Shanahan Building Retrofit

towards ZERO ENERGY

Eleni Katrini | Kristen Elizabeth Magnuson

Contents Introduction .................................................................................................................................................... 5 Objective ......................................................................................................................................................... 5 Required Codes and Standards ....................................................................................................................... 6 a. Urban Redevelopment Authority Requirements .................................................................................... 6 b. ENERGY STAR速 for Homes Version 3.0, IECC 2009 and 2012 ................................................................. 7 Location and Climate Data .............................................................................................................................. 7 The Shanahan Building .................................................................................................................................... 8 a.

Thermal boundary ............................................................................................................................... 8

b.

Apartment: Unit 5A ............................................................................................................................. 9

Changes on the building Envelope .................................................................................................................. 9 a.

Infiltration ............................................................................................................................................... 9

b.

Exterior Walls .......................................................................................................................................... 9

c.

Roof ....................................................................................................................................................... 11

d.

Glazing ................................................................................................................................................... 11

e.

Floor above unconditioned space ......................................................................................................... 13

Garage ........................................................................................................................................................... 14 Appliances and Lighting ................................................................................................................................ 14 a.

Appliances [Refrigerator, Dishwasher, Dryer, Range].............................. Error! Bookmark not defined.

b.

Lights ..................................................................................................................................................... 14

Mechanical equipment ................................................................................................................................. 15 1.

Californian Loop System........................................................................................................................ 15

a.

Heat pumps ........................................................................................................................................... 16

b.

Boilers.................................................................................................................................................... 17

c.

HRV and Ventilation .............................................................................................................................. 17

d.

Leakage ................................................................................................................................................. 17

Natural resources .......................................................................................................................................... 18 1.

Solar Heating ......................................................................................................................................... 18

HERS rating and Energy Charts ..................................................................................................................... 19 1.

HERS rating, site EUI + Design Loads ..................................................................................................... 19

2.

Energy Spreadsheets ............................................................................................................................. 20

Conclusions ................................................................................................................................................... 21 References........................................................................................................ Error! Bookmark not defined.

Introduction The scope of this project was to study, analyze, and push an old brick masonry building, currently slated for retrofit, towards net zero energy. The building selected for study, the Shanahan Building at 1801 Forbes Ave. near downtown Pittsburgh, was originally a biscuit bakery that has been used as a warehouse and storage building for the past two decades. Currently, FortyEighty Architecture is developing architectural plans for Action Housing to convert the space into 43 new, low-energy, affordable residential units.

Attempting to a push an existing building of this nature towards zero energy proved to be quite a challenge, considering both the limitations inherent in a renovation project and the multi-faceted approach necessary in designing a zero energy building. When compared to new construction, net zero renovations are by far more difficult to achieve, yet there is a far larger need to renovate existing buildings. Thus, the appeal of this project was the motivation to contribute to revitalizing a city core through contributing to a knowledge base focused on zero energy solutions and strategies. Every renovation project pushing towards zero energy will serve as teaching tools for further renovation projects. Because FortyEighty Architecture's proposed architectural drawings were planned and drafted with energy efficiency in mind, implementation of zero energy strategies proved to be that much more difficult to attain.

Objective Objectives of the project included:  

  

Understanding the existing building envelope, its mechanical systems, and analysing all aspects of the building from a sustainable point of view.

Understanding URA's requirements and what those requirements meant in terms of codes and standards which the building was required to meet—in particular what it takes to earn the ENERGY STAR®® Understanding energy use in the apartment considered the building's worst case scenario.

Modeling the conditions of this worst-case (baseline) apartment in REM Rate 12.96, based on FortyEighty Architecture’s drawings.

Developing strategies and experimenting with ideas which to push this apartment towards net zero while complying with IECC 2009 and all other performance targets set forth in ENERGY STAR® v3.0. for New Homes.



  

Analyzing the building assemblies in the architectural drawings and suggesting higher performing assemblies; performance of each assembly was verified through testing each ones' effect on energy consumption and observing the associated HERS score in REM Rate.

Selecting appliances with the highest energy efficiency which was still in accordance with the architectural specifications.

Resizing parts of the mechanical system, calculating Solar Hot Water and modeling them one by one in REM Rate.

