Radiant Heating vs. Forced Air: A Park City Builder's Honest Take

Walk through twenty new homes in Park City this winter and ask one question at every door: how is this house heated? You will get twenty different answers, almost all of them confidently delivered, and most of them wrong on at least one detail.

Radiant. Forced air. Hybrid. "We have radiant on the main and forced air on the upper level." "We have radiant ceilings." "We have a heat pump and we never turn it on." The category is genuinely confusing — the engineering has changed faster than the conversation, and the people selling the systems are not always the people designing the house.

This is the breakdown we wish every owner had before they signed an HVAC scope. We are not in the business of telling people what to put in their home. We are in the business of telling them what each system actually does at 7,000 feet, what each one costs in 2026 dollars, and what a builder thinks about — past the brochure — when we have to make this call on a $5M to $20M custom build. By the end, you will know which system fits your house, your climate, and your tolerance for compromise.

What Each System Actually Is

Before any cost or efficiency conversation, two definitions:

A forced-air system moves heated (or cooled) air through ductwork to supply registers in every room. The heat source is usually a furnace (natural gas, propane, or in newer builds an electric heat pump). The same duct system handles cooling, ventilation, and often filtration. It is the system most homes in America have because it is fast to install, mature in its supply chain, and easy to share with central air.

A hydronic radiant system moves heated water through PEX tubing embedded in the floor — usually in a 1.5-inch lightweight concrete pour over the subfloor — and the floor itself becomes the radiator. Heat moves into the room by radiation and gentle convection, not by blowing air. The heat source is a boiler (gas, propane, or, increasingly, an electric heat pump) and the system is zoned room by room.

There are also electric-resistance radiant mats, which are a different animal — almost always reserved for bathrooms or small spot-warming applications. We are not focused on those here. When a Park City builder says "radiant," they almost always mean a hydronic system, and that is what we are comparing.

The Comfort Question — Why Radiant Won the Mountain Conversation

Forced air heats a room by replacing its air with warmer air. Radiant heats a room by warming its surfaces — floor, then mass, then objects, then the air last. That difference is the whole story.

In a tight, code-built mountain home with R-49 ceilings, R-21+R-10 walls, and 3.0 ACH50 air leakage, a radiant system runs at 85–110 °F supply water and holds the room at a perfectly even temperature for hours after it cycles off. The thermal mass of the slab is the buffer. There is no fan noise. There is no whoosh from a register. Air at the floor is not 4–6 degrees colder than air at the ceiling, because the floor is the heat source.

A forced-air system delivering the same comfort has to push 140–160 °F supply temperature through ducts, drop it across a register at 95–105 °F, and then mix that air with the cooler room air until the room reaches setpoint. The fan cycles. Air dries out — already a problem in a Park City winter, where outside relative humidity often runs 15–20%. Dust and pet dander move with the air. Stratification happens — warm air rises to the ceiling, the floor reads cold underfoot, and the thermostat overshoots.

If you have ever stood in an old Park City lodge with high ceilings, you have felt this. The room is "warm" — 72 degrees at the thermostat — but your feet are cold and the fan never stops. That is forced air doing exactly what it is designed to do, in a building it was never designed for.

The Efficiency Question — and Where the 20–30% Number Actually Comes From

You will see "radiant is 20–30% more efficient than forced air" repeated across the internet. The number is real, but the reasons are more interesting than the number.

Three things drive that gap:

1. Lower supply temperature. A boiler making 105 °F water for a radiant system runs at higher condensing efficiency (often 95%+ AFUE) than a furnace producing 140 °F air. Modulating condensing boilers in Park City builds we have done are pulling 96–98% combustion efficiency on cold mornings. A high-efficiency furnace tops out around 96% but rarely sees that number in the field at altitude.

2. No duct losses. A typical forced-air system loses 10–25% of its heat to leaky ducts running through unconditioned attics or garages. A hydronic system has effectively zero distribution loss — water in a PEX loop in a conditioned slab does not lose heat to anywhere it doesn't want to.

3. Lower thermostat setpoint at the same comfort. Because radiant warms surfaces, occupants report the same thermal comfort at a setpoint 2–3 degrees lower than forced air. That single behavioral difference is often the largest energy savings in the package.

