Floors - Upper
Many commercial and public buildings have areas of
exposed upper floor whether it is above a car park or access way,
or simply formed as a result of the design of the
building.
Overview
It is important that these
floors are correctly insulated to ensure that the building meets
with the appropriate Building Regulation requirements and the floor
does not compromise the energy efficiency of the building.
Advantages
It is possible to achieve very high
levels of thermal insulation in exposed upper floors. The designer
has a choice of where to position the insulation: either above,
below or within (in the case of timber joisted floors) the
structural floor.
If insulating below the structural floor, the insulation can be
laminated to a robust construction board that will provide a finish
to the soffit. This method allows for insulation and cladding in
one process.
When insulating between timber joists, the whole depth of the
joists can be utilised as an insulation zone. If mineral wool
insulation is installed between the joists, this method of
construction achieves a very good insulation value without
increasing the depth of the floor construction. Insulating above
the structural floor reduces the thermal mass of the floor allowing
for fast warm up. However, if only part of the floor on that storey
is exposed it may cause problems with finished floor levels.
Knauf Insulation Products
- Polyfoam Floorboard is a high performance, 100% ozone friendly,
extruded polystyrene, rigid board insulation. It is lightweight,
yet has excellent structural strength and long term effectiveness.
The boards are square edged.
- Polyfoam High Impact Board is a laminate of Polyfoam high
performance, 100% ozone friendly, extruded polystyrene, rigid board
insulation and a tough, weather resistant fibre reinforced cement
facing board. It is highly thermally efficient yet provides a tough
faced solution suitable for exterior use. The board is square
edged.
- Crown Loft Roll 44 is made from glass mineral wool and formed
into unfaced rolls which are lightweight, flexible, resilient and
non-combustible.
- Rocksilk Universal Slab RS45 is a semi-rigid slab of
non-combustible rock mineral wool.
Summary
Knauf Insulation provide
thermal insulation products that are suitable for timber and
concrete upper floor constructions, giving a range of options that
will comply with the Building Regulations.
Building Regulation Requirements
U-value requirements in the Building Regulations for exposed upper
floors
| |
U-value (W/m2K) |
|
| England, Wales & NI |
0.25 |
|
| Scotland |
0.20 or 0.22 |
|
| Ireland |
0.25 |
|
In the Building
Regulations, upper floors must be insulated when they are exposed
to the outside air. Floors between heated and unheated spaces, such
as an office floor over an enclosed underground garage, must also
be insulated.
.
Shelter Factors
Under previous versions of
the Building Regulations and standards where the space under an
upper floor was enclosed, but unheated, the floor was treated as a
semi exposed element and a less demanding U Value was
required. Current Building Regulations require such a
floor to be regarded as an exposed element.
There is, however, a sheltering effect that an unheated space would
have on the upper floor. This can be allowed for by applying a
shelter factor to the U-value of the upper floor structure. The
amended U-value is calculated using the following formula:
Heated floors
When the floor is to be
heated by hot water pipes or electrical cables then the position of
the insulation will be determined by whether the floor slab or the
screed is to be heated.
If the screed only is to be heated then the insulation is laid
between the structural slab and the screed. The insulation should
be overlaid with a vapour control layer/building paper which acts
as a slip sheet and prevents wet concrete penetrating between the
boards.
Air Leakage
With suspended timber
ground floors, care is needed to minimise air leakage. The floor
perimeter should be sealed by applying expanded foam tape under the
skirting and a continuous bead of sealant to the back of the
skirting prior to fixing. The perimeter of the ceiling should also
be sealed with a flexible sealant. Gluing the joints between the
floor deck panels will also reduce potential airpaths.
Compressive Strength
All materials are
compressed under load. Insulation materials used below screeds and
floating chipboard decks should be capable of accommodating the
applied loads with the minimum of compression. The applied load has
two components:
- the dead load, which is due to the weight of the materials laid
on the insulant, and
- the design load.
BS 6399: 1996
outlines guideline figures for expected design loads in
UDL for
various non-domestic and some industrial applications. However, in
a sector where future use is potentially unknown and point loads
can be huge, the engineer is often required to assess the service
needs of the floor on a project by project basis.
Dead loads applied by various building
components
|
Element |
Dead Load (kN/m2) |
| Flooring grade chipboard |
0.1 to 0.2 |
| 40mm concrete screed |
0.95 |
| 75mm concrete slab |
1.75 |
| 200mm concrete slab |
4.70 |
| 12.5mm plasterboard |
0.10 |
British Standards
Designers should consult
BS EN 312 Parts 1-7 when selecting
chipboard or other floor decking boards.
Typical Specification Clauses
1a) Insulation below screed
Polyfoam Floorboard Standard ......mm thick, to be closely butted
and placed over the whole area of the concrete floor. Polyfoam
Floorboard, minimum 25mm thick, to be cut and placed to full depth
of screed at the floor perimeter.
The insulation to be overlaid with 1200 gauge polythene, taken up
and over the perimeter insulation. A 75mm thick sand:cement screed
with wire mesh*/ polypropylene reinforcing fibres* to be laid on
top. (NHBC recommend a D49 fabric mesh for use in floating
screeds.) Floor finish as specified by the designer. (* delete as
appropriate)
Alternatively, refer to NBS clause: M10/40 or M10/290
1b) Insulation below chipboard
Polyfoam Floorboard Standard ...... mm thick, to be closely
butted and placed over the whole area of the concrete floor.
The insulation to be (overlaid with a vapour control layer of 1000g
polythene and)* covered with 18mm t&g flooring grade chipboard.
(*delete as required)
Alternatively, refer to NBS clause: K11/25 or K11/225
1c) Insulation below soffit
Polyfoam Soffit Liner Board*/Rocksilk Soffit Linerboard
Extra* to be screwed to the structural soffit at maximum 550mm
centres using ...... fixings manufactured by ...... . Fixings to be
set in at least 50mm from any board edge and penetrate at least
40mm into the structure. All gaps between boards to be sealed
with ...... sealant manufactured by ...... .
(* delete as appropriate)
2) Timber suspended floor
Crown Loft Roll*/Rocksilk Universal Slab RS45* ......mm thick,
supported on the ceiling to fit tightly between the joists. Crown
Loft Roll*/Rocksilk Universal Slab RS45* to be cut and placed to
fully fill in the gap between the last joist and the perimeter
wall. (* delete as appropriate)
T&g flooring grade chipboard to be nailed or screwed to the
floor joists, all as specified by the designer.
Alternatively, refer to NBS clause: P10/240 or P10/250