"All I ever do is staple-up."

That was my friend and competitor’s response after he asked me to determine why a recent radiant heating installation was not working satisfactorily because the owners were ticked off. Staple-up installations consist of PEX tubing attached to the underside of the sub-floor with staples or similar fastener. The only direct contact for heat transfer is where the staples are located while the remainder of the PEX droops between fasteners much like wires strung between telephone poles. 

Insulation, if present, and it was not in this case, cannot be packed tightly to the underside of the sub-floor and there needs to be a 2-inch air gap so the air, which is a poor conductor, can be heated to transfer its heat upward through the flooring into the living space. Carpeting with composite padding (the worst type for heat transfer) covered the radiant floors. 

I wish I could tell you this was the exception to the rule, but after many forensic investigations into why so many failed radiant systems exist, there emerged a definitive pattern of things missing from the installers’ radiant toolbox. 

The Toolbox

Lack of training. Universally common to failed or under-performing radiant heating or cooling systems is the absence of training. Had my friend availed himself of readily available training, he would have known that staple-up requires the hottest water temperature while delivering the lowest Btu per square foot when compared to other installation methods. 

Instead of an average 170° F loop temperature, he could have achieved better results and met the space requirements for comfort utilizing water delivery temperature below 100°. Lower water temperature conserves energy. Your customers will love the lower operating costs. Any class taught by John Siegenthaler, aka Siggy, is well worth your investment in time, as is obtaining a copy of Modern Hydronic Heating at www.hydronicpros.com. 

Dan Holohan’s Pumping Away book will change the way you pipe hydronic heating and cooling systems for the better.

RPA training to ASSE 19210 shows that your knowledge of industry best practices, state of the art installation techniques and compliance with applicable codes and standards has been tested and certified — helping you stand out in a competitive market. Visit www.radiantprofessionalsalliance.org.  

Failure to utilize a design program. Like taking a shot in the dark, not using a design program results in a high probability of shooting yourself in the foot! Look to PEX tubing and circulator manufacturers for installation and design methods training. Many have design software that is super easy to use and will enable you to provide first-class radiant heating and cooling systems. Look to PEX tubing manufacturers for installation/design education and software programs that are very easy to use. The same applies to circulator manufacturers. 

Communication from the radiant contractor to the owners, and then all others on a construction site. If you are bidding to a general contractor, it is vitally important you communicate directly with the owners. You need to know their needs, wants and desires before you can design a radiant heating system. 

Things like who is responsible if the electrician drills through a tube, or the flooring installer fails to follow the tubing pattern you laid out and, instead, uses it as the guide for the staples or nails! The general contractor has the gold and can withhold the cost from the subcontractor responsible — a very important bit of communication! 

Tubing uncoiler. If you’ve never installed PEX tubing before, take my word for the fact that your bundle of tubing will quickly become a tangled mass looking much like a bowl of spaghetti if you don’t use a tubing uncoiler. Don’t ask me why I know this to be true. 

Attaching PEX tubing. Wire ties with twist tool or plastic zip ties you need to cut off tails so they don’t end up protruding through the freshly poured concrete surface both work well, but can be a back strain on larger jobs. If the job is large enough to justify the cost, invest in a rebar tie tool like the RB398 tools we use (bit.ly/2N3k2Jb). 

This bad boy ties a triple wrap, twists it and cuts off the tie in under one second! This truly is a tool that will pay for itself in labor savings. We have used ours on over 30-miles of PEX tubing attached to both rebar and wire mesh with zero break downs. 

Control joints in concrete. Another vital communication issue. Concrete will crack as it cures, so placement of control joints prevents random cracks that would be unsightly. Control joints are often saw-cut and the depth of the cut needs to be negotiated and agreed upon to avoid damaging your PEX tubing. 

The PEX tube needs protection at the control joint to avoid crack-stress and we use strips of automotive ribbed plastic tubing (used to conceal bundled wiring under the vehicle’s hood) that are quickly secured using the rebar tie tool. 

Testing the loops before and during the concrete pour. If you plan on using water to pressurize the loops be sure to use a mix with hydronic glycol if there’s any chance of freezing temperatures. PEX embedded in concrete that has water will freeze and split! 

Even if using compressed air, the moisture in the air can and will condense as temperatures fall, which can create an ice plug. That happened to us when we installed tubing in a three-foot thick floor and prestressed beams to create a radiant heated bunker to preheat aggregate that is added to the prestressed concrete beam molds. 

Note to self: Do not stand in front of the loop that is not allowing air to flow. When the air pressure finally dislodged that ice plug, it sounded like a shotgun blast and we never did find the ice plug! We’ve had more than one commercial installation with outdoor air temperatures near 0° F and no ability to warm the PEX before wrestling it into position. Wear safety goggles because cold PEX can snap back if it slips your grip!

Patch kits. We always include costs for at least one of our installers to be present during concrete pours and ensure they have coupling repair kits — just in case. Knock on wood, we have never had tubing compromised during the concrete pour. If you have an installer present, they can control things like ensuring the metal knuckle(s) on a pumped pour are not allowed to rest on the tubing and the tines on rakes are always pointed skyward. No sharp tools and no tossing lit cigars into the tubing field. In fact, we have a strict no smoking policy during the concrete pour or while our tubing is exposed. 

Another bit of communication: Will the owner even allow a loop to be repaired where concrete is to be installed? If not, you’ll want to have extra PEX on the job site. We’ve had other trades drill through flooring and concrete where our PEX tubing is concealed. One thing I can guarantee you: If there is a radiant slab on grade and the home is treated for termites, they will find your tubing — repeatedly! 

Expansion/contraction noises. One of the more common complaints I have investigated centers on noises generated as PEX expands. One home in particular stands out in memory. During the initial contact, the owners told me they had to turn off their radiant system at night in order to get any sleep. They were using portable electric space heaters overnight. 

On the first day I was to visit, I asked them to leave the radiant heating system OFF so I could get an accurate sense of just how much noise they were experiencing. We turned the system ON and within a minute the tick-tick-tick noises became loud enough to wake the dead! On all three floors. 

What in the world could possible cause so much noise in a radiant heating system? The installer had drilled 3” holes through the wooden joists and somehow managed to pack each one tightly with both supply/return PEX runs. Not only were noises being generated by PEX expansion against wood, but also by the constricted PEX against itself. Other noise complaints in other homes caused by cheap aluminum plates made from thin flashing material and staple-up systems. 

Do it once and do it right: Cutting corners to dumb down the up-front cost costs more in the long run.