 30.03 degrees South, while Houston is at 29.76 degrees North. That being said, we adapted the main façade’s orientation to South.

The building is located in an urban context, having neighbor buildings of the same high located at the site’s vicinities. It was designed in a rectangular shape, following the site’s geometry. The main floor measures 50.15 x 7.50 meters, total area of 2672 square meters (or 164.50x 24.60 feet, area of 28761 square feet). In terms of program, there are two types of apartments accommodated in the main floor plan: studio apartments and 1 dormitory. The studio unit is situated at the left side of the façade, having one big windows measuring 9.85 square meters (amplifying the space sensation inside of the unit); the 1 dorm unit is situated at the right side of the main façade, having 2 windows of 2 square meters each unit.

N

FIRST FLOOR - COMMERCIAL

TYPICAL FLOOR - RESIDENTIAL

Envelope analysis

6

Baseline Building

WEST FACADE

SOUTH FACADE

EAST FACADE

NORTH FACADE

Windows - Glass Grondzik, Walter T. 2010. Mechanical and electrical equipment for buildings. Hoboken, N.J.: Wiley. Page 1627

In terms of materiality, we opted for materials as indicated on the tables on the left. The choice was made in order to stablish an initial baseline. This baseline will guide our analysis, giving us hints on each strategies would be more adequate in order to make the building pass the minimum code’s standards (aiming on positive values).

Walls

Roof and Floors

Alfonso E. Hernandez - class presentation page 44

Envelope analysis

6

Baseline Building COM check

Software Version 4.0.5.1

After entering all the values and parameters into the COMCHECK tool, the building was evaluated being 9% under the metrics stablished by energy code.

Envelope Compliance Certificate

STRATEGIES FOR IMPROVED PROPOSAL:

Project Information 90.1 (2013) Standard

Energy Code: Project Title: Location:

A) The first strategy suggested would be reduce the total area of the buildings windows throughout the facades. In addition to that, thinking about different glazing alternatives, like the adoption of Low-E glazing could help to reduce the heat gain through radiation.

Houston, Texas 2a (weather data: USA_TX_Houston-Bush.Intercontinental.AP.722430_TMY3.epw) New Construction 33% EnergyPlus Version 8.1.0.009

Climate Zone: Project Type: Vertical Glazing / Wall Area: Performance Sim. Specs:

Construction Site:

Owner/Agent:

Building Area

B) Providing shading devices, especially for the walls located on the south and east facades would also reduce the direct radiation into the windows, helping to mitigate aspects as glare and excessive luminosity on the Studio units’ windows.

Designer/Contractor:

Floor Area

1-1 (Multifamily) : Residential 2-2 (Retail) : Nonresidential

C) Other strategy would be to increase the resistance of other parts of the envelope; more specifically, improving the wall’s resistance to conduction. This could be achieved maintaining the wall’s materiality, but increasing its thickness.

28761 7922

Envelope Assemblies Assembly

Gross Area Cavity or R-Value Perimeter

Floor 1: Slab-On-Grade:Unheated, [Bldg. Use 2 - 2] (c) Floor 2: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1]

455 1765

-----

Floor 3: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1] Floor 4: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1]

4109 4109

-----

Floor 5: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1] Floor 6: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1]

4109 4109

-----

Floor 7: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1]

4109

Floor 8: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1]

4109

Floor 9: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1] Roof 1: Attic Roof with Steel Joists, [Bldg. Use 1 - 1] NORTH Exterior Wall N: Concrete Block:8", Partially Grouted, Cells Empty, Normal Density, Furring: None, [Bldg. Use 1 - 1] small window: Metal Frame:Operable, Perf. Specs.: Product ID singleglazed bronze 2, SHGC 0.69, VT 0.52, [Bldg. Use 1 - 1] (b) Window 5: Metal Frame:Fixed, Perf. Specs.: Product ID single-glazed bronze 2, SHGC 0.69, VT 0.52, [Bldg. Use 1 - 1] (b) EAST Exterior Wall E: Concrete Block:8", Partially Grouted, Cells Empty, Normal Density, Furring: None, [Bldg. Use 1 - 1] Window CTRL WL: Metal Frame:Operable, Perf. Specs.: Product ID single-glazed bronze 2, SHGC 0.69, VT 0.52, [Bldg. Use 1 - 1] (b)

Cont.

