The aluminum in a package containing 75ft^2(2 is for square) of kitchen foil weighs approximately 12 ouncesAluminum has a density of 2.70 g/cm^2What is the approximate thickness of the aluminum foil in millimeters? (1oz 28.4 g.)I'm getting the answer 0.5521mmBut apparently, that's wrong (according to the book)The solution in the answer key is 1.8 x 10^-2mmHere is what I did:I divided the volume by the area; logically, that should give me the thickness:340.8g / 2.70g/cm^3 126.2275ft^2 (100cm^2 / 3.281ft^2)126.22cm^3 / 2285cm^2 0.055221cm0.05521cm x 10mm 0.5521Tell me where I went wrong.
You were right on track but you messed upI think your main problem was significant figures340.8g/2.70g/cm^3 126 cm^3 - It should only be 3 sig figs, so it ends up being 126Then, you want to convert the 75 ft^2 into cm^2So you use dimensional analysis: 75ft^2 X 144 inch^2/ 1 ft^2 x (2.54cm)^2 / 1 inch^2 75 x 144 x 2.54 x 2.54 69677.28 cm^2Due to having only two sig figs in the 75 ft^2, you would change 69677.28 cm^2 into 70000 cm^2Now you have to use the thickness formula, T V/ASo: 126 cm^3/ 70,000 cm^2 .0018 cmConvert this into milimeters using dimensional analysis: .0018 cm x 10 mm / 1 cm .0018 x 10 .018 mm 1.8 mm x 10^-2mm.
You could raise the walkway area the thickness of the new insulation to get the full benefit of savings to your heating and cooling bills.This isn't easy though, as access to attics is usually tight, and getting lumber up there is difficultThe other factor to consider is the loss of headroom in the storage area if you do thisAlthough this is a lot of work, it is the way I recommend doing itDon't forget to seal off the entry areaA uninsulated hatch or door into the attic is a hole for heat to escape fromWhichever way you choose to go, do not use insulation with a vapor barrier (paper or foil), as there should be one facing down on the existing R-19 nowDon't allow insulation to come in contact with the roof, leave a 2 airspaceDon't cover any recessed ceiling lighting fixtures that are not rated 'IC' In Contact with insulation is okNon IC must have a 3 space on all sides and top to prevent overheating and possible firesLook inside for ceiling 'can' for ratingMake sure you have adequate ventilation in the atticThe best is a continuous ridge vent and soffit vents on both sidesEnjoy your warm homeYou say 'will I still have problems what problems?
