Pushing the Envelope with Wall Retrofit Designs

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Abstract For the JUMP into STEM challenge, I selected “Pushing the Envelope with Wall Retrofit Designs” to create an idea that could improve retrofitting residential walls for lower-income residents. Building envelopes that are poorly insulated can lead to huge amounts of energy usage, causing large electrical payments. Current solutions involve removing the exterior finish of the building envelope and using spray insulation to retrofit the walls. This increases the R-value of the wall, which decreases the U-value, and this shows the increase in thermal resistance. My solution will be a cost-effective strategy to retrofit lower-income residencies.   Background As the human race evolves and continues to grow, the need and desire to be comfortable in our own home also grows. Building envelopes separate indoor, conditioned spaces from outdoor environments that may be cold, hot, windy, raining, or more. Building envelopes also protect people from the sunlight, noise, and weather. A buildings foundation, walls, windows, doors, ceiling, roof, and the items inside these elements, such as insulation, all make up the building envelope. The envelopes purpose is to support the structure and control the heat transfer, amount of light, and air between the inside and outside environment. However, many building envelopes are not tightly sealed and this allows for uncontrolled air exchange and unwanted heat transfer. Poor building envelopes allow conditioned air to escape to the outside environment and allow unconditioned air to enter inside. A poor building envelope increases the amount of energy needed to keep the inside of the building at a comfortable temperature and with a good quality of air. The total amount of air that needs to be heated or cooled is increased through a poor building envelope. Improving the building envelopes will reduce the need for heating and cooling of the air and will save the amount of energy needed for the building. A problem many homeowners are facing is that their homes were built before insulation requirements were in place. This causes some owners to have energy bills that are equal to twenty to thirty percent of their total income. Economists consider six percent to be affordable, which shows how much restraints having a poor building envelope can be. Having high energy costs can limit the amount of money American families have for necessities. This is why it is important to create a solution that retrofits existing building envelopes in a way that is affordable to the average American homeowner. Solutions are needed that allow the existing building envelope to be retrofitted to make the walls more energy-efficient, airtight, and moisture-resistant. Problem Definition For this challenge, I will be looking at my hometown of Gibsonville, NC since the community and stakeholders consists of lower income and middle-class homeowners. The community is made up of mainly single-family residences. Communities like Gibsonville, NC can be found all across the united states in small towns. Most of the houses in the community were built in the early 1900’s, with my previous house being built in 1937. For the challenge, the wall retrofit solution must be appropriate for the stakeholder community’s climate region and should meet or exceed the 2015 International Energy Conservation Code for the climate in question. We assume that the original infrastructure the product will update or replace is from a base model single family home of 2,400 ft², built in 1975. This makes the stakeholders and community of Gibsonville, NC Being in the southeast part of the United States, this community experiences drastic weather changes; hot summers, cold winters, rainy spring and fall seasons, large snowstorms, and even tornadoes. The challenge is to design a product or system that can be used for a residential building wall retrofit intended to replace or supplement current leaky and unhealthy walls. The submission should include a solution that prevents moisture buildup in the wall to reduce the potential for mold growth. The submission should also be structurally sound and address air infiltration and insulation needs. The wall retrofit solution must be appropriate for the stakeholder community's climate region and should meet or exceed the 2015 International Energy Conservation Code for the climate in question (Table C402.1.3). Assume that the original infrastructure the product will update or replace is from a base model single family home of 2,400 ft2, built in 1975.   Introduction For the JUMP into STEM challenge, I selected “Pushing the Envelope with Wall Retrofit Designs” to create an idea that could improve retrofitting residential walls for lower-income residents. For this challenge, I will be looking at my hometown of Gibsonville, NC since the community and stakeholders consists of lower income and middle-class homeowners. The community is made up of mainly single-family residences. Communities like Gibsonville, NC can be found all across the united states in small towns. Most of the houses in the community were built in the early 1900’s, with my previous house being built in 1937. Being in the southeast part of the United States, this community experiences drastic weather changes; hot summers, cold winters, rainy spring and fall seasons, large snowstorms, and even tornadoes.   