Underfloor Heating Systems - CMS

CI/SfB
53/In6
Hep 2O ® Underfloor Heating Systems
50
years
GUARANTEE
As a result
of its rigorous
Quality Management
Programme, Hepworth
Building Products offer a
50 year guarantee against
defects in materials or
manufacturing of
Hep 2O underfloor
heating pipe.
September
2004
Product Guide

Contents
Introduction 3
Hep 2O ® Underfloor Heating Pipe 4-5
Hep 2O ® Environmental Considerations 5
Hep 2O ® Underfloor Heating System 6-7
Hep 2O ® Underfloor Heating Design 7-8
Hep 2O ® Underfloor Heating - FAQ’s 8
Hep 2O ® Underfloor Heating Conservatory Pack 9
Hep 2O ® Underfloor Heating Installation
2
Pipe Layout 10
Floor Construction 11
Solid Screed Floor 12-13
Suspended Floor 14
Floating Floor 15
Hep 2O ® Underfloor Heating Manifold
Manifold Introduction 16
Manifold Operation 17
Manifold Kit Components 17
Hep 2O ® Underfloor Heating Installation - FAQ’s 18
Hep 2O ® Underfloor Heating - References/Further Information 19
Hotlines Back Cover
Page

Introduction
The Company
Hepworth Plumbing Products is a division
of Hepworth Building Products Limited and
a member of the Vaillant Hepworth Group.
The company manufactures the market
leading Hep 2O ® flexible push-fit plumbing
system, for hot and cold-water services,
central and underfloor heating.As well as
rainwater and soil and waste systems.
Continuing Research and
Development
Central to Hepworth’s product
development is an ability to harness
different material technologies to optimise
product performance. Materials and
production expertise combines with
constant research among user groups to
identify and respond rapidly to changing
market requirements. Multi-disciplinary
teams use this knowledge to translate
innovative ideas into practical solutions to
today’s plumbing and above ground drainage
challenges and to reflect changing
construction techniques.
Working with Others
To further consolidate our continuing
product development and ensure current
and future building requirements are met,
Hepworth Plumbing Products has industrial
affiliation with the Institute of Plumbing &
Heating Engineering (IPHE), the Scottish &
Northern Ireland Plumbing Employer’s
Federation (SNIPEF), and the National
Association of Plumbing, Heating &
Mechanical Services Contractors (APHC).
Environmental Policy
Hepworth Building Products is committed
not only to compliance with environmental
laws and the adoption of acceptable
standards, but also to the introduction of
measures to limit the adverse effects of its
operations on the environment.
Hepworth Plumbing Products have
implemented an environmental management
system aligned to: ISO 14001: 1996, to
prevent pollution and reduce the adverse
EMS 77364
EMS 82340
impact of our activities upon land, air, water,
property and the public.
Continuous Improvement
Hepworth Plumbing Products are
committed to continuous improvement in
all areas of our business including Safety,
Quality and Environmental performance.
Hepworth Plumbing Products has industrial
affiliation with:
3

Hep 2O ® Underfloor Heating Pipe
Introduction
Hep2O ® is an innovative, flexible, push-fit
plumbing system especially developed for
use by architects, designers and professional
installers. Hep2O ® has been used in the UK
for 25 years and throughout Europe and
the rest of the world for over 20 years.
The Hep2O ® system is particularly suitable
for domestic hot and cold water supply
including potable water, central and
underfloor heating.
Hep2O ® pipe used in underfloor heating
systems is backed by a proven track record
of over 25 years experience of the
production of flexible pipe for heating and
cooling applications.
Features and Benefits
Hep 2O ® has evolved over 25 years to offer
improved installation advantages whilst
maintaining long-term performance benefits.
Figure No. 1 Hep 2O ® Straight Coiled Pipe
Unlike other forms of coiled plastics pipes,
Hep2O ® pipes utilising ‘straight coil’
technology do not return to their coiled
state when uncoiled from their convenient
SmartPackTM dispensers but instead remain
straight with no less flexibility.
These characteristics provide a significantly
faster, safer and more cost-effective
installation, making Hep2O ® the ideal
material for underfloor heating systems.
4
Figure No. 2 Hep 2O ® SmartPack TM
Installation
Hep 2O ® introduces a new flexibility for the
professional to exploit during installation:
● Cabling Ability
● Low Wastage
● Measure and Cut In-situ
● High Resistance to Impact
● Easier Handling
Performance
Once installed Hep 2O ® offers considerable
benefits over traditional rigid systems:
● No Scale Build-up
● No Burst Pipes
● Corrosion Free
Hep 2O ® Underfloor Heating
Barrier Pipe
Hep2O ® Underfloor Heating Pipe is
designed for use in underfloor central
heating systems. It is principally
manufactured from polybutylene (PB), which
is more flexible than other materials
commonly used for underfloor heating such
as crosslinked polyethylene (XPLE/PE-X),
polypropylene (PP) and multi-layer pipe.
Polybutylene’s inherent ‘all weather’
flexibility allows sub-floor heating circuits to
be installed quickly and easily even in
adverse conditions without the need to
pre-temper the pipe on site.This eases
installation and eliminates both the need for
contractors to use temporary water
heating systems to condition pipe prior to
laying and the attendant health and safety
issues associated with this.
Hep 2O ® Underfloor Heating Pipe
incorporates an oxygen diffusion barrier
offering maximum protection against
oxygen ingress.
Polybutylene
Adhesive ensures secure
bonding of polybutylene to
barrier layer
Figure No. 3 Hep 2O ® Underfloor Heating Pipe
Hep 2O ® Underfloor Heating Barrier Pipe is
manufactured principally from polybutylene
using an advanced five-layer co-extrusion
process, with a layer of EVOH enclosed
between polybutylene inner and outer
layers to form the oxygen barrier.The
design of the barrier within the wall of the
pipe offers significant advantages over
underfloor heating pipes with an external
coating. Because the barrier is fully enclosed
it is not subject to physical damage.
Pipe Lengths
Hep 2O ® Underfloor Heating Pipe is
available in a variety of coil lengths, enabling
the installation of continuous circuits with
minimal pipe wastage.
Table No. 1 Pipe Lengths
Diameter Code Coil Length Available
(mm) (m)
16 UH06016 60 ✔
16 UH08016 80 ✔
16 UH10016 100 ✔
16 UH15016 150 ✔
16 UH20016 200 ✔
16 UH50016 500 ✔
Performance
EVOH oxygen
barrier layer
Polybutylene
Although the design temperatures and
pressures encountered in underfloor
heating systems are generally lower than
that of conventional heating systems Table
No. 2 illustrates the peak life cycle
operating temperatures and pressures of
the Hep 2O ® system.

