There are many tubing installation options available for installing radiant floor heating. In fact, this is one of our most common questions. Depending on the application, you may have several different options to choose from. This page details many of our most popular radiant tubing installation practices including:
The concrete slab installation is one of the simplest and most efficient ways to install radiant heat. While it is simple, it is very important to do it correctly. If it is not, you can have a floor heating system that is inefficient, costly to operate, and may not work at all. Here are some general guidelines to follow. Keep in mind that these recommendations are general in nature and you should always consult your code official for proper installation.
On top of your compacted earth or sand, you should install a vapor barrier. 6 or 8-mil Visqueen plastic (polyethylene plastic) has always been the material of choice. Studies show that this may not be effective as other options. You should check with your code official for code compliance. This website is a good resource for why and how to install the vapor barrier.
Once the vapor barrier is in, you should insulate the slab from the earth. Extruded or expanded polystyrene (rigid blue or pink board) is the material of choice. Typically, we recommended 2″ but some states now require 3″ or R-15.
Some promote the use of thin sheets of foil/bubble or an insulating blanket. These products claim a high R-value but most of this comes from its reflective properties. You lose the reflective properties of the material once you pour concrete over it. Then, you are stuck with a 1/2″ of true insulation. This is a quick and easy product to install but in this case, quick and easy definitely isn’t the way to go.
Crete-heat is the name of one product that many of our customers use. This product has nubs on top to hold the tubing in place. All you have to do is walk the tubing in place, step it down between the nubs and keep going. There is no need for spending extra time bending over and tying the tubing to the mesh or rebar. Crete-heat has a built in vapor barrier and is tongue and groove so it snaps together. There is no need to tape any of the seams.
Since much of the heat loss in a concrete slab actually occurs on the outer edge, it is important that we insulate there as well. Here are a couple of details. The first shows what happens if only the side edge is to be insulated. The second depicts the proper way to insulate a concrete slab when used for radiant underfloor heating. Keep in mind that some will insulate the side edge all the way down to the footing.
For more details on insulating methods, please read our Design and Construction Suggestions Manual.
Once the insulation is in, the next step is to layout the radiant tubing. If you install the Crete-heat product then this part is easy. Simply step the tubing into the nubs. If you used traditional foam board then you still have a couple of options. Some will staple the tubing down to the foam using Pex staples and a special gun which makes the work go quickly. The only downfall is that the staples can be somewhat expensive.
Another option is to attach the tubing to the wire mesh or rebar using zip ties. This is the most common method because the zip ties are inexpensive and most are willing to sacrifice a little time if it means saving a lot of money.
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These are also called heat transfer plates or aluminum fins. A study conducted by Kansas State University some years ago showed that systems using heat transfer plates vs. systems that do not are able to transfer twice as many btu’s. The significance is that you can typically lower the water temperature and reduce cycle times which can lower your operational cost.
Radiantec also conducted our own plate study experiments and you can find the results here. The most cost effective solution is to install the thin heat transfer plates in continuous coverage. We did find that the thicker, extruded aluminum plates transferred about 6% more heat but at more than double the cost.
Ideally, the heat transfer plates should be spaced continuously but they don’t have to be. Our general rule of thumb is to space the aluminum plates continuously in carpeted rooms, bathrooms, and high heat loss areas such as great rooms. Space them about every 8″ or so in all other areas.
Insulation is usually put in after this (see next step) so if you can find a foil faced insulation with high enough R-value, you can forgo this product.
Many people ask us if it’s necessary to also install insulation below the radiant tubing, heat transfer plates, and reflective barrier. If you can only do this once because the ceiling will be finished then the answer is absolutely yes. The amount of insulation is dependent on what is above and below. If there is carpeting or a high heat loss area above then you should put in R-19. If not, you can probably get away with R-13 but R-19 is better. The type of insulation doesn’t really matter all that much.
If there is an unheated basement below then you should use R-19. Most people don’t mind if they lose a little bit of heat downward in this scenario. If the heat loss downward is entirely wasted to a crawl space, for example, then your insulation method should be extensive. You should try to get in a minimum of R-30. Some will insulate between the joists with fiberglass and then seal the entire underside with rigid foam.
If the ceiling will not be finished, some will wait and see how the system performs and then add the insulation after if necessary. What can happen if you don’t insulate? Since radiant heat will go in all directions, the heat will just as easily go downward. The basement will get too warm and you won’t get enough heat into the space above.