Compiling all proposals into a single model in REM Rate and analyzing results in terms of a HERS score and annual energy consumption.

Throughout carrying out these objectives, it was realized that REM Rate poses serious limitations when attempting to model a multifamily building, in fact it is impossible to model any building greater than 3 floors. Aside from the 3 floor limitation, one major obstacle was the fact that the heating, cooling, and hot water systems in the building are shared systems and therefore not sized for a single home, which is the way that REM Rate is geared. Because of these limitations, a series of assumptions had to be made in order for the model to accurately represent the energy use of the studied unit. Achieving a “Pass” rating for ENERGY STAR® for Homes Version 3.0 proved to be quite a difficult task to achieve.

Required Codes and Standards a. Urban Redevelopment Authority Requirements The Urban Redevelopment Authority of Pittsburgh [URA] is Pittsburgh’s economic development agency and is dedicated to improving the city’s neighborhoods. URA relates to a great variety of projects from mixeduse developments to housing construction and rehabilitation (URA, 2011). The Shanahan building is one of URA’s current projects, and, therefore must conform to the stringent requirements for energy efficient new homes set forth in the URA guidelines. The most important aspects of the guidelines are outlined below: 

All new residential construction projects must earn the ENERGY STAR®®



ENERGY STAR®® for New Homes Program incorporates Checklist requirements (below) and URA requirements for quality HVAC installation



ENERGY STAR® homes are at least 15% more energy efficient than those meeting the 2004 International Residential Code (IRC), and typically 20–30% more efficient than standard homes.



Third–party verification by a certified Home Energy Rater is required.



Beginning January 1, 2012, the following checklists will be required to attain ENERGY STAR® (they will replace the currently required Indoor airPLUS checklist) ◦ Thermal Enclosure System Rater Checklist (currently being enforced) ◦ HVAC System Quality Installation Contractor Checklist ◦ HVAC System Quality Installation Rater Checklist

◦ Water Management System Builder Checklist 

All homes with permit date after January 1, 2012 and completion date beyond January 1, 2012 may qualify under Version 3.0 of the guidelines.

b. ENERGY STAR® for Homes Version 3.0, IECC 2009 and 2012 Because URA mandates the earning of ENERGY STAR®®, the first task was to understand how the building was to achieve this requirement. In researching this, it was realized that there is more than one way by which a building can do so. For the building in study, the path options available are certification under the New Home Program (v3.0) or the Multi Family High Rise Program (MRHR, v1.0). The decision came down to weather the building would provide 50% or more of its domestic hot water with solar heating. Because the requirements for meeting the latter program seemed much less stringent (need only be designed to be at least 15% more energy efficient than MFHR buildings built to ASHRAE Standard 90.1-2007) than the former, and, considering the nature of this project's ultimate goal of zero energy, it was determined that the building would be modeled to conform to the performance targets set forth in New Homes v3.0. Implicit in the earning of this certification is the adherence to the requirements contained in IECC 2009. A further goal of the proposed zero energy case was to adhere to the stricter requirements of IECC 2012. The major changes between 2009 and 2012 which the Department of Energy estimates will increase energy efficiency which affected this project include: 

building thermal envelope



infiltration control



wall insulation with structural sheathing

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ventilation fan efficiency

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lighting



air distribution systems



hot water pipe insulation and length

Location and Climate Data The Shanahan building is located in downtown Pittsburgh on Forbes Avenue. It is on a corner lot, and bordered by Forbes Avenue to the South, Miltenberger Street to the West and Watson Street to the North. It is one of the highest buildings around, and the roof, therefore, is not shaded by taller, surrounding buildings. The latitude of the plot is N40°58’52.32” and the longitude is W79°26’19.68”.

Based on IECC 2009, Pittsburgh falls into climate zone 5A. Pittsburgh’s climate is cold and humid. It is a heating-based design climate. Average temperatures range from 25°F to 80°F. Relative humidity ranges between 30-70% most months and often surpasses 70%. Hence, great attention was paid on properly insulating the building, minimizing the glazing U factor, as well as understanding the best practices for dealing with humidity—which proved especially important for a masonry construction renovation. For the summer months, natural and fan forced ventilation, as proposed by Climate Consultant, were taken into consideration.