Hep 2O ® Underfloor Heating Pipe - continued
Table No. 2 Peak Life Cycle Operating Temperatures/Pressures
Safe pressures:
Approvals
20°C 30°C 40°C 50°C 60°C 70°C 80°C 95°C Short
Malfunction
at 114°C
Bar 12 11.5 11 10.5 9 8 7 6 3
psi 174 167 160 152 131 116 102 87 43.5
Head of water (m) 120 115 110 105 90 80 70 60 29
The Hep 2O ® Underfloor Heating System
(Pipe & Manifolds) is covered by British
Board of Agrèment Certificate 92/2823.
Hep 2O ® Environmental Considerations
Introduction
Hepworth Plumbing Products is committed
to promoting measures for limiting the
adverse environmental impact of its
operations.With the increasing awareness
of environmental issues and growing
legislative controls, an environmental policy
and cohesive management system has been
implemented to co-ordinate control and
continually improve standards of
environmental performance.
The endorsement of a product for any
particular application is increasingly
influenced by its potential impact on our
environment.The two main factors taken
into account in calculating this impact are:
● The period of time for which a product
fulfils its intended use before the need
for replacement, otherwise know as its
‘sustainability’.
● The negative impact a product has on
the environment during its manufacture
and use, both in terms of its fuel
efficiency and environmental damage,
and also taking into account the
possibility of recycling.
The following information on sustainability
has been taken from a paper entitled:
‘Polybutene-1 Piping Systems in Use’ issued
by the Polybutene Piping Systems
Association, (PBPSA).
Hep 2O ® Underfloor Heating Pipe is
manufactured within a Quality Management
System, which satisfies BS EN ISO 9001
requirements.
Sustainability
FM 01415
The performance of polybutylene pipes has
been proven through long-standing, troublefree
service in applications worldwide.
Polybutylene has been used successfully in
pipe applications for over 30 years. In
Austria and Germany, district heating and
underfloor heating schemes of the early
1970’s are still offering trouble-free
operation.
Perhaps the most noteworthy success to
date as a material for pipework is its use in
the Vienna Geothermal Project. Since 1974,
very aggressive geothermal water has been
utilised as the heating medium and is still
operating today at a constant temperature
of 54˚C and a 10 bar pressure.
The sustainability of Polybutylene pipes is
therefore proven through long-standing,
trouble-free service.
Since the first installations, advances in both
material technology and production
processes, combined with the introduction
of stringent standards, has furthered the
performance of Polybutylene piping
systems.
For further information on the PBPSA visit
www.pbpsa.com
Guarantee
Hep 2O ® has a minimum design life
expectancy of 50 years provided the system
is installed in accordance with the
manufacturer’s recommendations.These
recommendations include service
temperatures and pressures. Peak life cycle
operating temperatures/pressures are given
in Table 2. As a result of its rigorous
Quality Management Programme,
Hepworth Building Products offer a 50 year
guarantee against defects in materials or
manufacturing of all Hep 2O ® Underfloor
Heating Pipe.
Environmental Impact
Polybutylene is produced from crude oil by
refining and polymerisation.The polymer is
extruded to create the finished pipe.The
environmental impact of the production
process, in terms both of energy usage and
emissions, is markedly less than is the case
for alternative metal pipe systems and many
other plastics. In common with other
polyolefin thermoplastics, polybutylene can
be readily recycled, if required.
5

Hep 2O ® Underfloor Heating System
Introduction
Underfloor heating offers significant benefits
over traditional central heating systems and
has become very popular for both domestic
and commercial installations. Once seen as
the preserve of specialists, underfloor
heating can now readily be installed by
professional plumbers, particularly in
domestic properties and extensions.
Hep2O ® Underfloor Heating Systems make
a positive contribution towards ease of
installation.
Underfloor heating provides a comfortable
highly energy efficient type of heating. It
delivers an invisible warmth, with no
unsightly heat emitters compromising the
building layout. It is ideal for both
renovation and new build methods of
construction, thus allowing maximum usable
area within the building.A modern
underfloor heating system consists of
continuous plastics pipe circuits buried in a
concrete screed or run below a timber
floor system, (either floating or suspended).
Benefits
The major benefit of an underfloor heating
system to the end user is the comfort level
provided by this form of heating.
The Hep2O ® Underfloor Heating System
utilises low temperature hot water, typically
40-55˚C unlike flow temperatures of 80˚C
from traditional heating methods such as
radiator systems.The warm water is
circulated through the pipe circuits
providing an even heat distribution across
the whole installed area.This warms the
floor to a maximum surface temperature of
29˚C in normally occupied areas with a
room temperature of 20˚C and 23˚C in
bathrooms with a floor temperature of
24˚C. Even with ‘cold’ materials such as
quarry tiles and stone flags the floor
becomes comfortable to walk on in bare
feet.
Underfloor heating provides an optimum
form of comfort by providing a greater
eye level
6
270
170
theoretically
ideal heating
underfloor or
slab heating
degree of warmth at a low level degrading
over the body to a cooler head level.The
heat gradient of an underfloor heating
system creates a ‘warm feet, cool head’
environment in which heat is concentrated
at ‘living level’ rather than being wasted
warming the ceiling space.This is achieved
when the feet are a few degrees warmer
than the head.
Underfloor heating has the nearest
temperature profile to the ideal, as opposed
to radiator systems which cause a higher
temperature at a high level with resultant
discomfort and excessive use of energy. By
virtue of a predominately radiant form of
heat transfer, comfort conditions can be
achieved with an air temperature 2˚C
below what would normally be anticipated
with general forms of heating.
The only type of heating which delivers this
is underfloor heating.As a consequence
energy costs are significantly reduced,
typically in domestic applications by in
excess of 20 per cent and in larger buildings
such as factories and warehouses savings of
up to 50 per cent are not unusual.
Removing the need for radiators,
underfloor heating maximises the useable
room space, improves interior aesthetics,
eliminates redecoration problems and
allows greater flexibility when designing
room layouts.
There are additional secondary advantages.
Notable among these is the fact that there
are no hot radiators that may cause a
potential hazard to elderly or very young
residents. Underfloor heating primarily
utilises radiant heat, rather than convection,
so less dust is moved around rooms.This
can be a particularly useful feature for
residents with respiratory conditions such
as asthma.Warm floors can also assist in
keeping bathroom and shower areas dry.
For the home owner/occupier there is, of
course, less maintenance since there are no
radiators to paint or decorate behind.
Temperature profiles for various methods of heating
radiator heating
system on
inside wall
radiator heating
system on
outside wall
forced air
heating
ceiling
heating
˚C 16˚ 20˚ 24˚ 16˚ 20˚ 24˚ 16˚ 20˚ 24˚ 16˚ 20˚ 24˚ 16˚ 20˚ 24˚ 16˚ 20˚ 24˚
Figure No. 4 Temperature profiles.
Advantages
● Energy efficient ‘invisible’ warmth
– Savings on running costs compared to
radiator systems
● Uniform heat – good distribution over
the whole room
● Greater level of comfort – the
temperature profile is very close to ideal
human comfort levels
● No cold floors – stone and ceramic
floors are more pleasant underfoot
when warm
● Compliments the operation of
condensing boilers – underfloor
heating is designed to operate at lower
temperatures than radiator systems
● Ideal for modern lifestyles – allows
total freedom on furniture layout and
room utilisation
● Clean interior design – no dusting
behind radiators required
● Safe for children, elderly and the
less able – no exposed hot surfaces to
create a burn hazard
● Low allergy – convected airborne dust
levels reduced and underfloor heating
discourages house dust mite within floor
coverings
● Low maintenance – no decoration or
renewal of radiators, and no radiators to
‘drop’ to enable redecoration of rooms
● No staining of walls – convective air
currents above radiators often stain
decorations
● No visible second fix piping – less
trade co-ordination problems
● Less likelihood of insurance leak
claims – no risk of leaks from
radiators and associated connections
● Silent running – no expansion creaking
or water flow noise via radiators
● Ideal for high ceilings – maintains the
heat at the same level as the occupancy

