Radiant heating warms a room from the floor up, using warm water in tubing or electric cables buried in or under the floor surface. New construction is the ideal setting because the system can be embedded in a slab, stapled under subfloors, or set in a thin overlay, choices that are hard to make after the house is finished. The result is even heat without duct noise or dust circulation. On the jobsite, heat takes on a second meaning: while the system manages indoor comfort, keeping construction workers safe in the summer heat is a separate concern with its own training and scheduling rules.
Hydronic vs Electric Radiant Systems
The two families of radiant heat differ in how they generate and carry heat. Hydronic systems pump warm water from a boiler, heat pump, or solar setup through PEX tubing; electric systems run resistance cables or mats directly under the floor. Hydronic costs more to install and less to run; electric installs fastest and suits small rooms and retrofits.
Both systems put installers around hot equipment. Testing a hydronic loop means circulating water at 120 to 160 degrees Fahrenheit, and pouring slabs in warm months adds environmental stress, so the heat safety standards that protect construction workers from heat illness on the jobsite apply to radiant crews as much as to any other trade.
Hydronic Basics
PEX tubing is laid in loops spaced 6 to 12 inches apart, connected at a manifold, and buried in a slab or tucked under the floor. A boiler or heat pump supplies water at 100 to 140 degrees, far cooler than the 180-degree water in old radiator systems, which is why modern hydronic floors pair well with condensing boilers and heat pumps.
Boiler and Water Heater Options
Condensing boilers reach 90 percent or higher efficiency at low water temperatures, and heat pump water heaters can double as a heat source for small floors. Tankless and tank water heaters can feed a small zone, but they cycle more and wear faster than dedicated boilers.
Electric Mat and Cable Systems
Electric systems use spooled cable or pre-spaced mats that roll out over the subfloor and get covered with thin-set or self-leveling compound. They respond fast and cost little to install, but electricity per BTU runs two to three times what gas or a heat pump costs in most markets, so electric radiant is usually limited to bathrooms and small rooms.
When Electric Makes Sense
Bathrooms, entries, and kitchens are the classic electric zones: small areas, tile floors, and short run times. Whole-house electric radiant is hard to justify on operating cost unless the house sits off the gas grid and uses low off-peak rates.
| Factor | Hydronic radiant | Electric radiant |
|---|---|---|
| Install cost per sq ft | $6-$15 | $5-$10 |
| Operating cost | Low with boiler or heat pump | High in most markets |
| Response time | Slow: warms the floor mass first | Fast: warm within minutes |
| Best fit | Whole-house, slabs, large areas | Bathrooms, small rooms, retrofits |
| Maintenance | Boiler service, occasional purging | Little beyond thermostat checks |
| Lifespan | Tubing 50+ years, boiler 15-25 | Cables 30+ years |
Energy Performance and Operating Costs
Radiant floors earn their efficiency reputation from how heat is delivered, not from magic. Because warm air rises from the entire floor, rooms feel comfortable at air temperatures 3 to 5 degrees lower than forced-air heating needs, and every degree of setback saves roughly 2 to 3 percent of heating energy. Hydronic floors also sidestep the 10 to 30 percent of heat that ducted systems lose through leaks and uninsulated runs.
The efficiency case shows up in both new builds and upgrades. Research on efficient housing old and new links densification via new construction and retrofit to some of the fastest residential energy savings, and radiant floors appear in both halves of that trend, embedded in new slabs and added over old subfloors.
Floor Surface and Coverage
The floor covering determines how much heat reaches the room. Tile and stone conduct well; engineered wood and laminate work within limits; thick carpet and cork insulate and cut output sharply. Manufacturers publish output tables per square foot for each covering, and the number drops roughly 30 to 50 percent under carpet.
Thermostat Setbacks
Radiant mass does not react like forced air, so aggressive night setbacks can waste energy by forcing the system to reheat a cold slab. Slab systems respond best to small setbacks of 2 to 4 degrees or to smart controls that learn the thermal lag. Thin overlays and staple-up floors respond quickly enough for normal setbacks.
- A 3-degree lower thermostat setting cuts heating energy roughly 6 to 9 percent.
- Duct losses in forced-air systems run 10 to 30 percent, and hydronic floors have no ducts to leak.
- Hydronic floors pair with condensing boilers at 90+ percent efficiency and with air-to-water heat pumps at a coefficient of performance of 3 or better.
- Zoning each room lets unused spaces run cooler, adding 10 to 20 percent savings in larger homes.
Installation Methods in New Construction
New construction offers three main installation paths: slab-on-grade, staple-up under wood floors, and thin-slab or gypcrete over a subfloor. The choice drives cost, response time, and which floor coverings work, so most builders settle it when the foundation is designed because slab systems change the pour.