Solution Current solutions are either very expensive or they do not work well enough. The expensive solution to retrofit the building envelope is to remove the exterior layering and spray insulation in between the wall studs. The spray expands and fills all the cracks and voids, therefore sealing the wall and making it well insulated. While this is a great solution, many homeowners who need to have their house retrofitted can not afford this solution. Currently, those who can not afford the previous solutions will look at other options. The best budget value solution is called drill and fill wall retrofit. This is where one- to two-inch holes are cut in the walls between each stud and cellulose insulation is sprayed into these holes to fill the wall and insulate it. While this is the lesser expensive option and is certainly beneficial to homes that currently have very poor or no insulation at all, it still allows heat transfer around the edges of the walls. Figure 1: Drill and fill wall retrofitting For my solution, it must prevent moisture buildup in the walls to reduce the potential for mold growth. It must be structurally sound and address air infiltration and insulation needs. It must be appropriate for the stakeholder community’s climate region that I selected and it should meet or exceed the 2015 International Energy Conservation Code for that climate (Figure 2). I must also assume that the solution is for retrofitting a base model single family home of 2,400 ft2 that was built in 1975. Figure 2: Table C402.1.3 – 2015 International Energy Conservation Code Knowing the target is single family homes in Gibsonville, NC, we select climate zone 4 and wood framed and the results are R-13 + R-3.8ci or R-20. My solution involves the drill-and-fill method to add or improve the insulation in the existing walls of the building envelope. However, this method does not properly seal the edges of the walls so great value thermal laminate dry wall will be placed on the interior of the building envelope. This will allow the building envelope to be insulated and not have any leaks for heat, air, or moisture transfer. Warmline insulated plasterboards are a simple solution that is quick and relatively easy to install. They have all thickness’s readily available that range from 30mm to 90mm and the U-Values range from 0.613 to 0.223 (W/m2K) respectively. This allows thicknesses to be chosen based on the needs of the building. While Warmline insulated plasterboards are more expensive than regular dry wall, they have a cost-effective return on investment by preventing energy loss through heat transfer. The plasterboards also seal the building envelope, preventing moisture from entering that could turn into a safety hazard in the future. The R-value for a typical wood stud wall that is not insulated is 1.49 m2K/W and this means the original U-value of the wall would be 0.67 W/m2K. The R-value of the drill and fill cellulose insulation is 3.5 m2K/W and an average R-value for the insulated plasterboard is 2.426 m2K/W. Once the drill and fill insulation are added and the new insulated plasterboard is installed, the U value of the wall will now be 0.1348 W/m2K. This is a significant improvement from the original wall and the wall is also properly sealed now to prevent moisture from entering. Figure 3: Warmline insulated plasterboard installed to building envelope Before the new dry wall is placed, new windows will replace the current windows. Windows are the main source of heat transfer in a building envelope and windows installed in 1975 will have major loss of conditioned air and could allow moisture in. EnergyStar recommends a U-value of 0.30 or less for our climate we are studying. High performance double-pane windows can reach U-values of 0.30 and triple pane windows can reach values as low as 0.15. Depending on the owner’s budget and preference, one of these windows should be selected and replace all current windows. It is important to note that the high-performance triple pane windows will cost more but save energy and money in the long run. Homeowners who are having the building envelope of their houses retrofitted can opt to have a solar rooftop installed. This is a more expensive option and that is why it is optional and not necessarily needed. It will save the owner money from energy usage in the long run but most of the stakeholder’s in the community will not be able to afford this option. As technology advances, solar panels are becoming more affordable with the price dropping about 70% in the past ten years.  Conclusion Retrofitting an older single-family house made in 1975, with little to no insulation, can be very challenging if you’re on a budget. Most of the best options require a lot of construction on the building envelope; from tearing down siding, panel boards, and everything else to install insulation and air and moisture barriers. My solution involved cutting small holes between every wall stud and spraying insulation into the wall. Then we replace the windows with high performance double or triple pane windows and seal everything up. After everything is sealed, warmline insulated plasterboards are installed on the interior side of the walls. This process insulates the walls and windows and then seals everything with the new insulated plasterboards. Overall, we assumed an original U-value of 0.67 W/m2K. After my design is installed, the U-value decreases to 0.1348 W/m2K. The decreased U-value shows the effectiveness and how much less heat transfer will occur through the building envelope.   References https://basc.pnnl.gov/resource-guides/continuous-air-barrier-exterior-walls https://www.buildingscience.com/document-search?term=&field_doc_topic_tid=All&type%5B%5D=7 https://betterbuildingsinitiative.energy.gov/alliance/technology-solution/building-envelope http://www.wbdg.org/guides-specifications/building-envelope-design-guide https://www.taitem.com/wp-content/uploads/2011/01/TT-NC-Calculating-U-values-Nov-2008.pdf https://www.efficientwindows.org/ufactor.php https://www.just-insulation.com/brands/warmline-insulated-plasterboards-thermal-laminates.html http://www.insulation-online.com/buy-insulated-plasterboard-thermal-laminate.html https://www.gni.ca/insulation-101/insulation-basics https://news.energysage.com/residential-solar-panels-for-home/

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Idea No. 313