Underfloor Heating With Polished Concrete-What To Know
- htouchstonecare
- Dec 12, 2025
- 8 min read
San Jose and the Bay Area have a unique climate profile. You experience warm afternoons and surprisingly cool nights. This "diurnal swing" challenges standard heating systems. Forced air systems turn on and off constantly to keep up. You hear the fans running, but the heat dissipates the moment they stop.
Underfloor heating with polished concrete offers a different solution. It turns your floor into a massive thermal battery. The slab absorbs heat and releases it slowly. It stabilizes the temperature of your home.
This system aligns perfectly with the architectural history of our region. Modern homes and mid-century Eichlers rely on slab-on-grade construction. When you polish that slab and heat it from within, you create the most efficient heating system available today.
Heavenly Touch Stone Care specializes in this exact intersection of technology and geology. We understand the thermodynamics of concrete. We know the local Title 24 codes. Most importantly, we know how to polish a heated slab without destroying the tubes embedded inside it.
This guide explains the physics, the costs, and the critical commissioning protocols you must follow.
Why San Jose homes need high-mass radiant flooring
You might think of concrete as cold. That is true for unheated concrete. It has high "thermal effusivity." It draws heat away from your bare feet.
Heated concrete reverses this dynamic. It becomes a radiant surface. It warms objects and people in the room directly rather than heating the air. This improves your "operative temperature." You feel warmer at a lower air temperature. You will likely set your thermostat 2°F to 4°F lower than you would with a furnace.
The advantage of thermal conductivity
Efficiency relies on heat transfer. You measure this with thermal conductivity (k-value). Concrete has a high k-value. It transfers heat rapidly from the water tubes to the surface.
Wood and carpet act as insulators. If you install wood flooring over a radiant system, you place a blanket over your heat source. The boiler works harder. It requires higher water temperatures to push heat through the wood.
Concrete eliminates this resistance. The Department of Energy confirms that radiant slab systems are more efficient because they operate at lower temperatures. You get instant access to the thermal energy you pay for.
Meeting Title 24 energy standards
California leads the nation in energy codes. Title 24 pushes builders and renovators toward electrification. The state discourages gas boilers in favor of Air-to-Water Heat Pumps (AWHP).
Heat pumps work best when they produce low-temperature water (around 90°F to 100°F). Old-fashioned radiators need water at 140°F or higher. Heat pumps struggle to reach those temperatures efficiently.
Polished concrete supports the heat pump. Because the floor offers zero thermal resistance, the heat pump runs at its most efficient low-temperature setting. You satisfy the code requirements for San Jose electrification. You also lower your monthly electrical bill.
Hydronic vs. electric systems: Choosing the right heat
You have two ways to heat a floor. You pump warm water through tubes (hydronic), or you run electricity through wires (electric resistance). Your choice depends on the size of your project and local regulations.
Hydronic systems for whole-home efficiency
Hydronic systems use PEX tubing embedded in the slab. This is the standard for whole-house heating in San Jose.
You pay more upfront for this system. A full installation costs between $13,000 and $43,000 depending on the square footage. But the operating costs are low. You heat water with a high-efficiency heat pump or boiler.
This system handles the thermal mass of a large slab. It is the only viable option for an Eichler retrofit or a new custom home build.
Why electric heating is often restricted
Electric radiant mats use resistance wire. They heat up fast. They are cheaper to install in small areas.
But Title 24 restricts electric resistance heating. The code categorizes it as an inefficient primary heat source. You typically cannot use it to heat a whole house in California.
Use electric mats only for small "spot heating" applications. They work well in a small bathroom to warm the tiles for a short time. Do not rely on them for your main living areas. The electricity costs in the Bay Area will shock you.
The Eichler retrofit solution: Restoring mid-century modern floors
Joseph Eichler built thousands of homes in Willow Glen, Sunnyvale, and Palo Alto. He used radiant heating in the original slabs. Those systems used copper or steel tubes.
Those tubes are now failing. They corrode and leak. Homeowners face a difficult choice. You cannot easily jackhammer the slab to fix the leaks. That destroys the foundation.
We recommend a retrofit strategy. You abandon the old leaking tubes. You install a new radiant system on top of the old slab. Then you pour a fresh surface to polish.
Using overlays for a seamless look
You cannot pour 4 inches of new concrete over your existing floor. It would block your doors. You need a thin solution.
We use high-performance overlays like Duraamen Param 5500. This is a calcium-aluminate cement. It is self-leveling. It creates a hard, dense surface at a thickness of only 1/2 inch.
The process works like this:
We grind the old floor to clean concrete.
Your plumber installs a low-profile radiant panel system (like Warmboard).
We pour the Param 5500 over the panels.
We polish the Param 5500 to your desired sheen.
This gives you a brand-new, salt-and-pepper concrete polishing finish. You get the look of a new slab without the demolition costs.
Handling active joints and preventing cracks
Heat makes concrete expand. A heated floor moves more than a cold floor.
