If R-38 is our code, why do I recommend R-49 for attic insulation?

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Code requirements are minimum standards imposed on home builders by county governments. Most every county in the USA has a code enforcement department.

These folks are tasked with the responsibility of enforcing the building standards that the county government has adopted. Each county is a little different.

We once owned land in extreme NW Ga. When I wanted to build a house, I found that there were only two county inspections: one for the septic tank system, and one for the electrical system. Everything else was the “wild west”. The local government didn’t interfere with what you built… so long as the septic system and the electrical system met their standards.

However, not so in metro Atlanta counties!

Codes are Strict Minimum Guidelines
Every home builder in our area must insulate the attic to a minimum of R-38. (I am restricting this article to vented attics. This does not apply to attics that are sealed and encapsulated with spray foam insulation).

R-38 is the minimum standard by which an Atlanta area builder will pass his county code inspection for residential attic insulation.

However, there is no law that says you cannot have more protection against extreme temperatures. And more insulation generally means your home will be more comfortable, more energy efficient, with a higher resale value.

In fact, the U.S. Department of Energy recommends that homes in north GA, (including metro Atlanta) have R-49 attic insulation.


Minimum vs Recommended
So, for your attic insulation, we have a minimum standard of R-38, and a recommended standard of R-49.


Bob’s explanation of R-Value
R-Value is explained as thus: “the resistance, or strength of a material to slowing down the flow (movement) of heat”.

Generally speaking, cellulose attic insulation doesn’t care which way the heat is moving. It just wants to slow it down! So the thicker the layer of cellulose insulation, the higher the R Value. Cellulose performs at around R 3.7 per inch.

The higher the R-Value, the better the job of slowing the movement of heat.

Will you be satisfied with R-38 attic insulation?
Is R-38 enough? Afterall, our county governments have a lot of smart folks that come up with these requirements.

In my experience, R-38 is just enough to keep you comfortable and happy for about half the year. Afterall, it’s the minimum. Don’t expect anything more from it.

> R-38 is Fall & Spring protection.

> R-49 gives you Winter & Summer protection.

During Atlanta’s hot sunny days, you might squeak by with R-38 if you have plenty of mid-day and afternoon shade and a lighter colored roof. R-38 is fine if you don’t mind hearing your AC run on-and-on, hour-after-hour from noon to bedtime, barely holding the inside temperature at 78 to 80 degrees.

When you go with R-49, that extra 3” of cellulose insulation makes all the difference! Regardless of winter heat loss, or summer heat gain, your cellulose attic insulation will protect you from those extremes.

It doesn’t matter if your attic roof is low-pitched, dark colored, poorly ventilated, with full sunshine. R-49 will do a good job of protecting your ceilings from the extreme inferno-like temperatures of 130-140 degrees in your attic.

Think about it. If it’s 140 degrees in your attic, and you’re trying to hold 75 degrees inside the house, your attic insulation has to protect you from 65 degrees of heat gain. Hot is always moving to cold. That’s the 2nd Law of Thermodynamics.

Choose R-38, and that same house will likely realize heat gain through the ceilings every sunny afternoon during summer.

In the winter, it’s just as powerful. Only your R-38 is trying to slow the flow of heat loss, as hot always moves to cold.


Choose R-49, and move on with life!

R-49 cellulose attic insulation may be overkill during fall and spring. However, during the winter and summer months, when you need it most, R-49 cellulose attic insulation will leave you feeling just right!

With our services, we provide R-40 and R-50. With these two levels of service, you’re guaranteed that if we are a little thin somewhere in your attic, you still get the required (R-38) or recommended (R-49) levels of protection.

Thanks for reading!
Bob Bird
Bird Family Insulation
“Your home comfort re-imagined!”


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