The Shanahan Building a. Thermal boundary The Shanahan building is a five-storey building with a full below-grade basement. Based on the renovation drawings, a tenants’ storage room and a utility room with mechanical equipment is planned for the basement. Aside from the garage which takes up the majority of it, the first floor will also contain the building's lobby along with a resident lounge, a community room, the laundry room, and two offices. The remaining 4 floors will contain a total of 43 new apartment units. On the fifth floor, the apartments will be double height; hence they will be of a larger volume compared to the ones on the floors below. Of the 43 units, 35 are one-bedroom and 8 are two-bedroom apartments. Based on these numbers, it was assumed that the total occupancy of the building would be 94 residents—each unit's occupancy was counted as the number of bedrooms plus one occupant.

The building’s thermal boundary includes the all of the top four floors as well as the first floor except for the garage. Though it is outside of the thermal boundary, the garage is heated in order to prevent freezing in the winter. The window to floor area ratio is 23.3%. The majority of the glazing is on the west and south façade, with window-to-wall ratios 35.5% and 37.3% accordingly. The north façade has a window-to-wall ratio of 8% and the east façade 8.5%.

b. Apartment: Unit 5A In order to test the building to ensure that it conforms to all ENERGY STAR®® requirements discussed previously, Unit 5A, was modeled in REM Rate Version 12.96. Because REM Rate does not allow the modeling of a multifamily building with more than 3 floors, the way in which to demonstrate compliance with ENERGY STAR® requirements is to prove that one apartment per floor will comply. ENERGY STAR® states that if one apartment per floor meets the requirements, then the whole building would meet ENERGY STAR® requirements, too. It was decided to model the “worst case scenario” apartment in terms of energy loads, which was unit 5A. When compared to the rest of the units, it has the greatest area exposed to the exterior [three facades and roof], and, additionally, with a doubleheight, it is one of the apartments with the largest volume. It is on the 5 th floor of the building and has two bedrooms and a mezzanine. Its conditioned area is 1,433 ft² and its conditioned volume is 30,809 ft³. The window-to-wall ratio is 12%, with 204.7 ft² of glazing on the South façade and 40 ft² on the North façade. The window-to-floor area ratio for the entire unit is 17%.

View of the fifth floor

Changes on the building Envelope a. Infiltration Per IECC 2009, infiltration should be equal or less than 5 ACH at 50 pascals. This is the input rate which was modeled in the REM Rate baseline case. Because there must be certain assumptions made on the infiltration of the modeled building, it was determined that the building would be built to “tight” standards per the Stein Reynolds text and therefore be able to achieve 5 ACH at 50 pascals for the baseline model. With the proposed infiltration-reduction techniques discussed in the following scetions, it was decided that proposed model would be able to meet 3 ACH at 50 pascals, which is the performance target set forth in IECC 2012.

b. Exterior Walls All above grade walls are comprised of three wythes of solid masonry. The baseline wall assembly includes 3 5/8” steel studs with 3” (minimum) of closed cell polyurethane foam in the cavity and gypsum board as the interior finish. The total R value is 22.98 ft² °F h/Btu [U-Value: 0.04 BTU/ft² °F h]. While it is advisable to hold the steel studs off of the masonry wall (as shown in the architectural drawings) in order to eliminate conductive bridging transfer which would take place between the studs and the masonry, additional consideration was given to how to treat the cavity insulation, discussed below.

Considering the well-known challenges with insulating existing masonry from the inside, the first aspect of the building envelope considered was the wall assembly. Much care was given to understanding how to best treat the existing masonry in order to prevent freeze-thaw damage and/or decay of the embedded wood structure, both related to moisture control. The addition of insulation must take indoor

