Roof and wall insulation calculator
Choose the construction, the rafters and the wood fibre board and enter the area in m². You get quantities, pallets, the price including VAT, recommended membranes and an approximate U-value.
Want to see the construction in section? The generator for walls, floors and roofs shows the layers, the dew point and a condensation check.
| Layer | d, mm | λ |
|---|---|---|
| Plasterboard / lining | 12.5 | 0.25 |
| Isocell AIRSTOP DIVA vapour barrier · sd 0.5–30 m · recommended, not in the quote | 0.2 | 0.2 |
| naturheld FLEX between the rafters (90 %) · rafters 80/200 mm @ 800 mm | 200 | 0.036 |
| naturheld 140 | 60 | 0.041 |
The U-value is approximate (ISO 6946, parallel-path method, without thermal bridges from fixings). Reference: Bulgarian Ordinance No. 7 — 0.28 W/m²K for walls; the roof figure is an indicative value. For an exact moisture and phase-shift check, use ubakus.
Quote
120 m² · waste 5 %| Item | Qty | € incl. VAT€ excl. VAT |
|---|---|---|
| Insulation | ||
| naturheld FLEX 200 mm 1220×575 mm · between the rafters (90 % of the area) · 6.8 pallets | 162 pcs | €4,854.17€4,045.14 excl. VAT |
| naturheld 140 60 mm 1880×615 mm, tongue & groove · 132.96 m² gross · 3.0 pallets | 115 boards | €3,650.10€3,041.75 excl. VAT |
| Membranes · recommended, optional | ||
Isocell AIRSTOP DIVA vapour barrier recommended on the inside, behind the lining — the airtight layer; +10 % for overlaps | 2 rolls (128 m²) | + €1,216.51€1,013.76 excl. VAT |
| Tapes and accessories · recommended, optional | ||
Isocell AIRSTOP FLEX 60 tape recommended overlaps, junctions with walls, chimneys and roof windows · approx. 156 m | 7 rolls (25 m) | + €178.50€148.75 excl. VAT |
| Labour (indicative) | ||
| Fitting FLEX between the rafters €6 excl. VAT/m² | 120 m² | €864.00€720.00 excl. VAT |
| Laying the boards above the rafters €12 excl. VAT/m² | 120 m² | €1,728.00€1,440.00 excl. VAT |
The membranes and tapes are a recommendation for the selected construction. Tick the ones you want in the quote — until they are ticked they are not included in the total.
Prices are ex warehouse in Bulgaria — shown excluding VAT and including 20 % VAT. An extra charge may apply to orders under €10,000 excl. VAT. Quantities are approximate — the final quote is confirmed by MODOPAN.
What the calculator works out
- The quantities of naturheld boards and of naturheld FLEX flexible insulation between the rafters or studs — in m², number of boards and pallets, with a waste allowance of your choice.
- The price including VAT from the current price list; optionally also indicative labour at average market rates in Bulgaria.
- The recommended membranes and adhesive tapes — optional, they are added to the total only if you tick them.
- An approximate U-value of the roof or wall and a moisture check against the simplified DIN 4108-3 rule.
- Notes depending on the roof pitch: below 15° a roofing underlay is needed on top of the board, below 10° a waterproof layer.
Roof area: how to work it out
The calculator does not work out the roof area from the dimensions of the house — you enter the area along the slope in m². For a gable roof (and any roof whose slopes all have the same pitch) it is:
area along the slope = horizontal roof area (including the eaves) ÷ cos(pitch)
| Pitch | Slope area = plan area × | For 100 m² in plan |
|---|---|---|
| 15° | 1.035 | 103.5 m² |
| 20° | 1.064 | 106.4 m² |
| 25° | 1.103 | 110.3 m² |
| 30° | 1.155 | 115.5 m² |
| 35° | 1.221 | 122.1 m² |
| 40° | 1.305 | 130.5 m² |
| 45° | 1.414 | 141.4 m² |
Example: a roof of 10 × 8 m in plan (80 m² including the eaves), pitch 30° → about 92.4 m² along the slope. Do not add the waste to the area — the calculator adds it separately.
How the roof is insulated — from inside, between and over the rafters or entirely from above — is shown in the roof system.
