Hydronic Heating & Boiler Contractor Serving Denver

Aug 25

6 min read

Denver has more pre-1940 housing than almost any city its size in the West, and a very large share of it is still heated by water.

That's the work. Brick bungalows in Wash Park, Congress Park, Baker, Berkeley and Park Hill, most of them running distribution systems that were designed before anyone had heard of a circulator pump. Post-war ranches. Scrape-and-rebuild infill on the same block as a 1908 four-square. Light commercial in the older corridors where the boiler room hasn't been touched since the eighties.

We're based in Littleton and we work Denver constantly. We don't have a Denver office and we're not going to pretend otherwise — we're a service-area contractor, we come to you, and the license is the same one either way.

What we do in Denver

• Boiler installation and replacement — condensing and standard-efficiency, chosen against the distribution system rather than a square-foot chart

• Boiler repair and diagnosis — including the systems that run but have never worked properly

• Radiant floor heating — new slabs, staple-up retrofits, panel systems

• Snowmelt and heated driveways — residential and commercial walks, ramps and entries

• Hydronic system and mechanical room design — zoning, pumps, controls, near-boiler piping

• Light commercial and multifamily boiler plants — ASME vessels, CSD-1 trim, zone-by-zone control

→ Boiler installation and replacement · → Radiant floor heating · → Snowmelt systems

The Denver bungalow problem

If you own a brick bungalow or four-square heated by cast iron radiators, you own a system with a specific history, and it explains most of what's wrong with it.

It started as gravity hot water: three- and four-inch mains, no pump, water circulating because hot water rises and cool water falls. It worked, slowly and quietly, and it was sized for water around 180°F reaching radiators sized to match.

Then at some point — usually between 1960 and 1995 — someone bolted on a circulator and dropped in a smaller boiler. The distribution stayed exactly where it was. That's the system you have now, and it has three properties that break modern equipment:

Enormous thermal mass. All that iron and water takes a long time to come up and a long time to give up its heat. A control strategy that assumes a fast, light system will hunt all day.

Almost no resistance to flow. Those mains were sized for gravity. Put a normal circulator on them and you can move water far faster than you need to, which wastes pump energy and can strip heat off the loop before it reaches the far radiators.

Emitters sized for hot water. Cast iron radiators sized for 180°F supply cannot deliver their rated output at the 120–140°F a condensing boiler needs to actually condense.

That last one is the trap. A mod-con installed on an unmodified gravity conversion either runs hot and never condenses — you paid 95% money for mid-80s performance — or runs cool and can't heat the house on a design day.

The answers exist: an outdoor reset curve matched to the emitters you actually have, primary/secondary piping to decouple the flow rates, sometimes a buffer tank, sometimes adding emitter surface, and sometimes the honest recommendation of a standard-efficiency cast iron boiler for that particular house. Which one depends on the building. It cannot be decided from the driveway.

A mile up, and the boiler needs to know

Denver is at 5,280 feet. Combustion equipment loses capacity in thin air, and every manufacturer publishes a derate table for it.

Applied correctly, it's routine. Applied wrong, it goes one of two ways:

• Skipped entirely — the unit is sized off the sea-level nameplate, real output lands under the load, and the house doesn't recover during a cold snap.

• Stacked on top of padding — someone oversizes "for altitude" on a load that was already inflated, and now there's a boiler two to three times the size of the house.

We pull the altitude data for the specific model and site and write down the number we used, so it's checkable rather than assumed.

Oversizing is the default failure in this city

Most of the boilers we replace in the Denver metro are two to three times larger than the house needs.

That isn't a slight on anyone. It's what happens when every replacement is sized off the last one: the padding compounds, generation after generation.

Real numbers for real Front Range houses: an older Denver brick home with some weatherization runs around 40 BTU per hour per square foot. Newer, tighter construction is closer to 25. Not the 60 or 80 that a rule-of-thumb replacement quietly assumes.

An oversized condensing boiler short-cycles — fires, satisfies, shuts down, repeats — which wears the equipment, and it keeps return water too warm to condense, which erases the efficiency you bought.

The only fix is a room-by-room heat loss on the actual building, before any model number is chosen. It's slower. It's also the part everything else depends on.

→ Read: why most Denver boilers are two to three times too big

The water heater nobody mentions in the quote

Here's a Denver-specific hazard that most boiler quotes leave out.

In a house with a standard-efficiency boiler, the boiler and the gas water heater very commonly share one masonry chimney, sized for the combined heat of both. The boiler's exhaust keeps the stack hot, and hot stacks draft.

Replace that boiler with a sealed-combustion condensing unit venting out the sidewall in PVC, and the heating load leaves the chimney. The water heater is now alone on a flue far too big for it. Draft may never establish, flue gases cool and condense in the chimney, and combustion products including carbon monoxide can spill back into the house.

It's called an orphaned water heater, and on Denver's older housing stock it comes up constantly. It's one of the first things we check before quoting a boiler replacement, and if a quote you're holding doesn't mention the water heater at all, ask about it.

→ Read: the water heater nobody talks about during a boiler replacement

Commercial and multifamily

Older Denver corridors are full of boiler rooms running well past their design life. Different rules apply than in a house — ASME vessels, CSD-1 safety trim per boiler, floor-mounted expansion tanks — and zone-by-zone control matters a great deal more when a property manager is reading supply temperatures on a display at four in the morning.

Sidewalk, entry, ramp and loading-area snowmelt as well.

Where we work

Denver and the Front Range: Littleton, Lakewood, Golden, Wheat Ridge, Arvada, Morrison, Highlands Ranch, Centennial, Englewood, Greenwood Village, Ken Caryl, Columbine, Castle Rock, Parker, Aurora, Broomfield, Boulder, Longmont, Conifer, Evergreen and Idaho Springs. Statewide for larger snowmelt and boiler-plant work.

Colorado license #LIC00254926. Service-area contractor — no storefront, no showroom, and we'll come to the building.

→ Hydronic heating in Littleton

Start with a site review

Tell us what's there and what it's doing. We'll look at the mechanical room, the distribution, the venting and the gas line — then run the heat loss before naming any equipment.

📞 (303) 908-5658 · Schedule a consultation

Common questions

How much does boiler replacement cost in Denver?

More of the number lives outside the boiler than in it — the state of the distribution system, the venting route, the gas line, and whether the water heater is orphaned by the change. A clean swap and a job that needs the near-boiler piping rebuilt are different projects with different numbers. The site review tells you which one you have before anything is written down.

Boiler or furnace for a Denver house?

If the house already has hydronic distribution, replacing it with forced air means running ductwork through a building that has none — expensive, disruptive, and it usually costs you finished ceiling. If you're building new, it's a genuine choice with real trade-offs. If you have radiators or a slab already, the answer is almost always to keep heating with water.

Can a condensing boiler work with my old cast iron radiators?

Sometimes, and it depends entirely on whether the system can be made to return water cold enough to condense. Outdoor reset, primary/secondary piping and sometimes added emitter surface get you there on many systems. On some, they don't, and a standard-efficiency boiler is the honest recommendation. Anyone who answers this question without seeing the radiators is guessing.

Do you have a Denver office?

No. We're based in Littleton and serve the Denver metro as a service-area contractor. We'd rather say that plainly than list an address we don't work out of.

Do you do emergency no-heat calls?

Call and we'll tell you honestly whether we can get to you and when. We're a small shop — we won't promise a two-hour window we can't hold.

Can you take over a system another contractor installed?

Yes, and a fair amount of our work is exactly that. We'll tell you what we find and what it would take to make it right, without a running commentary on whoever was there before.