thermal comfort into consideration without drastically changing the temperature gradient of the wall assembly. When considering the choice of an insulation material, it was realized that sprayed polyurethane foam is a popular choice for a number of reasons. It provides an excellent, necessary air tight barrier and works well with the irregularity of the brick surface. Most importantly, the spray foam acts as a moisture barrier; any amount of rain penetration is localized and controlled by the foam. This means that all interior finishes will be protected and that water will not run down and collect at the structural floor pocket. Any water that is absorbed into the masonry can dry to the outside or wick to the inside, where it will diffuse through the semi-permeable spray foam. This understanding came from consulting various sources (Colantonio) (R.S.Dumont, L.J.Snodgrass, D.Hill, M.D.Goncalves, 2001) (M.Goncalves, 2001) (J.Straube, 2009) (C.Schumaker, 2007). After a consultation with Ibacos, it was determined that a spray foam thickness of over 3 inches would not be cost effective, but that a combination of 2” of spray foam with a high density fiberglass batt may be the best practice to follow in terms of buildability and cost. The strategy decided upon was one inch of continuous foam directly against the brick to create an unbroken air barrier. The second inch of spray foam would overlap with the framing members and would effectively be considered cavity insulation. After the polyurethane foam, 5” (5-1/2” roll compressed to 5”) of high density fiberglass batt insulation would be used. The assembly is finished with gypsum board attached to 6”, 25 gauge steel studs. The total R-Value is 32.3 ft² °F h/Btu [U Value: 0.03 BTU/ft² °F h]. According to the REM Rate results, this additional assembly would result into a 6.4% decrease in annual energy consumption.

91.7 mmBTU/yr

85.8 mmBTU/yr

c. Roof Because roofs in cold climates are particularly important part of the building envelope, the strategy for the roof assembly was to increase the R-Value of to meet the more stringent requirements of IECC 2012, which mandates an R value of 49. To reach this, the rigid polyisocyanurate board insulation was increased from 4” to 8” to achieve a total R-Value of 53.1 ft² °F h/Btu [U-Value: 0.19 BTU/ft² °F h]. Beyond calculating the R value, attention was also given to infiltration which may occur at the connection between the roof and walls if that area is detailed improperly. It was decided that the 2” of spray foam of the wall assembly should be extended up and onto the underside of the roof decking all around the perimeter in order to both prevent moisture from seeping into the wall from the interior and to fully close any paths through which cold air may enter the building from the exterior. With the above changes, the roof conforms to both IECC 2009 and 2012, and a 5% decrease in the energy consumption of the building was achieved.

91.7 mmBTU/yr

87 mmBTU/yr

d. Glazing In order to understand glazing which might be used in the base case building, the architectural specs were consulted. The manufacturer given was EFCO. When searching EFCO's standard windows available, it was determined that the highest performing windows offered had overall U factors of .42 for fixed and .38 for single hung, both with thermally broken aluminum frames. Because it appeared that the highest performing options offered by the specified manufacturer would not meet the .35 overall U factor required

by IECC 2009, Efficient Windows Collaborative was consulted for the proposed case windows. The singlehung windows modeled in the proposed case were “Jeldwen Premium Vinyl Energy Saver Max K: Triple

Glaze Low-E 366 Krypton” with no grids, a U-factor of 0.20, an SHGC of 0.19, and a visible transmittance of 0.37. The fixed windows modeled were “Jeldwen Premium Vinyl Energy Saver Max K: Triple Glaze Low-E 366 Krypton” with Wide Contoured Grids, a U-factor of 0.18, an SHGC of 0.2, and a visible transmittance of 0.39.

91.7 mmBTU/yr

83.4 mmBTU/yr

As far as window shading is concerned, no shading specification is provided for the baseline. Because the project is a masonry retrofit, it was decided proposing exterior shading would not be appropriate. Due to these limitations and assumptions, it was decided to propose interior shading—an innovative form of venetian blinds.

In order to maximize sun shading during the summer months without compromising visibility and to maximize ambient lighting during winter, retro Lux blinds were selected from RetroSolar (Koester). These blinds have a folded form that enables them to reflect 70-90% of the solar radiation during the summer. During the winter, they can capture the lower-angled rays and diffuse light into the space.

e. Floor above unconditioned space While the floor above the unconditioned spaces does not directly affect the apartment under study, it was decided to propose a new assembly, as this is a crucial detail of the building's thermal boundary.

Additionally, due to the fact that there are multiple known issues with attached garages and contaminants, this detail became of significant importance (Stuart Batterman, Gina Hatzivasilis, Chunrong Jia, March 2006).