Hep 2O ® Underfloor Heating System - continued
Floor Types
Historically, underfloor heating has most
often been used in concrete screed floors.
However, it can also be installed in
suspended timber and floating floors. It can,
therefore, be specified with confidence for
ground and intermediate floors.
In concrete floors the heating pipes are
typically laid above the sub base and on top
of the insulation prior to pouring the
screed. In timber floors they are laid on top
of insulation positioned between the joists
before the floorboards or sheets are fixed.
Hep 2O ® Underfloor Heating Design
Introduction
Underfloor heating designs should take into
account the desire to maintain an even
surface temperature throughout the floor
area.
The most important part of the underfloor
heating design is the heat loss calculation.
As with the design of any other heating
system, the calculation determines how
much heat is required to make a room
comfortable.
To ensure the efficiency of the calculation,
specific and accurate information is
required. Data that determines the
outcome of the calculation includes: room
dimensions including height; desired room
temperature (this is typically 18˚C for
bedrooms, 21˚C for living areas and 22˚C
for bathrooms); outside design temperature
(generally set at –3˚C); air changes per hour
(generally set at 1.5 for rooms in constant
use, 2 for kitchens and bathrooms and 1 for
bedrooms), and type of floor covering.
Underfloor Heating Quotation
Hepworth offer an on-line underfloor
heating quotation service.This can be found
by logging onto the underfloor heating
section of www.hep2o.co.uk and clicking
on the Underfloor Heating link.The
calculator will provide the enquirer with an
estimated products cost for their project. If
this cost is within the scheme’s budget, the
enquirer can send the information to the
Underfloor Heating Design Department for
verifying.This information should include
drawings and design information. From this,
an accurate bill of materials will be
produced from which the enquirer can then
place an order with a Hepworth Plumbing
Products stockist.
Individual pipe layout plans are not provided
as part of the quotation service. Generic
floor type pipe layout plans will be provided
which, along with a Design Data Sheet that
has details of pipe spacings and flow
temperatures.
In most cases underfloor heating is laid in
new properties or extensions but it can be
retro-fitted provided that floors are being
taken up as part of the project.
Forward Planning
Underfloor heating should not be an ‘afterthought’
in the design and construction
process. Rather, its use and the implications
for other parts of the building programme
should be considered at the outset.
Most significantly, installation of underfloor
heating affects the overall floor/screed
Figure No. 5 Underfloor Heating Design
Manifold Location
Ideally the manifold should be located in
the centre of the building in order to
minimise unequal circuit lengths.
Figure No. 6 Manifold Location
Heat Outputs
The maximum heat output from a solid
floor is normally 100W/m 2 and for a
suspended or floating floor 70W/m 2 . If a
greater heat output is needed additional
heating may be required. Generally if the
materials selected for the structure are in
accordance with the Building Regulations
most buildings should have heat
requirements that are easily met by a
Hep 2O ® Underfloor Heating System.
depth and so has implications on the
finished floor level and other elements.
The most common design errors in
underfloor heating installation are the
failure to take into account floor depth and
the incorrect location of the insulation layer
which should be installed beneath the
concrete sub base.
Unheated Areas
When designing an underfloor heating
system it is important to remember there
are certain areas which do not need
heating.These are generally in kitchens
under the units and appliances and in
bathrooms under the sanitary appliances.
Because of this, the effective floor area that
can be used for heating is reduced.This may
mean that additional heating could be
required in the form of a towel rail or kick
space heater to achieve the desired level of
comfort.
Heat Sources
Most standard central heating boilers are
suitable for use with underfloor heating
systems. However underfloor heating
systems are especially compatible with
modern high efficiency condensing boilers,
which can operate at lower temperatures
than traditional boilers, offering higher
efficiencies and delivering fuel savings to the
end-user. Please refer to page 19 for the
contact details of manufacturers of suitable
standard and high efficiency boilers.
Figure No. 7 High Efficiency Boiler
7

