What is the best R-value insulation?

Author: Joshua Lemke  |  Last update: Friday, August 8, 2025

For the most cost-effective results, follow the recommended insulation R-values for your region:
  • North/Northeast: Attic R-49–R-60 | 2×4 walls R-13–R-15 | 2×6 walls R-19–R-21 | floors & crawl spaces R-25–R-30.
  • West/Midwest: Attic R-38–R-60 | 2×4 walls R-13–R-15 | 2×6 walls R-19–R-21 | floors & crawl spaces R-25–R-30.

What type of insulation has the best R-value?

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.

Is R30 insulation better than R19?

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.

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 R60 insulation worth it?

R49 or R60 insulation is necessary for extreme climates, but they can be an unnecessary expense if you live in a more temperate area. Typical R-values range from R13 to R60, although some products may offer higher or lower values. The higher the R-value, the better the insulating power of that material.

How to Choose the Best Insulation for Your Home | DIY Home Renovation

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).

Does doubling up insulation increase the R-value?

The thermal barrier of a home should consist of a continuous layer of insulation on all sides—including the lowest floor, the exterior walls, and the ceiling or roof. Doubling the thickness of insulation will double the insulation's R-value, cutting heat loss in half.

What happens if you over insulate an attic?

Blocked vents in a vented attic will lead to poor energy efficiency, moisture buildup in your attic space, and most importantly, it will lead to mold.

What is the R-value for a garage?

Exterior Garage Walls

Typically these will be constructed from standard 2-by-4 studs which will define the amount of insulation that you can have installed. You should be targeting an R-Value of R-13 or R-15 in these areas to properly maximize your insulation in this application.

Can I put R19 in a 2x4 wall?

The DOE Insulation Fact Sheet (DOE/CE-0180) can be ordered from the Energy Efficiency and Renewable Energy Clearinghouse or accessed from the Internet at www.ornl.gov/ roofs+walls. Fiberglass and rock wool batts—2x4 walls can hold R-13 or R-15 batts; 2x6 walls can have R-19 or R-21 products.

Can you stack insulation on top of each other?

In many cases you can add new insulation on top of old insulation, unless the old insulation is wet, mouldy, or vermiculite. If the old insulation is dry but appears to have previously been wet, you should look for the cause and repair the problem.

Should you use faced or unfaced insulation in a crawl space?

Faced insulation is ideal for spaces that have no existing insulation, such as exterior walls, attic ceilings, crawl spaces, and exterior basement walls. Please note that the proper way to install it is to have it installed facing outward or towards the person installing it.

What is the highest R-value for a 2x4 wall?

For standard 2x4 walls, which are common in older homes, an R-value of R-15 is considered good, while R-21 is excellent. This can be achieved with high-performance fiberglass batts, dense-packed cellulose, or a combination of cavity insulation and continuous insulation.

What is the most efficient insulation?

The Five Most Efficient Insulation Materials
  • Fibreglass. Fibreglass is the most widely used insulating material these days. ...
  • Cellulose. Cellulose is made from recycled paper products and isn't just an efficient insulator, it's very environmentally friendly. ...
  • Mineral wool. ...
  • Polystyrene.

What type of foam has the highest R-value?

Polyisocyanurate: Known as polyiso for short, polyisocyanurate foam has the highest R-value per inch (R-6.5 to R-6.8) of any rigid insulation. This type of rigid foam usually comes with a reflective foil facing on both sides, so it can also serve as a radiant barrier.

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.

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).

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 use R13 or R19?

R-value is used to judge thermal insulation performance and the higher the number, the better the product's insulating ability. So R19 has better insulating ability than R13. Now R-Value ranges widely across products and home applications.

What is the R-value of Thinsulate?

The thermal resistance R-value provided by Thinsulate products varies by the specific thickness and construction of the fabric. Values (US units) range from 1.6 for 80-gram fabric to 2.9 for 200-gram fabric. Thinsulate is considered "the warmest thin apparel insulation" available.

What is the pink cotton in my attic?

Fiberglass: This insulation that looks like cotton candy is commonly seen in long strips — called batts or rolls — between wall studs and ceiling joists. It might be pink, white or yellow, and it also comes in a loose-fill form, often blown into attic spaces.

How thick is Owens Corning R 38?

10¼ ” thick, R-38C EcoTouch® Thermal Batt insulation prevents moisture damage and help assure long roof life by providing 1" of ventilation air space between the insulation and roof deck.

What is the best R-value for an attic?

The U.S. Department of Energy recommends attic insulation levels of R-49 to R-60 for most homes in colder climates, and R-30 to R-49 for homes in warmer climates.

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