In the base case, sound control mat and one inch thick gypsum concrete is specified above the existing wooden subfloor. 9 ½” of R30 batt insulation is specified above the suspended gypsum board ceiling in the garage. Although the assembly has an R value of 41, it was reasonably assumed that this detail may not provide the necessary air tightness. Additionally, no detail was provided on the connection between this ceiling and the walls. Also, it was unclear whether the garage ceiling should provide access panels to piping or other MEP-related components above the suspended ceiling.

Considering all of the above concerns, the insulation strategy was to keep the insulation mostly above the existing wood floor deck while using spray foam around the perimeter of the underside of the floor to seal any gaps. In order to create the most air-tight assembly possible in order to prevent air movement which would contain garage contaminants between the conditioned and unconditioned spaces, the proposed ceiling/floor assembly employs a 8 1/4” structurally insulated panel [SIP] with an R 38.2 above the existing decking and subfloor. Finished floor can then be laid directly on top. Below the wooden joists, now only the suspended gypsum board is placed. The above detail would reduce by 6”-7” the interior space of the apartment on the second floor, but it seems from the section drawings, that space could be replaced by the extra space between second floor’s ceiling and third floor’s floor. This new assembly would increase its total R Value up to 49.1 ft² °F h/Btu [U Value: 0.02 BTU/ft² °F h]

Garage One main concern with the existing layout is that the garage is attached to the building. Multiple studies indicate that this is not an advisable adjacency . Although ensuring that the garage always maintain a negative pressure compared to the adjacent, occupied space within the thermal boundary on the first floor, is a practice which would be necessary, this strategy does not ensure that dampers, controls, etc. would not malfunction or that air tight seals would not degrade over time or fail to function as designed. Because the adjacency seems to be unavoidable, one strategy discussed for addressing the concern was be completely eliminate the door which currently opens between the garage and Corridor 109. The alternative route, as seen in the sketch below, would provide access into the Entrance Lobby 101 through a covered walk area to the north and east of the new elevator shaft. It appears that the space gained from eliminating the current interior stair leading up to the garage from the first floor space could provide space for a ramp and stairs down to grade. Additionally, one compact parking spot would have to be relocated, as seen in the sketch below. This strategy would need to be investigated further but would be worth considering.

Appliances and Lighting The architectural specs were consulted in order to grasp the energy use regulations of the appliances in the project. For all appliances, three manufacturers were stated as acceptable: Whirlpool, GE, and Frigidaire.

a. Refrigerator As outlined in the specifications, the refrigerator was to be 30”W x 33”D x 66”H (specified), ≥18.1 cubic feet in volume and use no more than 423 kWh per year.

The model chosen as the baseline was Whirlpool, model GR2FHT*V*0*, which uses 422 kWh per year, is 21.7 cubic feet, and is configured with the freezer on top.

The proposed model is from General Electric Co., model GTH18EBCWW, which uses 311 kWh per year, is 18.1 cubic feet, and is configured with the freezer on top.

b.

Dishwasher

Per Energy Star requirements, the dishwasher was to have a .66 EF or higher. The model used in the base case was GE model GDWT1**R, with an EF of .68, using 322 kWh per year, and uses 5.1 gallons of water per cycle. For the proposed case, Whirlpool model WDF730PAY**, with an EF of 0.87, using 250 kWh per year, and uses 2.85 gallons of water per cycle.

c. Range Per Energy Star requirements, the range was to be Energy Star qualified. However, there are no residential ranges currently ES qualified. It was assumed that the model selected would be a gas model (which uses less energy than an electric counterpart) and was modeled in REM Rate such.

d. Clothes dryer Per Energy Star requirements, the clothes dryer was to be Energy Star qualified. However, there are no clothes dryers currently ES qualified. Although the laundry room is a common space and the units will not each have their own clothes dryer, a clothes dryer was modeled in REM Rate. When investigating on the ENERGY STAR website, it was found by the Department of Energy's Appliance Standards program that clothes dryers are not labeled because most dryers use similar amounts of energy, meaning that there is little difference in the energy use between models. This is the reason why the Federal Trade Commission (FTC) does not require clothes dryers to have a yellow Energy Guide label. However, over the next few years, the DOE Appliance Standards program is going to be revisiting this study and determining whether to revise the current federal energy conservation standards for clothes dryers.

e. Fans Because it was not clear weather ceiling fans are planned for the units, the base case was modeling without fans. The proposed case included a fan which was 79 cfm/watt.