R-Value

Proposed U-Factor

Budget UFactor(a)

---

0.730

0.730

30.0 30.0

0.030 0.030

0.087 0.087

30.0 30.0

0.030 0.030

0.087 0.087

30.0

0.030

0.087

---

30.0

0.030

0.087

---

30.0

0.030

0.087

4109

---

4109

0.0

30.0 38.0

0.030 0.026

0.087 0.027

11108

---

1.1

0.297

0.123

905

---

---

1.300

0.650

129

---

---

1.300

0.570

1732

---

1.1

0.297

0.123

172

---

---

1.300

0.650

Assembly

Exterior Wall S: Concrete Block:8", Partially Grouted, Cells Empty, Normal Density, Furring: None, [Bldg. Use 1 - 1] Smaller window: Metal Frame:Operable, Perf. Specs.: Product ID single-glazed bronze 2, SHGC 0.69, VT 0.52, [Bldg. Use 1 - 1] (b) Bigger window: Metal Frame:Operable, Perf. Specs.: Product ID singleglazed bronze 2, SHGC 0.69, VT 0.52, [Bldg. Use 1 - 1] (b) Door 3: Glass (> 50% glazing):Metal Frame, Entrance Door, Perf.

Specs.: Product ID single-glazed bronze 2, SHGC 0.69, VT 0.52, [Bldg.

Use 1 - 1] (b) WEST Exterior Wall W: Concrete Block:8", Partially Grouted, Cells Empty, Normal Density, Furring: None, [Bldg. Use 1 - 1]

Gross Area Cavity or R-Value Perimeter

Cont.

R-Value

Proposed U-Factor

Budget UFactor(a)

7276

---

1.1

0.297

0.123

1033

---

---

1.300

0.650

3710

---

---

1.300

0.650

1334

---

---

1.300

0.770

1700

---

1.1

0.297

0.123

(a) Budget U-factors are used for software baseline calculations ONLY, and are not code requirements. (b) Fenestration product performance must be certified in accordance with NFRC and requires supporting documentation. (c) Slab-On-Grade proposed and budget U-factors shown in table are F-factors.

Envelope FAILS: Design 9% worse than code

SOUTH

Project Title: Data filename:

Report date: C:\ARCH_EnvTech\COMCHECK\Tatiana Luzardo-Assignment 6- baseline2.cck

Page

10/27/16 1 of

10

Envelope analysis

6

Proposal : Applying Strategies

WEST FACADE

SOUTH FACADE

EAST FACADE

NORTH FACADE

PROPOSAL

Windows - Glass Grondzik, Walter T. 2010. Mechanical and electrical equipment for buildings. Hoboken, N.J.: Wiley.

Page 1627

Walls

Alfonso E. Hernandez - class presentation page 44

PROPOSAL

PROPOSAL

Shading device: Projection Factor A=2 meter B= 2.30 meters PF=A/B PF=0.86

Shading device: Projection Factor A=2 meter B= 1.27 meters PF=A/B PF=1.57

SHADING DEVICES PERSPECTIVE: NORTH AND WEST FACADES NORTH FACADE WINDOWS REDUCTION

Envelope analysis

6

Proposal : Results Analysis COM check

Last page illustrates the strategies applied to the building’s envelope, in order to make it more energy efficient.

Software Version 4.0.5.1

The reductions in the windows area affected the project following the following percentages:

Envelope Compliance Certificate

• • • •

Project Information Energy Code: Project Title:

90.1 (2013) Standard

Location: Climate Zone:

Houston, Texas 2a (weather data: USA_TX_Houston-Bush.Intercontinental.AP.722430_TMY3.epw) New Construction 18% EnergyPlus Version 8.1.0.009

Project Type: Vertical Glazing / Wall Area: Performance Sim. Specs:

Construction Site:

Owner/Agent:

Building Area

The general ration of windows versus walls in the project was reduced by approximately 55% (baseline being 33% to 18% on the proposal).

The utilization of shading devices were effective as well, providing shading and the avoidance of excessive exposure to sunlight on the south façade. We were also able to improve the building efficiency by reducing wall heat gain through conduction (by keeping the same material, concrete blocks, but changing its thickness from 8” to 12”) and glazing gains through radiation (applying Low-e glass to the windows with a lower solar heat gain coefficient – SHGC – and improving the visible light transmittance – VTL – in 0.04 points, compensating the reduction in the windows area applied in the project as a whole).

Designer/Contractor:

Floor Area

1-1 (Multifamily) : Residential 2-2 (Retail) : Nonresidential

Studio windows(Big windows) : 50% reduction 1 Dormitory windows: 17% North façade windows: 50% First Floor doors: 50%

PERSPECTIVE: SOUTH AND EAST FACADES SHADING DEVICES

28761 7922

Envelope Assemblies Assembly

Floor 1: Slab-On-Grade:Unheated, [Bldg. Use 2 - 2] (c)

Gross Area Cavity or R-Value Perimeter

Cont.

