Attic Knee Wall Insulation R Value

Don t forget to verify that the r value of the roof insulation meets minimum code.

Attic knee wall insulation r value.

Now that the kneewall is located within the home s thermal enclosure it s no longer necessary to air seal electrical boxes or access doors in the kneewall. 0 19 btu hft f loft ladder hatch u value 1 1 8 insulation thickness 5 2 attic ladder r value the knee wall access door dwk is intended to be built into l shaped walls. Bring the attic inside insulating between the rafters simplifies the air sealing details. 1 use an r value map to determine the amount of insulation you need.

Walls are entered by the type of assembly and the r value of insulation. This knee wall has been encapsulated with 2 part closed cell spray foam. All r values are insulation only tested labeled per ftc rule16 cfr 460. Cavity insulation as indicated in approved construction documents completely fills the knee wall cavity with no compression or gaps the manufacturer s r value mark is readily available and meets the approved r value per construction documents.

By adding an r19 to the existing r13 cavity insulation the knee wall assembly total r value is near r30 and is air tight. A 2 x 4 wall cavity with blown in fiberglass insulation will provide on average an r 13 to r 15 insulation value. A 1 5 wide strip of 3 4 polyiso held in place with a 1 5 wide strip of 3 4 cdx or 1x furring doubles the r value of 2x4 framing and 5 deep cavity can fit a compressed r20 which would deliver a true r18 3 slightly better than an r19 stuffed in a 5 5 deep 2x6 cavity. The best way to provide that sheathing is to use a rigid material.

Most computer programs allow the user to calculate gross wall areas and subtract window and door areas. This gives a total r value of r 17 r 13 fiberglass plus r 4 for the solar guard sometimes we will change the solar guard out for r 30 fiberglass rolls which gives a total r value of r 43. Georgia recognized this problem about a decade ago and started requiring all attic kneewalls to have sheathing on the attic side and to be insulated to at least r 18. According to a report by the washing state university extension energy program blown in fiberglass insulation provides an r value of between 2 2 and 2 7 per inch.