The overlay will crack if you ignore this movement. We honor the "active joints." If there is a crack or joint in the original slab beneath, it will move. We do not grout over it.
We cut a matching joint in the new overlay. We fill it with a semi-rigid polyurea filler. This material absorbs the expansion and contraction. It keeps the surface smooth but allows the floor to breathe mechanically.
Technical risks: Ghosting, blushing, and how we prevent them
You need a contractor who understands the chemistry of heated concrete. Standard polishing methods fail on radiant floors.
"Ghosting" happens when you see the outline of the heating tubes on the finished floor. This occurs if the tubes are too close to the surface or if the concrete cures unevenly. The concrete dries faster directly over the warm tubes. This changes the color.
We prevent this by managing the tube depth and curing process. But the biggest risk comes from the sealer you choose.
The danger of topical sealers
Radiant heat creates "vapor drive." The heat pushes moisture from the bottom of the slab up to the surface.
If you apply a topical sealer, you trap that moisture. Topical sealers act like a plastic sheet. The vapor pressure builds up behind the coating. It forces the sealer to lift. The floor turns white (blushing) and the sealer peels off.
This is why we treat radiant floors differently than epoxy floor coatings. Epoxy is excellent for garages where you need chemical resistance. But in a radiant living room, a thick topical coating creates a failure point unless you install an expensive moisture mitigation system first.
Why we use penetrating densifiers
We use breathable chemistry for radiant floors. We apply a penetrating densifier like Ameripolish 3D HS.
This product reacts with the concrete itself. It creates calcium silicate hydrate in the pores. It hardens the surface.
We finish with a penetrating guard. This protects against stains like wine or oil. Crucially, it allows water vapor to pass through. The floor "breathes." The heat drives the moisture out without damaging the finish. Prosoco provides extensive data on why breathable systems outlast film-forming sealers in radiant applications.
The "2-Degree Rule" and commissioning protocols
The most dangerous day for your new floor is the day you turn on the heat.
If you turn the system to "high" immediately, the floor will fail. The bottom of the slab heats up faster than the top. This causes "curling." The slab pulls away from the subfloor and cracks.
You must follow a strict commissioning protocol. We explain this in detail in our FAQs, but the rules are simple.
The 28-day cure period
Do not turn on the radiant heat for 28 days after we pour the concrete or overlay.
Concrete needs water to hydrate and gain strength. Heat evaporates water. If you heat the slab too early, you stop the hydration process. The concrete becomes weak and dusty. It will not take a polish.
The rigorous ramp-up schedule
Once the 28 days pass, you must ramp up the temperature slowly.
Start with the water temperature matching the room temperature. Increase the water temperature by only 2°C (about 3-4°F) per day.
This slow process allows the entire thermal mass to expand evenly. It prevents thermal shock. You protect your investment by being patient.
Frequently asked questions about heated polished concrete
Is polished concrete cold in the winter?
No. Unheated concrete feels cold because it absorbs body heat. Radiant polished concrete does the opposite. It radiates warmth to your body. It feels organic and comfortable. Most users find it more pleasant than forced-air heating because the warmth is constant and starts from the feet up.
Can you put radiant heat under existing concrete floors?
You cannot put it under an existing slab on grade. You must go on top. We use a retrofit method. We install a low-profile radiant panel system on top of your existing concrete. Then we pour a specialized self-leveling overlay (like Param 5500) over the tubes and polish that new surface.
How much does a heated concrete floor cost in San Jose?
Costs vary by project size. A full hydronic system installation typically runs between $13,000 and $43,000 for the plumbing and heat pump. The concrete polishing or overlay work adds another $6 to $12 per square foot. While the upfront cost is higher than carpet, the energy savings and durability provide a strong ROI.
Does radiant heat cause concrete to crack?
It causes cracks only if you ignore the protocols. Concrete expands when heated. If the installer cuts proper control joints and uses flexible fillers, the floor handles this movement. If you shock the floor by turning the heat up too fast, it will crack. Follow the 2-degree ramp-up rule.
What is the best sealer for heated floors?
The best sealer is a penetrating guard, not a topical coating. We recommend products like Ameripolish SR2 or Prosoco LSGuard. These penetrate the surface to stop stains but allow vapor to escape. Topical sealers (like thick urethanes) often bubble or turn white due to vapor drive from the heating elements.
Secure your investment with San Jose’s concrete experts
Polished concrete with underfloor heating creates a premium, energy-efficient home. It honors the Eichler aesthetic. It meets strict Title 24 codes.
But this system is intolerant of errors. One mistake in the ramp-up schedule or the wrong choice of sealer will ruin the finish. You need a partner who views the slab as a technical system, not just a cosmetic surface.
We bring the expertise required to navigate these complexities. From the grind to the seal, we protect your floor.
Ready to discuss your project? Contact Heavenly Touch Stone Care today. Let us build a floor that looks beautiful and works perfectly.
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