R-Value

Proposed U-Factor

Budget UFactor(a)

455

---

---

0.730

0.730

Floor 2: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1]

1765

---

Floor 3: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1] Floor 4: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1] Floor 5: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1] Floor 6: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1]

4109 4109 4109 4109

---------

30.0 30.0 30.0 30.0

0.030 0.030 0.030 0.030

0.087 0.087 0.087 0.087

Floor 7: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1] Floor 8: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1]

4109 4109

-----

30.0 30.0

0.030 0.030

0.087 0.087

30.0

0.030

0.087

Floor 9: Concrete Floor (over unconditioned space), [Bldg. Use 1 - 1]

4109

---

Roof 1: Attic Roof with Steel Joists, [Bldg. Use 1 - 1]

4109

0.0

30.0 38.0

0.030 0.026

0.087 0.027

11108

0.0

1.3

0.222

0.123

452

---

---

0.300

0.650

65

---

---

0.300

0.570

1732

0.0

1.3

0.222

0.123

143

---

---

0.300

0.650

NORTH Exterior Wall N: Concrete Block:12", Solid Grouted, Normal Density, Furring: Metal, [Bldg. Use 1 - 1] small window: Metal Frame:Operable, Perf. Specs.: Product ID doubleglazed low-e 8, SHGC 0.44, PF 1.57, VT 0.56, [Bldg. Use 1 - 1] (b) small window base: Metal Frame:Fixed, Perf. Specs.: Product ID double-glazed low-e 8, SHGC 0.44, VT 0.56, [Bldg. Use 1 - 1] (b) EAST Exterior Wall E: Concrete Block:12", Solid Grouted, Normal Density, Furring: Metal, [Bldg. Use 1 - 1] Window CTRL WL: Metal Frame:Operable, Perf. Specs.: Product ID double-glazed low-e 8, SHGC 0.44, PF 1.57, VT 0.56, [Bldg. Use 1 1] (b)

Assembly

SOUTH Exterior Wall S: Concrete Block:12", Solid Grouted, Normal Density, Furring: Metal, [Bldg. Use 1 - 1] Smaller window: Metal Frame:Operable, Perf. Specs.: Product ID double-glazed low e 8, SHGC 0.44, PF 1.57, VT 0.56, [Bldg. Use 1 1] (b) Bigger window: Metal Frame:Operable, Perf. Specs.: Product ID double-glazed low-e 8, SHGC 0.44, PF 0.86, VT 0.56, [Bldg. Use 1 1] (b) Door 3: Glass (> 50% glazing):Metal Frame, Entrance Door, Perf.

Specs.: Product ID double-glazed low-e 8, SHGC 0.44, PF 1.57, VT 0.56, [Bldg. Use 1 - 1] (b) WEST Exterior Wall W: Concrete Block:12", Solid Grouted, Normal Density, Furring: Metal, [Bldg. Use 1 - 1]

Data filename:

Proposed U-Factor

Budget UFactor(a)

7276

0.0

1.3

0.222

0.123

853

---

---

0.300

0.650

1846

---

---

0.300

0.650

667

---

---

0.300

0.770

1700

0.0

1.3

0.222

0.123

Envelope PASSES: Design 1% better than code Envelope Compliance Statement Compliance Statement: The proposed envelope design represented in this document is consistent with the building plans, specifications, and other calculations submitted with this permit application. The proposed envelope systems have been designed to meet the 90.1 (2013) Standard requirements in COM check Version 4.0.5.1 and to comply with any applicable mandatory requirements listed in the Inspection Checklist.

Report date: C:\ARCH_EnvTech\COMCHECK\Tatiana Luzardo-Assignment 6- improve2.cck

Cont.

R-Value

(a) Budget U-factors are used for software baseline calculations ONLY, and are not code requirements. (b) Fenestration product performance must be certified in accordance with NFRC and requires supporting documentation. (c) Slab-On-Grade proposed and budget U-factors shown in table are F-factors.

Name - Title

Project Title:

Gross Area Cavity or R-Value Perimeter

Page

Signature

Date

10/27/16 1 of

10

Envelope analysis

6

7

HVAC Calculations

HVAC

1. You are designing a chilled water cooling coil for a new fan coil unit serving an office space. You’ve completed a load calculation and determined that the peak load is 5 tons of cooling. Your building chilled water system runs at 42F supply and 54F return temperatures at design conditions and you would like your coil to use the same design temperatures in sizing the coil. What is the peak chilled water flow rate required in GPM to meet the cooling load?Peak of cooling = 5 ton 42° F supply 54° F return Δt = 54-42= 12° F Water flow?