Real-world data published in Contractor Magazine and the U.S. Department of Energy's Radiant Heating page describes 20–30% reductions in heating energy for hydronic radiant retrofits versus forced-air baselines. In our Park City new-construction projects, we typically model a 22–28% gap, depending on house geometry and how much glass the architect lets us conditioned-loop.

For a 6,500 sf Park City home, that gap routinely translates to $1,800–$4,200 per year in heating cost on propane or natural gas. Over a 25-year ownership horizon, the math gets serious quickly.

The Cost Question — What Each System Actually Costs in 2026

Honest numbers, current as of Q2 2026 in Summit County, for a 6,000–8,000 sf custom home:

Forced-air system (high-efficiency furnace + AC, fully zoned, ECM blower): $14–$22 per square foot installed, all-in. For a 7,000 sf home, that is roughly $98,000–$154,000.

Hydronic radiant system (modulating condensing boiler + PEX in slab + manifolds + zone controls): $18–$28 per square foot installed, all-in. For a 7,000 sf home, that is roughly $126,000–$196,000.

Hybrid (radiant on the lower levels + forced air for upper levels and cooling): $24–$34 per square foot installed. The premium pays for two parallel mechanical systems, but it is what we install on the majority of our high-end Wasatch builds.

Heat-pump-driven hydronic radiant (air-to-water heat pump + buffer tank + electric backup): $28–$38 per square foot installed. The upfront cost is the highest of the four, but the operating cost can be the lowest, particularly as Rocky Mountain Power's residential rates and time-of-use programs evolve.

A few things to know about these numbers:

• The "per square foot" all-in figure is the right way to think about HVAC at this scale. Equipment alone is misleading. The labor, the controls, the zoning, the design coordination, the testing — that's where the real cost lives.
• Nobody in Park City is finishing a $5M+ custom home with a single-zone, cheap-equipment forced-air system. The honest forced-air comparison is a quality, fully zoned ECM system, not a tract-home setup.
• The cost gap between radiant and forced air shrinks every year, because the boiler and heat-pump market has matured faster than the furnace market.

The Cooling Problem Nobody Talks About

Here is the awkward truth about Park City: the climate is changing, and cooling matters now in a way it did not twenty years ago. Average July highs at 7,000 feet have risen 3–4 °F over the last two decades. South-facing glass in a modern Park City home can drive interior temperatures into the mid-80s on a clear August afternoon, even at altitude.

Hydronic radiant heats. It does not cool. Some systems can run chilled water for "radiant cooling," but in our climate that approach is fraught — condensation risk on the slab in a humid weather event, slow response time, and limited capacity for the sun-driven loads that actually matter in this market.

So the question becomes: how do you get the comfort and efficiency of radiant heat and a cooling system that can knock down a 90-degree day?

The two answers we install most:

1. Radiant heat + ducted forced air for cooling only. A high-efficiency variable-speed AC or air-source heat pump with a separate, smaller duct system designed almost exclusively to move cool air in summer. Heating runs almost entirely through the radiant. Cooling runs through the air handler. Each system is sized and designed for one job.
2. Radiant heat + ductless mini-split heads for cooling. Cleaner installation in a tight envelope, individual zone control, often lower upfront cost. The compromise is the architectural intrusion of the indoor heads — though concealed and ducted-mini-split options have closed this gap dramatically since 2023.

Either approach gives you the radiant experience in winter — when you spend 80% of the year at altitude — and a real cooling answer for the increasingly real summer.

The Domestic Hot Water Bonus

There is a side benefit to a hydronic system that almost nobody sells properly. The same modulating condensing boiler that heats your floors can heat your domestic hot water through an indirect-fired tank. One piece of mechanical equipment, two services, one combustion event, dramatically less standby loss than a separate water heater.

In a 7,000 sf Park City home with three or four full baths, a Hubbard tub, and a steam shower, the domestic hot-water load is a real number. Pulling it onto the boiler — or onto an air-to-water heat pump with electric backup — simplifies the mechanical room, reduces the number of vents in the building envelope, and almost always reduces 25-year operating cost.

Forced-air homes need a separate water-heating system, full stop. That is one more piece of equipment, one more service contract, one more thing that fails on a holiday weekend.