Mechanical equipment 1. Californian Loop System In Shanahan building the proposed baseline for the mechanical system is a closed water loop heat pump, or else called California loop heat pump system, with geothermal wells. This system is widely applied, especially in commercial buildings and it uses water to air heat pumps, which are connected into a closed water loop. The water that circulates around the loop has temperatures between 60°F to 90°F. The advantage of the system is that it can regulate the temperatures between all the heat pumps and hence minimize the temperature difference that it has to meet. Heat is rejected or added to the loop only when the internal system is unable to satisfy the loads. Moreover, a great advantage of it is that every zone can be treated differently and it is possible to have individual control.

The loop consists of 22 vertical geothermal wells. As it is known, the ground has a stable temperature almost through the year which is equal to the annual average air temperature and it is about 55°F. Hence, during the winter when it is colder than 55°F ground is used as a source of heating up the water, and during the summer when the temperatures are higher it is used as a heat sink. So in this system, water is pumped into the wells, and it comes up slightly heated or cooled accordingly. Afterwards, there are two centrifugal pumps that move the water up and distribute it into the heat pumps. Every apartment has its own water-toair heat pump. In the heat pumps the refrigerant exchanges temperature with water [in the evaporator], and moves through the condenser coil where loses or gains latent heat in order to heat or cool the air accordingly. After that air is distributed into all the unit’s spaces through ducts. In Shanahan building’s units

there are heat pumps of various capacities [from 1 ton to 3 tons] depending on the size of the unit. In unit 5A a 3 ton heat pump is proposed.

In order to handle the air exchange between indoors and outdoors and provide proper ventilation to the apartments, there is a Heating Recovery Ventilator unit [HRV] on the roof of the building. The HRV brings fresh air into the apartments, usually in the living areas and bedrooms while exhausting humid indoor air from the bathrooms and the kitchen. The most important part of the HRV system is its ability to warm the cooler incoming air by the warm exhaust air, and hence recover a great amount of heat that in any other case would be lost. Generally, the recovery percentages vary from 70% to 90% depending on the unit.

Finally, the system is connected to a gas boiler as a backup heating system, whenever the geothermal wells fail to serve the demanding loads.

a. Heat pumps As mentioned above, the heat pumps in the building vary from 1 ton to 3 tons. In unit 5A a 3 ton Climate Master heat pump is selected [TRM36] with a coefficient of performance of 4.02 [COP] and 94.6% AFUE. However from the baseline modeling and calculations the heating load is 27.2 kBTU/hr, hence even designed for the peak load a 2.5 tons heat pump would be sufficient for the apartment.

After the changes that are being suggested for the building envelope the heating loads decreased down to 15.6 kBTU/hr, allowing to propose a 1.5 ton heat pump [Climate Master TRM18] with COP of 4.02 and EER: 13.3 BTU/W. By resizing the heat pump only there was 4% decrease in annual energy consumption.

(Climate Master)

b. Boilers The boiler assigned on the baseline model is the gas Knight Boiler KB-601 by Lochinvar, it has a capacity of 567.6 MBH and 94.6% AFUE. Dealing with a building with the size of a commercial building, having one boiler for the whole system might turn out to be uncertain. For the new model, three smaller modulating boilers are proposed from Lochinvar [Knight Boiler WH 199] with 189 MBH capacity and 96% AFUE. Having three smaller boilers instead of a big one, is a real advantage as they are more efficient overall and they can work in sequence. Moreover, the risk of the boiler malfunctioning and having no back up heating is eliminated. Even if one of the three boilers is not working, there are two more that can handle some of the heating demand until the problem gets repaired.

