Radiant barriers are made from materials with excellent heat reflecting properties (usually aluminium). They come in different shapes and concepts: foils, paints, chips etc.
Our experience with chips is minimal. Definitely we don't endorse reflective paints. We use various kinds of aluminium foils, with one or two reflective sides, usually laminated on a plastic foil or kraft paper and possibly reinforced with a scrim. Our experience with these radiant barriers is very positive.
Reflectivity is the ratio of the reflected heat energy divided by the incident heat energy.
The philosophy of radiant barriers is to reflect back radiant heat or prevent its emittance. Thus they can be used to reduce summer heat accumulation or prevent winter heat loss. In Greece it's the former case that interests us.
Roofs here absorb big quantities of heat energy during summer season. Temperatures in attics can reach phenomenal heights.
Radiant barriers help us control the situation and reduce the air conditioning bills.
Their use for winter heat loss prevention is controversial. We prefer to increase conventional insulation.
Radiant barriers work synergistically with conventional thermal insulation.
On no occasion they can replace it as some charlatans might allege!!
There is no way and no meaning to attribute an R-value to radiant barriers since they don't absorb heat.
Radiant barriers work otherwise: they retard heat flow. Their place is between the heat source and the conventional insulation of which they increase considerably the R-value.
The installation of radiant barriers is more advantageous when effected on the attic floor, immediately above the thermal insulation.
To prevent water vapor accumulation, condensation and freezing we use only breathable products for this application.
The only disadvantage is the possible dusting of the barrier with an eventual reduction of it's reflecting capacity.
Alternatively it can be installed draped under the roof deck and over the rafters.
A third choice is the installation under the rafters.
Radiant barriers can have one or two reflective surfaces and they need an open air space of about 2cm on at least one of the two sides.
It's irrelevant which side will face the heat source because the final emittance will be the same.
When there is only one reflective side, it may be advantageous to put it facing down so as to avoid dusting.
Chris Strogilis
Civ. Eng. - MBA - DipM
Our experience with chips is minimal. Definitely we don't endorse reflective paints. We use various kinds of aluminium foils, with one or two reflective sides, usually laminated on a plastic foil or kraft paper and possibly reinforced with a scrim. Our experience with these radiant barriers is very positive.
Reflectivity is the ratio of the reflected heat energy divided by the incident heat energy.
The philosophy of radiant barriers is to reflect back radiant heat or prevent its emittance. Thus they can be used to reduce summer heat accumulation or prevent winter heat loss. In Greece it's the former case that interests us.
Roofs here absorb big quantities of heat energy during summer season. Temperatures in attics can reach phenomenal heights.
Radiant barriers help us control the situation and reduce the air conditioning bills.
Their use for winter heat loss prevention is controversial. We prefer to increase conventional insulation.
Radiant barriers work synergistically with conventional thermal insulation.
On no occasion they can replace it as some charlatans might allege!!
There is no way and no meaning to attribute an R-value to radiant barriers since they don't absorb heat.
Radiant barriers work otherwise: they retard heat flow. Their place is between the heat source and the conventional insulation of which they increase considerably the R-value.
The installation of radiant barriers is more advantageous when effected on the attic floor, immediately above the thermal insulation.
To prevent water vapor accumulation, condensation and freezing we use only breathable products for this application.
The only disadvantage is the possible dusting of the barrier with an eventual reduction of it's reflecting capacity.
Alternatively it can be installed draped under the roof deck and over the rafters.
A third choice is the installation under the rafters.
Radiant barriers can have one or two reflective surfaces and they need an open air space of about 2cm on at least one of the two sides.
It's irrelevant which side will face the heat source because the final emittance will be the same.
When there is only one reflective side, it may be advantageous to put it facing down so as to avoid dusting.
Chris Strogilis
Civ. Eng. - MBA - DipM