If you need to increase insulation thickness or achieve a higher R-value, you can stack two sheets of Celotex insulation on top of each other.
Understanding Double Insulation
This can be achieved by using two different types of insulation materials or doubling up on the same material. The purpose is to create an extra barrier against heat transfer, thus enhancing the energy efficiency of a building.
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.
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.
Thicker is better
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.
As a general guideline, it's advisable to install double layers of thermal insulation throughout your house.
Because its structure is more complex than single-layer insulation, the cost is relatively high. Additionally, in some cases, double-insulated cables may fail due to spalling between the inner and outer insulation layers.
Adding two R-13, 3.5” batts to a 2”x6” (5.5”) wood stud cavity will not provide an R-26. The total of 7” of insulation is reduced in thickness to 5.5” thereby losing the R-value associated with its full thickness.
thick, thermal resistance gains may be limited, especially if the wall already contains some insulation. However, next to adding either interior or exterior insulation, good results can be had. Before proceeding, try looking behind electrical outlets – with the power off – to find out what already exists in the walls.
Installing more insulation in your home increases the R-value and the resistance to heat flow. In general, increased insulation thickness will proportionally increase the R-value.
It is recommended to have an external wall insulation thickness of 100mm to achieve better thermal efficiency and reduce the U-value by 0.3W/m2K.
Leaving Too Many Gaps
One of the biggest problems DIY homeowners face is leaving too many gaps in their insulation. Gaps or insulation that isn't secured correctly can leave the building structure open to air and moisture leaks. Spray foam insulation is best for reaching into small cracks and any areas left open.
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.
R19 Insulation offers superior thermal insulation compared to R13. With a typical thickness of 6.25 inches, R19 fiberglass is designed for use in 2x6 wall cavities, making them suitable for colder climates where higher thermal resistance is necessary.
The primary purpose of double insulation is to protect the user from the risk of electric shock. If the first layer of insulation fails for any reason, the second layer acts as a backup, preventing any live parts from becoming exposed.
In the case of dampness, the insulation may need to be removed and replaced. For underfilled cavities, the loose-fill insulation can be topped up, though this is expensive.
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.
An over-insulated house is susceptible to mold since it is so tightly sealed that it prevents moisture from escaping. It also prevents air from entering, circulating, and exiting, which can significantly reduce indoor air quality.
If you double the thickness of your insulation, you're essentially giving its R-value a twin sibling. Double trouble, double warmth!
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.
It's a reasonable question—after all, if one layer of insulation is good, wouldn't two be better? Unfortunately, the answer is no. Stacking insulation doesn't improve R-value in the way you might think, and it can actually create more problems than it solves.
Loose-fill insulation can be installed on top of old insulation. Whole-house air sealing is a wise idea before adding new insulation, as leaks will reduce energy efficiency and comfort.
For most long-term applications, double bubble foil insulation is going to be the better option to use. Because of the double layer of polyethylene bubbles, double bubble insulation provides the most effective thermal break, making it harder for radiant heat to transfer through than with single bubble insulation.
It is a 2×6 wall with drywall, insulation, and sheathing. Then, a thick layer of rigid foam and an outer layer of sheathing. The middle double wall uses 2x4s for both the inner and outer walls with a gap between them to allow for ample insulation between the walls and eliminates thermal bridging.