PC02 - Between and above joists two layers
Advantages
- Lowest cost solution
- Familiar construction method
- Excellent thermal performance
- Longer roll lengths
- Greater coverage per roll than all other comparable
products
- Enhances acoustic performance
- Widely available through National stockist network
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Products
Loft Roll 44 and Loft Roll 40 are made from glass mineral wool
and formed into unfaced rolls which are lightweight, flexible,
resilient and non-combustible – their manufacture have a very low
impact on the environment and are classified as Zero ODP and Zero
GWP*
CarbonZero Roll is made from glass mineral wool and formed into
unfaced rolls which are lightweight, flexible, resilient and
non-combustible – its manufacture have a very low impact on the
environment and are classified as Zero ODP and Zero GWP. Further
the effect of the carbon emitted from the manufacture and transport
of the product is balanced with financial support for carbon
reduction initiatives such as renewable energy and
reforestation
| CarbonZero Roll is the first “carbon neutral” loft insulation
product available in the UK. Although glasswool is already a highly
sustainable product, we balance the effect of the carbon emitted
from the manufacture and transport of the product with financial
support for carbon reduction initiatives such as renewable energy
and reforestation. CarbonZero Roll is intended to be used on high
profile “Eco-Projects” for which “Low Environmental Impact” is a
key design consideration. |
Optional
Knauf Breatheline is a breathable membrane and Type LR Roof Tile
Underlay with a polypropylene non-woven coating on both sides
* Ecohomes and Code for Sustainable Homes
classification
Typical construction
A pitched roof of timber trussed rafters with tiles or slates on
battens and Roof Tile Underlay optionally on sarking board.
Plasterboard ceiling below.
Loft Roll 44 or 40 is installed in two layers, the first layer
between the joists and the second layer across the joists. This
minimises thermal bridging through the ceiling joists.
Ventilation requirements
If using Breatheline or similar third party accredited type LR
roof tile underlay with a well sealed ceiling – no ventilation
required In all other circumstances ventilation at eaves and ridge
required.
Installation
The first layer of Loft Roll 44 or 40 or CarbonZero Roll, the
same depth as the ceiling joists, is laid between the joists. The
insulation should be taken over the wall plate to link up with the
wall insulation. If the roof requires ventilation this is most
easily done just before the eaves ventilator is fixed, during
installation of the roof tile underlay.
The second layer of Loft Roll 44 or 40 or CarbonZero Roll is
laid At right angles to the ceiling joists, with all edges butt
jointed. The insulation should be pushed up tight against the roof
tile underlay if no ventilation is required or tight against the
eaves ventilator, taking care not to block the ventilation air path
if ventilation is required.
Performance
Thermal performance
- Loft Roll 44 has a thermal conductivity of 0.044 W/mK
- Loft Roll 40 and CarbonZero Roll have a thermal conductivity of
0.040 W/mK
Table 2 gives U-values for typical constructions insulated with
Loft Roll 44 and Loft Roll 40 or CarbonZero Roll.
Table 2: Typical U-values of
pitched roofs with ceiling level insulation
| Solution |
Product |
Thickness
(mm) |
U-Values (W/m2K) |
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Between
joists* |
Over joists |
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| Pc02 |
Loft Roll 44 |
100 |
400 (2 x 200) |
0.09 |
| 100 |
300 (2 x 150) |
0.11 |
| 100 |
200 |
0.15 |
| 100 |
170 |
0.16 |
| 100 |
150 |
0.17 |
| Loft Roll 40 |
100 |
300 (2 x 150) |
0.1 |
| 100 |
200 |
0.13 |
| 100 |
150 |
0.16 |
| Pc04 |
CarbonZero Roll |
100 |
300 (2 x 150) |
0.11 |
| 100 |
200 |
0.15 |
| 100 |
170 |
0.16 |
*Joist sizes assumed to be 100 x 48mm at 600mm centres (8%
bridging plus 1% for cross noggings). The U-values have been
calculated in accordance with BS EN ISO 6946:1997
Fire performance
Loft Roll 44, Loft Roll 40 or CarbonZero Roll are classified as
Euroclass A1 to BS EN ISO 13501-1.
Airtightness
Where enhanced airtightness performance is required the designer
should consider the specification of a separate and fully sealed
air leakage barrier to the underside of the ceiling joists, i.e. a
500 gauge polyethylene sheet.
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Typical specification
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 The whole area of the ceiling to be insulated with two
layers of Loft Roll 40*/44*/CarbonZero Roll* of total thickness
......mm.
Width of first layer of insulation to be appropriate to the
joist spacings and of a thickness equal to joist depth. The
insulation to be laid between the joists and to finish over wall
plate on external walls.
The second layer to be laid at right angles to the first layer.
All joints between the rolls of insulation to be close butted.
(*Delete as appropriate)
Maintain a minimum 25mm airspace between insulation and sarking
felt/sarking board at the eaves.
Do not insulate under cold water tanks unless they are elevated.
Cold water tanks and pipes to be separately insulated.
Loft hatch to be insulated with a minimum 100mm depth of
insulation.
Alternatively, refer to NBS clauses: P10/120 and 130.
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Typical section