Hep 2O ® Underfloor Heating Design - continued
Electronic Controls
Accurate room temperature is necessary in
order to minimise the energy consumption
of a heating system.This has benefits in
environmental protection and also in fuel
saving which is particularly important to the
homeowner.Therefore it is paramount that
an underfloor heating system is correctly
controlled to gain maximum benefit
environmentally as well as financially.Years
of development and practical experience
indicate that this temperature control can
be maintained by the use of thermoelectric
actuators coupled to the underfloor heating
manifold.The use of electronic room
thermostats further facilitates the ease of
control, allowing zones (rooms) to be
controlled individually or collectively.
Figure No. 8 Temperature Control
8
Further information on control and wiring
products can be found in the current
Hepworth Plumbing Products Price List or
by contacting the Underfloor Heating
Design Department.
Figure No. 9 Wiring Centre
Floor Coverings / Finishes
It is imperative with an underfloor heating
system that the floor covering allows
sufficient heat transfer to heat the room.
Ceramic, stone and marble are all good
heat emitters, as are vinyl and chipboard
floorings. Most carpets and underlay
combinations are satisfactory, however the
use of very thick carpet and underlay will
create a resistance to the passage of heat,
slowing down the response time of the
Hep 2O ® Underfloor Heating - Frequently Asked Questions
General
1. How does Hep2O ® Underfloor
Heating work?
Warm water is circulated through a series
of pipes laid in the floor of the room.These
pipes form a continuous loop and act to
create a large radiant surface that will heat
the room to a comfortable temperature.
2. What is the best way of estimating
the requirements and costs of an
underfloor heating installation?
The www.Hep2o.co.uk website has a
simple to use underfloor heating calculator
in the underfloor heating section. By
inputting the room size and floor
construction, the calculator will return circuit
lengths of pipe required for installations
along with suitable manifolds. It will also
calculate the estimated cost for the
materials required. Whilst this should be
the first point of call for underfloor heating
requirements, further consultation with our
design department is imperative to clarify
and finalise each installation.
3. Can underfloor heating be installed
in an existing building?
Yes, in many cases this is possible, but it will
depend upon the building’s current
insulation levels and whether there is space
to install the pipework and insulation in the
floor to ensure that the correct
temperatures can be achieved.
4. Can underfloor heating be installed
in timber floors?
Yes, by using heat spreader plates and
insulation within the floor.
5. Will underfloor heating affect
timber floors?
Underfloor heating will not affect chipboard
or laminate flooring, however natural wood
flooring may be affected due to shrinkage
and expansion from changes in moisture
content.
6. Can underfloor heating be installed
in a conservatory?
Yes, Hepworth offer the Hep2O ®
Underfloor Heating Conservatory Pack for
conservatories with solid floors up to 15m2 .
For suspended floors a manifold type
system can be installed. On cold winter
days supplementary heating may be
required in some types of conservatory.
7. Will underfloor heating work
through a carpet?
Yes, underfloor heating will work with
carpeted floors provided that the design
takes this into account and that thick
carpets and underlays are avoided.
8. Will the room be warm enough?
Yes, provided that the room meets the
minimum insulation requirements of the
building regulations, and the system is
designed and installed correctly.
underfloor heating system. Hepworth
recommends carpet underlay have a
maximum tog rating of 1.0, further details
on tog ratings should be sought from carpet
underlay manufacturers.
Care should be taken when fixing carpet
grip strips and door threshold strips as not
to damage the pipework.
Laminate Flooring
Laminate flooring is suitable floor covering
for underfloor heating systems. However it
is important to check with the
laminate/underlay manufacturer to ensure
the underlay is compatible with an
underfloor heating system. Some types of
laminate underlay are foam based and act as
an insulating layer, slowing down the
response time of the underfloor heating
system in a similar way as thick carpet and
underlay.
9. What is the heat output from an
underfloor heating system?
As a guide, a screeded floor system will
provide up to 100 W/m2 and a timber
suspended floor up to 70 W/m2 .
10. Do I need a special boiler?
No, generally any type of boiler using any
fuel can be used. Condensing type boilers
are particularly suited to underfloor heating
because the low return temperature means
that the boiler will frequently operate in
condensing mode when the system is
running.
11. Is underfloor heating more
efficient than a radiator system?
Yes, savings in running costs of 20-25% can
be achieved using underfloor heating.This
energy saving is increased in buildings with
higher ceilings. In high ceilinged buildings
such as churches, savings of 50% have
been achieved.
12. Can I use an underfloor heating
system as a cooling system?
Yes, incorporating a chiller unit (as well as a
boiler) allows the floor to operate as a
cooling system in warm weather.The floor
must incorporate a dew point sensor to
avoid condensation forming on the finished
floor. A chilled floor is capable of absorbing
up to 40 W/m 2 , depending upon design.

Hep 2O ® Underfloor Heating - Conservatory Pack
For small areas sometimes the installation
of a manifold system may be unfeasible, It is
in these smaller areas that Hepworth
Plumbing Products have developed a
purpose designed package ideally suited to
conservatories, bathrooms and small
extensions.
The pack comes complete with everything
required to install a system for rooms with
a solid floor construction up to 15m 2 .It
allows the underfloor circuits quite literally
to be ‘plugged in’ to an existing 15mm
radiator system, without the need for
separate pumps or manifolds.
The pack is suitable for all types of
extension and is particularly appropriate for
conservatories where the presence of
dwarf walls often makes installing traditional
radiators difficult and inefficient.
The Hep2O ® Underfloor Heating
Conservatory Pack utilises Hep2O ®
Underfloor Heating Pipe and a return
temperature limiter valve and sensor, which
monitors water temperature.The controller
maintains a constant return temperature by
varying the amount of water that is allowed
to flow through the underfloor circuit.The
return water temperature is maintained at a
user-defined level, and as a result, so is the
floor temperature.This type of control does
not require its own separate circulating
pump or mixing valve.
Advantages
● Simple to install and operate
● Ideal for use in smaller systems
● No need for extra pump and
mixing valve
● No wiring
● Controls water temperature
leaving the circuit
● Maintains a constant floor
temperature
● No room temperature distortions
from short term free heat gains
● Ideal solution for areas with high
heat gains such as conservatories
● Handy pack solution supplied with
instructions
The Hep2O ® Underfloor Heating
Conservatory Pack is only suitable for solid
floor constructions of a minimum 75mm
thickness up to 15m 2 floor area and
systems where pipes are laid in a spiral
pattern to achieve an even floor
temperature.
Floor insulation and polythylene membrane
are required for the successful installation
of the underfloor heating pack and the
installer will need to source these items.
For further information on the Hep 2O ®
Underfloor Heating Conservatory Pack visit
www.hep2o.co.uk
9

