EPS vs XPS Insulation Cost Calculator

How this calculator works

This calculator works in ranges rather than single figures, because real quotes, yields and tariffs genuinely vary that much. It starts from typical UK price, output and savings ranges drawn from published 2026 industry guides and official scheme documentation, then scales them by the quantities you enter and adjusts them for each choice you make below. The result is a low-to-high band that a realistic outcome is likely to fall within, not a promise of the figure you will achieve.

EPS costs roughly to per square metre at 100 mm against to for XPS in 2026, roughly half the price for the same chemistry in a different structure: EPS is steam-expanded beads fused into blocks, XPS a continuously extruded closed-cell foam. Thermally they sit close together, EPS at 0.030 to 0.038 W/mK and XPS at 0.028 to 0.035, so the doubled price buys structure rather than warmth.

Area to insulate (square metres)

Enter the area to be covered in the material. Both options are priced per square metre for the same area so the totals compare directly; allow around 10 percent extra for cuts and waste when ordering boards, and check coverage per pack for rolls and quilts.

Board thickness

Rigid insulation is priced largely by volume, so thickness moves the per square metre cost almost linearly: 50 mm boards cost roughly 60 percent of the 100 mm price and 150 mm around 40 percent more. The thickness you need depends on the U-value target for the element under Building Regulations Approved Document L and the material’s thermal conductivity, which is why higher-performing boards can hit the same target with less depth.

What else affects the figures

XPS’s extruded closed-cell body delivers compressive strengths of 300 to 700 kPa and near-zero water absorption, properties EPS’s fused-bead structure cannot match, which cleanly divides the territory: inverted roofs where insulation sits above the waterproofing in the wet, below-ground perimeter and basement work, and heavily loaded floors belong to XPS, while everything protected and normally loaded, external wall insulation systems, standard floor build-ups, void formers and general boarding, belongs to EPS at half the money. High-density EPS grades blur the boundary for moderately loaded floors at prices between the two, and graphite-enhanced grey EPS closes much of the thermal gap for a small premium, both worth pricing before defaulting to XPS. The honest rule mirrors the XPS-versus-PIR one: pay for XPS only where water or load demands it.

Certification, planning and grid connection

If a calculation here prompts a project, Building Regulations Approved Document L is the standard the work should meet, with U-value targets for each element, and installers registered with TrustMark or a competent person scheme can self-certify compliance. Check grant eligibility before paying for anything: ECO4 runs to 31 December 2026 and the Great British Insulation Scheme continues alongside it, both funding measures partly or fully for qualifying households, and domestic insulation carries 0 percent VAT until 31 March 2027 in any case. An EPC assessment before and after larger projects evidences the improvement for future buyers and lenders.