A PPT on the types of insulation used in cavity walls

1. Cavity Walls
Cavity Wall
Insulation

2. Tutor Copy

3. Cavity Wall Insulation (New Build)
To meet Building Regulation
requirements any cavity wall
built of 100mm facing bricks
and 100mm blocks has to
be well insulated between
the two walls. This simple
measure greatly increases
the thermal insulation
qualities of the building.

4. Existing Cavity Walls
Existing cavity walls
that are not insulated
can be upgraded by
adding the insulation
at a later date.

5. There are three
methods of
insulating
cavities:
1. Constructing the
wall so that the
cavity is fully filled
(full fill cavity).

6. 2. Constructing the
wall so that the
cavity is partially
filled (partial fill
cavity).

7. 3. Injecting
insulation
into existing
cavity walls.

8. Cavity insulation materials
1. As a cavity bat which is soft and
flexible, 455mm high and
1200mm long and available in
various thicknesses. They are
made from layers of mineral
fibres treated with a water
repellent. Water will not
penetrate through the bats but
will drain down between the
laminations of the bat. This type
of insulation material is
designed to completely fill the
cavity.
Cavity insulation material is
available in three forms:

9. 2. As a cavity board which is a
rigid board made of expanded
polystyrene bead board,
extruded polystyrene or
polyisocyanurate foam and
glass fibre. This insulation
material is designed to be
fixed flat against the cavity
face of the inner leaf of the
wall and to partially fill the
cavity.
Cavity insulation materials

10. 3. As expanded foam, granules or mineral wool
fibres which can be injected into the cavity
completely filling the cavity. Urea-
formaldehyde or polyurethane foam is widely
used. Mineral wool types of insulation are
treated with a water repellent to make them
more effective. Expanded polystyrene beads
are usually lightly coated with an adhesive
just prior to injection so that they will not settle
over a period of time.
Cavity insulation materials

11. Full fill cavity insulation
This type of cavity
insulation makes use of
soft flexible bats which
completely fill the cavity.
They are squeezed
between two rows of
ordinary wall ties spaced
at 450mm apart vertically.
Two ties are required at
the top and bottom of each
bat and at least 600mm
apart horizontally.

12. It will sometimes be
necessary to use small strips
cut from bats to gain the
correct height required
around windows and door
openings. The cut surfaces
of the pieces should not be
placed in contact with the
outer leaf as this will allow
water to be conducted
through the bat to the inner
leaf.
Full fill cavity insulation

13. When fitting insulation
bats over wall ties, a
neat slit is cut through
so that the bat can be
slipped over the wall tie.
The insulation bat
should never be forced
and damaged through
tearing or breaking off
the back of the bat.
Full fill cavity insulation
Fitting bats over wall ties

14. Storing bats and boards prior to
installation
Adequate and suitable storage must be
provided for bats and boards after delivery
to protect them from damage and theft.
Care must be taken to ensure that the
correct specified type, height and
thickness of insulation material is used.

15. Partial fill cavity insulation
This type of cavity insulation makes use of rigid flat
boards which are secured to the face of the inner
leaf and partially fill the cavity. They are securely
fixed using rows of special wall ties spaced 450mm
apart vertically. The ties have a round plastic device
which keeps the boards flat against the inner surface
of the wall.
When the boards are fixed in place, the clear space
between the face of the board, and the outer wall is
usually not less than 50mm and should be clear of
any mortar droppings.

16. Partial Fill Cavity

17. Insulation continued into
cavity to prevent
cold bridging
occurring
Full fill cavity
insulation
Soffit
ventilation
Loft insulation

18. Good installation workmanship
The following precautions should be taken when fixing insulation in cavity
walls to avoid remedial work at a later stage:
• Mortar droppings should not be allowed to accumulate on top of the
bats positioned in the cavity.
• All bed and cross joints should be solidly filled.
• Excess mortar should be removed from the inner face of both leaves.
• Always follow the manufacturer’s guidelines enclosed with the
insulation materials. These will also recommend the best sequence of
construction.
• Wall ties should be level or slightly sloping to the outer leaf.
• Use only wall ties specified, as they may be specially designed for
use with insulating materials.
• Bats must be closely jointed as condensation will form in the gaps.
• Always store insulation correctly, flat and never on bearers, to avoid
sagging out of shape.
• If insulation is required below ground level, resting on the cavity fill,
cut the insulation to fit below the first row of wall ties at DPC level.
Then start from DPC with a full height bat.

19. How to determine the U Value