Hep 2O ® Underfloor Heating Installation
PIPE LAYOUT - SOLID FLOOR
Where possible pipe should be laid in a spiral pattern, as shown in Fig
No 10, this ensures an even spread of heat and allows faster response
times. It is important to note that the flow from the manifold is taken
around the outside edge of the room first, this is particularly important if
the room has an external wall.
When the pipe reaches the centre of the room be sure not to bend the
pipe more than the maximum bending radius (128mm or 8 x radius of
pipe) see Fig No 21 on page 13.
N.B:
Do not run pipework beneath pantries, kitchen units, or other
permanent fixtures.
PIPE LAYOUT - SUSPENDED FLOOR
Pipe should be laid in the pattern shown in Fig No 11. Pipe spacing for
suspended floors is generally a maximum of 300mm centres or two pipes
between joists that are at 600mm centres or less.
PIPE LAYOUT - FLOATING FLOOR
Pipe should be laid in the single serpentine pattern as shown in Fig No 12.
The pipe centres are pre-determined by the Floating Floor Panels.The
channels formed in the panels are at 300mm centres.
10
Figure No. 10 Solid/Screed Floor Layout
Figure No. 11 Suspended Floor Layout
Figure No. 12 Floating Floor Layout

Hep 2O ® Underfloor Heating Installation - continued
FLOOR CONSTRUCTION
Underfloor heating can be used on any of the typical floor constructions commonly used in the UK, although the configuration of the system may vary.
The three most common types of floor construction are:
● Solid/screed floor
● Timber/intermediate floor
● Floating floor
Methods of using underfloor heating within these constructions are set out below:
Edge Insulation
Insulation
Subfloor
Floor Surface
Insulation
Joist
Floor Surface
Insulation
Subfloor
75mm Screed (Min)
Conductor Plate
16mm Hep 2 O ® UFH Pipe
16mm Hep 2 O ® UFH Pipe
Conductor Plate 16mm Hep 2 O ® UFH Pipe
Vapour Barrier
(if required)
Damp Proof
Membrane
Wooden Batten
Damp Proof
Membrane
Solid/Screed Floor
Timber/Intermediate Floor
Floating Floor
11

Hep 2O ® Underfloor Heating Installation - continued
SOLID/SCREED FLOOR CONSTRUCTION
UH50/25 Edge
Insulation Strip.This
must extend from
the sub floor to the
upper edge of the
flooring layer.
SOLID/SCREED FLOOR
Concrete screed/solid floor applications are the
most common type of underfloor heating
installation.
Edge Insulation
The Edge Insulation Strip (UH50/25) should be
provided around the perimeter of the room
including internal walls. It should be placed along
the walls prior to the laying of the screed.Any
excess Edge Insulation Strip above the slab can
be easily trimmed once the slab has cured.
Figure No. 13 Edge Insulation Strip placed against wall
The Edge Insulation Strip serves two purposes;
firstly it forms an insulation barrier around the
floor slab minimising heat loss through the
surrounding walls. Secondly, it acts to
accommodate for any expansion of the slab.
Single areas of screed should not exceed 40m 2
or be longer than 8 metres in length.Where
areas/lengths are greater than this, Edge
Insulation Strip should be used to form an
expansion joint.
Where the pipe passes through the Edge
Insulation Strip, at an expansion joint or where
pipe enters and exits a room, it should be
shielded using Conduit Pipe for 400mm either
side of the joint.This allows for the possibility of
differing temperatures between slabs or rooms
(Fig No 14).
12
Figure No. 14 Expansion Joint
Floor Insulation
Thermal Insulation is positioned under the pipe
circuits in order to prevent downward heat loss,
thus ensuring maximum heat output into the
room.
Generally most kinds of board insulation can be
used. However, foiled high-density polyurethane
foam is likely to suffer less site damage due to its
high compressive strength. Pipe Fixing Staples
also fix very well into this type of insulation.
Figure No. 15 Insulation placed up against Edge
Insulation
The thickness of insulation currently required
should be calculated to achieve a U-value of 0.25
W/m 2 K in accordance with the Building
Regulations. Insulation requirements will
therefore be different for every building and
should be calculated at the design stage of the
Screed minimum
75mm from top of
insulation. Reinforced
if required.
16mm Hep 2O ®
Underfloor Heating
Barrier Pipe, laid in a
spiral pattern, at
designed centres.
UH54 Pipe Staples.
Vapour Barrier (if
required).
Floor insulation in
accordance with
Building Regulations.
Damp Proof
Membrane.
project.The poorer the insulating properties of
the material the thicker the insulation that will be
required.Advice on insulation should be sought
from specialist manufacturers.
Vapour Barrier
A vapour barrier should be provided on top of
the insulating material if its structure is porous
e.g. polystyrene, to stop any absorption of
moisture from the screed.A polyethylene film is
generally used of at least 0.15mm thickness.The
vapour barrier should be turned up at the edges
around the perimeter.The vapour barrier is not a
damp proof membrane.A damp proof membrane
must be provided to structural slabs in
accordance with the Building Regulations.
Pipe Installation
Hep2O ® Underfloor Heating Pipe can be fixed in
a number of ways prior to the laying of a
concrete screed floor:
Figure No. 16 Pipe Staples pushed into Insulation
For ease of installation Screed Floor Tiles may be
utilised on solid floor applications.The Screed
Floor Tiles can be easily cut to the room shape,
forming a grid to facilitate the quick and easy
laying of pipe.The design of the grid is such that,
when laid, the pipe is firmly held at
predetermined centres preventing movement
during the screeding process.The Screed Floor
Tiles do not have sufficient insulating properties

