Tf04-Insulation Between Studs and to Exterior of Sarking
Tf04 - Timber frame walls - Insulation between studs and to
exterior of sarking
Advantages
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Very low U-values can be achieved
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No need for firestopping (full fill)
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Utilises non-combustible Euroclass A1 insulation throughout
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Partial fill system accepted by NHBC
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Crown FrameTherm and Crown DriTherm are Zero ODP and Zero GWP
insulation products
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The manufacture of Crown FrameTherm and Crown DriTherm products
has a very low impact on the environment
-
The insulation is compressible and can be cut slightly oversize
to friction fit preventing cold air penetrating through
joints
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Products
Crown FrameTherm Roll/Slab is a lightweight
unfaced glass mineral wool available in both slab and roll form and
a range of thermal conductivities. Its manufacture has a very low
impact on the environment and is classified as Zero ODP and Zero
GWP*
Crown DriTherm Cavity Slab is a semi-rigid
slab, non-combustible glass mineral wool having a water-repellent
additive. Its manufacture has a very low impact on the environment
and is classified as Zero ODP and Zero GWP*
Knauf Breatheline is a breathable membrane with
a polypropylene non-woven coating on both sides.
* Ecohomes and Code for Sustainable Homes
classification
Typical construction
Inner leaf comprising 12.5mm plasterboard, vapour control layer,
Crown FrameTherm between studwork, 9.5mm plywood sheathing and
Knauf Breatheline. Cavity between timber frame and outer leaf
either fully or part filled with Crown DriTherm Cavity Slab. Outer
leaf typically of brick.
Performance
Thermal performance
-
The thermal conductivity of 50mm Crown DriTherm Cavity Slab and
Crown FrameTherm 35 is 0.035 W/mK.
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Crown FrameTherm Roll 40 has a thermal conductivity of 0.040
W/mK.
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Crown FrameTherm Roll 32 has a thermal conductivity of 0.032
W/mK.
Tables 44 and 45 gives U-values for twin insulated timber frame
walls
Table 44: Typical U-values for
Crown Twin insulated wall – partial fill
|
Insulation product |
U-values (W/m2K) |
| Timber studs filled
with: |
Thickness
(mm)
|
Crown DriTherm Cavity
Slab
thickness (mm)
|
Masonry outer
leaf
|
Low e
service duct |
| Crown FrameTherm 32 |
140 |
50 |
0.19 |
0.17 |
| 90 |
50 |
0.24 |
0.21 |
| Crown FrameTherm 35 |
140 |
50 |
0.19 |
0.18 |
| 90 |
50 |
0.24 |
0.22 |
| Crown FrameTherm 40 |
140 |
50 |
0.2 |
0.19 |
| 90 |
50 |
0.26 |
0.23 |
Table 45: Typical U-values for
Crown Twin insulated wall – full fill
|
Insulation product |
U-values (W/m2K) |
| Timber studs filled with: |
Thickness
(mm)
|
Crown DriTherm
Cavity Slab
thickness (mm)
|
Masonry outer
leaf
|
Low e service
duct |
| Crown FrameTherm
32 |
140 |
100 |
0.15 |
0.14 |
| 90 |
100 |
0.19 |
0.17 |
| Crown FrameTherm
35 |
140 |
100 |
0.16 |
0.15 |
| 90 |
100 |
0.19 |
0.18 |
| Crown FrameTherm
40 |
140 |
100 |
0.17 |
0.16 |
| 90 |
100 |
0.20 |
0.18 |
Notes: The U-values have been calculated to BS EN ISO 6946:
1997 and BR 443. Studs assumed to be 38mm wide at 600mm centres
(allowances for sole plates etc, give a 15% proportional area for
the timber). Stud depth is taken to be the same as the thickness of
insulation specified. Thermal conductivity of timber studs is 0.120
W/mK. Unventilated low emissivity airspace in service duct assumed
to provide R value of 0.44 m2K/W as specified in BR443.
Higher values can be achieved with proprietary products. Please
contact Knauf Insulation Technical Advisory Centre for calculations
that include specific products.Brick face area is assumed to be 215
x 65mm with mortar joints 10mm wide.
Fire performance
Crown FrameTherm 40, Crown FrameTherm Roll/Slab and Crown
DriTherm Cavity Slab are classified as Euroclass A1 to EN
13501-1. Building Regulations state that external walls in domestic
construction shall achieve half hour fire resistance. In tests and
assessments carried out TRADA Technology Ltd in accordance with BS
476: Part 21: 1987, different timber frame external walls
incorporating Crown FrameTherm Roll/Slab gave the required fire
resistance.
Installation
The installation of Crown Frametherm, vapour control layer and
Knauf Breathline are the same as for solution Tf01. If a service
duct is to be included then refer to Tf02. The principles for
installing Crown DriTherm Cavity Slab in a twin insulated wall are
essentially the same as for installation in a masonry cavity wall
when the inner leaf is constructed first.
The instructions to be found in British Board of Agrément
Certificate 95/3212 apply to the use of Crown DriTherm Cavity Slabs
in masonry wall constructions and can therefore be deemed relevant
to this application. However, this certificate does not cover the
specific use of Crown DriTherm Cavity Slabs in timber frame
walls.
Installation sequence – full fill
The timber frame 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
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.
Note that the NHBC will not accept this form of construction on
projects where their guarantee is required.
Installation sequence – part fill
The timber frame 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 used.
This will require longer than normal wall ties with a clip to
hold the DriTherm back to the timber frame wall. Small cavity
barriers should be installed to the full width of the cavity. The
DriTherm is installed to the same standard as for full fill, but
should be fully clipped back to the timber frame wall.
Note The NHBC will accept this form of construction providing a
50mm residual cavity between the Crown Dritherm Cavity Slab and
masonry outer leaf is maintained.
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Typical specification
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Twin insulation full fill system
External wall panels to be insulated between studs using Crown
FrameTherm Roll 40/35/32* ......mm thick (*Delete as appropriate)
Insulation to be cut as necessary and friction fitted between
studs.The breather membrane stapled*/nailed* to the sheathing and
extend below the lowest timber member (*Delete as appropriate).
Cavity formed between internal and external leafs to be fully
filled with Crown DriTherm Cavity Slab ......mm thick. The lowest
run of wall ties to be located at 600mm centres horizontally. Ties
thereafter to be at 450mm centres vertically and at 600mm centres
horizontally. All work to be in accordance with manufacturers
instructions.
Twin insulated part fill system
Frame and breather membrane as above, then:
Crown DriTherm Cavity Slab ......mm thick to be fitted against
the breather membrane on the face of the sheathing and held back
using insulation retaining clips fixed to the wall ties. The lowest
run of wall ties to be located at 600mm centres horizontally. Ties
thereafter to be at 450mm centres vertically and at 600mm centres
horizontally. All work to be in accordance with manufacturers
instructions.
Cavity barriers and fire stops should be installed as required
to meet the Building Regulations.
Alternatively, refer to NBS clauses: P10/210, F30/10, 150
and F30/12, 155
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Typical section
