Underfloor Heating Guidelines

Underfloor Heating Information and Advice

Scandinavian countries have been using underfloor heating since the 1920's, now over 100,000 homes per year are fitting underfloor heating and it is now available in the UK to the DIY market.

Why Underfloor Heating?
We are most comfortable when a high proportion of the warmth we feel is radiant, with our heads slightly cooler than our feet. It is nature's way. An underfloor heating system closely matches this idea. The absence of radiators gives extra space and freedom to design your rooms as you want. Our electric underfloor heating systems can be used in any room, but are extremely popular in conservatories, bathrooms and kitchens. In most cases our systems can be used as the main sole source of room heating. Alternatively they can be used as comfort warming - taking the chill off cold floors.

Bathrooms Sometimes limited wall space and regulations on which heaters can be fitted in bathrooms can be a problem. Installing underfloor heating eliminates both problems and creates a warm floor that will be a pleasure to step out of the bath or shower on to.

Conservatories With low dwarf walls, and very little room to spare on the existing house walls underfloor heating is ideal. Transform your conservatory into a room that can be used all year round with a warm inviting environment, whilst retaining the benefits of tiles or laminates.

Kitchens Come down in the morning to a welcoming warm tiled or laminate floor. Leaving your walls free for more units, thus more storage space to utilise.

Suddenly the floor's a nicer place to be...

Welcome to the Comfort Zone

Thermofloor underfloor heating mats
With Thermofloor underfloor heating, cold feet really are a thing of the past. The heat emitted from under the floor gently dissipates into the room giving even, draught-free and comfortable warmth. Being only 3mm thick the FTT-Twin heating mats can be used in either new-build or refurbishment projects. The mats can be laid on either concrete or wooden sub-floors provided that appropriate measures are taken beforehand to seal the floor.
If the final floor surface is to be ceramic tiles, the mat can be buried directly within the tile adhesive, but if either laminate, carpet or a wood finish is planned the mats should be covered by a thin screed.

Simple, quick and safe.

The FTT mat is only 3mm thick and can be laid directly onto the screed and buried in the tile adhesive. The floor temperature sensor should be located in a piece of conduit.

Selection and Installation is Simple

To ascertain which mat you need, simply measure the floor area that you want to heat and select the appropriate size mat that best fits that area. The mats can be cut and shaped to fit any room dimensions and as the FTT- twin has just one electrical connection tail it makes the pre-planning and installation procedure very simple. Multiples of mats can be used to cover larger areas, provided that they are connected in parallel. The FTT - twin mats must be used in conjunction with, and controlled by, a Stiebel Eltron RTF or RTF-Z underfloor heating controller (see below for details).

Underfloor Heating Controllers

The ability to control your underfloor heating system effectively is vitally important for both comfort and economy as well as for safety. The RTF and RTF-Z controllers are simple to use, functional and good looking. Both units are designed to be fitted within a flush back-box(45mm) or surface mounted pattress box. The controllers come complete with a floor temperature sensor probe that is on a 4 metre long lead. The probe should be buried in the sub-floor (ideally within a piece of conduit) within the heated area and in a position that is representative of the whole area. Positioning next to heat emitters, e.g. Radiators and cookers, should be avoided.

RTF-Z

RTF

The RTF-Z is a multi-programmable controller, enabling you to set the system to switch on and off, up to 3 times each day, for each of the 7 days of the week. It also gives you the facility to select, a full comfort temperature and a lower set-back temperature, as well as having a frost protection mode.

The RTF gives basic temperature-regulated control of the heating system. By simply adjusting the dial control, the temperature is either increased or decreased. The unit also includes an on/off switch.

Underfloor Frequently Asked Questions

Q: Can the heating mats be fitted to screeded sub-floors?
A: Yes, but newly laid floors must have dried out fully (4-6 weeks minimum). Insulation of the sub- floor should also be considered, as this can enhance the heating performance significantly.

Q: Should I use self levelling compound, and if so what depth is required on top of the mats?
A: The use of self levelling compound is only necessary if the mats are to be laid under carpet, wood or laminate floors. In these cases the depth of self levelling compound should be 3-5mm above the mats, i.e. 6-8mm in total. If ceramic tiles are to be used, the mats can be laid directly in the ceramic tile adhesive.

Q: Can I use more than one heating mat in a room?
A: Yes, but they must be connected in parallel, or each controlled by its own separate controller. If more than one mat is being controlled by one controller, it will be necessary to connect the mats to the controller via a junction box.

Q: What sort of wiring is required?
A: Areas up to 20 square metres can usually be supplied direct from a 13 Amp- fused spur. The circuit should be protected by an RCD.

Mat Selection Chart

All mats are 0.5m wide and are 3mm thick with one connection tail per mat.
Price includes vat @ 17.5% and delivery to most UK postcodes (excludes Highlands & Islands and NI).

Area to be Covered M²	Mats Required M²	Mats to Order	Total Wattage (w)	Cost of Mats (inc VAT)	Cost of Mats with RTF stat	Cost of Mats with RTF-Z stat
1	1x1m	1xFTT150	150	53.46	113.50	131.60
1.5	1x1.5	1xFTT225	225	68.27	128.31	146.41
2	1x2	1xFTT300	300	81.43	141.47	159.57
2.5	1x2.5	1xFTT375	375	92.94	152.98	171.08
3	1x3	1xFTT450	450	106.10	166.14	184.24
4	1x4	1xFTT600	600	132.42	192.46	210.56
5	1x5	1xFTT750	750	157.10	217.14	235.24
6	1x6	1xFTT900	900	170.26	230.30	248.40
7	1x7	1xFTT1050	1050	178.48	238.52	256.62
8	1x7 + 1x1	1xFTT1050 1xFTT150	1200	231.94	291.98	310.08
9	1x7 + 1x2	1xFTT1050 1xFTT300	1350	259.91	319.95	338.05
10	1x7 + 1x3	1xFTT1050 1xFTT450	1500	284.58	344.62	362.72
11	1x7 + 1x4	1xFTT1050 1xFTT600	1650	310.90	370.94	389.04
12	1x7 + 1x5	1xFTT1050 1xFTT750	1800	335.58	395.62	413.72
13	1x7 + 1x6	1xFTT1050 1xFTT900	1950	348.74	408.78	426.88
14	2x7	2xFTT1050	2100	356.96	417.00	435.10
15	2x7 + 1x1	2xFTT1050 1xFTT150	2250	410.42	470.46	488.56
16	2x7 + 1x2	2xFTT1050 1xFTT300	2400	438.39	498.43	516.53
18	2x7 + 1x4	2xFTT1050 1xFTT600	2700	489.38	RTF-Z only	567.52
19	2x7 + 1x5	2xFTT1050 1xFTT750	2850	514.06	RTF-Z only	592.2
20	2x7 + 1x6	2xFTT1050 1xFTT900	3000	527.22	RTF-Z only	605.36

If you would like to order please go to the underfloor heating section, then simply add to your basket the necessary mats and your choice of thermostat.
i.e. if you would like 15m² and a digital thermostat add the following:
2 x FTT1050
1 x FTT150
1 x RTF-Z