japaneseiorew.blogg.se - Radiant barrier

For foil-backed OSB to perform correctly, builders must make sure there is an open air space adjacent to the foil layer not less than ¾ -inch.

Moisture can lead to mold which is both unhealthy to the occupants of the building and can rot the ceiling framing or wall assembly.

Water spots may appear on the ceilings of the living spaces.

If the insulation becomes damp, it will lose some of its insulating values.

When installing foil-backed OSB, builders must pick a location where the barrier is unlikely to reach the dew point temperature.Ĭondensation on the underside of foil-backed OSB can cause several problems: If water vapor from the interior of the building moves into the attic, and the foil-backed OSB is cooler than the dew point, the moisture may condense on the underside of the barrier.

Foil-backed OSB acts as a vapor barrier, particularly when it is cold outside.

It is crucial to keep the workspace clean when installing foil-backed OSB. Dirt and dust are particularly problematic in attics where the foil-backed OSB is applied horizontally, which makes it prone to dust and dirt. Dust and dirt make the foil less reflective.

Only clean and shiny foil will emit heat.

However, foil-backed OSB often requires additional thermal insulation to prevent the transfer of thermal energy by conduction and convection.

The foil layer of the OSB lowers the Delta-T by reflecting the thermal energy due to radiation (sun’s heat) away from the insulation layer, which keeps the top layer of the insulation just several degrees warmer than the outside air temperature.

Five Problems with Foil-Backed OSB Radiant Barriers Even with excellent airflow in an attic, the temperature of the top surface layer of the insulation will only drop a few degrees.

Without the foil layer, the OSB sheathing will absorb heat and radiate it into the attic space in the summer, or outside during the winter.Īdding more attic ventilation will help, but not much. Similarly, when heat rises into an attic during cooler months, the foil layer reflects it into the living spaces of a building. So, when the sun hits the roof and radiates into the attic or wall, the foil layer of the OSB sheathing reflects the heat to the roof or exterior wall, which keeps the top layer of the insulation just a few degrees warmer than the outside air temperature. The foil layer of the OSB lowers the Delta-T because the foil is low emitting and does not emit or absorb heat.

The Delta-T is the difference in temperature between the top layer of the insulation and the living spaces. When this occurs, the top surface of the insulation can reach a temperature of 130 degrees and more, which is much higher than the temperature in the living spaces (68-70 degrees). Through the process of infrared radiation, the heat from the roof is emitted (or radiated) into the attic where the insulation absorbs it. The bottom of the roof deck will be 20 or 30 degrees lower. For example:ĭuring the hot summer, the heat of the sun can raise the temperature of the top shingles of the roof to nearly 180 degrees. What is Delta-T?ĭelta-T is the difference between the temperature of the top layer of insulation in the attic or wall system and the living spaces. The goal of a foil-backed OSB is to cool the air within the top layer of insulation in the attic or wall by emitting the radiant heat absorbed through the roof or exterior walls, which reduces the Delta-T and lessens the overall energy use in a building. Foil-backed OSB is applied mostly in attics however, it is also used in wall systems. Oriented strand board (OSB), with a thin layer of low emitting aluminum foil attached to one side, is a common type of thermal-radiant-barrier sheathing.