Engineering Building No W. 32 nd St. Chicago, IL 60616

Transcription

1 CAE 524: Building Enclosure Design Engineering Building No W. 32 nd St. Chicago, IL November 13, 2013 Performed By: Jay Shetty Firas Putros Gilberto Osornio

2 Table of Contents I) Building and Inspection Overview pg. 2 II) Building Enclosure Inspection pg. 3 III) Analysis of Building Enclosure Design/Drawings pg. 19 IV) Energy Modeling of Existing Conditions and Proposed Improvements pg. 20 V) Summary/Conclusion pg. 48 Page 1

3 Building and Inspection Overview: Building The Engineering Building No. 1 was designed in 1966 by the architect Myron Goldsmith and the engineering firm Skidmore Owings & Merrill. Construction of the building was completed in The Engineering 1 building is a 2 story, 120 x290 rectangular building with a basement. The basement has a larger footprint than the rest of the building. The foundation of the building is made of concrete bell caissons. Above the caissons are a concrete basement floor slab, reinforced concrete columns, and reinforced concrete foundation wall. Supported by the columns and foundation wall is the reinforced concrete slab of the 1 st floor. Sitting on the 1st Floor slab is the primary structural framing and the building enclosure exterior walls. The primary structural framing is comprised of steel beams and columns encased in concrete that support the 2 nd Floor concrete slab and the Roof deck. The typical section of the exterior walls of the building enclosure is basically comprised of single layer 3/8 plate glass framed with aluminum mullions, double wythe brick, and steel structural members. The brick wall is made of two wythes of 3.37 thick bricks and a.5 thick mortar joint between the two wythes, which form an 8 thick brick wall. Steel structural members are cast into the mortar joints of the brick wall. The aluminum window mullions are mechanically fastened to the steel members and are sealed with neoprene gaskets w/ adhesive. The glass is sealed to the mullions with typical glazing sealant. This typical section makes up the majority of the building perimeter. The entrances of the building are a storefront façade that is made up of large sections of 3/8 plate glass framed with aluminum mullions and steel structural members. The roof deck is made up of 1.5 corrugated metal decking, 1.5 rigid fiberglass, and 4 ply built up roofing. Inspection In order to evaluate the performance of this building, we started off by doing a general walkthrough of building exterior walls from both outside and inside of the building. During the walkthrough we took pictures of noticeable building defects and examples of poor building enclosure performance such as moisture infiltration. After this, we obtained a copy of the original engineering drawings from the IIT Facilities Department. We studied these drawings in order to gain a better understanding of how the building enclosure was constructed. During this process we were able to identify many construction details that have caused poor performance of the building envelope. The next phase was to take infrared photos of the exterior of the building in order to visually display the poor thermal performance of the building envelope. Using all of the information we gathered in our inspections, we were then able to created computer simulations and create a proposed list of improvements to the building enclosure. Page 2

4 Building Enclosure Inspection: Thermal Imaging: Figure (1) Thermal picture at the east elevation shows the heat loss mainly is through the windows Figure (2) Thermal picture at the south entrance. In addition to red surfaces that represent the glass, warm surfaces indicated by the green surfaces are the door frame, the exposed steel columns and beams. Door opening directly to the outdoor allows a significant amount of heat loss that is invisible for the thermal imaging Page 3

5 Figure (3) Thermal picture at the south west corner shows significant heat loss through the steel column at the corner Figure (4) Thermal picture at north elevation shows the heat loss through the spaces that are heated and occupied in the ground floor compared with spaces on the second floor that were not occupied at the time Page 4

6 Figure (5) Thermal picture at the east elevation shows the warm air from the basement heating part of the façade Figure (6) Thermal picture at the north elevation shows a significant amount of heat loss through the glass, window frame, and exterior steel column in the occupied spaces Page 5

7 Figure (7) Thermal picture at north east corner shows the glass and the steel beam above the window have the same color and therefore the same heat loss rate Figure (8) Thermal picture at the west elevation indicates the greatest heat loss in this area of the facade is through the steel columns Page 6

8 Figure (9) Thermal picture shows the blinds effect on reducing the heat loss through the window glass. The window on the left has partially open blinds and the one on the right has closed blinds. However the window with the closed blinds still has heat loss at the top of the window Figure (10) Thermal picture at the roof shows the heat transfer from an occupied space in yellow and reddish Page 7

9 Figure (11) This is not actually heat loss, the roof is being heated by the exhaust air Figure (12) Thermal picture shows a big spot on the roof is heated by exhaust air from one of the HVAC equipment Page 8