Hep 2O ® Underfloor Heating Installation - continued
SOLID/SCREED FLOOR CONSTRUCTION - CONTINUED
to satisfy the requirements of the Building
Regulations, they must be used in conjunction
with additional insulation.
Figure No. 17 Pipe laying with Screed Floor Tile
Figure No. 18 Clip Rail fixed to insulation
Figure No. 19 Pipe fixed to reinforcing mesh
Pipe Circuits
Pipe circuits are formed by coiling the pipe in a
pre-determined pattern. Hepworth recommend
the use of the spiral pattern, see Fig No 10 page
10.This allows the flow to sit alongside the
return balancing the temperature of the hot and
cooler water to achieve an even heat. More than
one circuit may be needed in larger rooms in
order to avoid too large a water temperature
drop.The maximum circuit length to avoid
excessive pressure drops and too large a
temperature drop is 100 metres. There should
be no joints in the pipe circuit.
Once the pipe circuits have been formed a water
test should be applied to the system to a
pressure of 6 bar to check for any leaks.This
pressure of 6 bar should be maintained during
the screeding and curing processes to prevent
any damage occurring to the pipe.
Figure No. 20 Pressurising pipe circuits
Bending Radii
Hep 2O ® Underfloor Heating Pipe can be easily
manipulated by hand to form bends of any angle.
In order to prevent kinking or any long term
detrimental effect to the material, the curvature
of Hep 2O ® Underfloor Heating Pipe should be
not less than indicated in Fig No 21.
r = 128mm
Figure No. 21 Minimum Bend Radii
Concrete Screed
In most cases a normal sand and cement mix
screed is used on underfloor heating applications.
The optimum depth of the screed is generally 65-
75mm. If a screed any less than 65mm is required
advice should be sought from a specialist screed
supplier. Generally the screed is installed in a
fairly dry state.When screeding an underfloor
heating system it is important that the screed
envelopes the pipe fully, eliminating air pockets
for the system to work to its full potential.
Adding a plasticizer to a mix can help the screed
flow better, thereby avoiding air pockets.Advice
on plasticizers should be sought from specialist
manufacturers.Wet screed mixes should be
avoided as this can cause shrinkage and cracking
of the screed during the curing process.
The screed should be allowed to cure and dry
naturally until full strength is achieved, usually 28
days. Heat commissioning should not be carried
out for at least 21 days after the laying of the
screed.The system should be run at 20-25˚C for
at least 3 days and then subsequently increased
by 5˚C every day until design temperature is
achieved.
‘I’ Beam Joists
Figure No. 22 If the suspended floor is of ‘I’ beam
joist construction, installation is carried out from the
underneath.Two holes are drilled in the central web of
the ‘I’ beam joist. Holes should be drilled in accordance
with the manufacturers recommendations.The pipe is
then looped through as illustrated in Fig 23 and attached
to the underside of the flooring or side of the joists
using cable type pipe clips.Thought must be given at the
design stage as to whether access under the floor may
be needed; this will obviously have an effect as to how
the pipe will be fixed.Alternatively conductor plates can
be tacked over the pipe from underneath.This will give a
more uniform heat and improved response time.
Figure No. 23 Insulation board is then pushed up
against the pipe work and fixed in place.
13

Hep 2O ® Underfloor Heating Installation - continued
SUSPENDED FLOOR CONSTRUCTION
UH51 Conductor
Plate.
16mm Hep 2O ®
Underfloor Heating
Barrier Pipe, laid
parallel to joists.
SUSPENDED TIMBER FLOOR
CONSTRUCTION
The installation of Hep2O ® Underfloor Heating in
intermediate or suspended timber floors is
suitable for both new and existing buildings.
The method of installation used in intermediate
and suspended floor applications involves the use
of heat conductor plates supported above
insulation that is fixed between joists.
Conductor Plates
Conductor Plates (UH51) are used to hold the
Hep2O ® Underfloor Heating Pipe and direct the
heat upwards through the flooring material to
ensure a comfortable level of heat is achieved
within the room.The Conductor Plates are
manufactured from aluminium and give the
advantage of a more uniform heat and improved
response time.
Insulation
Insulation is used to stop the downward
transmission of heat.A sheet type insulation is
most suitable for suspended floor applications.
The insulation requirement must be in
accordance with the Building Regulations.
Pipe Centres
The pipe spacing for this type of installation is
generally a maximum of 300mm centres or two
pipes between joists that are at 600mm centres
or less.
Pipe Installation
With this type of installation, the work is carried
out from above, although for ease the battens
may be installed from below if working on an
intermediate floor.
Battens are fixed at a pre-determined depth from
the top of the joist, to take into account the
depth of both the insulation and the Conductor
Plates.The Conductor Plate should be touching
the underside of the flooring material.
14
Figure No. 24 Insulation is cut to the required width.
Figure No. 25 The insulation board is placed between
the joists and placed on the battens.
Figure No. 26 The Conductor Plates are fixed to the
joist along one edge and supported along the other by a
narrow piece of insulation.This prevents the Conductor
Plate from sagging. Conductor plates should be cut if
required.
Wood/Chipboard
Flooring.
Insulation Strip.
Floor insulation in
accordance with
Building Regulations.
Figure No. 27 The ends of the joist should be notched
to allow the pipe to form the heating circuit. Notching
of joists should be in accordance with the Building
Regulations.
Figure No. 28 Hep2O Underfloor Heating Pipe is laid
into the conductor plates and pipe clips used to fix pipe
to insulation.
Figure No. 29 The flooring material is laid on top of
the joists.

