Insulating A Knee Wall With A Vented Roof

Senior engineer manager at icynene john broniek makes the case for the unvented attic assembly and why insulating the underside of the roof makes sense.

Insulating a knee wall with a vented roof.

You can use foam board to make baffles near your soffit vents and then blow in enough insulation to reach the r value you want. How to insulate knee walls 1. Ventilating knee wall attics is challenging. The first point is sealing the soffit venting.

The quest for greater energy efficiency in buildings has led to increasing interest and need for insulation improvements in hvac equipment more airtight construction new materials and assemblies. Bring the attic inside insulating between the rafters simplifies the air sealing details. If you choose to insulate along the horizontal and vertical walls you have four key air sealing points. Fill the remaining space with fiberglass or cellulose.

In the knee wall area the insulation is in the floor and on the back of the knee wall. The third shows the baffle extending up into the roof attic. If you want the attic to be outside then using foamboard on the attic side of the knee wall is a good idea. The specific r value for the insulation you need.

The ceiling and knee wall drywall will act as your air barrier. If there is a well defined air barrier following the upper roof slope to the knee walls and down into the floor joists sealed blocking and the lower slope insulation is not blocking roof ventilation then there s no harm in leaving the lower slope insulation or repairing it as. I installed baffles between the roof and insulation shown to allow for the air to flow from the soffit to the roof attic as shown in the second picture. More details online 1.

Cut unfaced batt insulation to fit between the floor joists in the space behind the knee wall. Use an r value map to determine the amount of insulation you need. In an ideal world we install soffit vents as intakes make sure the slopes can breathe with ventilation baffles and exhaust through a ridge vent. Keep the attic outside insulating a kneewall and the attic floor behind the kneewall is possible but tricky.

Old school roof vents which look like rectangles on the roof work pretty well too. The first picture is looking up at the angled roof of the knee wall. Insulating the floor and kneewall requires more careful air sealing but is sometimes easier to insulate since you can use blown insulation. Insulating and air sealing knee walls vented version.

Sometimes though there are no soffits. Lay each unfaced strip of insulation between the.