Pie chart of energy distribution

Step 5: Assume standard appliance profile and occupancy for the home. Make a list of all the energy uses other than heating and cooling for your home.

   

The total electricity needs is approximately 34.72 BTU per year, or 1.18 kW.

Step 4: Now determine the total heating and cooling energy needs for your home using the equations developed in class for thermal envelopes. Data for temperatures and wind conditions can be obtained on the web (monthly averages are sufficient)

The total heating and cooling energy needs of our home for an entire year can be found using the equations discussed in class for thermal envelopes:


c_p= 0.241 BTU/(lb*F) for air


Q_Heat= (UA + m_dotc_p)HDD = 65.7 x 10^6 BTU per year = 2.2 kW


Q_Heat =65.7 x 10⁶ BTU per year = 2.2 kW


Q_Cool=(UA + m_dotc_p)CDD + Qlatent = 7.36 x 10^6 BTU per year = 0.25 kW

Step 3: Assume standard air exchange for homes. What is the ventilation rate for your home?

Assuming standard air exchange for homes, we will calculate the ventilation rate for the home.  The density of air is about 0.075 lb_m/ft³ at 70 ⁰F.  By using the volume of the house of 8000 ft³ and neglecting the area taken up by the objects in the house and the walls separating the two rooms, we can see that 619.6 lb_m of air is in the house at all times. We will say that 40 percent of the air needs to be circulated to prevent stagnant air, which is a valid assumption. Also, this air change per hour is assumed to be 2 times, so 48 times over the course of a day. 


m_dot = (619.8 lbm)(0.40)(2 times per hour) = 495.7 lbm/hr = 8.26 lbm/min

Ventilation rate = Q = m­_dot/density of air = (8.26 lbm/min)/(.075 lbm/ft^3) = 110 CFM

Step 2: Determine the heating and cooling degree days for a typical year

Next we will determine the heating and cooling degree days for a typical year.  These values help is find the amount of energy that will need to be supplied to the house over the entire year.  First we will look at the cooling degree days (CDD).  We will reference the Iowa Environmental Mesonet ^[40] to get averages from 1951 until 2011.  The average number of CDD is about 1045 and cooling days typically are needed between the months of April and September.  Heating degree days (HDD) are taken into consideration for all months except for June thru August.  The average for HDD is taken to be about 6140 for a typical year.

Step 1. List the R-values of the building materials and compute the overall thermal conductance of the home

Let’s say we want to design a way to heat and cool a house in Iowa City, IA using renewable energy.  For a simple analysis we will say that the house is a 1 story, 2-bedroom, 1000 square foot home.  The design will be planned around the goal of maintaining an interior temperature of 70 ⁰F.  We will assume that there is no basement, and therefore we will not consider heat flow in or out of the bottom of the house(adiabatic).  We will also assume the overall dimensions of the house are as follows: base of the house is 25 ft x 40 ft and the walls are 8 feet tall.  Next, we assumed that windows in the house can be neglected. The ceiling and the four exterior walls will be modeled using the same R-values as those used for a wood construction wall.  This is a valid assumption because a typical R-value for a ceiling is usually between 10 and 15 (hr*ft^2*F)/BTU . Below is a figure that shows the generic components of a wall along with their specific R-value and the R-value of the wall assembly as a whole. [39]

As shown in the figure, the total one wall assembly R-value is 13.31 (hr*ft^2*F)/BTU. When we set R₁=R₂=R₃=R₄=R₅=13.31, find the area of the exterior walls to be 1040 ft² and the area of the ceiling to be 1000 ft², we can then find the overall thermal (UA) conductance of the home. UA = (1/13.31)(5)(25*40+2*8*40+2*8*25) = 766.4 Btu/(hrF)

Pick a project. What is the LEED rating of this project and what made this project LEED certified?

The 2,216 square foot Chipotle Mexican Grill in Gurnee Mills, Illinois is an example of LEED retail and was granted LEED Platinum certification on May 18, 2009. For LEED retail, the maximum possible points you can receive is 71; Chipotle received an astounding 53. The following is a breakdown of how Chipotle received its points: 10 out of 16 for sustainable sites, 4 out of 5 for water efficiency, 13 out of 17 for energy and atmosphere, 7 out of 13 for materials and resources, 14 out of 15 for indoor environmental quality, and 5 out of 5 for innovation and design.

Overall, this particular Chipotle is the first stand-alone restaurant to receive LEED Platinum certification. When designing the Gurnee Mills Chipotle, two main goals were stressed: increasing energy efficiency and to install an onsite renewable energy source. Since Lake Michigan is in close vicinity and the surroundings are fairly windy, Chipotle partnered with Chicago to build a 6 kwh wind turbine, which would be used to power the lighting and other needs in the restaurant.

Also, the project expects to increase water savings by 43 percent and increase outdoor water savings by 100 percent through the installation of a 2,500 gallon cistern to collect rainwater.

Overall, the project estimates that energy savings will decrease by 33 percent, water savings by 43 percent, and 86 percent of construction waste would be diverted from landfills.

What is core-and-shell construction?

Core-and-shell construction entails the base building elements, including the structure of the building, the building envelope, and the HVAC system.

What are the categories of LEED profiles?

There are 8 different categories of LEED profiles: new construction, existing buildings, commercial interiors, core-and-shell, school, homes, retail, and neighborhood development.

Brief description of the LEED rating system

The most recent LEED rating system came out in 2009 and contains 9 different LEED rating systems for the design, construction, and operation of buildings, homes and neighborhoods. Of the 9 rating systems, 5 categories are most commonly employed: green building design and construction, green interior design and construction, green building operations and maintenance, green neighborhood development, and green home design and construction.

In general, if buildings are accepted for LEED certification, they are given one of four statuses by the USGBC based on a 1-100 point scale. There is also a 6 point bonus for innovation in design and a 4 point bonus for regional priority. The four statuses are given below, with 1 being the least green to 100 being the most green.

Certified: 40-49 points
Silver: 50-59 points
Gold: 60-79 points
Platinum: 80 points and above

Note: These point ranges apply to most of the profiles, not all. For example, for LEED Retail, the maximum point value is 71.

What are the components of LEED?

The implementation of LEED accreditation is a whole-building approach, aiming on attaining high performance in five crucial areas: sustainable site development, water savings, energy efficiency, materials selection, and indoor environmental quality.

High performance in these five areas work together to lower operating costs and increase asset value, conserve energy and water, reduce greenhouse gas emissions, reduce waste to landfills, and make the living conditions healthier.

What is LEED?

The acronym LEED stands for Leadership in Energy and Environmental Design and the system was set up by the United States Green Building Council in March of 2000.  The main goal of the system is to give building owners and operators a basis for developing and integrating green building designs, construction, and operation and maintenance. While the initial costs may be larger in the short-term when compared to non-green solutions, LEED applications make business sense in the long-run. These applications include both commercial and residential estates.