Do R30 and R38 make a difference?

Author: Prof. Gunner Stehr  |  Last update: Friday, August 15, 2025

R-value measures insulation's heat resistance, with higher values indicating better performance. R38 insulation has a higher R-value than R30, providing greater resistance to heat flow. This increased resistance translates to improved energy efficiency and better temperature regulation in homes.

Is there a big difference between R30 and R38?

Selecting the correct insulation level is crucial for optimizing building performance and energy efficiency. Comparing R-30 and R-38 insulation highlights the key differences in thermal resistance, thickness, and suitability for various climates.

How big of a difference does R-value make?

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.

Is R30 enough insulation for an attic?

Depending on where you live and the part of your home you're insulating (walls, crawlspace, attic, etc.), you'll need a different R-Value. Typical recommendations for exterior walls are R-13 to R-23, while R-30, R-38 and R-49 are common for ceilings and attic spaces.

What is the best R-value for an attic?

The recommended amount of attic insulation can vary based on your location and local climate. However, a general guideline is to aim for an insulation level of R-30 to R-60. Here's a breakdown: R-30: Suitable for warmer climates, providing adequate insulation for moderate temperature variations.

Batt vs Blown Insulation - What's the Difference?

Is R38 insulation good for an attic?

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.

Can insulation 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.

Is it worth upgrading attic insulation?

Heat naturally rises, and without proper insulation, it escapes through your attic, forcing your HVAC system to work harder. 💰 Upgrading insulation can reduce energy costs by up to 30%! ✅ Better insulation = less heat loss in winter and less heat gain in summer.

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.

Do you want a high or low R-value?

It's more efficient to use a higher R Value rated product in the upper levels of your home, such as the attic and in rooms with particularly high ceilings - this makes sense if you consider that heat tends to rise.

Should attic insulation be faced or unfaced?

You can use faced or unfaced batting when installing between the roof rafters of finished attic spaces. When using paper or plastic batting insulation, that moisture barrier should face outward toward the attic space. Even if the attic space is unheated, it's typically warmer than the outside air in winter.

Does doubling insulation double R-value?

The dip from R10 to R4 seems odd, as one would expect more R as you travel further north through the zones. Thicker is not better! Doubling the amount of insulation will double the R-Value, but so what? Doubling the insulation from R-19 to R-38 does NOT cut the heat loss in half (50%) it cuts it by around 3%!

How much blown insulation is R38?

Using the known R- values per inch of each type of insulation, we know that to install R-38 you need from 10” to 12” of cellulose and 14” to 17” of fiberglass.

Does higher R-value mean better insulation?

The higher the R-Value, the greater the insulation performance. Example: A 0.22m thick insulation slab with a thermal conductivity of λ=1.2W/mK has an R-Value of 0.18 m2K/W. Structures such as walls, roofs, and floors tend to be made up of multiple different layers of materials.

Is R30 insulation good for a garage?

Here, the level of R-Value you apply is largely going to depend on whether or not you have a finished room over the garage. If you do, this is going to be resting on joists and will give you roughly 10 inches of play in which you can apply high-density R-30 style insulation.

Is R30 enough insulation?

While both types provide insulation, R30 is the better option for maximizing energy savings in areas where heat loss or gain is a major concern. For example, R19 may suffice for interior walls, but R30 is more appropriate for exterior-facing attics or floors.

How thick is R30 batting?

8¼ ” thick, R-30C EcoTouch® Thermal Batt insulation prevents moisture damage and helps assure long roof life by providing 1" of ventilation air space between the insulation and roof deck. Easy Installation R-30C EcoTouch® Thermal Batt insulation is easy to handle and install.

Is cellulose or fiberglass insulation better?

At 3.5 per inch of material, the R-value of blown-in cellulose is 23% better per inch than fiberglass batts! According to research done at the Oak Ridge National Lab, fiberglass loses up to 50% of its R-value in very cold conditions; making cellulose a better choice for homes in northern climates.

Should I remove old attic insulation before adding new?

Do I Have To Remove Old Insulation? Unless your insulation is wet, moldy or infested with pests, you don't need to remove it before adding insulation on top of it. ENERGY STAR® recommends that you inspect your insulation for signs of mold, mildew, moisture and pest infiltration before making this determination.

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.

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).

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

The thinnest insulation material currently available on the market is the 10mm Aerogel blanket. Its manufacturing technology is highly interesting, and its appearance resembles frozen smoke. For some, aerogel is synonymous with time frozen and suspended in space.

Is it okay to cover attic insulation with plywood?

Can I put plywood over insulation in the attic? Yes you can install plywood subflooring directly over the floor joists and insulation on your floor. You need to install rigid insulation boards on top of the attic flooring joists and then install plywood over the top.

Should I double insulate my attic?

The most common situation for adding an extra layer of thermal insulation is in the attic floor. If your loft is not used for storage purposes, doubling the insulation layers is highly recommended.

Previous article
How do you increase the yield of cucumbers?
Next article
Is growing hydroponics worth it?