Heat Load Analysis for 139 National Brad Peirson EGR 468 – Heat Transfer Instructor: Dr. Fleischmann School of Engineering Padnos College of Engineering and Computing Grand Valley State University February 6, 20081.0 Introduction 139 National is a home on the west side of Grand Rapids that is being renovated by Westown Jubilee Housing to be sold to a low income, west side family. Westown has discovered through many such renovations that the conditions of the homes on the west side are less than ideal from a heat transfer standpoint. Homes that have significant heat losses through both conduction and infiltration require a significant amount of energy, and therefore money, to maintain a comfortable living environment. The excessive cost of heat in an area such as Grand Rapids’ west side removes more money from the community and makes the entire area more and more poor. In an attempt to aid Westown Jubilee to renovate the home and decrease it’s heating costs the Heat Transfer class at Grand Valley State University’s School of Engineering has performed a heat load analysis on the structure. This analysis will aid Westown Jubilee Housing in making the decisions for materials to be used in the renovation to maximize heating efficiency. 2.0 Heat Load Analysis Different laboratory sections from the Heat Transfer class visited the house in order to gain dimensional and air infiltration data. This data was compiled and is provided in Appendix A. Effectively the lab sections found that in the entire house there was a single wall on the second floor that had any insulation whatsoever. The rest of the walls were primarily plaster lathe, ½” board, a 4 inch air gap, another ½”board and wood siding. The majority of the windows were found to be single pane windows with no storm window. An Excel spreadsheet was created to carry out the calculations involved in the heat load analysis. This spreadsheet is provided in Appendix B. Effectively, the heat lost from the house via conduction is found via equation 1. ݍ=ܣ∆ܴܶ (1) Where q is the heat transfer rate, A is the area of the wall or window with a given R value, and ∆ܶ is the temperature difference between the inside of the house and the outside of the house. For this analysis the doors on the first floor were neglected. The back porch was also neglected as it is completely un-insulated and un-heated. The summation of the results of equation 1 over all of the doors and all of the windows gives the total heat loss via conduction for the house. As Appendix B shows, assuming an outside temperature of 0°F the heat lost from conduction is approximately 61,000 BTU/hr. Once the conduction losses are accounted for, the infiltration losses are derived from the data obtained from Nu-Wool’s building leakage test (Appendix A). The total of the infiltration losses and the conduction losses determine the total heat load of the house. Table 1 shows the current heat load and the resulting ccf of gas used by 139 National.Table 1: Current Heat Load for 139 National Outside Temp (°F) Heat Load (BTU/hr) ccf of Natural Gas required per day 0 89,000 22.3 32 48,000 12.1 At a cost typically between $0.70 and $0.90 per ccf of natural gas, the current cost to heat 139 National could easily be several hundred dollars per month. This type of situation is not uncommon in the west side and is why Westown Jubilee Housing is renovating homes as they do. 3.0 Improvements The primary improvement to 139 National should be insulation in the attic. Because heat rises a significant amount of heat is lost through improper insulation in the attic. Nu-Wool cellulose insulation is well suited to this application because of its safety. Nu-Wool will not burn when placed in direct contact with hot lighting or wiring in the attic, and can be applied significantly thicker than spray in fiberglass insulation. In the future state spreadsheets given in Appendix C it was assumed that the Nu-Wool would be applied in the attic at least 6 inches thick. Another major improvement will be the installation of insulated windows. Single pane windows have an R value of approximately 0.91, but that doesn’t take into account additional air leakage around the wooden window frame. In contrast, double insulated, low-E windows with suspended film have an R value above 4 and when mounted properly allow very little air leakage around the frame. The last major improvement considered in this analysis was the installation of Nu-Wool insulation and ½” gypsum board on all of the exterior walls. The Nu-Wool not only adds a significantly higher R value than the open wall, it also seals many smaller air leaks that other insulations may miss. The suggested improvements were modeled in Excel the same way the current state of the home was. This analysis is given in Appendix C. Table 2 shows the comparison between the current state of the home and the proposed improvements. Table 2: Comparison Between Current and Improved Home Outside Temp (°F) Old Heat Load (BTU/hr) New Heat Load (BTU/hr) Old ccf per day New ccf per day 0 89,000 18,000 22.3 4.1 32 48,000 9,700 12.1 2.2 The proposed improvements to 139 National will decrease the required ccf of gas each day by nearly 5 times. This directly corresponds to a 5 time decrease in the monthly heating bill. Overall, when the people that live in the home are spending less money on heat, they have more excess income that will be left in the community.4.0 Conclusions The problems shown through this analysis are typical of the older homes on Grand Rapids’ west side and of older homes in many poorer urban areas around the country. Burning so much gas to heat so many homes definitely causes environmental issues such as excess pollution and an unnecessary overuse of the resource. The greater impact is, however, social. As shown above, the heat bill for such a home can exceed several hundred dollars in a single month. In the case of the low income people that live on the west side this leads to a choice between staying warm and doing anything else. The money that is spent on heating leaves the community for the utility companies, while the community also loses important people because they don’t have any money left to function in their neighborhoods. Westown Jubilee Housing has set an example of how such a situation should be handled by local governments in large cities. They do