Products
- Crown FrameTherm is a lightweight unfaced glass mineral wool
available in both slab and roll form and a range of thermal
conductivities.
- Crown DriTherm Cavity Slab is a lightweight, semi-rigid slab of
non-combustible glass mineral wool having a water-repellent
additive.
- Knauf Breatheline is a breathable membrane with a polypropylene
non-woven coating on both sides.
Typical Construction
Inner leaf comprising 12.5mm plasterboard, vapour control layer,
Crown FrameTherm between studwork, 9.5mm plywood sheathing and
Knauf Breatheline, breathable membrane. Cavity between timber frame
and outer leaf either fully or partially filled with Crown DriTherm
Cavity Slab. Outer leaf typically of brick.
Installation
The principles for installing Crown DriTherm Cavity Slab in a twin
insulated wall are essentially the same as for installation in a
double-leaf masonry wall when the inner leaf is constructed first.
The instructions to be found in BBA Certificate 95/3212 Crown
DriTherm Cavity Slab can therefore be taken as relevant. However,
this BBA Certificate does not cover use in timber frame
walls.
Installation sequence – full
fill
The timber frame shell is erected in the normal manner. The
sequence and methods are the same as for conventional timber frame
except that small cavity barriers are omitted from the cavity, as
Crown DriTherm Cavity Slab is non-combustible and therefore
performs the function of a small cavity barrier.
Crown DriTherm Cavity Slab should fully fill the space between the
external cladding and the internal timber frame. Adjacent slabs
should always be close butted leaving no gaps. Any mortar droppings
or other debris, lying on the top edge of a slab, must be removed
before installing the next row above.
The construction sequence ensures there is no cavity into which
debris can fall to an irretrievable position. Adoption of these
principles will ensure that any rainwater penetrating the outer
leaf is not transmitted to the timber frame.
Installation sequence – part
fill
The timber frame shell is erected in the normal manner. The
sequenced method is the same as for conventional timber frame
except that a wider cavity than normal is being used. This will
require longer than normal wall ties with a clip to hold the
DriTherm Cavity Slab back to the timber frame wall. Small cavity
barriers should be installed to the full width of the cavity,
cavity trays may be required. The DriTherm Cavity Slab is installed
to the same standard as for full fill, but should be fully clipped
back to the timber frame wall.
Performance
Thermal performance
The thermal conductivity of 50mm Crown DriTherm Cavity Slab and
Crown FrameTherm 35 is 0.035 W/mK and Crown FrameTherm 40 is 0.040
W/mK.
The table gives U-values for twin insulated timber frame walls
insulated with a combination of Crown DriTherm Cavity Slab and
Crown FrameTherm.
Typical external U-values (W/m2K) for
Crown Twin Insulated wall FULL fill
| Depth of
studs (mm) |
Insulation
between studs: |
Crown
DriTherm Cavity Slab Thickness (mm) |
U-values (W/m2K) |
| |
|
|
Masonry outer leaf |
Tile/timber clad outer leaf |
| 90 |
Crown FrameTherm 35 |
50 |
0.26 |
N/A |
| Crown FrameTherm 40 |
50 |
0.27 |
N/A |
| 140 |
Crown FrameTherm 35 |
50 |
0.21 |
N/A |
| Crown FrameTherm 40 |
50 |
0.22 |
N/A |
All dimensions are nominal
Typical external U-values (W/m2K) for
Crown Twin Insulated wall PART fill
| Depth of
studs (mm) |
Insulation
between studs: |
Crown
DriTherm Cavity Slab Thickness (mm) |
U-values (W/m2K) |
| |
|
|
Masonry outer leaf |
Tile/timber clad outer leaf |
| 90 |
Crown FrameTherm 35 |
50 |
0.25 |
0.28 |
| Crown FrameTherm 40 |
50 |
0.26 |
0.29 |
| 140 |
Crown FrameTherm 35 |
50 |
0.20 |
0.21 |
| Crown FrameTherm 40 |
50 |
0.21 |
0.22 |
All dimensions are nominal
Notes: The U-values have been calculated to BS EN ISO6946:1997.
Studs assumed to be 38mm wide at 600mm centres (allowances for sole
plates etc, give a 15% proportional area for the timber). Brick
face area is assumed to be 215 x 65mm with mortar joints 10mm
wide.
Fire performance
Crown FrameTherm 40, Crown FrameTherm 35 and Crown DriTherm
Cavity Slab are classified as Euroclass A1 to EN 13501-1
Advantages
- Lowest U-values
- Lowest system width (full fill)
- No need for firestopping (full fill)
- Utilises non-combustible insulation to Euroclass A1
throughout