GMP = Qtot (tons) x 24/Δt GMP = 5 x 24/12 = 5 x 2 = 10GMP The resulting chilled water flow necessary to provide 5 tons of cooling is 10 GMP. The water flow through the coil allows the exchange of heat between air in the environment and the coil surface – sensible and latent cooling. As air hits the coil surface, heat is removed from it and transferred to the coil surface, resulting in water vapor (latent cooling). The temperature of the air lowers as a result of the contact (sensible heat).

2. You tour a building with large water-cooled chillers. The cooling tower flow rate is reading as 1,200 GPM at design conditions, the temperature leaving the chiller condenser is 95F and the temperature entering the chiller condenser is 85F. What is the approximate cooling capacity of the system in tons of refrigeration using rule of thumb?

1200 GPM Leaving = 95° F Entering = 85° F Δt = 95-85 = 10° F Q=?

1200 = Q x 24/(95-85) 1200 = Q x 24/10 12000 = Q x 24 Q = 500 ton, but Rule of thumb: Δt = 10°F -> 3gpm/tons 1200 gpm/3 = 400 ton

3. You survey an operational building when you encounter a large VAV (variable air volume) air handler. You see from the nameplate data that the air handler is designed to handle a peak airflow rate of 20,000 cfm, however you see from the read-out on the supply fan’s variable frequency drive (VFD) that the fan is currently operating at half speed (10,000 cfm). You also see on the nameplate that the supply fan motor has a nominal size of 30 HP with a peak operating point of 26.5 brake HP (fans motors are normally rounded up to the next nominal size from the required power output). What is the required brake HP with the fan operating at half speed? Use the fan affinity laws and assume friction losses are negligible. q1/q2 = (n1/n2)(d1/d2) p1/p2 = (n1/n2)^3(d1/d2)^3 p1/p2 = (n1/n2 X d1/d2)^3 (n1/n2 X d1/d2) = (p1/p2) q1/q2 = (n1/n2 X d1/d2) = (p1/p2) 20000/10000 = ((26.5)/p2) 26.5/p2 = (20000/10000)^3 26.5 = (2)^3 x p2 P2 = 26.5/8 = 3.31 HP As the exercise proposes the re-evaluation of the brake horsepower in function of a decrease in the fan airflow rate and speed, we considered the affinity law to establish the relationship between airflow and power.

As fan speed appears in both flow rate calculations and brake horsepower, it was possible to conclude that powerhorse equals to the cube of flow rate, as demonstrated above. N1/N2 would remain the same for the two equations (fan speed for normal operation and to the half speed operation). D1/d2 would also be the same, as the diameter of the fan wheel would not change – the equipment remains the same.

The calculation of the cooling capacity in this exercise indicates a total of 500 ton, however utilizing the rule of thumb indicates the use of 3 gpm per ton. As the system’s reading is 1200gpm, we conclude that a total of 400 tons would be sufficient for this system.

HVAC

7

4. Using a psychrometric chart for Houston (assume sea level) and the design weather data for Houston Bush Intercontinental Airport, determine the dew point at summer design conditions of 0.4% for peak dry bulb and mean coincident wet bulb(provide image of the psychrometric chart) Utilizing the psychometric chart and the design weather data for Houston Bush Intercontinental airport, it was possible to get the Dew point temperature of 68°F. Dry bulb temperature and mean coincident wet bulb temperature were extracted from the 2013 ASHRAT Handbook – Fundamentals, DB = 97.3 and MCWB = 76.6 for the month of June (summer).

Knowing the dew point temperature is important to evaluate the conditions on which the humidity present in the air will condensate. This change in the state of air can lead to excessive moisture and mold inside of the conditioned environment.

HVAC

7

5. You are designing a duct system to meet the peak cooling load in an open office space. Your supply air temperature from the air handling unit is 55F and you are trying to maintain a space setpointof 75F. What is the required airflow rate in cfm if the sensible cooling load in the space has been calculated at 120,000 Btu/hr?

Supply = 55 Maintain = 75 Δt = 75-55 = 20°F Cfm = ?

Sensible cooling load = 120,000 Btu/L Q = 1.08 x cfm x Δt 120,000 = 1.08cfm (20) 120,000 = 21.6 cfm Cfm = 120,000/21.6 = 5555.55 cfm In order to allow a decrease in temperature of 20°F, (sensible heat transfer), an airflow of 5,555.55 cfm is required.

HVAC

7

Thank You! TATIANA ZUCCO DA SILVA LUZARDO tatiana.luzardo@gmail.com