It is not insulation, and that matters
A radiant barrier has no R-value. It reflects radiant heat off a hot roof, which in a Houston August is worth having, but only when it is installed with an air gap and only on top of insulation that is already doing its job. Here is the version nobody selling foil will give you.
What it actually does
Heat moves three ways. Conduction through solid material, convection through moving air, and radiation across open space. Insulation slows conduction, and its R-value is a measure of exactly that. A radiant barrier does not have an R-value because it is not working on conduction at all.
What it does is sit between your hot roof deck and everything below it, and reflect the radiant heat the deck throws downward. On a Houston afternoon that deck is the hottest surface on your property. Intercepting what it radiates is a real effect.
The air gap is the whole thing
A radiant barrier needs an air space facing its reflective side, generally at least an inch. Without it the product fails completely, and not partially.
Foil laid flat on top of attic insulation, or stapled tight against decking with no gap, conducts heat straight across the point of contact. At that point you have an expensive sheet of foil doing nothing. This is the most common bad install in this market, and it is why we would rather talk about the gap than about the reflectivity number.
If a quote does not say how the air gap is maintained, it is not a radiant barrier quote.
About the 97% number
You will see it everywhere. It is a property of the foil, not a prediction about your house, and on its own it tells you nothing about what you will save.
The figure that is usually cited for actual results is 5 to 10 percent off cooling costs in the southern United States, with field studies in hot climates landing in that range. Two things move it: whether your ductwork runs through the attic, which roughly doubles the effect when it does, and how much insulation you already have.
When it is worth doing, and when it is not
| Your situation | Our honest answer |
|---|---|
| Insulation at or near code depth, ducts in the attic | Good candidate. This is the best case. |
| Insulation is thin or settled | Fix the insulation first. A barrier over an under-insulated attic is the wrong order. |
| Equipment already inside the conditioned space | Smaller effect. Worth doing, worth less. |
| Planning a sealed roof deck | Skip it. Foam at the deck solves the same problem, and an existing barrier has to come out for the foam to bond. |
That last row costs us the sale about as often as it makes one, and it is still the right answer. We go through the same tradeoff for foam in how much spray foam saves on a Houston electric bill.
Where we work
Across Greater Houston, with a lot of this work in the surrounding areas: Katy, Sugar Land, Cypress, Spring, The Woodlands, Conroe, Tomball, Pearland and the rest of the service area.
What to do next
Before anything else, find out how deep your current insulation is. Book the free assessment or text a photo of the attic to (281) 703-2700, and we will tell you whether a barrier is the next thing you need or the third thing.
Radiant barrier questions
Does radiant barrier actually work in Houston?
In this climate, yes, within limits. It is commonly credited with 5 to 10 percent off cooling costs in the southern United States, and the effect is largest where ductwork runs through the attic, which is most Houston homes. It does nothing for heating, and in a cold climate it can work against you. Houston is about the best case there is for it.
Does it replace insulation?
No. It has no R-value and it does not slow conduction, which is what insulation does. It reflects radiant heat coming off a hot roof. Anyone selling it as a substitute for insulation is selling you the wrong product. It is a supplement, and it only makes sense on top of insulation that is already at or near code depth.
What is the air gap about?
It is the whole thing. A radiant barrier needs an air space facing its reflective side, usually at least an inch. Foil pressed flat against decking or laid directly on top of insulation conducts heat straight through the contact and stops being a radiant barrier at all. That is the single most common bad install we see.
What does 97% reflective mean?
It means the foil reflects most of the radiant energy that reaches it. It is a property of the material, not a prediction about your house. What it saves you depends on your roof, your attic temperature, where your ducts run and what insulation is already there. A number on a product sheet is not a number on your bill.
Can I have both radiant barrier and spray foam?
Not usefully in the same assembly. A sealed roof deck already brings the attic inside the envelope, which solves the problem the barrier addresses. If we are foaming the deck, an existing barrier stapled to the rafters comes out so the foam can bond. Pick one strategy for the attic, not both.