Double Layer Timber Framed Wall
Using an insulated plasterboard to enhance the thermal
performance of standard timber frame walls
 |
Brick outer leaf |
 |
Cavity |
 |
Knauf Breatheline |
 |
Plywood sheathing |
 |
Crown FrameTherm between timber studs |
 |
Vapour control layer |
 |
Polyfoam Linerboard |
Products
- Crown FrameTherm is a lightweight unfaced glass mineral wool
available in both slab and roll form and a range of thermal
conductivities
- Polyfoam Linerboard is a laminate of Polyfoam high performance
100% ozone friendly extruded polystyrene, rigid board insulation
and 9.5mm plasterboard
- Knauf Breatheline is a breathable membrane with a polypropylene
nonwoven coating on both sides
Typical Construction
A 90mm deep timber frame stud wall infilled with Crown
FrameTherm faced internally with Polyfoam Linerboard and externally
with 9.5mm plywood and Knauf Breatheline, breathable
membrane.
The use of an insulated liner board reduces thermal bridging
through the timber studs. A 50mm cavity separates the timber frame
from the outer leaf, typically of brick.
Installation
Knauf Insulation products are dimensioned to suit studs at
standard 600mm centres. The nominal thickness of the insulation
should not be greater than the nominal stud depth.
Crown FrameTherm is friction fitted between studs at standard
centres and is self supporting. Generally two slabs fully fill the
space between sole and head plates for standard floor to ceiling
height.
Subsequently, Polyfoam Linerboard is fixed to the timber
frame. It may be nailed or screwed to the timber framework at
maximum 150mm centres. The boards are taper edged and should be
finished using standard drylining techniques.
Knauf Breatheline should be stapled or nailed to the sheathing
board at maximum 500mm centres. It should be lapped so that each
joint is protected, with upper layers lapped over lower layers to
shed water away from the sheathing.
Horizontal laps should be at least 100mm wide and the membrane
should extend below the lowest timber member. Vertical laps should
be at least 150mm and be staggered.
Performance
Thermal performance
- Crown FrameTherm Roll 35 has a thermal conductivity of 0.035
W/mK.
- Crown FrameTherm Slab 38 has a thermal conductivity of 0.038
W/mK.
- Crown FrameTherm Roll 40 has a thermal conductivity of 0.040
W/mK.
- The insulation element of Polyfoam Linerboard has thermal
conductivity of 0.030 W/mK and the plasterboard element has a
thermal conductivity of 0.19 W/mK
Typical U-values (W/m2K) for
prefabricated timber framed wall with Crown FrameTherm 40 between
the studs and Polyfoam Linerboard as the internal
lining
| Crown FrameTherm 40 |
Polyfoam linerboard |
U-Values (W/m2K) |
| Thickness
(mm) |
Thickness
(mm) |
Masonry Outer
Leaf |
Tile/timber clad outer
leaf |
| 140 |
17.5/9.5 |
0.25 |
0.27 |
| 90 |
36/9.5 |
0.27 |
0.29 |
| 90 |
25.5/9.5 |
0.30 |
0.33 |
| 90 |
17.5/9.5 |
0.33 |
0.36 |
Notes: The U-values have been calculated
to BS EN ISO 6946:1997. Studs assumed to be 38mm wide at 600mm
centres (allowances for sole plates etc, give a 15% bridging area
for the timber).
Fire performance
Crown FrameTherm is classified as Euroclass A1 to EN 13501-1.
Advantages
- Insulation fitted in one process
- Crown FrameTherm dimensioned to friction fit tightly between
timber studs at standard centres
- Crown FrameTherm enhances acoustic performance of walls
All Residential Timber Wall Solutions