c. HRV and Ventilation As far as the ventilation is concerned, an HRV unit is placed on the roof of the building that handles the exhaust air and reheats the incoming air. Based on the specifications given on the mechanical drawings the HRV has a ventilation rate of 2,335 cfm. However, as only one apartment was modeled, some assumptions needed to be made in order to be able to get some realistic results from the software. Based on Energy Star Version 3.0, there should be an exhaust type of ventilation and the cfm rate should be: 0.01 x Conditioned Floor Area + 7.5 x [No bedrooms+1]= 43.215. As far as the fan watts are concerned based on Energy star V 3.0, they should be 43.215/ 2.2 cfm per watt= 41.015 watts. However there is not any existing HRV unit with such a low cfm rate. Hence, one of the lower possible was modeled. The unit is from Renewaire LLC, and the model is BR70. It has a cfm rate of 86 at 25 pascals. (HVI Publication 911, 2011) Nevertheless, even by modeling a smaller HRV unit, it was not still possible to achieve the Energy Star version 3.0 from the software, because the cfm rate was too high for one apartment. In order to make for the model to be more realistic it was assumed that a timer will be installed in the unit that will enable it working only 12 hours per day.

d. Leakage Based on Energy Star version 3.0, the total leakage to outdoors should be less or equal to 4 cfm at 25 pascals per 100ft² of conditioned area. Based on the building that equals to 57.32 cfm at 25 pascals.

Moreover, the total duct leakage to anywhere should be less or equal to 6 cfm at 25 pascals per 100ft² of conditioned area, which translates to 85.98 cfm at 25 pascals. Consequently, both those maximum values were inputted for both our baseline and proposed models.

UNIT 5A

Whole building

“Cartoon” of mechanical systems on the building and on apartment 5A

Natural resources 1. Solar Heating Given that the difference between earning the ENERGY STAR® New Construction or the Multi Family High Rise comes down to weather the building provides at least half of its hot water demand through solar hot water, it was important to explore the feasibility of doing this in Pittsburgh. Many aspects were considered in order to make this determination. Initially, large scale residential case studies with similar hot water demands and in similar climates were reviewed in order to understand how to practically implement solar hot water. The two most relevant studies were a retirement community in Pittsburgh which uses evacuated tubes and a dormitory near Boston, MA which uses flat plate collectors. Pittsburgh average annual solar insolation of 3.53 kWh/m2/day and Boston has an average annual solar insolation of 3.9 kWh/m2 /day. The case study in Pittsburgh is Ross Hill Retirement Residences, a retirement community of around 94,000 square feet and about 100 occupants. It is an evacuated tube system—one of the largest evacuated tube installations in Western Pennsylvania—located on a south-facing roof and designed to provide 100% of the hot water demand and to produce 1.7 MMBTU/day per day effectively eliminating 38 tons of carbon emissions annually. The total collector area is ~2,070 square feet of evacuated tubs from the manufacturer Sunda Corp. The storage includes two 500 gallon solar storage tanks with four 100 gallon auxiliary tanks. Currently, the system is providing around 20% of the demand in the Winter and 50% in

Spring. The solar heating project was funded with $210,000 from the Pennsylvania Energy Harvest Grant program. Tudi Mechanical fitted the system and engineered the installation.

The other building studied is a Sophia Gordon dormitory on the Tufts campus in Medford, MA which utilizes a flat plate collector system. The system consists of 33 flat plate solar collectors and serves 30% of the hot water demand for 30 dormitory units, 126 students, and 61,100 ft2. The manufacturer of the panels is SunEarth Empire EC-21. Each collector has a gross surface area of approximately 21 ft 2 (693 ft2 total collector area). The engineering department at Tufts provides real time energy data online at http://engineering.tufts.edu/cee/sgh/graph_it.asp?graph_period=current&graph_id=hot_water&graph_scal e=hourly After determining that solar hot was feasible in Pittsburgh for the given scale, a rough estimate of the building's hot water demand and corresponding total energy needed to meet 75% this demand was calculated. Based on the assumptions that there are 94 occupants in the building who each use 20 gallons of water per day (based on low-flow fixtures), it was determined that the hot water demand would be around 1700 gallons, which would require around 1 million BTU per day. It is important to note that while each person uses around 20 gallons per day on average, this does not account for the hot water used by dishwashers and appliances. ENERGY STARÂŽ mandates that all solar hot water systems be rated by the Solar Rating & Certification Corporation (SRCC). However, no solar commercial scale systems are currently rated

by SRCC. Considering this fact and a literature review and a conversation with the engineer of the Ross Hll Residence, who stressed that the success of this scale system depended on proper engineering, it was decided to not size the solar system, but rather to demonstrate that it is possible through the case studies.

