In plain words: how to find the right insulation thickness for your wall — with no formulas and no engineering degree. Enter your wall layers and city, and get a concrete number.
What you'll learn
You want to insulate your home but don't know how many centimetres of insulation to use: 5, 10 or 15? This is the most common question, and the answer is just a number that's easy to work out yourself. In this article, with no formulas, we show what the thickness depends on and how to check it in a minute.
Why "eyeballing it" doesn't work
More insulation means better warmth — but also more money. Less means you save now, but the wall won't reach the standard and the house will be cold. The right thickness is a balance that depends on three things:
- what the wall is made of (brick, aerated concrete, concrete) and how thick it is;
- which insulation you choose — each has its own "thermal conductivity" (denoted λ, lambda): the lower the λ, the thinner the layer you need;
- where you're building — the standard is stricter for a colder region.
What the standard says
In Ukraine the standard in force is ДБН В.2.6-31:2016. It sets the minimum "thermal resistance" of a wall — how well it holds heat. This resistance is denoted by the letter R: the higher the R, the warmer the wall. For residential walls you need roughly R = 3.3 m²·K/W (the exact value depends on the region).
The calculator takes your wall's layers, adds the chosen insulation and computes the final R. If it reaches the standard, the thickness is enough. If not, it will show that the wall "doesn't pass", and you simply increase the layer.
Don't try to guess λ from memory. In the materials library the λ of each insulation is already listed — mineral wool, expanded polystyrene, PIR and so on. Pick a material from the list and the calculator fills in the value for you.
How to do it in a minute
- Open the thermal conductivity calculator.
- Add your wall's layers (for example, 300 mm of aerated concrete + plaster).
- Add insulation and pick a thickness — start with 10 cm.
- Choose your city.
- Look at the result: your wall's R and a "meets / doesn't meet ДБН" mark.
If the wall doesn't pass, increase the thickness by one step and recalculate. In 3–4 tries you'll find the minimum thickness that passes the standard.
Безкоштовно · без реєстрації
Example
A D500 aerated-concrete wall 300 mm thick has an R of about 2.3 m²·K/W — that's not enough. We add 50 mm of mineral wool (λ ≈ 0.042) and the R rises to roughly 3.5, so the wall passes the standard. So 5 cm of insulation is enough for this wall, not 15. It's exactly this kind of check that saves money on materials.
Frequently asked questions
Can I take more insulation "to be safe"? You can, but every extra centimetre costs money and gives less and less benefit. The calculator shows where "enough" is.
Do different insulations give different thicknesses? Yes. PIR and polyurethane have a lower λ, so they can be thinner; mineral wool needs to be thicker. You can compare them in the materials library.
Where to next? If the wall is also cold to the touch or damp, read about why a wall gets damp and where condensation forms.
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