Does rockwool lose R-value when compressed?

Author: Elmore Stiedemann  |  Last update: Tuesday, July 15, 2025

Compressing the insulation will cause it to lose its effective R-Value – instead install ROCKWOOL Comfortbatt R-15.

Does compressing insulation affect R-value?

Compressing fiberglass batts enhances the R-value per square inch because the material is packed tightly together. However, compression also reduces the R-value of the batt overall because you lose some inches of insulation when it is packed tightly.

Can you compress ROCKWOOL sound insulation?

As these slabs are semi-rigid, they can be compressed to fit into tighter spaces, e.g. partition walls or floor space. In practice, these semi-rigid slabs can compress by up to 10% of their starting thickness.

Can ROCKWOOL be squashed?

Cutting our slabs is simple, using a sharp, long-bladed knife or insulation saw. Accurately measure out how much you need to cut to avoid leaving gaps. Don't squash down any existing insulation.

Does ROCKWOOL insulation degrade over time?

Our stone wool insulation is so durable, it can last at least 65 years – but probably longer – with no degradation in its quality or performance.

Busting R-value insulation MYTHS

What is the lifespan of ROCKWOOL insulation?

There is now a suitable range of field research and independent test evidence to suggest that, when correctly installed, ROCKWOOL stone wool insulation can retain its insulation properties for more than 65 years in external wall systems.

Does insulation lose its R-value over time?

Over the course of time, the R-value drops because the added blowing agents found in the final product eventually is replaced with air making the product less heat resistant. An initially rated R-value 5.0 XPS product will eventually drop to closer to an R-value of 4.3.

What are the disadvantages of ROCKWOOL insulation?

Cons of Rockwool Insulation

Rockwool insulation tends to be more expensive than other insulation options, which may be a consideration for budget-conscious homeowners. Rockwool also has a higher pH level which can make it unsuitable for certain environments, especially where chemical sensitivity is a concern.

Do I need a vapor barrier over ROCKWOOL?

Insulation can help reduce noise pollution from showers or other bathroom appliances in shared living spaces. Does a basement ceiling need a vapour barrier? Installing a vapour barrier is optional when utilising ROCKWOOL solutions, as stone wool insulation is water repellent.

Does ROCKWOOL sag over time?

Robust – our solutions keep their shape, don't sag over the lifetime of a building and are resistant to rot and mould, providing high thermal performance for life4/5. Recyclable – ROCKWOOL insulation can be recycled to create new products, reducing our production carbon footprint by 10 percent6.

Does ROCKWOOL lose R-value if compressed?

Compressing the insulation will cause it to lose its effective R-Value – instead install ROCKWOOL Comfortbatt R-15.

Can you double up ROCKWOOL insulation?

Yes, ROCKWOOL products can be double layered.

Which is better for soundproofing ROCKWOOL or fiberglass?

Mineral wool may be a better option for high-demand acoustic spaces. It offers increased density and absorbs low-frequency sounds. Fiberglass suits noise control in residential or commercial spaces. Cost-effective and durable, it works well for large-scale projects.

Does squashing insulation stop it from working?

Squashing Reduces Thermal Performance: Compressing insulation can decrease its ability to trap air and prevent heat from escaping. Studies have shown that squashing insulation from 270mm down to 100mm will reduce its performance by over 50% significantly affecting your home's energy efficiency.

Can you have too much R-value?

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.

What is the R-value of rockwool blown insulation?

R-Value. The R-value or thermal resistivity indicates effectiveness in stopping heat flow. The higher the R-value, the better the performance. Rockwool has an R-value of 3.6 per inch.

What happens to ROCKWOOL when it gets wet?

What happens if ROCKWOOL insulation gets wet? ROCKWOOL stone wool insulation is moisture resistant yet vapor permeable. This means that in the event the insulation becomes damp or wet, the insulation can be allowed to dry out.

Do you need to wear a mask when using ROCKWOOL?

Ventilate the area well and keep a distance to the heated equipment. For high concentrations in enclosed spaces, use a supplied air respirator. For lower concentrations, an approved mask with particle filter type N95 or better is adequate.

What can I use instead of ROCKWOOL insulation?

4 Mineral Wool Insulation Alternatives to Consider When Insulating a Home or Building
  • Sheep's Wool.
  • Cotton.
  • Aerogel.
  • HempWool®

What is better than Rockwool?

If fire resistance and soundproofing are important factors, Rockwool may be the better choice. However, if thermal efficiency and space-saving are your primary concerns, PIR insulation might be the better option.

Why does Rockwool not have a vapor barrier?

Mineral wool insulation has an open-cell structure that allows moisture vapor to pass through, helping to manage moisture and prevent condensation within the building assembly.

Do mice like rockwool insulation?

While mice's teeth are strong enough to chew through any material, they dislike chewing through thin aluminum sheets because its sharpness harms their mouths while chewing. Rockwool is a rodent's favorite because it creates a great nest that provides warmth during cold winter nights.

Does Rockwool lose R-value over time?

ROCKWOOL stone wool insulation has a unique physical structure which keeps its shape and toughness despite changes in temperature and humidity. This dimensional stability means it will never shrink and maintains a stable R-value over time.

Is 50 year old insulation still good?

Insulation lasts much longer than you would think. According to the International Association of Certified Home Inspectors, house wrap, spray foam, and wrap tape can last upwards of 80 years or more. Cellulose, foam board, white loose-fill, rock wool, fiberglass, and loose fill can all last more than 100 years.

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.

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