Attic finishing. Price per m2

Attic insulation. Does it matter?

The most important thing is to insulate the attic, because as much as 30% of the heat from the house can escape through an uninsulated roof. To ensure thermal insulation, we must ensure that the roof insulation is of appropriate thickness and installed correctly. If this is the case, we will reduce heat losses to a minimum. Good attic insulation also guarantees thermal comfort of the rooms under the slopes, so we can use them as a living space. Therefore, we should think about our plans for the attic well in advance. Maybe it will be necessary to change the insulation material proposed in the project? Maybe it will be necessary to increase the thickness of the insulation itself? By the way, you should consider the location of roof windows. Is their location functional and will it provide enough daylight in the residential attic? Insulating the attic and illuminating it are the most important tasks that we face before we start finishing the attic.

Insulating the attic with wool. What material to choose?

The best thermal insulation materials for attic insulation are elastic materials that wedge well between the beams. Mineral wool is the most valued by professionals. Be sure to check its thermal insulation before purchasing it. Mineral wool can be glass or rock. Mineral wool is sold in the form of mats or boards with a density of 20 to 100 kg/m3. The wool thermal insulation layer must be 20-35 cm. This thickness does not fit between the rafters, so the rest is suspended from the bottom of the roof. Other thermal insulation products, such as wood fiber boards, can also be placed between roof rafters. However, these cannot compete with mineral wool. Mineral wool is unrivaled when it comes to attic insulation. It is best suited for insulating attics because it is non-flammable.

Attic insulation What thickness of insulation should be used?

The question about the thickness of the attic thermal insulation is asked very often. This is usually stated in the house design. The heat transfer coefficient through the roof depends on the thickness of the insulation and the value of the lambda coefficient of the material selected for insulating the attic. There is a relationship: when the lambda coefficient is low, we can successfully decide to lay a thin layer of mineral wool. We will obtain the same U value as when laying material with a higher lambda coefficient. A layer of mineral wool used to insulate the attic that is larger than specified in the regulations will not hurt, but why overpay? Insulating the attic slopes with a thicker layer will also reduce the volume of the rooms under the slopes. On the other hand, if we insulate the attic from the outside, too thick a layer of mineral wool will make the roof surfaces look disproportionate.

The total insulation thickness when insulating the attic with mineral wool should be 20-35 cm. The Styrofoam layer is 20-25 cm (assuming that we use EPS 100 boards). We can reduce the thickness by 10 cm by using PIR instead of EPS. We will keep the U value the same.

Attic insulation with mineral wool. What is the cost of insulating the attic with mineral wool?

According to the Murator monthly: to obtain a U of 0.15 W/(m2.K) for a sloping roof, you need, for example, 20 cm of mineral wool with a coefficient of λ = 0.031, or 23 cm of mineral wool with a coefficient of λ = 0.033, or 25 cm of wool with a coefficient of λ = 0.033. lambda 0.035 W/(mK). Many manufacturers offer such mineral wool for attic insulation in various thicknesses, for example 5, 10, 12, 15, 18, 20 cm.

Attic insulation up to U = 0.15 W/(m2.K) A wool mat with λ = 0.035 and a thickness of 15 cm, depending on the manufacturer, costs PLN 36-48/m2. A 10 cm thick mat costs PLN 30-39/m2. Therefore, we will pay PLN 66-87/m2 for mineral wool for attic insulation.

Attic insulation up to U = 0.12 W/(m2.K) If we wanted to insulate the roof with mineral wool to the level of 0.012 W/(m2.K), we would need to lay 25 cm of wool with a coefficient of λ = 0.031. Such a 15 cm thick mat costs PLN 50-58, depending on the manufacturer, and a 10 cm thick layer costs PLN 40-48/m2. The total cost of attic insulation material would be PLN 90-106/m2.

Insulating the attic with wool. Cost of labor and foil

Of course, the value of labor may vary greatly, but generally the contractor will pay approximately PLN 100/m2 for attic insulation work with wool. This price includes making the grate and covering the mineral wool with foil. A good quality foil costs about PLN 2/m2.

Attic insulation. How much will you pay?

To sum up, insulating the attic with wool may cost: in the basic variant (U = 0.15) – PLN 168-189/m2 and in the very warm variant recommended for passive houses (0.12) – PLN 192-208/m2.

However, we reserve that with today’s inflation, the amounts we will have to pay for attic insulation with wool may change from week to week and be much higher.