Most standard insulation materials (like fiberglass batts, blown-in cellulose, and open-cell spray foam) provide about π- π to π- π.π of thermal resistance per inch of thickness. A three-inch layer of these standard materials will provide roughly R- 9 to R- 11 total.
Spray foam insulation R-value represents the heat resistance for every inch of insulation applied. In essence, a recommended thickness of R-30 is achieved by applying a 5.5-inch depth of spray foam with an R6 rating.
Once againβyou would expect the R-value of 18 for 3β thickness, but the actual R value for rigid insulation is R-18.5 for 3β thick polyiso boards.
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.
R60 insulation is worth it if you live in a very cold climate (like the northern U.S. or Canada), but it is often considered overkill for mild climates. While it maximizes comfort and thermal efficiency, you will experience diminishing financial returns compared to standard R38 or R49 insulation.
It's recommended to leave an air gap insulation of at least 25mm or 1 inch for the walls and ceilings. This should be enough to allow for ventilation and prevent moisture buildup. The same rule may be applied when using foil insulation. On roofs, the air gap should be larger, typically around 50mm or 2 inches.
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.
What time of year is Insulation cheapest?
Achieving an R-30 insulation value in a 2x6 wall (which provides a standard 5.5-inch cavity) requires combining high-density cavity insulation with exterior continuous insulation (such as rigid foam boards) to prevent thermal bridging.
The absolute thinnest insulation with the highest Rcap Rπ -value is Aerogel, which provides an incredible Rcap Rπ -10 to Rcap Rπ -12 per inch. For more budget-friendly applications, Polyisocyanurate (Polyiso) foam board offers the best everyday value, delivering about Rcap Rπ -6 to Rcap Rπ -6.5 per inch.
R60 insulation represents the premium tier of attic thermal protection. Achieving R60 requires approximately 17 to 22 inches of blown-in fiberglass, 16 to 18 inches of blown-in cellulose, or carefully layered batt insulation systems.
R-30 insulation thickness varies by material, typically ranging from 8.25 to 10 inches for fiberglass batts and up to 10 to 12 inches for blown-in loose-fill. This thickness allows it to meet the strict thermal resistance standards required for attics and cathedral ceilings.
WD-40 affects foam in different ways depending on the type of foam. It is highly useful for cleaning, holding, or dissolving, but can cause permanent damage to certain materials.
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.
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. Use the JM insulation calculator to determine the recommended R-value for your project, as well as how much insulation you'll need.
Thermal Resistance: R-21 polyiso boards offer higher thermal resistance compared to R-19, which makes them more effective at reducing heat transfer in colder climates.
Mice are curious and always searching for safe, snug, and warm nesting sites. Attics filled with blown-in insulation provide an excellent optionβfrom 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.
Interior walls are frequently left uninsulated during construction because the energy efficiency benefits aren't as great as insulating exterior walls, floors and ceilings.
Yes, you can insulate the underside of your roof, but doing so converts your attic from a vented "cold" space to an unvented "conditioned" space. This requires careful moisture control to prevent roof rot. You can accomplish this in two primary ways:
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.
Yes, insulation is tax-deductible in the form of a federal tax credit, specifically the Energy Efficient Home Improvement Credit (Section 25C). You can claim 30% of the cost of insulation and air sealing materials, up to a maximum annual credit of $π,πππ.
Foam insulation is a common target because it's easy for them to chew through. The material offers little resistance, allowing mice to create tunnels or nests within the insulation. But mice aren't just interested in chewing for the sake of itβthey're also drawn to the warmth and shelter insulation provides.