Yes, too much loft insulation can cause
The depth of loft insulation in some new-build homes is being increased above the government-recommended 270mm to 300mm. That said, the amount of insulation needs to be balanced with levels of airflow and ventilation. Too much insulation without sufficient ventilation can cause condensation, dampness, and mould.
Your walls or floors are always cold. Your home is drafty, especially in certain areas. You notice water leaks or moldy insulation, especially in attic spaces.
While over-insulated attics aren't as common as under-insulated attics, it is possible to put so much insulation in your attic that it has a negative impact.
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.
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.
R15 insulation offers slightly better thermal insulative properties than R13. Some of its formats are a fraction of an inch thicker than R13, making it more effective at helping with energy efficiency. However, the difference is minimal.
However, it is possible to have too much insulation. If there is too much insulation, and it comes in contact with the roof sheeting, it can block air circulation, which can lead to condensation, mould and mildew.
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.
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).
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.
Roof and ceiling insulation. Installing roof and ceiling insulation can save up to 45% (or more) on heating and cooling costs.
Conclusion. Attic insulation can last 80 to 100 years, though it loses its energy efficiency benefits with time.
Do you have any plans for furnishing/fitting out your attic in the future? Then you could simply insulate the pitched roof. But the best solution is actually to insulate both the attic floor and the underside of the roof.
As a general rule, insulation should be replaced or retrofitted every 15 to 20 years. However, it may need replacing or retrofitting sooner depending on the type of insulation installed, the R rating of the original insulation, compression and movement over time, and whether any damage has occurred.
Easier to heat and cool: When you have quality attic insulation, more heat stays in your home through the winter, and less radiates down from your attic in the summer. This resistance to heat makes it more affordable to heat or cool your home to the temperature you're comfortable with.
Given that the roof is a primary source of heat loss in buildings, doubling up on insulation in this area comes highly recommended. If your roof has insulation between the rafters, it's considered good practice, according to current standards, to double its thickness to achieve a U-value of 0.16W/m2K.
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 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.
One way that excessive loft insulation can cause dampness is by blocking ventilation. Proper ventilation is necessary to allow moisture to escape from the building. If insulation is installed too thickly or packed too tightly into the loft, it can block air flow and prevent moisture from escaping.
Yes, an air gap between the roof and insulation is needed, especially for traditional materials like fibreglass, mineral wool, and foil insulation.
Too much of anything is bad, including too much insulation in an attic. Over insulating your house and tightly sealing it too much creates a vapor barrier and forces moisture to settle on fixtures inside your home (hello, water damage!).
R13 insulation is commonly used in ceilings in moderate climates. It helps to prevent heat loss in the winter and heat gain in the summer, which can improve energy efficiency and comfort. R15 insulation is used in ceilings in colder climates or buildings with high energy usage.
Excellent Thermal Performance Owens Corning™ R-15 EcoTouch® insulation is specifically engineered to solve the efficiency problems of exterior 2x4 walls. “High density” means more fibers per square inch. It delivers a higher R-value per square inch in less space than standard insulation products.
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.