Hep 2O ® Underfloor Heating Installation - continued
FLOATING FLOOR CONSTRUCTION
UH53 Floating Floor
Tile, additional
insulation may be
required in
accordance with
Building Regulations
Part L.
Damp Proof
Membrane.
Sub Floor.
FLOATING FLOOR
CONSTRUCTION
Floating floors may be used where a ‘dry’ method
of construction is preferred.This method of
construction is particularly suitable for
refurbishment and renovation work.
Floating Floor Panels
The UH53 Floating Floor Panel is designed
specifically for use with a floating floor
construction.These panels are 1.2 x 1.2 metres
square and are available in a standard depth of
50mm thick and 35mm for refurbishment work.
The Floating Floor Panel can be used above
existing timber floors or a solid sub-base.The
panels are manufactured from CFC/HCFC free
expanded polystyrene (EPS).
Insulation
Floating Floor Panels do not have sufficient
insulating properties to satisfy the requirements
of the Building Regulations; they must be used in
conjunction with additional insulation.The
insulation requirement must be in accordance
with the Building Regulations.The K Value of the
Floating Floor Panels is 0.036 W/mK.
Pipe Centres
The pipe centres are pre-determined by the
Floating Floor Panels.The channels formed in the
panels are at 300mm centres.
Pipe Installation
Figure No. 30 A vapour barrier must be laid on top of
the existing timber or solid floor.This is to stop any
possible interstitial condensation. Edge Insulation Strip
should be fixed around the perimeter of the room in
the same manner as detailed in the solid/screed floor
section.
Figure No. 31 The Floating Floor Panels should be laid
on the vapour barrier or additional insulation if it is
required.
Figure No. 32 Conductor Plates should be laid into
the pre-formed channels of the Floating Floor Panels.
Wood/Chipboard
Flooring.
UH51 Conductor
Plate.
16mm Hep 2O ®
Underfloor Heating
Barrier Pipe.
Figure No. 33 Hep2O Underfloor Heating Pipe is then
laid into the channels formed by the Conductor Plates
in the Floating Floor Panels.
Figure No. 34 Fix the pipe in place with Pipe Staples.
The flooring should be laid directly on top of the
Floating Floor Panels.The Conductor Plates
should touch the underside of the flooring.A
small expansion gap should be left between the
edge of the flooring and the walls.
15

Manifold Introduction
The Hep 2O ® Underfloor Heating Manifold kit is
a pre-assembled brass manifold available in
configurations of 2-12 ports.The manifold mixes
and regulates, allowing effective distribution of
water at low temperature (typically 40-55˚C), to
the underfloor heating circuits by drawing off
from the primary circuit, which is at a higher
temperature.
Figure No. 35 Installed Hep 2 O Underfloor Heating 4 Port Manifold
16
The advantage of this means that the manifold is
particularly useful with mixed systems, where in
the same property radiators are supplied at high
temperature and circuits with underfloor heating
are supplied with water at low temperature and
used in the same system.
The manifold features; injector valve,
thermostatic head, safety bypass, lock shield valve,
flow meters, temperature sensors and automatic
air vents as standard. Comprehensive manifold
assembly, installation and commissioning
instructions are supplied as part of the manifold
kit.

Manifold Operation
The injector valve (4) and the lockshield valve (7)
are the connection points to the primary circuit
from the heat source.Water from the heat
source, at a temperature of 70-80˚C, flows
through the injector valve (4) and is pumped past
the sensor (6) into the upper flow manifold (1)
passing through the pipe circuits to the return
manifold (2). A large proportion of this water is
then re-circulated via the pump (3) past the
sensor and back into the flow manifold. If the
water temperature at the sensor is greater than
the limit set by the thermostatic head (5), the
injector valve (4) closes so that the water is recirculated
until it reaches a low enough
temperature to re-open the injector valve,
allowing in more hot water. It is this process that
maintains the relatively low temperatures
required by underfloor heating.The addition of
Actuator Heads (UH15) to the return manifold
allows the temperature of different rooms, or
areas, to be controlled by their own individual
thermostat or sensor.
The differential valve (8) automatically regulates
pressure changes within the manifold allowing for
Manifold Kit Components
The components comprising the manifold kit are
illustrated in Figure No. 37.The diagram also
indicates which parts of the manifold are factory
sealed.
Figure No. 37 Manifold Kit Components
1 Upper flow manifold
2 Lower return manifold
3 Pump (not supplied)
4 Injector valve
5 Thermostatic head
6 Sensor
7 Lockshield valve
8 Differential valve
9 Drain cock
10 Flow and return temperature gauges
11 Flow meters
12 Auto air vent
13 Regulating valve
14 Immersion sensor pocket
15 Manifold Extension Piece (UH17,
optional)
Note:
The use of a Security Overheat Thermostat
with Immersion Sensor (UH13) is
recommended.This is fitted to the flow
manifold and stops the pump in the event that
the flow temperature exceeds the design
temperature.The UH13 will automatically
restart the pump when the system cools.
accurate setting of flow rates via the flow meters
(11).
For added safety the Thermostat with Immersion
Sensor (UH13) is recommended, this operates in
Figure No. 36 Manifold Operation
5.Thermostatic
Head
4. Injector
Valve
H
4
5
15
14
6
3. Pump
Overall Dimensions (without extension piece)
10
10
12
6. Sensor
3
2
11
9
the event of the thermostatic head (5) failing by
shutting down the pump (3) allowing water to
pass directly from the injector to the lockshield
valve (7) without passing through the circuits.
L
13 1
1. Flow Manifold
7. Lockshield
Valve
2. Return
Manifold
Ports 2 3 4 5 6 7 8 9 10 11 12
H (mm) 450 450 450 450 450 450 450 450 450 450 450
L (mm) 515 565 615 665 740 790 840 890 940 990 1040
9
8
7
17

