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New Guide for Standard Guide for Evaluation of Changes to the Thermal, Moisture and Ventilation Performance of Existing Roof Enclosures (with Vented or Sealed Attic or Rafter Spaces)
1. Scope
1.1 This guide addresses the evaluation of hygrothermal impacts beneath existing roof enclosures resulting from the addition of insulation, vapor retarders, air barriers or any other alterations that could impact the drying potential, ventilation, thermal performance, or vapor resistance of the roof enclosure or changes to the interior environment beneath the enclosure. Changes to the interior environment beneath the roof enclosure can include, but are not limited to, mechanical conditioning of a previously unconditioned space, changes in attic or enclosed rafter space ventilation, altering the ventilation openings in a naturally ventilated attic space, adding habitable space within an existing attic space, or any other alteration that will impact the temperature, relative humidity, or air flow beneath the existing roof deck.
Keywords
Continuous insulation, retrofit, moisture damage, hygrothermal analysis, roof enclosure, slate roof, metal roof, shingled roof, attic space, energy code
Rationale
Energy conservation is being addressed more often on existing and/or historically significant buildings originally constructed with uninsulated and/or unconditioned attics and roofs. Without proper evaluation, changes to the thermal and moisture properties beneath roof assemblies or changes to the conditioning of the space below the assemblies could have serious negative impacts, particularly on the integrity of the existing structure and the potential for condensation and other moisture accumulation related issues. This standard seeks to provide guidance on how to properly evaluate such changes and alterations.
