How can I insulate an exposed flooring system properly?
hi,. i have an addition on my house thats aproximately 11×14 on piers and 5 ft off the ground over sandy soil and exposed on all sides.It has a 2×8 ,16″ on center floor system framed lengthwise over 2 , triple 2×10 beams, one for each set of piers.The subfloor is 3/4 tongue and groove plywood and i will be installing prefinished 3/4 x 2-1/4 tongue and groove strip oak flooring. I insulated the floor a couple years ago and used 2 layers of owens corning unfaced R-13 in the joist bays and then a layer of 3/4inch polyshield by cellofoam with/metalized poly facer facing towards the interior , fastened to the bottom of the joists and then a layer of 1/2 osb over that to keep rodents out.When i pulled the existing carpet up to redo the floor i made a couple access hole to inspect the cavity and found signs of frost and condensation on the foam insulation but only certain areas, closer to where the addition is attached to the house.My questions are how do i avoid this?…The oak flooring manufacturer recommends 15lb. felt under their floor and im concerned i might make the situation worse because of possibly trapping the moisture in and slowing or stopping the drying to either side and causing structural damage and mold.Should i remove the foam and reinstall the osb alone to cover the unfaced fiberglass,then use the 15lb.felt under the oak as a vapor retarder and allow any moisture to dry to the outside ?Or should u add more foam to the existing foam on the bottom to isolate the floor system more from the cold?Or should i pull all the fiberglass down and foam and osb and install/friction fit 2 inches of some type of rigid insulation to the bottom of the subfloor and sill area where the addition attaches to the house and use that as the vapor retarder and then the 2 layers of unfaced fiberglass and cover that with the osb??…Also the existing poly foam on the bottom of the joists runs between the triple 2×10 support beams i previously mentioned and was wondering if that might be contributing to the condensation allowing air to seep into the floor cavity and if the top of the beams should be covered with foam , overlaping onto the existing foamboard,…any advice and info would be greatly appreciated,..thank you
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