Too often in the past underfloor heating companies have shrouded the specification of underfloor heating systems in mystery. The fact is, it is pretty straight-forward to work out what exactly you would require if you follow these principles;
Firstly, there are a few questions we need to answer;
- What’s the floor construction? Screed, Joists, Overlay?
- New build or refurbishment? If it’s a refurbishment, how old is the property?
- What’s the heat source? Boiler, Heat Pump?
- Preferred Manifold position. This is not essential at pricing stage but can avoid confusion and any crossing of pipe on the installation.
- How many heating zones will be required?
Once we have these answers, in general, we can specify what materials will be required.
We’ll take a new build house as an example;
Block and beam construction, therefore generally a screed will be used. The building will be using a heat pump as a heat source, therefore we would suggest installing the pipe at 150mm centres to allow for lower running temperatures and a more efficient system (Where a gas boiler is being used this can be moved out to 200mm centres in account of higher supply temperatures available).
Next we need to decide how many heating zones are required. Single room systems are just that, a single zone, regardless of size (Exceptions in very large commercial or multi-use domestic rooms may apply). In a building with multiple rooms on the ground floor, for example a large house, more than one zone would be required. Living room, dining room, kitchen, hallway, WC etc. can all be monitored individually allowing for greater control and a more efficient use of energy.
Each zone should be measured in square metres. Once we have this we can calculate the amount of pipe required. At 150mm centres the calculation would be m2 x 7.5. Therefore a room of 20m2 would require 150 linear metres of pipe (this figure includes additional pipe to allow flow and return to the manifold). It is important to remember that when using 16mm multilayer pipe, any single loop on the system should not exceed 120 linear metres. In the case of the 20m2 room you would therefore require 2 ports on the manifold. This process should be repeated for each room within the building remembering that not all rooms will have a single port on the manifold.
Often we see that 2 areas in close proximity may have very little pipe required. In this case, the hallway and WC have just 67.5m combined. In cases such consider combining them on a single loop. Doing this will reduce the number of ports on the manifold and the number of thermostats required. Here we have highlighted this by blanking the WC in red.
Based on this information we can now begin to create our bill of materials. In this example, we will require 517.5 metres of pipe, a 6 port manifold and 4no. thermostats. This is the basis of the complete system. Everything else required can now be calculated.
We would recommend at least 3no. ‘U’-Clips per linear metre of pipe if this is your preferred method of attaching the pipe to the insulation. If you prefer to use clip-rail we recommend using 1 linear more of clip-rail per square metre of floor area. Experienced installer may use a combination of the two for speed of installation and money saving.
To calculate the the amount of edge insulation required we recommend calculating as 1.1 linear metres of edge insulation per square metre of the project. In this case, circa 76m.
On the Manifold
Pump & Blend Valve.
As we have discussed, this example uses a heat pump as a heat source. In cases such as this it is often the case that a pump and blending valve is not required. Please check this before ordering.
If you are specifying a system for a single room, actuators will not be required. However, once you move to multiform or multi zone underfloor heating systems, each port on the manifold will be required to control the flow of warm water. Each actuator will be connected, via the wiring centre, to the relevant room thermostat and out or close depending on the required room temperature and any time programme enabled.
In terms of the manifold itself, this should come complete with ball valve, fill and drain caps and pipe connectors. Please check that your supplier provides all of this as a kit. Do not assume this.
In this example we have assumed that the client would require 4no. thermostats as the hall and WC are going to be combined. There are a mass of options on the controls front available in the market. Anything from the traditional dial thermostat to the higher costs internet enabled intelligent systems. Each has their place in the market, just make sure that you or your client are capable of using the more advanced systems as some are more complicated than others.
You will require a wiring centre to control the multi-zone system. This is a central control point that communicates between the thermostat, actuator, pump (if required) and the heat source. Placed next to manifold, this controls the entire system.
Do I require an underfloor heating design?
Many, many people install underfloor heating just using their knowledge and a little common sense. We are a nation of DIYers after all. However, it is alway a good idea to get a design done, especially if you have little experience of underfloor heating or if the system is for multi-room dwellings. Things on site can get a little confused when you have to get the pipe to and from rooms some distance from the manifold. A design should also provide you with the exact length of pipe required, the flow rates and outputs of the system which all comes in very handy. In short, our answer is that you don’t need one but we’d advise you do. Your supplier should be able to provide the underfloor heating design.
Tick List of materials required;
Manifold – Check your supplier provides all the required components.
Pump & Blending Valve
Other – Pipe conduit, Polythene insulation cover, Remote sensor for bathrooms etc.
So, you’ve got a number of questions to answer before you create your list. Take your time and double check it with your supplier, they should be able to help. Or, if you have any questions for us, please call us on 01245 490 401.
B-Hive Supplies is a specialist underfloor heating and plumbing supplier based in Chelmsford Essex. www.bhiveunderfloor.co.uk Tel: 01245 490 401
B-Hive accepts that there are many different types of underfloor heating available on the UK market and that not all systems suppliers apply the same rules to the specification of UFH Systems. All of our designed systems are produced in line with the relevant UK guidelines and this article is based on these principles.
B-Hive also accepts that this example is just one of any number of possible system type required in any given situation. All projects are different and should be considered on their individual merits.
Should anyone wish to discuss anything in this article, please feel free to comment.