We get this question a lot because let’s face it, people want to save money. Aluminum is expensive. We get it! Radiantec considers itself to be an “energy efficiency” company. Everything we do and everything we quote is for the sole purpose of creating the most energy efficient system possible.
We also adhere to the “keep it simple” approach so we only quote components that we believe are truly necessary. This in turn will save you money every single day that you operate the heating system. So, in our opinion, it’s foolish to save a little bit of money up front and forgo an essential element that will save you money forever.
Will a radiant system without aluminum plates work? The best answer is “maybe.” If plates are not used then you are relying on air and the few locations where tubing is in contact with the floor to transfer the heat. The problem is, air is an insulator and Pex directly in contact with wood is a poor conductor. In order to make up for this poor heat transfer, the water temperature must be raised significantly. In some cases, as high as 180 degrees F.! Even then, on a cold day, the floor may not put out enough heat to heat the room if the home is older and not energy efficient.
In new construction with today’s well insulated structures, a system without plates will more than likely work. But, it won’t work as well or as efficiently as it could. Also, you may not be able to use a water heater as the heating source because the system requires much warmer water to make up for the poor heat transfer. In turn, your project may not be a great candidate for a solar hot water assist, either. What makes more sense, to install a system that can operate at lower temps (around 120-130 degrees F.) or to eliminate components that make you run the system at high temps (around 180 degrees F.)? It’s also easy to tell which system will cost less to operate.
We get calls on a daily basis from people with existing systems (not ours) that are looking to improve the performance. They complain of not getting enough heat on cold days and/or high energy costs. We’re thrilled when they call back later and rave about how well their system works after installing plates!
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The suspended slab radiant floor heating installation is sometimes used in new construction. It was once a common installation but we don’t see it used as much anymore. This method involves the radiant tubing being installed on top of the subfloor. Then, a 1 1/2″ slab is poured over the top. This slab is usually a lite-weight concrete mix or gypsum based material called “gypcrete” which seems to be the most common.
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Typically, this is not a good retrofit possibility because existing homes were not engineered to withstand the added weight. Even lite-weight concrete can weigh 12-14 pounds per square foot for a 1 1/2″ pour.
Many people ask the question “how can I install radiant floor heating if I don’t have access to the floor from below?” One way is to go with a manufactured grooved board system that you can put down and simply lay the Pex in it. These products typically have a layer of aluminum on the surface for optimal heat transfer.
While these products work very well they all have one common fault: they are just too expensive for the average homeowner to even consider at prices of $8-$10 per square foot. This price doesn’t even include any of the radiant material.
Radiantec has come up with a practical alternative to these expensive products. If you are a competent do-it-yourselfer and don’t mind working with power tools then you can install a highly efficient radiant floor heating system on top of your existing floor for a fraction of the price of the manufactured panel systems.
The “plywood and plates” installation involves ripping 3/4″ plywood into strips 12″ wide and securing them to the subfloor. You will leave a groove just wide enough for the tubing and plate which will be roughly 3/4″.
Before the tubing is installed, an aluminum heat transfer plate is installed to help conduct heat through the floor. Now, the tubing can be installed and the finished flooring put in. If the floor covering will be soft, carpet or vinyl for example, then a thin layer of wood (called luan) should be installed. Most other hard flooring can be installed directly over the tubing and plates.
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Before undertaking an underfloor heating project, it’s important you have the right tools for the job. You will need a tape measure, a quality pipe cutter and sufficient pipe fixing clips if you intend to fix directly to insulation boards using a pipe staple gun. Alternatively, you can use egg crate panels for securing the pipework. You will also need a pipe re-rounding tool to ensure the cut end of the pipe is perfectly spherical.
For an electric underfloor heating installation, a pair of scissors and a sharp knife will be required for cutting the matting and a pair of wire cutters and wire strippers are needed for cutting the electrical wire at the end only. Joint tape is needed for holding the sheets of matting together. A screwdriver and a multimeter could also be required.
The materials required for the job will depend on which type of installation you decide to choose. Materials might include, insulation boards and screws and washers for securing insulation boards to timber subfloors. Also, pre-grooved pipe boards, water pipe, pipe fixings or egg crate panels, levelling compound or screed and floor sensors.
A wet underfloor heating system will also require a manifold, which is necessary for connecting the pipework, a thermostat, plus a heating pump. An electric underfloor heating system will require the correct number of heating mats or loose heating cable, joint tape and some conduit.
