As I mentioned yesterday, once you decide what your “needs” are when it comes to insulation, you can begin to narrow down your choices. Just knowing the “R” value is not enough. Sometimes insulation is used in other ways – like a reflective radiant barrier.
We use a product which “just is what it is”. Meaning, it’s not high on the R value, but the “use” is of far greater importance than true insulating value.
Our standard insulation is what is known as “A1V”. This is a layer of closed air cells sandwiched between a reflective aluminum (A= Aluminum) facing on the exterior and a white vinyl (V= vinyl) facing on the interior. This product is “directional” when installed on a roof – it is better at preventing heat gain, than heat loss. Laboratory test results have given it values as great as R-14 against heat gain. Under no circumstances should you necessarily expect numbers close to this, or rely upon a reflective radiant barrier as the sole method of preventing heat loss or heat gain. The way I think of reflective radiant barrier is this: If you have a steel roof – it is a condensation barrier so it doesn’t rain on whatever I have in my building.
I have folks who tell me, “but I live in Arizona so I don’t need vapor barrier”. Or they think because their “roof only” building where they are stacking hay underneath is totally open to the air underneath – it’s going to stay dry. Think again. No matter where you are, at some point in time the warm air rises from the ground after being bathed in sun all day. And when it hits the cooler temperature of the steel roof, the moisture condenses and yes, it will rain on you!
Another thing – because my newest building has a black roof which loves those sun rays, the aluminum facing reflects the heat and keeps my cooling costs down in the summertime.
There is also A2V – which is just what it sounds like: A=Aluminum, then 2 layers of air cells – and then V=Vinyl backing. This is the insulation I have underneath my concrete floor to aid in keeping the heat – in the concrete and not end up trying to heat “halfway to China” as my Mother used to say. The 2 layers of air cells are necessary from the standpoint of the bearing the weight of the concrete floor. This time the aluminum side is “face down”, as the aluminum will react with the chemicals in the concrete. A2V is also pretty handy (easy to apply) around foundations, around water heaters and insulating garage doors.
One more product I want to mention is A2A – which as the name implies, has two layers of air cells between a layer of aluminum on both outer surfaces. Once again, the layers of air cells are giving you two layers of tiny pockets of air to resist the transfer of heat through materials. More layers of air cells means more layers of insulating value. Back to the purpose of why you are using it – if indeed you are looking for some heavy duty insulation – A1V or even A2V alone is not the answer. In combination with other products – you get the best of both worlds.
And this is why I wrapped my entire building in A1V, but then filled the attic and exterior wall cavities with BIBS® insulation. My heating and cooling bills for this 7200 square accessory building are less than the costs for heating/cooling my double wide 2100 square foot 1994 home across the street. Now that’s scary! Back tomorrow with more on insulation – the itchy kind!