 Here in this problem. We are trying to calculate the heat loss from the entire house Heat loss through windows heat loss through roof heat loss through walls and add them up We can directly calculate heat loss through windows area is given as 580 Square feet our value is given as 1 and HDD For state college is 6,000 degrees Fahrenheit days So heat loss season Is equal to 580 foot square Times 6,000 degrees Fahrenheit days times 24 hours in a day divided by one our value Foot square degrees Fahrenheit our or BTU So we can cancel these the heat loss through windows is 83,000,520,000 BTUs Similarly, we can calculate heat loss through roof area of the roof is given as 2,750 square feet Times 6,000 degrees Fahrenheit days Times 24 hours over a day divided by 22 Foot square degrees Fahrenheit our or BTU when you do this calculation We lose about 18 million BTUs through the roof For the wall heat loss we need to calculate the composite our value Because we are not given the our value straight away and we are given the area so let's calculate the composite our value the first layer is wood siding and wood siding is 0.81 in our value and The next layer is three-quarters inch plywood and whose our value is 0.94 and we got three inches of fiberglass and Each inch provides an our value of three point seven therefore three inches would be eleven point one Zero and we have another inch and a half of polyurethane Which has six point two five per inch our value Therefore one and a half inches would provide an our value of nine point three seven five At the end or inside we have half inch drywall and whose our value is point four five So together all these layers would provide an our value of twenty two point seven So heat loss now can be calculated we know the area that is 1920 foot square given and same six thousand degrees Fahrenheit days times 24 hours per day divided by 22.67 and This comes out to be 12 million 119 thousand 164 BTUs So when you add all these three heat losses the total heat loss is equal to 113 million 753 thousand 164 BTUs for heating season