Case Study using Grey EPS Bead

The following shows difference in prices and U values of houses built with different insulation methods. Prices are for insulation and internal blocks, not including bricks and plasterboard as these would be identical in both builds (50 homes @ 120m2 each would need 6000m2 of blocks and insulation):

Build 1:

Brick outer leaf 50mm Celotex Board Celcon Block 3.6N 600kg/m3 Dot and Dab Inner

Celotex Boards	£3.35 per board covering 0.54m2	£37,222
Celcon Block 3.6N	£9.95m2	£59,700
	Total:	£96,922

The total cost does not include the extra wall ties and fittings for the cavity boards. Also does not account for any damage/waste for board cutting/shaping.

U Value for Build 1 is 0.29

Build 2:

Brick outer leaf 100mm Grey EPS Bead Dense concrete block 7.3N Dot and Dab Inner

Grey EPS Bead	£7.94m2	£47,652
Dense Concrete Block 7.3N	£4.70m2	£28,200
	Total:	£75,852

U Value for Build 2 is 0.27

Saving on materials would be £21,070 for this project, while getting a better thermal performance. U Values calculations are detailed below.

Build 1

Element type: Wall - Masonry - partial cavity fill
Calculation Method: BS EN ISO 6946

Layer	d (mm)	λ layer	λ bridge	Fraction	R layer	R bridge	Description
					0.130		Rsi
1	12.5	0.210			0.060		Plasterboard (standard wallboard)
2	15	R-value	0.430	0.200	0.170	0.035	Drylining - plaster dabs
3	100	0.150	0.940	0.0670	0.667	0.106	Celcon Block (600 kg/m3) - outer
4	50	0.022			2.273		Celotex 50mm
5	50	R-value			0.180		Cavity unventilated
6	105	0.770			0.136		Brick outer leaf
					0.040		Rse
	333 mm (total wall thickness)				3.655

Total resistance: Upper limit: 3.584 Lower limit: 3.407 Ratio: 1.052 Average: 3.495 m2K/W

U-value (uncorrected): 0.286

U-value corrections:

Air gaps in layer 4	ΛU = 0.004	(Level 1)
Wall ties in layer 4	ΛU = 0.003	(2.50 per m2, 12.5 mm2 cross-section, λ = 17.0)
Total ΛU	0.007	(2.5% of U)

U-value (corrected): 0.286 (ΛU not added since it is less than 3% of U)

U-value (rounded): 0.29 W/m2K

Build 2

Element type: Wall - Masonry - full cavity fill: injected
Calculation Method: BS EN ISO 6946

Layer	d (mm)	λ layer	λ bridge	Fraction	R layer	R bridge	Description
					0.130		Rsi
1	12.5	0.210			0.060		Plasterboard (standard wallboard)
2	15	R-value	0.430	0.200	0.170	0.035	Airspace / plaster dabs
3	100	1.130			0.088		Concrete block (dense)
4	100	0.032			3.125		Grey EPS Bead
5	105	0.770			0.136		Brick outer leaf
					0.040		Rse
	333 mm (total wall thickness)				3.749

Total resistance: Upper limit: 3.722 Lower limit: 3.675 Ratio: 1.013 Average: 3.698 m2K/W

U-value (uncorrected): 0.270

U-value corrections:

Wall ties in layer 4	ΛU = 0.003	(2.50 per m2, 12.5 mm2 cross-section, λ = 17.0)
Total ΛU	0.003	(1.1% of U)

U-value (corrected): 0.270 (ΛU not added since it is less than 3% of U)

U-value (rounded): 0.27 W/m2K