10 Figure (13) Thermal picture at the roof shows a heat loss through the storm water piping to the roof drainage Figure (14) Thermal picture shows the heat loss through the steel pan underneath the cooling tower Page 9

11 Figure (15) Thermal picture from inside one of the classrooms shows how the blinds and the steel column have the same temperature. Figure (23) Temperature of different interior surfaces Page 10

12 Figure (24) Temperature of exterior surfaces Page 11

13 Air leakage and moisture penetration: Figure (17) Window sill rust is likely caused by condensation from the window or by a leak along the edge of the window frame The glass gasket seems to be replaced with low quality sealant therefore it seems that the main reason was a leak from the window that caused the rust on the window sill. The picture on the right is for newly painted sill and the rust starts to accumulate Figure (18) Storefront glass wall at the south entrance: the gasket begins to dry out, shrink, and crack. Because of the ultraviolet radiation and freeze thaw cycles, the elastic material degrades, much like an old rubber band. This allow in air, which in turn brings moisture and finally condensation. As the gaskets Page 12

14 further disintegrate, they may loosen and pull away from the frame. Glass mullions also appeared to be warped which may have compromised the sealant and gaskets. Figure (19) Leak at the bottom of the exterior door and storefront glass. The threshold was not set in sealant, the aluminum was attached to floor without any joint sealant, and the flooring was cracked. All of these things are allowing air and moisture infiltration. Crack and Metal Corrosion Metal corrosion Figure (20) Steel column corroded and created a hole that create an open bridge for air leakage, water penetration and heat loss Page 13

15 Figure (21) the window sill extrusion was warped and detached from the window frame because of the structure and frame movement. Therefore, the original sealant could not seal the larger gap Figure (22) the sealant of the window frame, the sill, the brick and the column is dried out and fall off Page 14

16 Figure (23) Uncontinuous backer rod was installed without setting it in sealant Page 15

17 Analysis of Building Enclosure Construction Drawings List of Poor construction details Flow of heat loss Exterior wall structural members completely penetrate the building enclosure thereby creating a direct thermal bridge from the outside environment to the inside environment. (This is the cause of the large heat losses in the steel members that were seen in the thermal imaging in figures 3,7,8,9) At the connection of window mullion to structural member, the building enclosure is made up of only a 3/8 thick steel flange ( this contributes to the large heat losses that were seen at the exterior steel members) Page 16

18 The top, bottom, and side mullions, which are not thermally broken, create a direct uninsulated metal thermal bridge around the brick and glass (also contributes to the large steel heat losses) The glazing is only a single 3/8 plate (This is why the greatest heat loss seen in the thermal imaging of the facade was from the windows) Structural steel supporting the typical windows create a thermal bridge through the brick Aluminum framing of storefront glass is not insulated or thermally broken There is a thermal bridge at the edge of the Second Story Floor through the exterior structural steel horizontal members and the concrete floor Page 17

19 The bottom flashing of the exterior brick wall is below grade which does not allow moisture absorbed by the brick to escape easily and water can build up in the cavity and leak into the interior of the building Side framing of roof creates a direct uninsulated metal thermal bridge to steel deck (detail 1/A 5) Page 18

20 No expansion joint where concrete stoop meets the 1 st story slab which creates cracking of flooring and warping of window sill mullions (which was photographed during the inspection, see figures 19 & 21) Plumbing for roof drains is not insulated and there is a thermal bridge to the drain assembly through the roof deck (The reason for the roof drain heat loss seen in figure 13) Page 19

21 Thermal bridge through roof deck to cooling tower metal pan (heat loss seen in figure 14) Page 20

22 Energy Modeling of Existing Conditions & Proposed Improvements Thermal and Condensation analysis of wall assemblies: Existing Wall Assembly The wall is composed by two layers of exposed brick masonry joined with mortar that we assumed with a density of 120 lb/ft3. The bricks are 3.75 in width with a conductivity k=8.4 Btu in/h ft2 F, and the steel beam was assumed with a density of 490 lb/ft3 and a conductivity k=0.25 Btu in/h ft2 F according to ASHRAE book of fundamentals 2007 table 4 chapter 29. Figure (34) Existing Wall assembly Figure (35) Existing Wall assembly Therm isothermal lines. Page 21

