welcome to the solar decathlon building science education series i'm paul tercellini and in this episode we'll talk about the impact of your design decisions as well as the importance of setting goals and how measurable goals are better what do we mean when we say every decision has an energy and environmental impact well say you have a cup of coffee every morning where did that coffee come from what kind of cup is it in if it's a disposable cup it gets used once and likely ends up in a landfill so there were energy and environmental resources that were used to make the cup and then it gets used once before more energy and environmental resources are used to dispose of it what if you choose a reusable ceramic coffee cup instead this decision has a different energy and environmental impact it probably uses more energy to make the coffee cup but it can be used over and over many times before it is disposed of however washing the coffee cup takes water energy and soap which also has environmental impacts the decision on which cup to use can be quite complex often depending on the amount of coffee you drink that example was just one coffee cup but think about an entire building and the countless decisions that are made during design and construction every single one of those decisions has some level of energy and environmental impact we also have to consider the fact that these decisions related to building design have a larger impact because buildings are used for a long time design decisions made today are going to be with us for the next 30 50 or more than 70 years think of the building you're sitting in right now when was it built what decisions were made back at that time that are still impacting you today when you really think about it you realize that buildings have a huge energy and environment impact not just during their useful life but also in the materials used to build it and in the environmental consequences associated with those materials when it gets demolished to make a change we need to think about design decisions with regard to this overall environmental impact of buildings and so how do you do this how do you succeed in reducing the environmental impact of buildings well frankly it's difficult without measurable goals a lot of people say something like i want a green building but the problem with that is that nobody really knows what the statement means without defining it more people sort of know what it means but you can't measure how green a building is so in the 1990s the us green building council came up with the lead rating system and they basically developed a set of rules a bunch of criteria and points that began to quantify how green or how sustainable a building was the level of lead certification a building was awarded was determined by how many points it got in the lead scoring system you can kind of think about it like taking a test in school and how your grade on that test depends on how many points you get but there's a range of potential outcomes with this type of system depending on how motivated a person is to get a certain grade what is their definition of success some people might want to make sure they get an a but some other people might just want to simply pass the test what's important is that the system helped to establish a system of setting sustainability goals a portion which was for advancing building energy performance the idea was to exceed the energy codes and goals are all tied to a set of performance criteria but what if you wanted to define a more specific energy goal for a building if you really want to focus on energy you can talk about setting a goal for a building to use something like 30 percent less energy than the 2016 version of the ashrae 90.1 standard so now we've got some metric of comparison and we create a baseline measurement which is a version of the building that meets the ashrae 90.1 level of energy consumption and then we design the building we evaluate it against the base case and we try to create something that is 30 percent better this can be really difficult because the base cases are somewhat fictitious and often a little hard to define so an even better goal is to set absolute energy use targets that are easily measurable an example of this is to design a building to use less than 25 000 btus per square foot annually this really gets to the point about how much energy the building uses and when the building is complete and it's occupied you can measure its energy use and determine if you've succeeded and met the goal goals like this are great because they put you on a path to success and allow you to design a building that will result in a measurable reduction of those energy and environmental impacts we talked about earlier and really the concept of zero energy buildings is just another type of specific measurable goal on a source energy basis the actual annual delivered energy has to be less than or equal to the on-site renewable exported energy that's a specific measurable goal and it's a goal that's easily evaluated every year you can say whether or not the building has met the goal another measurable goal that you might hear about is for a building to be zero energy ready these buildings are designed and constructed such that their annual energy use intensity is low enough for on-site renewable energy production to balance with the consumption these buildings are ready for zer energy they just don't have the on-site renewables yet so how do we actually define these targets for energy consumption well we talked in another episode about using maps of solar energy availability to determine how much renewable energy could be produced at a given location and therefore what the corresponding energy consumption budget would be to get to the zero energy balance this information has been summarized in the tables of eui targets based on climate zone as shown here in this example from the advanced energy design guide for office buildings often these eui targets are extended to high-rise buildings even though they do not have the footprint to achieve the renewable energy production on site and so they would have to procure it off-site and so this zero energy ready gold does represent a realistic goal for energy efficiency it is an energy first strategy representing a forty to sixty percent reduction from energy codes to summarize this episode i want to re-emphasize that your design decisions have both energy and environmental impacts and measurable goals are always better if you define a goal that's quantifiable and easily measurable your project will be on the path to success as always please take a look at our additional resources page for more information and thanks for watching you