For upgrading wall insulation from R13 to R15, the jump is usually worth it if you want better thermal performance without taking up more space. Both fit into standard 3.5 3.5-inch wall cavities (like 2 ×4 stud walls), but R15 uses denser material.
R15 is essentially R13's slightly beefier cousin. It fits the same 3.5-inch cavity but uses denser fiberglass or mineral wool to achieve better thermal resistance. The difference might seem small (just 2 R-value points), but in practice, that translates to about 13% to 15% better insulation performance.
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.
The Best Type of Insulation for a Garage
To keep heat from escaping from adjoining areas of your home, you generally need a minimum R-value of R-13 or R-15 in 2-inch by 4-inch studs for your garage's insulation.
R13 insulation costs less than R15 per square foot, while R15 offers slightly better thermal resistance for your walls and floors. R13 faced fiberglass rolls cost about $0.49 per square foot, while R15 costs about $0.89 per square foot for the same format.
Mice are curious and always searching for safe, snug, and warm nesting sites. Attics filled with blown-in insulation provide an excellent option–from the mice's point of view. As long as there is a ready food source. Mice are omnivorous and will eat and chew on almost anything including wood and electrical wires.
It is a common measure adopted by manufacturers, retailers, and even some contractors to ascertain the performance of insulation. Although R-value is important, it will not help you save on your power bills. The fact is, the energy efficiency of your home does not just rely on a number.
Insulating a 24x24 two-car garage typically costs between $𝟗𝟎𝟎 and $𝟓,𝟔𝟎𝟎, with the national average sitting around $𝟒,𝟕𝟎𝟎. This cost varies primarily by whether you choose budget-friendly fiberglass batts or premium spray foam, and whether you also need to insulate the ceiling or the garage door.
When balancing upfront cost and overall thermal efficiency, the cheapest and most effective standard insulation is fiberglass batt insulation. However, if you are looking for long-term savings through superior air sealing, dense-pack cellulose often provides the best overall value.
The majority seem to agree that insulated, unheated garages, should be allowed to breathe. If the garage is heated, you will need a vapor barrier, otherwise you will get frost and mold.
Spray Foam Insulation: Offers the highest R-value (~R-6.0 to R-6.5 per inch), providing exceptional air sealing and moisture resistance. It's ideal for irregular spaces and maximizing energy savings.
Yes, you can double insulation layers to effectively increase your total R-value. Stacking or layering insulation adds thermal resistance, but to get the full benefits without losing performance, you must use the right materials and avoid compressing the insulation.
Attached, non-heated garages should have insulation with an R-value of 7 to 9, since heat loss in this type of garage can affect your home's heating costs. Heated garages should have insulation with an R-value of 10 to 13.
Because spray foam can trap moisture, hide the condition of the roof, make it difficult for surveyors to inspect, which means risks like timber decay, dry rot, and not forgetting increased fire risk. If you've got it or you're buying a property that does, this is something you need to know upfront.
Homes with crawlspaces or unheated basements benefit from R-15 insulation installed in floors. This insulation effectively blocks cold drafts and enhances indoor warmth. It's instrumental in milder climates or as an additional insulation layer.
But with all that being said, you don't necessarily need to insulate your garage if it is detached and: You don't pay to heat or cool it (maybe you simply use it for storage space and to park your car), and/or. No living spaces are over the garage—and you don't plan to create an above-the-garage apartment in the future ...
What time of year is Insulation cheapest?
You'll likely need a permit since this project may require soil grading to avoid drainage issues. Repairing your floor may be more cost-efficient than replacing it if grading is necessary. No permit may be required to hang drywall on exposed wooden wall studs in your garage.
Closed cell spray foam is rigid once set. It is a better thermal insulator and was previously sold to stabilise failing roofs. But if it has been used inappropriately or installed poorly, it might put stress on timbers, restrict air circulation and put them at risk of decaying.
Cellulose Blown-In Insulation or Spray Applied Insulation. Covers 48.8 sq. ft.
The Environmental Protection Agency banned spray-on asbestos insulation in 1973, certain types of pipe and block insulation in 1975 and new asbestos insulation products in 1989. In 2024, the EPA banned most uses of chrysotile asbestos products, including imports.
A freezing bedroom above a garage is almost always caused by a lack of proper insulation in the garage ceiling (the room's floor), poorly sealed walls (kneewalls) in attic spaces, or inadequate HVAC airflow.
Insulating an unheated garage is generally worthwhile if you plan to spend time there (e.g., as a workshop) or if it shares walls with living spaces. It moderates temperature extremes, dampens noise, and protects stored items, though it will not keep the space perfectly room-temperature without an active heat source.