23 The isothermal lines show the temperature distribution in an even heat flow, showing no resistance to the thermal conductivity. Figure (36) Existing Wall assembly Therm simulation The gradient shown in the simulation demonstrates the uniform parameter of the heat flow through the material. Figure (37) Existing Wall assembly Therm simulation The colors evidence a higher temperature flow through the mortar sections of the wall and it is clear the thermal bridge by the increment of temperature. Figure (38) Therm Existing Wall R and U values. The U value calculated with Therm for the total length of the existing assembly is 1.06 Btu/h ft2 F and the R resultant factor is 0.93 h ft2 F/ Btu, this represents almost no resistance at all for the heat flow. Page 22

24 Figure (39) IES Apache existing wall assembly The existing wall was constructed in Apache, IES VE with a correction factor to resemble a similar assembly as the one calculated in Therm, the resultant U value was.56 Btu/h ft2 F minus the surfaces resistances to obtain a total R value of 0.93 h ft2 F/ Btu, that was used on the baseline simulation. Figure (40) IES Condensation Analysis Page 23

25 There is risk of condensation at the interior surface, in case of a cold day below 35.6 F and 60% outdoors RH assuming that the set points for the Room are 68F and 65 RH. When outside temperatures > 36 F do condensation risk is not presented. Proposed Wall Assembly The proposed wall is composed by two layers of exposed brick masonry joined with mortar that we assumed with a density of 120 lb/ft3. The bricks are 3.75 in and 1.75 in width with a conductivity k=8.4 Btu in/h ft2 F, and the steel beam was assumed with a density of 490 lb/ft3 and a conductivity k=0.25 Btu in/h ft2 F, a rigid XPS 1.0 in of continuous insulation R 10 was implemented between the brick layers and around the I steel beam to reduce the thermal bridge and increase thermal resistance, also the resulting cavity between the insulation and the I beam is filled with insulation foam R 20, all values are assumptions according to ASHRAE book of fundamentals 2007 table 4 chapter 29. Figure (41) Proposed wall assembly Figure (42) Proposed wall assembly Therm isothermal lines The isothermal lines show the temperature distribution along the insulation layer, there are no lines shown on the brick layers due to the required distance, this means that the temperature is even in the Page 24

26 brick layers that do not oppose resistance and the heat exchange is occurring in the XPS rigid insulation layer. Figure (43) Proposed wall assembly Therm thermal gradient The thermal gradient shows clearly that the heat exchange is happening in the insulation layer, there is still thermal bridge effect, but to increase the insulation could change the interior appearance of the Architecture. Figure (44) Proposed wall assembly Therm simulation The temperature is even in the whole assembly but on the steel I beam, there is still some heat flow occurring that affects the U value of the whole assembly. Figure (45) Therm Proposed Wall R and U values. Page 25

27 The U value calculated with Therm for the total length of the proposed assembly is 0.53 Btu/h ft2 F and the R resultant factor is 1.85 h ft2 F/ Btu, this is still a low resistance but a considerable increment on the Resistance from the original assembly. Figure (46) IES Apache Proposed Wall R and U values. The proposed wall was constructed in Apache, IES VE with a correction factor to resemble a similar assembly as the one calculated in Therm, the resultant U value was 0.36 Btu/h ft2 F minus the surfaces resistances to obtain a total R value of 1.87 h ft2 F/ Btu, that was used on the proposed simulation. Existing Glazing Assembly The existing glazing is composed by one single pane clear 6mm floated glass assumed with a conductivity k=87.3 Btu in/h ft2 F, aluminum frame and jambs with a density of 171 lb/ft and a conductivity of 128 Btu in/h ft2 F, the steel beam was assumed with a density of 490 lb/ft3 and a conductivity k=0.25 Btu in/h ft2 F. This offers no resistance and it is the critical element of the building due to the window to wall ration above 50% of the total facades. All values are assumptions according to ASHRAE book of fundamentals 2007 table 4 chapter 29. Page 26

28 Figure (47) Existing Glazing assembly Figure (48) Existing Glazing assembly Therm isothermal lines The isothermal lines show some flow through the sealant and the cavity of the frame, it is not clear the temperature difference but it can be intuited that the thermal resistance is null. Page 27

29 Figure (49) Existing Glazing assembly Therm thermal gradient The thermal gradient shows clearly that the heat flow through the window and aluminum is higher than the temperature flow through the I beam, There is no resistance at the assembly and the heat is scaping directly trough the window. Figure (50) Existing Glazing assembly Therm simulation The temperature is even in the glaze, in the aluminum we can perceive an increment on the flow. Page 28

