Building a home and want to check yourself whether the contractor calculated the wall and the heating power correctly? A step-by-step way to verify the numbers before you pour the concrete.
What you'll learn
The contractor proposes a wall and a boiler and says "it's all up to standard". Trust, but verify — especially when it's about your money and a home you'll live in for years. In this article we show how to check the two main numbers yourself: whether the wall passes the standard and whether the heating power is chosen correctly.
Two things worth checking
- The wall. Whether the proposed build-up reaches the ДБН thermal-protection standard.
- The heating. Whether the boiler power matches the house's actual heat loss (it's often proposed "to be safe" — and you overpay).
Both checks take a few minutes and require no engineering background.
Step 1. Check the wall
- Ask the contractor for the exact wall make-up — the material and thickness of each layer.
- Enter these layers into the thermal conductivity calculator.
- Choose your city.
- Look at the wall's R and the "meets / doesn't meet ДБН" mark.
If the calculator says "doesn't meet", and the contractor insists it's all fine — there's something to discuss before building.
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The details of this check are in the articles does my wall meet the ДБН standard and how much insulation a wall needs.
Step 2. Check the heating power
- Take the house dimensions (from the plans) and the proposed insulation.
- Enter them into the heat-loss calculator.
- Set the desired room temperature and the design temperature of your region.
- Compare the resulting kW with the boiler power the contractor proposes.
If the boiler is twice as powerful as the calculation, it's most likely an unnecessary overpayment. If it's weaker, the house may not warm up in a hard frost.
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Example
The contractor proposes a 24 kW boiler for a 120 m² house. The heat-loss calculation for this house gives ~10 kW. A 12–15 kW boiler is quite enough — the difference in equipment cost is noticeable, and you have grounds to discuss it.
Frequently asked questions
Does this replace the design documentation? No. It's a quick self-check, so you can ask the contractor the right questions rather than arguing "verbally".
What if I don't know all the parameters? Ask the contractor for the wall make-up and the dimensions from the plans — that's enough for the check.
Where's more detail on the self-builder scenario? On the page check what the contractor calculated.
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