Rigid Mineral Wool Foundation Insulation vs. XP Insulation

Generally speaking, it is preferable to have a warm, comfortable house than a drafty one. A warm, comfortable and especially healthy home today, means to be properly ventilated and well insulated. Insulation for a house is like clothing for a human being. It protects you from vagaries of weather.

Insulation Type
Rigid Mineral Wool Foundation Insulation

So basically there cannot be a comfortable and healthy home without proper insulation. There are many types of rigid insulation used to insulate foundations. One of the most popular types is of course, XP insulation board. However, lately has started to be widely used another type of insulation, namely Rigid Mineral Wool Insulation.

Rigid Mineral Wool Insulation could be indeed a great competitor of the most famous XPS insulation board.


Because this relatively new type of insulation is distinguished by several qualities such as:

a)    It drains water very quickly;
b)    It is fireproof;
c)     It is insect resistant;

Could Be Rigid Mineral Wool Insulation a Viable Alternative to XPS Insulation Board?

It is well known that the most foundations, regardless of the building profile, industrial, commercial or residential are insulated generally on the exterior. For the insulation is used in an overwhelming proportion XPS Insulation Board (extruded polystyrene). It is actually the type of insulation that is the best suited for a foundation.

a)    XPS board insulation is widely available;
b)    It has an affordable price;
c)     It has a low absorption coefficient, so it is moisture resistant;
d)    It has thermal resistance (R-Value) R – 5;

Despite these obvious advantages, it has yet several drawbacks:

a)    Generally, the concerns are related to the poor resistance to insects. Carpenter ants and termites tunnel through insulation without any problems. These insects often use XP as a safe way to get into your home;
b)    If XP insulation board isn’t properly protected, it can be affected easily by the sunlight;
c)     Because XP is in fact, extruded polystyrene, it is extremely flammable. Therefore, this type of insulation requires in composition a fire retardant such as HBCD (hexabromocyclododecane). Unfortunately, this chemical is extremely toxic. It is known as PBT (or bio-accumulative toxin) and it is under close examination in the European Union.

Rigid Mineral Wool Insulation

Rigid mineral wool insulation could be indeed a great alternative to XPS board insulation. I have listed above the qualities of this type of insulation.

Mineral wool is made by melting iron-ore slag or basalt (which is an igneous rock) and spinning fibers (like cotton candy). These compounds are homogenized together by a binder (a phenolic binder).

Rigid mineral wool unlike XP is fireproof, therefore it is no need for flame-retardant additives.

Unfortunately, the R-value is slightly lower than XP, only between R – 4 and R – 4.3, but it is still a respectable value.

The price of this kind of insulation is half the price of XP, but rigid mineral wool is insect resistant, drains the water better and quickly and is not affected by the sunlight, although a protective coating may be required.

In conclusion it is obvious that this product is superior to XP. The question is, why this insulation is not yet set to work extensively in the United States?

The answer is simple. Because it is a relatively new product this type of insulation is not found yet in large quantities in the United States.

Icynene – Spray Foam Insulation | How To Build A House (howtobuildahouseblog.com)