30 Figure (51) Therm Existing Glazing assembly R and U values. The U value calculated with Therm for the total length of the existing glazing assembly is 1.18 Btu/h ft2 F and the R resultant factor is 0.84 h ft2 F/ Btu, this represents almost no resistance at all for the heat flow. Figure (52) IES Apache existing glazing assembly The existing glazing assembly was constructed in Apache, IES VE just including a single pane of clear floated glass with a thermal conductivity of 7.34 Btu in/h ft2 F, to obtain a similar R value according to the Therm simulation R=0.87 h ft2 F/ Btu, the Frame is Steel and the surface resistances are reduced to a minimum. Page 29

31 Figure (53) IES Apache existing glazing assembly derived parameters The existing glazing assembly has a SHGC of and a Net U value including frame of 1.11 Btu /h ft2 F, in the simulation the outside and inside surface air film resistances are also included. Proposed Glazing Assembly The proposed glazing is composed with the existing base of one single pane clear 6mm floated glass assumed with a conductivity k=87.3 Btu in/h ft2 F, aluminum frame and jambs with a density of 171 lb/ft and a conductivity of 128 Btu in/h ft2 F, the steel beam was assumed with a density of 490 lb/ft3 and a conductivity k=0.25 Btu in/h ft2 F. It is improved by a double pane glazing unit filled with Argon gass that accounts for a cavity resistance of R=2.1, the unit is located behind the existing glass, with a PVC frame and a 1 inch of rigid XPS insulation layer to reduce the thermal bridge through the I steel beam, the remaining cavity is filled with Styrofoam. All values are assumptions according to ASHRAE book of fundamentals 2007 table 4 chapter 29. Page 30

32 Figure (54) Existing Glazing assembly Figure (55) Proposed Glazing assembly Therm isothermal lines The isothermal lines show an even flow through the insulated layer and also an even flow through the Argon cavity, the thermal exchange occurs as it is expected through the higher R value materials. Page 31

33 Figure (56) Proposed Glazing assembly Therm thermal gradient The thermal gradient shows an accentuated heat flow from the inside layer thorough the insulated materials, the thermal bridge is reduced and the temperature distribution is even through the external layer composed by the steel, aluminum and air cavity from the existing glass to the double glazed unit. Page 32

34 Figure (57) Proposed Glazing assembly Therm simulation The thermal bridge occurring in the aluminum and steel elements is almost confined, there is a small heat flow through the aluminum corner to the inside of the space. Figure (58) Therm Proposed Glazing assembly R and U values. The U value calculated with Therm for the total length of the proposed glazing assembly is Btu/h ft2 F and the R resultant factor is 4.13 h ft2 F/ Btu, this is an excellent resistance for a window assembly, because it could be considered almost as a high performance triple pane window. Page 33

35 Figure (59) IES Apache proposed glazing assembly The existing proposed glazing assembly was constructed in Apache, IES VE with a triple pane glazing unit, each glass has a thermal conductivity of 7.34 Btu in/h ft2 F, the cavities with a thermal resistance of R=1.7, to obtain a similar R value according to the Therm simulation R=4.34 h ft2 F/ Btu. Page 34

36 Figure (60) IES Apache proposed glazing assembly derived parameters The existing proposed assembly has a SHGC of 0.55 and a Net U value including frame of 0.26 Btu /h ft2 F, in the simulation the outside and inside surface air film resistances are also included. Page 35

37 Dynamic Thermal modeling Using IES Virtual Environment: Model Geometry For the purpose of this study the basement was disregard to make more evident the energy savings impact due to the envelope improvements that were proposed for the building, the geometry of the model is simple divided in five zones each floor with a partition at 15 ft to account for solar incidence variation. Figure (61) Dynamic Thermal Model Geometry Screenshot Baseline Assumptions The Thermal Template was settled up with a constant schedule from 8:00 am to 6:00 pm, the occupancy is established according to ASHRAE standards of educational facilities, the set point for cooling is 75 F and the one for Heating was input as 68 F, it uses a regular HVAC system generated by default with a minimum air flow of 0.05 cfm/ft2 and an additional free cooling capacity of 0.4 ACH. A default system is used because the purpose of the study is to evaluate the envelope performance disregarding the type of HVAC system, and this system as all the baseline assumptions do not vary between Baseline and Proposed model. Page 36

38 Figure (68) Occupancy profile Figure (62) Thermal Template set points and schedule Page 37

39 Figure (63) Default system Figure (64) Lighting gains Page 38

40 The lighting gains are according to 1.2 W/ft2, with a radiant factor of 0.45, they follow the occupancy schedule, the simulation was made with and without a Dimming strategy in order to perceive if there are any daylight impacts due to the increase of glazing and reduction of the SHGC. Figure (65) Equipment gains The equipment gains are 0.5 W/ft2, with a radiant factor of 0.22 and a maximum power consumption of.5 W/ft2, they follow the occupancy schedule, they can be identified as miscellaneous. Page 39