Hep 2O ® Underfloor Heating - Frequently Asked Questions
Installation
1. How do I connect my underfloor
heating system to the boiler
The underfloor heating system (with the
exception of the Hep2O ® Conservatory
Pack) should be connected to the boiler
through the manifold.The manifold controls
the heat requirement for the underfloor
system by blending hot water from the
boiler with cooler returned water from the
floor circuits. Most boilers have a high
output temperature (80 to 85°) to cater
for the other heat requirements of the
dwelling (e.g. hot water cylinder, radiators
and towel rails), which means that they
should not be connected directly to the
underfloor system.
2. Why do I need another pump on
the manifold
The pump circulates the water within the
underfloor heating system and will continue
to operate after the injector valve has
closed and hot water is no longer being
mixed with the return water. It is also
required where the pump on the boiler
would not achieve the required flow rates in
the system.
3. Where should the manifold be
positioned?
The manifold can be positioned virtually
anywhere in the building as long as there is
enough heat output to supply the demand,
however it is preferable to site the manifold
centrally in the building to ensure pipe runs
to circuits are kept to a minimum.
4. How do I connect my Hep2O ®
Conservatory Pack?
The Hep2O ® Conservatory Pack is
designed to operate using water at the
temperature of the radiator system, and
can be directly connected to the radiator
pipework.The purpose designed self limiting
valve ensures that the floor remains at the
correct, comfortable temperature.
5. Will putting carpet over the
underfloor heating have an effect
on it?
Yes, carpet will slow the heat transmission
down because of its thermal resistance,
however this should not significantly affect
the overall performance of the system. It is
important that carpeting is specified as a
requirement during the design of the
system and that the correct underlay is
fitted; this preferably should have a tog
rating of less than 1.
6. Will underfloor heating work with
laminate flooring?
Yes, however care should be taken when
selecting laminate underlay.The
manufacturers advice should be sought
regarding suitability for use with underfloor
heating, as some laminate underlays are
highly insulating.
18
7. Can underfloor heating be installed
on a pressurised sealed system?
Yes. It can be installed on any sealed or
open vented type system.
8. How long does underfloor heating
take to work?
Normally from cold, a typical solid floor
system will take 3-5 hours to reach
temperature. However when the system is
operational it will only loose an average
4°C in an 8 hour period, therefore it will
only take a couple of hours to reach
operating temperature in normal operation.
9. What type and thickness of floor
insulation should be used?
Any board type of insulation can be used,
however the foiled high-density
polyurethane foam is likely to suffer less
site damage due to the high compressive
strength. Pipe fixing staples also hold very
firmly into this type of insulation.The
thickness of insulation required is calculated
to achieve a U-value of 0.25 W/m2K which
is the minimum permitted by the Building
Regulations. Insulation thickness will
therefore be different for every building and
should be calculated when designing the
building.
10.What type of screed do I use?
In most cases normal sharp sand & cement
mix can be used for a standard 75mm
screed. If the screed is to be less than
75mm other options should be considered.
Advice should be sought from a screed
manufacturer as additives and fibres can
be added for additional strength and
flexibility. For very thin screeds a special mix
is required, however there is a possibility
that the floor temperature will not be even,
with warm strips above the pipe centres.
11. Do I need to add a plasticizer to
the screed mix?
No, however it is important when screeding
an underfloor heating system, that the
screed envelopes the pipe fully for it to
work to its full potential. Screed is normally
installed very dry; therefore care must be
taken to avoid air pockets around the UFH
pipe. Adding a plasticizer to the mix can
help the screed flow better, thereby avoiding
air pockets. Screed as a wet mix should be
avoided because this can cause shrinkage
and cracking when drying out. It is
advisable to seek expert advice from a
screed manufacturer.
12.What is the Edge Insulation Strip
for?
Edge insulation strip serves two purposes;
firstly it forms an insulation barrier around
the floor slab and therefore prevents heat
loss to surrounding walls. Secondly, it acts to
fill the expansion gap around the slab,
allowing the floor to expand and contract
as it warms up and cools down.
13.What is the conduit used for?
On screeded installations, the conduit is
installed over the underfloor heating pipes,
where they cross into adjoining rooms
(generally at doorways).This is important
because if a room is heated and an
adjacent room is not, the floors expand in
different directions and the pipe passing
through the doorway could be damaged.
The conduit pipe can also be used to sleeve
underfloor heating pipe when it passes
through an area that is not to be heated,
e.g. under kitchen units.
14.What pipe spacing should I use?
Hep2O ® underfloor heating systems are
designed with a standard pipe spacing of
200mm.
15. How is the system controlled?
Electrical actuator heads are fitted to each
underfloor heating pipe circuit.These
actuators are controlled either by a central
thermostat, or individual room thermostats
linked together with a time clock through a
wiring centre. A weather compensation
circuit may also be incorporated in the
system to adjust for outside temperature
variations.
16. How much water will there be in
an underfloor heating system?
A 16mm pipe will contain 110ml per metre
of pipe. In addition there will be an amount
of water in the manifold and pump.
17. Can I put a manifold in the floor
and feed up?
Yes, however airlocks may occur.
18. Can corrosion inhibitors be used in
the system?
Yes, corrosion inhibitors such as Fernox
MB1 and Sentinel 100 are suitable for use
in Hep 2O ® underfloor heating systems
and Hepworth recommend the use of an
inhibitor in all systems.

Hep 2O ® Underfloor Heating
References / Further Information
The Building Regulations – HMSO
BS EN 1264: 1998 Floor Heating –
Systems and Components (British
Standards Institute)
Underfloor Heating Systems –
The Designers’ Guide (BSRIA)
Underfloor Heating Systems –
An Assessment Standard for Installations
(BSRIA)
Boilers
For information on standard and high
efficiency boilers, please contact:
Notes
Guidance Notes –
Installation of Warm Water Underfloor
Heating Systems with Flexible Pipes (British
Plastics Federation - Plastic Pipes Group)
Screeds with Underfloor Heating –
Guidance for a defect-free interface
(BSRIA)
Web: www.vaillant.co.uk
Tel: 01634 292300
Web Details
HMSO:
www.tso.co.uk
British Standards Institute:
www.bsi.org.uk
BSRIA:
www.bsria.co.uk
British Plastics Federation:
www.plasticpipesgroup.com
Web: www.glow-worm.co.uk
Tel: 01773 596096
19

hotlines
Hep 2O ®
Orders & Enquiries
Telephone 01709 856400
Fax 01709 856401
Technical Support
Telephone 01709 856406
Fax 01709 856407
Literature
Telephone 01709 856408
Fax 01709 856409
Email
info@hepworthplumbing.co.uk
Web Site
www.hep2o.co.uk
Edlington Lane Edlington
Doncaster DN12 1BY UK
© Copyright Hepworth Building Products Limited
Underfloor Heating is an energy efficient form of heating, ideal for modern
living, allowing clean interior design and maximum useable wall space.
Hep 2O ® systems are suitable for both renovation and new build methods of
construction.
Telephone +44 (0)1709 856300 Fax +44 (0)1709 856301
Email info@hepworthplumbing.co.uk Visit www.hepworthplumbing.co.uk
® Hep 2O is a registered trademark of Hepworth Building Products. Our policy is one of constant development. Whilst this publication is
accurate at the date of printing, specification/approvals may be changed in the interest of continued improvement.
CWD 09/04 1750