The underfloor heating installation process begins with a survey of your property. When considering how to install underfloor heating, you should also think about the number of rooms and measuring the size of the rooms, in which you will want underfloor heating installed. This will help determine the extent of the job and have a bearing on the overall costs of the installation. You may find our measuring tool useful.
If it is a relatively new property and currently vacant then the installation process can be much easier than installing into an older property that is currently occupied. That’s because you will need to consider the upheaval and inconvenience of having your rooms cleared of furniture, and floor coverings taken up. In some cases, the existing subfloor may have to be lifted.
However, both wet and electric underfloor heating can be laid on top of existing floor surfaces such as timber, concrete, stone or tiles. It should be noted that electric underfloor heating is much quicker and easier to install than a hot water-based system but it will cost more to run. A wet underfloor heating system will involve many more components and ideally will require some prior plumbing experience. You will need to consider which system might be best for your property.
Also, remember that installing your underfloor heating on top of an existing subfloor will raise the floor level. It’s always best to consult an underfloor heating expert before planning your installation, especially if it is a wet heating system. A pre-approved underfloor heating installer will be able to advise you.
Step 1. For both wet and electric underfloor heating systems, ensure the entire underfloor heating area is thoroughly clean by sweeping or vacuuming beforehand. Check for jagged edges on concrete, stone and tiled floors and wood splinters on timber flooring. If the floor is excessively uneven or jagged then it’s best to lay a screed or levelling compound over the top. This applies to both timber subfloors and concrete subflooring.
Step 2. Next, lay down a damp-proof membrane over the subfloor and fit edge insulation against the base of all the perimeter walls. A layer of floor insulation will ensure the absolute minimum of downward heat loss. Insulation sheets can be pre-grooved or plain. Tape the joins and edges.
Step 3. The manifold will now need to be installed for a wet underfloor heating system. This needs to be connected to a wall that is strong enough to support its weight. All the pipework will be connected to the flow side of the manifold. This component is responsible for distributing large volumes of hot water from the heat source to the underfloor heating circuit.
Step 4. The next step is to connect and lay the pipework, or electric cables if installing an electric underfloor heating system. For a wet underfloor heating system laid on a timber floating floor, it’s easier to lay a series of pre-grooved chipboard panels first. For laying pipework on a denser subfloor such as concrete, use pre-grooved underfloor heating insulation panels. If you’re not using pre-grooved boards then ensure the pipe is coiled from the centre outwards with a minimum 200mm spacing between each coil. For an electric underfloor heating system, looped cables are available as pre-spaced underfloor heating mat kits. You should note that heating wires should never cross over when being laid and should not be cut and reconnected. Electric underfloor heating kits come with full instructions. Ensure the electrical connections to the mains supply are carried out by a certified electrician.
Step 5. The next step is to pressure test the system. Check for leaks at the connection with the manifold and around the pipework itself.
Step 6. If you have chosen to lay the pipework onto a standard insulation board, the whole floor area will now need to be covered in a screed or a levelling compound prior to laying the final floor covering. For example, tiles, carpet, laminate or vinyl. Most floor coverings have a heat limit of 27°C°.
Step 7. Finally, connect the manifold to the boiler pump and then connect the thermostat. The whole process from start to finish can take on average 2-3 days. Test the system again before laying the desired floor covering.
A newly installed underfloor heating system is best left switched off for a period of 7 days. This is to allow ample time for any screed, adhesive and grouting to settle and harden. The temperature of both wet and electric underfloor heating systems should be increased gradually to allow expansion and contraction of the pipes and the new floor surfacing, such as tiles. An increase of 3°- 5° daily is recommended, until the desired temperature is reached. In all cases, the temperature should never be allowed to exceed 50°C.
The next thing you will need to do is calibrate the system and set up the thermostats. Do this by first setting the temperature to 18°C and then increasing the temperature by 1° each day until you reach a comfortable level. Water-based systems may need to have the flow rate adjusted at the manifold to ensure there is an even heat distribution over the floor surface.
For wet underfloor heating systems, regularly check for leaks and also check the boiler pressure from time to time. Bleed air from the system if necessary and check the thermostat settings. For peace of mind have your system checked over annually by a professional. Electric underfloor heating systems require very little maintenance.
For more Floor Heating Pipe Clipsinformation, please contact us. We will provide professional answers.