Is 12 inches of insulation enough?

Author: Prof. Jasmin Homenick  |  Last update: Saturday, April 25, 2026

To find out if you have enough attic insulation, measure the thickness of the insulation. If it is less than an equivalent of R-30 (about 10 to 13 inches), you could probably benefit by adding more.

How many inches of insulation is good?

R-Value is a measure of insulation's ability to resist heat flow. The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R-38 or about 10 to 14 inches, depending on insulation type.

What is the recommended thickness of insulation?

For insulation rolls and batts, the recommended thickness level is 270mm. This is what you will have to insulate to in a new property, and what you should be aiming to insulate to in an older one. If starting from nothing, you will probably have to buy and install two rolls or batts.

Can you put too much insulation in your attic?

Mold and Mildew Growth

Having too much insulation in your attic can allow for the accumulation of moisture. This leads to mold and mildew growth, which can be extremely bad for your health.

Where should you not put insulation in the attic?

Also, when laying down additional insulation, work from the perimeter toward the attic opening. Never lay insulation over recessed light fixtures or soffit vents. Keep all insulation at least 3 inches away from recessed "can" lights, unless they are rated IC (Insulated Ceiling).

Insulation R-VALUE - What is R-Value?

Does extra insulation really help?

Unless your home was specially constructed for energy efficiency, you can probably reduce your energy bills by adding more insulation. Many older homes have less insulation than homes built today, but even adding insulation to a newer home can pay for itself within a few years.

What is the thinnest insulation with the highest R-value?

Thermablok® Aerogel is a revolutionary advancement in thermal technology offering the thinnest insulation available to prevent thermal and cold bridging. Classed as a Super Insulation, Aerogel has the highest insulation value of any known material with the lowest thermal conductivity value of any solid (0.015W/mK).

How thick should insulation be in attic R-value?

Attic insulation should be R49-R60, while floor insulation should be R25-R30 for those in the north of the United States. Insulation material with a minimum R-value can be an option if you only install more on top of the insulation installed.

What is the most effective insulation per inch?

Insulation R-Value Chart
  • Closed Cell Spray Foam: R-6 to R-7.
  • Foam Board: R-4.5 to R-5.
  • RetroFoam Injection Foam: R-4.6 to R-5.
  • Open Cell Spray Foam: R-3.6 to R-3.9.
  • Cellulose (Loose-Fill): R-3.1 to R-3.8.
  • Fiberglass (Batts): R-2.9 to R3.8.
  • Fiberglass (Loose-Fill): R-2.2 to R-2.9.

How do I know if my attic is insulated enough?

If your home, or upper floor, is too hot in the summer and too cold in the winter it is likely that you have insufficient attic insulation. If a visual inspection of your attic identifies that the insulation is level with or below the attic joists – you need more insulation.

Should old attic insulation be removed?

The bottom line is the old insulation needs to be removed because it hinders the airflow into the attic, it can promote mold growth, and it is dirty.

Is there a big difference between R13 and R15?

R15 insulation offers slightly better thermal insulative properties than R13. Some of its formats are a fraction of an inch thicker than R13, making it more effective at helping with energy efficiency. However, the difference is minimal.

Do I need faced or unfaced insulation?

For example, if you need extra soundproofing or don't want to spend time installing a separate vapor barrier, then face may be the best option for you. However, if cost savings are more important than convenience, then unfaced may be the better choice in this case.

What does R 12 insulation mean?

R-Value is a measure of insulation's ability to resist heat traveling through it. The higher the R-Value the better the thermal performance of the insulation.

Can you over-insulate a house?

It is possible to over-insulate your house so much that it can't breathe. The whole point of home insulation is to tightly seal your home's interior. But if it becomes too tightly sealed with too many layers of insulation, moisture can get trapped inside those layers. That's when mold starts to grow.

Should I insulate my attic floor or ceiling?

Insulating your attic floor can create a vented attic, which is ideal for storage and not needing temperature control upstairs. Insulating the ceiling will make an unvented attic, which allows you to control the temperature for temperamental storage items, living space, and HVAC ductwork.

How many inches should attic insulation be?

If you live in the Southern part of the U.S., the recommended insulation level is a minimum of R-38 or about 13-14 inches of insulation. If you live in the Northern part of the U.S., the recommended insulation level is a minimum of R-49 or about 16-18 inches of insulation.

What is the most affordable type of insulation?

It's essential to wear protective clothing and a mask when installing fibreglass insulation to prevent any health risks. Overall, fibreglass insulation is the cheapest and most effective insulation option available, making it a popular choice for homeowners and builders alike.

What insulation board has the best R-value?

The best kind of rigid foam insulation is polyisocyanurate, also known as polyiso. It has the highest R-rating of any rigid foam insulation and comes with a reflective foil on both sides, allowing it to act as a radiant barrier as well.

Is foam board insulation better than fiberglass?

High R-value: Because foam board insulation has a greater R-value than standard fiberglass/batt insulation, it is more effective at insulating and decreasing heat loss.

Where should you not put insulation?

Never place insulation close to water heaters, oil burners or anything hot. The backing is especially flammable and will be a major fire hazard for your home.

Can too much attic insulation be bad?

While loft insulation is an effective way to improve energy efficiency and reduce heating costs, over-insulating can lead to several potential issues. Firstly, over-insulation can lead to poor ventilation in the attic, which can cause moisture buildup and increase the risk of mould growth.

Can your R-value be too high?

The optimal R-value for most homes is 30, but you can go as high as 38 if you live in a tropical climate. Anything higher than 38 indicates an over-insulated space. While you might think that too much insulation can't be bad, there are some significant consequences to consider.

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