Gf01-Insulation below slab
Gf01 - Ground Floors - Insulation Below Slab
Advantages
- Long term exposure to water has negligible impact on the
thermal performance of Polyfoam
- Can be used above or below the DPM Above DPM Polyfoam protects
it from damage before and during the concrete pouring process Below
DPM Polyfoam protects the DPM from possible puncture from hardcore
and extremes of temperature at perimeter
- Resists tough site conditions
- Industry leading range of compressive strengths, providing the
specifier with a choice of the most appropriate solutions based on
expected floor loads
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Products
Polyfoam Floorboard is a range 100% Ozone
friendly extruded polystyrene rigid board insulation – it is
lightweight yet has excellent structural strength and long term
effectiveness.
It is available in four grades:
- Domestic – especially engineered for domestic
flooring applications
- Standard – domestic and light commercial
loading
- Extra – commercial, industrial flooring and
cold storage
- Super – very high load commercial, industrial
and cold storage floors
Typical construction
A solid concrete ground floor slab cast on insulation on a damp
proof membrane (DPM) laid over blinded hardcore. Alternatively
concrete floor slab cast on a damp proof membrane laid over the
insulation. A strip of Polyfoam Floorboard insulation, minimum 25mm
thick, should be placed vertically at the slab perimeter to
minimise thermal bridging.
The wall insulation should start a minimum of 150mm below the
top of the floor insulation. There should be a flexible sealant
between the wall finish and the floor slab to minimise air leakage
at this junction.
Installation
Level the sand blinding over the hardcore to receive the
insulation. Lay the Polyfoam Floorboard directly on the sand
blinding and then lay the DPM over the insulation and lap with the
wall DPC.
Alternatively, lay Polyfoam Floorboard over the DPM in a
staggered pattern to cover the whole floor area. The joints should
be tightly butted. Use spreader boards, as necessary, to prevent
point loads puncturing the DPM. A slip layer is required between
the insulation and the concrete slab.
Place a strip of insulation, minimum 25mm thick, vertically at
the slab perimeter to minimise thermal bridging. The height of the
perimeter insulation to equal the slab thickness. Ensure the
perimeter insulation boards are securely held in place to prevent
dislodgement by following work, eg by taping them to the main floor
insulation.
Lay the concrete slab. The concrete slab may be screeded or
alternatively have a power float finish.
Performance
Thermal performance
The thermal conductivities of Polyfoam Floorboard products are
as follows:-
- Domestic – 0.030W/mK
- Standard – 0.029W/mK
- Extra – 0.029 -0.034W/mK
- Super – 0.034 - 0.036W/mK
Unlike most other insulants, moisture has a negligible effect on
the thermal performance of Polyfoam Floorboard.
Table 63 gives U-values for a range of perimeter/area
ratios.
Fire performance
When Polyfoam Floorboard is installed in a concrete floor
construction, it will not contribute to the development stages of a
fire.
Moisture resistance
The moisture resistance of Polyfoam Floorboard enables it to be
laid exposed to ground water, with negligible impact on
performance. The boards themselves do not perform the function of a
damp proof membrane. However, they can be laid in damp conditions
or up against wet concrete without compromising their thermal
performance.
Compression resistance
Polyfoam Floorboard is highly resistant to compression – see
table 62.
Table 62: Compressive creep results
|
Product
|
Load applied
(kPa)
|
Initial compression
(%)
|
Further compression after 50 years
(%)
|
|
Polyfoam Standard
|
60 |
2 |
1.5 |
| Polyfoam Extra |
120 |
2 |
1.5
|
| Polyfoam Super |
175 |
2 |
1.5
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Typical specification
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The whole of the ground floor area between brick, block or
concrete subwalls to be insulated with Polyfoam Floorboard
Domestic*/Standard*/ Extra/*Super* …...mm thick and laid directly
over blinded hardcore. Polyfoam Floorboard Standard, at least 25mm
thick, to be cut and placed vertically against the subwalls to the
depth of the concrete slab.
The insulation to be laid above*/below* damp proof membrane,
which should lap the perimeter wall DPC. Concrete slab and floor
finish as specified by the designer. (*delete as appropriate)
Alternatively, refer to NBS clause: E20/30 or E20/200
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Typical section
Table 63: Typical U-values for Polyfoam
Floorboard below a concrete ground floor slab U-values
|
Thickness (mm)
|
Ratio of Perimeter (m) to Area
(m2)
|
| |
0.10 |
0.20 |
0.30 |
0.40 |
0.50 |
0.60 |
0.70 |
0.80 |
| Polyfoam Floorboard Standard |
| 160 (85 + 75) |
0.09 |
0.11 |
0.13 |
0.13 |
0.14 |
0.14 |
0.15 |
0.15 |
| 140 (65 + 75) |
0.09 |
0.12 |
0.14 |
0.15 |
0.15 |
0.16 |
0.16 |
0.17 |
| 125 (50 + 75) |
0.10 |
0.13 |
0.15 |
0.16 |
0.17 |
0.17 |
0.18 |
0.18 |
| 100 (50 + 50) |
0.11 |
0.15 |
0.17 |
0.19 |
0.20 |
0.20 |
0.21 |
0.22 |
| 85 |
0.12 |
0.16 |
0.19 |
0.21 |
0.22 |
0.23 |
0.24 |
0.24 |
| 75 |
0.12 |
0.17 |
0.20 |
0.22 |
0.24 |
0.25 |
0.26 |
0.26 |
| 65 |
0.13 |
0.19 |
0.22 |
0.24 |
0.26 |
0.27 |
0.28 |
0.29 |
| 50 |
0.14 |
0.21 |
0.25 |
0.28 |
0.30 |
0.32 |
0.33 |
0.34 |
| 35 |
0.15 |
0.23 |
0.29 |
0.33 |
0.36 |
0.38 |
0.40 |
0.42 |
| Polyfoam Floorboard Extra |
| 175 (100 + 75) |
0.09 |
0.11 |
0.13 |
0.13 |
0.14 |
0.14 |
0.15 |
0.15 |
| 150 (75 + 75) |
0.09 |
0.12 |
0.13 |
0.14 |
0.15 |
0.15 |
0.15 |
0.16 |
| 125 (50 + 75) |
0.10 |
0.13 |
0.15 |
0.16 |
0.17 |
0.17 |
0.18 |
0.18 |
| 75 |
0.12 |
0.17 |
0.20 |
0.22 |
0.24 |
0.25 |
0.26 |
0.26 |
| 65 |
0.13 |
0.19 |
0.22 |
0.24 |
0.26 |
0.27 |
0.28 |
0.29 |
| 50 |
0.14 |
0.21 |
0.25 |
0.28 |
0.30 |
0.32 |
0.33 |
0.34 |
| 35 |
0.15 |
0.23 |
0.29 |
0.33 |
0.36 |
0.38 |
0.40 |
0.42 |
| 25 |
0.16 |
0.26 |
0.32 |
0.37 |
0.41 |
0.45 |
0.47 |
0.49 |
| Polyfoam
Floorboard Domestic |
| 66 |
0.13 |
0.18 |
0.22 |
0.25 |
0.24 |
0.27 |
0.28 |
0.29 |
Note: The U-values have been calculated using BS EN ISO
13370: 1998 and assume a clay subsoil with a thermal conductivity
of 1.50 W/mK. U-values for floors insulated with Polyfoam
Floorboard Super can be supplied by the Knauf Insulation Technical
Advisory Centre