Altitude, Elevation, and Why "It Works in Denver" Doesn't Mean "It Works in The Colony"

Combustion efficiency drops at altitude. The atmosphere has less oxygen per cubic foot. Most residential HVAC equipment is rated at sea level and de-rated by manufacturers as elevation increases. By 7,000 feet, a residential furnace loses 18–20% of its rated output. By 9,000 feet (The Colony, parts of Empire Pass, parts of Deer Valley East Village), it loses 25%+.

Two practical consequences:

• A forced-air system designed by a contractor working off Denver-altitude software will be undersized on a Park City build, full stop. We have walked into homes where the furnace was rated correctly at sea level, never adjusted for altitude, and is now running 70% of the time on a cold January morning. The equipment will fail early and the bills will be higher than they should be.
• Modulating condensing boilers handle altitude better than furnaces, because the modulation and combustion analysis adjust dynamically. Air-to-water heat pumps do not care about altitude in the same way — their performance is driven by outside air temperature, not air density.

When we design a system for a build at elevation, we de-rate everything from scratch and we model the whole thing in Manual J / Manual S / Manual D against the actual location. If your HVAC scope does not include the altitude correction explicitly, you do not have a finished design.

The Honest Recommendation, by House

Here is what we actually do on builds, broken down by typical scope:

3,000–5,000 sf single-level or single-family contemporary: Hydronic radiant throughout the living space, with a small ducted air handler for cooling and outside air ventilation. One boiler. One air handler. Quiet, efficient, comfortable.

5,000–8,000 sf two-or-three-level with finished basement: Hydronic radiant on the basement and main level (where the slab can do the work and where you spend most of your time), forced-air heat and cool on the upper levels (where bedrooms benefit from quick response and cooling matters most). One boiler, one furnace or heat pump on the upper level. Most of our Park City builds in the $5M–$10M range fall here.

8,000+ sf compound or multi-wing estate: Often two boilers in N+1 redundancy, hydronic radiant in the public spaces, forced-air heat-pump systems for the bedroom wings, and a snowmelt loop on the driveway and entry running off the same plant. Snowmelt is a category we will cover in a separate guide — it is closer to the radiant world than most people realize.

Net-zero / electrified target: Air-to-water heat pump driving hydronic radiant and domestic hot water, ductless or ducted heat pump cassettes for cooling and supplemental heat, electric resistance backup, and a properly sized solar array. We have one of these in design right now in Promontory and the modeling shows a meaningful reduction in 25-year operating cost vs. the natural-gas baseline.

The Failure Modes That Tell You Who You're Working With

If you want to evaluate an HVAC contractor on a Park City build, ask them three questions. The answers will tell you everything.

1. What is your altitude correction factor for this elevation, and where does it appear in your equipment selection? If they pause, you are talking to a sea-level contractor.
2. What is your design heating-day temperature for this lot, and what is the source? If the answer is not a real number tied to ASHRAE 99% design data for the specific elevation, the load calc is going to be wrong.
3. What is the supply water temperature target on the radiant zones, and how does that match the floor finish? If the answer is a generic 110 °F or 120 °F across the whole house, they have not designed the system — they have copied it from another job.

A real Park City HVAC designer will answer all three without breaking eye contact, and they will have a written load calculation, a written equipment schedule, and a control sequence you can read like a screenplay. That is what you are paying for. The boxes on the wall are commodities. The design is the product.

So Which One Should You Build With

If you are building a custom home in Park City and you can afford it, the answer is almost always hybrid: hydronic radiant for heat in the spaces that matter, forced air for cooling and for upper-level fast-response heating. You will pay 20–35% more upfront than a forced-air-only system. You will recover that premium in operating cost, comfort, and resale value over a 10–15 year horizon. You will not regret it.

If your budget will not stretch, the honest answer is a high-efficiency, fully zoned forced-air system designed correctly for altitude — not a cheap radiant system stretched too thin. A great forced-air system will outperform a compromised radiant system every day of the week.

The worst version of either system is a half-designed one. The category of "we are putting radiant in the master bath because the wife wants warm tile" is not a heating system — it is a luxury feature, and that is fine, but it should not be confused with a primary-heat decision.

The best version is the one designed around your house, your altitude, your glass area, your roof assembly, and your lifestyle. There is no template. There is only the work.

That is what a builder is for.