41 Figure (66) People gains The people sensible gain is 250 Btu/h person and the Latent gain 200 Btu/h person with an occupancy density of 167 ft2/person, they also follow the occupancy profile ASHRAE 8am 6 pm and no lunch. Figure (67) Air Exchanges Page 40

42 In the model the assumption of Infiltration is accounted for ach. Figure (68) Solar Incidence In the baseline model it is perceived that the solar incidence is higher though the roof and the south façade, the glazing area will be a determinant factor of the reduction of the heating loads during summer, although some daylight savings can be obtain. Page 41

43 Figure (69) Daylight In the baseline model the 15ft zone affected by daylight can take advantage of the high iluminance factors, most of the area shows levels above 55 fc due to the large area of glazing and the height of the windows distribution. Figure (70) Dimming profile Page 42

44 A Dimming profile is used with a logic as if(e1>33, 0.38, if(e1>16.5, 0.71, 1.0)), this means that if the iluminance over the work plane area is registered by the sensor in a value of 33 foot candles or more then the light will operate at 38% ratio, and if the iluminance is above 16.5 foot candles the room will use electric light in a 71% ratio. Example of Savings from Daylight dimming on Existing Building Figure (71) Baseline Model Electric Light yearly energy consumption In this plot it was compared the baseline model (existing building) in two configurations, with and without a dimming strategy, the use of proportional electric light control accounts for more than 10% energy savings in the electric light energy use. Page 43

45 Figure (72) Baseline Model, Electric Light peak day energy consumption The reduction of the daylight use with dimming strategy is clearly perceived in the daily plot. Energy Consumption The baseline model (existing assemblies) has a total Energy consumption of 4,408 MBtu/year with the Boilers accounting for 1,799MBTu/year and Chillers for 504 MBtu/year, the proposed model consumes a total of 3,399 Mbtu/year, 843 MBtu/year of Boilers and 465 MBtu/year on Chillers. This represents a 22% of energy reduction with the proposed improvements to the envelope. Figure (73) Baseline Model, Energy Consumption Breakdown Page 44

46 Figure (74) Proposed Model, Energy Consumption Breakdown Figure (75) Baseline Model, Loads Summary Page 45

47 Figure (76) Proposed Model, Loads Summary The Baseline Building Energy Use Intensity of EUI =68.95 kbtu/ft2 yr while the Proposed accounts for EUI =51.54 kbtu/ft2 yr, the energy savings are clear just with the improvement of the glazing areas and wall assemblies. Thermal Comfort The perimeter zone facing south in the second floor of the Thermal model was used as worst case scenario to analyze the comfort rates, the percentage of people dissatisfied above 60% under unoccupied hours is higher in the baseline, shown in color red, the PPD above 10% is similar in both models under occupied hour, because of the space conditioning, this means that the comfort is met even with the less use of energy due to the envelope performance during occupied hours, and the comfort is improved by the envelope on unoccupied moments without mechanical conditioning. Figure (77) Baseline Model, Percentage of People Dissatisfied Page 46

48 Figure (77) Proposed Model, Percentage of People Dissatisfied Figure (78) Baseline Model, Plot of simulated hours inside comfort range Figure (78) Proposed Model, Plot of simulated hours inside comfort range Page 47

49 Summary: Majority of heat loss on exterior from windows and steel member from thermal imaging Little heat loss occurring thru roof per thermal imaging Single pane windows largest source of heat loss Thermal bridging structural steel thru exterior walls were second largest cause of heat loss Several poor construction details which cause moisture infiltration THERM simulations showed large heat loss thru aluminum mullions Walls were improved by adding continuous insulation inside brick wall which also cover steel Proposed wall assembly improvements showed a slight improvement in R value Glazing was improved by adding a double pane argon unit to the inside of the exsting plate glass and insulation over Al mullions Proposed Glazing improvements showed a large improvement in R Value Energy performance simulations show a reduction of loads and a energy usage reduction of 20% Occupant comfort level was increased by these improvements References: ASHRAE Fundamentals 2007 ASHRAE 62.1, Ventilation for Acceptable Indoor Air Quality ASHRAE 55, Thermal Environmental Conditions for Human Occupancy ASHRAE 90.1, Energy Standard for Buildings Straube, J. & Bernett, Building Science for Building Enclosures Page 48