Roof Insulation No Ventilation

A properly functioning un vented roof.

Roof insulation no ventilation.

If the attic is insulated with fiberglass batts just pull back any that are blocking the flow of air. If your attic is well insulated the insulation might be plugging the spaces between rafters just above exterior walls. The answer is rafter venting. The roof cavity between rafters can be filled with insulation followed by installation of a perfect vapor barrier followed by finish surface of drywall or whatever else.

Two basic approaches to insulating flat roofs. Covering up the soffit vents with loose fill or batts which can happen if you stuff insulation along the eaves is a huge no no. In cases where there is no under roof venting system no soffit intake vents no ridge vents a hot roof design is followed. Rafter vents or insulation baffles install in any rafter space to create narrow gaps that direct fresh air from the soffit vents to the peak of the roof.

Poor insulation is usually the culprit although if you enter the attic on sunny winter day your attic space can be warmed by the sun more than your furnace. In an un vented roof foam can serve as the air barrier and vapor retarder and prevent moisture from getting in to the roof cavities. The soffit vents are now installed but you still need to make sure there s no insulation blocking the new vents. Under a flat or low slope roof the usual rules about roof insulation and ventilation don t apply.

That means air can t flow from the soffit vents to the roof vents. Baffles are available at home centers. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow. If there s blown in insulation like ours rake back the fluffy stuff with a 3 or 4 ft long 1 x 6 or use a garden rake or hoe.

This article explains methods for avoiding moisture condensation problems in compact insulated roofs that have no roof cavity space and in steel or wood framed roofs that have a roof cavity space and. For the same reason insulation shouldn t touch the roof s underside. Foam and the roof assembly foam insulation can play an important role in both vented and un vented roof assemblies. The solution is to add baffles which allow air to flow past the insulation photo 9.