The structural system matters too. Radiant tubing suits timber frame construction especially well, since the open bays between exposed joists leave room for staple-up runs, and the same flexibility carries over to conventional stick framing.
- Compact and insulate the subgrade, with rigid foam under the whole slab.
- Lay the PEX loops at the planned spacing and tie them to wire mesh.
- Connect the loops to the manifold and pressure-test the system before concrete arrives.
- Pour and finish the slab, keeping the tubing pressurized so leaks show up immediately.
- After curing, fill the system with treated water or antifreeze mix and test again at operating temperature.
Staple-Up and Thin-Slab Methods
Staple-up systems attach tubing to the underside of the subfloor with aluminum heat-transfer plates that spread heat across the joist bay, though response is slower because heat must cross the floor assembly. Thin-slab systems pour 1 to 1.5 inches of gypsum over tubing laid on the subfloor, giving faster response and better output at the cost of added floor height and drying time.
Pressure Testing Before the Pour
The test before concrete is the most important step in the whole install. Loops typically hold 60 to 100 psi for 24 hours during the pour, and the gauge gets watched during placement because trowels and wheelbarrows can damage tubing. A leak found after curing means jackhammering the floor.
Working Conditions and Jobsite Heat Safety
Radiant installs concentrate work in the hottest part of the year in many regions: slab pours run spring through fall, and the curing process releases heat and humidity into the work area. Add boiler rooms and attics, and radiant crews spend long stretches in conditions that push body temperature up.
The industry response has become formal. Heat illness prevention for construction workers in extreme heat now centers on acclimatization, hydration, and scheduled rest breaks, and the same rules that govern highway crews and roofers apply to the crew pouring your slab. Supervisors should treat early symptoms as emergencies rather than toughness tests.
Scheduling Work Around the Heat
- Pour slabs in the early morning and finish interior rough-in before midday heat peaks.
- Rotate crews through shade and water stations every 20 to 30 minutes.
- Stage materials near the work area so workers carry less in the sun.
- Watch the heat index, not just air temperature, before approving outdoor work.
Signs of Heat Illness
- Muscle cramps and heavy sweating are the first warning signs.
- Nausea, dizziness, and headache signal heat exhaustion and need immediate rest and fluids.
- Confusion, slurred speech, or hot dry skin is a medical emergency; call for help and cool the worker fast.
Controls, Zoning, and Wiring the System
A radiant system is only as good as its controls. The manifold splits the supply into zones, each with its own valve, pump, and thermostat, so a bedroom can run cool while the bathroom floor stays warm. Modern controls add outdoor reset, which raises water temperature as the weather drops, and app-based scheduling.
Wiring the controls is precision work. Thermostats, manifold sensors, and valve actuators all need clean low-voltage connections, and electricians often reach for cordless heat pens to shrink insulation over splices, a faster alternative to a heat gun in tight electrical boxes.
Zone Design
Zones follow use, not room count. Open plans can share one zone, while rooms with big windows or slab edges get their own. A typical 2,000 square foot house runs 4 to 8 zones, and each zone needs a thermostat location away from sunlight and drafts.
Smart Thermostat Integration
Smart thermostats learn the thermal lag of a slab and preheat before you wake instead of reacting when you do. They also report water temperature, pump runtime, and fault codes to a phone app, which shortens service calls. Make sure the installer wires a common wire for powered thermostats.
Site Preparation, Layout, and Scheduling
Radiant work starts before the foundation. The tubing plan, manifold location, and pour sequence all get fixed in the design phase, because a mistake at layout shows up years later as a cold corner or a valve buried in concrete.
The survey discipline carries over from larger projects: establishing slab grades and alignments calls for the same care that goes into surveying new railway line construction, where small errors compound over distance, and a laser level and string line cost less than a cold room.
Coordination Checklist
- Confirm the floor-covering plan before choosing slab, staple-up, or thin-slab.
- Locate the manifold and controls where they stay accessible, not buried in a finished wall.
- Schedule the pressure test so the concrete crew cannot pour before it passes.
- Coordinate with electricians on thermostat wiring and with plumbers on the water source.
- Photograph the tubing layout before the pour for future reference.
Inspections and Documentation
Most jurisdictions inspect the tubing, manifold, and pressure test before covering. Keep the layout photos, test records, and a tube-spacing map in the house file, because they become the fastest way to find a loop when a future repair needs to drill through the floor.
Radiant heat rewards planning. Choose the system for the room sizes and floor coverings, pressure-test everything before covering it, and schedule the work so crews stay safe in the heat. Done that way, the system runs quietly for decades and turns the floor into the best heater in the house.