How much does internal wall insulation cost? What are the advantages of styrofoam, and what are the benefits of rock wool and glass wool when insulating a wall from the inside? Is the cost of materials and labor the only consideration? Which insulation is better for DIY projects, and when is a professional needed?
We have previously discussed internal wall insulation. Experienced insulators always advise, if possible, to aim for external insulation. More on why can be found at THIS LINK.
However, sometimes it’s not possible to insulate externally due to various reasons, such as cold walls in apartments on higher floors, or legal procedures required for external modifications to the building. Besides practical reasons, financial considerations often lead to choosing internal insulation. Generally, internal wall insulation is cheaper.
Styrofoam is cheaper than rock wool, but…
Covering an external wall with styrofoam costs about 30% less than stone wall, and if you opt for internal insulation, the amount can be half that.
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However, if you’re insulating small wall the price might not play a significant role, so the question arises – which material is better, rock wool or styrofoam?
In terms of insulation quality alone, rock wool is the better choice. Rock wool provides superior insulation, but its main advantage over styrofoam is greater vapor permeability. This is crucial when the insulation is installed internally.
Why is working with rock wool more complex?
However, installing rock wool insulation is a more complex task. The procedure requires first mounting a steel profile framework, known as a “grill,” on the wall. Then, rock wool panels are inserted, followed by a vapor-permeable foil and gypsum board panels. The process concludes with plastering and painting.
This task requires a certain level of skill, and to achieve satisfactory results, it is generally necessary to hire an experienced professional.
On the other hand, using styrofoam panels is much easier. The panels are glued directly onto the wall. Because styrofoam is firm and has precise dimensions, it results in a smooth surface with minimal need for skilled labor. After applying the styrofoam, a reinforcing mesh is used to fix the surface, followed by plastering and painting.
Installing styrofoam involves much less work, so the labor costs are lower, and it can be done more easily as a DIY project compared to rock wool. Additionally, less material is used, making it more cost-effective from that perspective as well.
What are the drawbacks of internal insulation?
It should be noted that installing two inch thick styrofoam panels, which provides adequate insulation for a cold wall, results in a thinner overall insulation layer, preserving more usable space in the room compared with rock wool.
As mentioned, in terms of thermal insulation and vapor permeability, rock wool is the better choice. Installing rock wool creates a sturdier surface because gypsum boards are more robust than styrofoam covered with reinforcing mesh and plaster.
This means nails can be driven in to support heavier pictures. However, shelving will not be possible. For both rock wool and styrofoam, installing heavy shelves requires special wall anchors that are fixed into the wall beneath the insulation, not the insulation itself.
Photo, Freepik, Rockwool