Considering the collector area of the given cases and then number of occupants they each serve, it likely that the Shanahan roof is (at around 9,000 sq. ft. of useable roof space) provides ample space to house a solar hot water system.

HERS rating and Energy Charts 1. HERS rating, site EUI + Design Loads In retrofit projects, reaching the net zero goal can become really challenging. The restrictions of space, changes on the exterior façade or alterations on the glazing are some of them. That is why the methodology of this study in REM Rate was based on separate changes on the baseline model and the analysis of their results. Apart from comparing the baseline with the proposed case, it is really important to value the effect of every change individually on the building. Therefore, the development of the study becomes a useful tool during the early decision design loads 30.0 making process of the project.

25.0 20.0 kBTU/hr

Firstly, the changes on the building envelope separately were compared. As it is seen from figure 1, with every proposal the heating loads drop significantly. The proposal that affected most the heating loads was the alteration of the windows, and the one that affected most the cooling was the modification of the roof assembly. As it is a heating based

Heating

15.0

Cooling 10.0 5.0 0.0 BASELINE

ROOF

GLAZING

Figure 1

climate the changes in cooling loads are slighter than the ones in heating loads.

site EUI kBTU/ft² ALL RETROFITS RESIZED HEAT PUMPS… SOLAR HOT WATER NEW GLAZING NEW ROOF NEW WALLS BASELINE 0

20

40

60

80

As far as the energy use intensities [EUI] of all of the proposals are concerned, the greater decrease is observed when solar collector is added for water heating. However, none of the models with the separate changes manage to drop below the EUI of the average US home that is 44 kBTU/ft². However, when all retrofits are put together, the apartment’s EUI goes down to 38 kBTU/ ft².

Finally, the proposed case achieved 45 in HERS rating compared to the 63 of the baseline.

2. Energy Spreadsheets Before Energy Balance Spreadsheet Site Energy (include renewable energy consumed) Natural gas, oil, propane, biomass, MBTUs biofuel MJ kWh natural gas 74,500

Electricity (kWh)

MBTUs 21,829

Source Energy MJ 81,354

kWh 23,837

kWh 17,200

5,040

16,958

26,868

40,795

26,868

64,632

Total Energy Consumed (kWh) Renewable Energy MBTUs Produced on site Imported or derived from on-site processes Purchased Total Renewable Energy

MJ

kWh

Net Balance in kWh (Renewable Energy Provided-Total Energy Consumed) Site EUI

63.99

Source EUI

97.16

After Energy Balance Spreadsheet Site Energy (include renewable energy consumed) Natural gas, oil, propane, biomass, MBTUs biofuel MJ kWh natural gas 37,200

Electricity (kWh)

MBTUs 10,900

Source Energy MJ 40,622

kWh 11,902

kWh 17,500

5,128

17,254

16,027

29,156

16,027

41,059

Total Energy Consumed (kWh) Renewable Energy MBTUs Produced on site Imported or derived from on-site processes Purchased Total Renewable Energy

MJ

kWh

Net Balance in kWh (Renewable Energy Provided-Total Energy Consumed) Site EUI

38.17

Source EUI

69.44

site EUIs | breakdown 70.0 60.0

kBTU/ft²

50.0 Lights+Appliances

40.0

Water Heating 30.0

Cooling Heating

20.0 10.0 0.0 baseline

proposed

Conclusions While the ultimate goal of this project was to achieve net zero energy use, it became clear throughout the project, that there are many practical hindrances to achieving net zero in a retrofit of this scale. Furthermore, because this is an actual, funded project planned for construction here in Pittsburgh, the focus of the project became naturally geared towards realistic, possibly implementable strategies rather than the proposal of strategies which were known would not be heeded. To this end, the process was extremely valuable as a teaching tool in terms of real-life experience. It is important to note, however, that while it was kept in mind that this was an actual project, cost was not a primary consideration. Because of this, it was difficult to determine whether a proposed solution would be cost effective or what the payback period may be.

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