Exterior Rigid Roof Insulation

Install roofing underlayment flashing and cladding as per best practices.

Exterior rigid roof insulation.

Rigid foam sheathing is a form of insulation continuous insulation to be exact that s applied to the exterior of the building. Eps is the most vapor permeable of the three types. Nailbase must be vented in high snow load areas. No matter the climate zone rockwool stone wool does not shrink and does not lose its r value from install to reroof.

Falls in the middle of the three types of rigid foam insulation in both cost and r value used most in walls or below grade applications recyclable and at about r 5 per inch costs around 42 per sq. By patrick mccombe issue 273 feb mar 2018 when combining exterior foam insulation with fiberglass cellulose or mineral wool roof insulation the foam layer must be thick enough to keep the sheathing temperature above the dew point. Thermax sheathing is a non structural rigid board insulation consisting of a glass fiber infused polyisocyanurate foam core laminated between 1 0 mil smooth reflective aluminum facers on both sides. The glass fiber reinforcement contributes to improved fire performance and dimensional stability.

At r 4 it also has the lowest r value per inch. Rockwool insulating roof boards offer warranties long term thermal performance. The ideal roof there s a reason polyiso rigid foam insulation is used in more than 70 of commercial roof construction as well as in many residential builds. Polyiso is an easy cost effective sustainable and energy efficient construction material.

1 inch and 2 inch thicknesses are common. Rigid foam must be thick enough to prevent condensation on the roof sheathing. Continuous rigid insulation is a construction solution that provides a thermally efficient building enclosure. The boards are available in several thicknesses and r values.

The easiest way to increase the value of your roof assembly is to insulate the insulation with a hybrid roof system. Insulated roof assemblies can be vented or unvented. Rigid insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance. For a 1 in thick 4 8 panel.

In its guide to insulating sheathing bsc describes the use of exterior rigid insulation board in the enclosure assembly to act not only as insulation but also as the primary sheathing and in certain areas as the drainage plane and vapor control layer for the wall assembly. There are at least two good reasons why this approach makes more sense than installing the insulation under the roof sheathing. Rigid insulation sheathing is made of a rigid plastic foam that is typically sold in 4 8 or 4 10 foot boards.