Key Takeaways
- Temporary heating construction is rented heat for trailers, tents, and finish work. You run it for the job, then send it back.
- Direct-fired units heat fast and cheap. They also dump combustion into the air you’re breathing.
- Indirect-fired units keep exhaust outside. That’s the right call for occupied trailers and tent heater rental.
- OSHA sets ventilation, clearances, and a 50 ppm carbon monoxide ceiling. Canvas needs 10 feet of space.
- North Texas usually sees its first freeze around November 22. Heat still shows up weeks earlier on night pours and finish work.
Temporary heating for construction is rented equipment that holds a space at a target temperature until the building’s own HVAC is live. Pick the fire type first. Size the BTUs second. Then check OSHA before you light it.
Direct-fired or indirect-fired?
A direct-fired heater burns fuel in the airstream it blows into the space. An indirect-fired heater burns fuel in a heat exchanger and dumps exhaust outside through a stack. The second one is what you want anywhere people sleep, tape drywall, or sit in a trailer.
| Type | Where the exhaust goes | Best for | Skip it when |
|---|---|---|---|
| Direct-fired (torpedo / salamander) | Into the heated air | Open bays, freeze protection, empty shells | Occupied rooms, curing finishes, tents with people |
| Indirect-fired | Outside, through a flue | Trailers, tents, paint, drywall, occupied work | You only need a blast of heat in open air |
| Hydronic | Closed glycol loop | Long, even heat with low fumes | You need heat in an hour, not a day |
Direct-fired wins on speed and fuel. Crews love that. Then someone zips the tent and the headache starts. If the space is enclosed and occupied, go indirect. That’s the whole decision.
Temporary climate control covers heat, cooling, and dehumidification on one rental. Summer cooling is a different math problem. We already walked that in the portable AC sizing guide.
How big does the heater need to be?
A British thermal unit (BTU) is the heat to raise one pound of water one degree Fahrenheit. Heaters are rated in BTUs per hour. The same unit shows up on cooling gear, where 12,000 BTU/hr equals one ton.
You need three numbers: cubic feet, temperature rise, and how leaky the space is. Length times width times height gives volume. Target indoor temp minus the overnight low gives rise. A sealed trailer leaks less than a tent with one wall open to a north wind.
A 12 by 60 trailer at 8 feet is about 5,760 cubic feet. That’s a small, tight box. The same footprint under canvas leaks heat every time a door flaps. Same square footage. Totally different machine.
Don’t size off a brochure photo. Size off the coldest night you actually expect, then add capacity for doors that stay open. If the unit runs wide open all night and still can’t hold temp, it’s undersized. If it short-cycles in a sealed room, it’s oversized and wasting fuel.
What OSHA actually wants to see
1926.154 is the construction rule for temporary heating devices. Fresh air has to be enough to keep people healthy. If natural air isn’t enough, you add mechanical ventilation. Confined spaces get extra care so the heater doesn’t cook the room or starve the flame.
Clearances are not suggestions. Circulating room heaters need 12 inches at the sides and rear. Radiant units need 36 inches. Chimney connectors need 18 inches. Heaters that aren’t listed for wood floors sit on insulating material or at least 1 inch of concrete, sticking out 2 feet in every direction.
The tarp rule is the one crews miss. Heaters near combustible tarps or canvas sit at least 10 feet away. The cover gets tied down so wind can’t knock the unit over. Solid-fuel salamanders are banned in buildings and on scaffolds. Period.
Carbon monoxide is the quiet killer. OSHA’s construction PEL is 50 parts per million, averaged over 8 hours. CO is colorless and odorless. It displaces oxygen in the blood. Headache, nausea, dizziness. Then it gets worse. If people are in the space, use indirect fire, vent it, and hang a CO alarm.
Texas heat calendars lie
Dallas-Fort Worth’s average first freeze is November 22. Austin’s long-record average is November 29. That sounds late. It isn’t a reason to wait.
Night work and finish work get cold weeks before the official freeze. A 45°F overnight in October will sweat a trailer and stall paint. Bergstrom can run about 10 degrees colder than Camp Mabry on a clear winter night. Same metro. Different low.
February 2021 is the reminder nobody in North Texas needed twice. DFW spent 139 hours at or below freezing in that stretch. If your winter plan is “we’ll buy a couple torpedoes at the box store,” that’s not a plan.
Gulf humidity also fights you. Heat a leaky tent and you can push moisture onto cold drywall. That’s a dehumidifier job as much as a heater job. Same climate control conversation.
Your heater is also a power load
Indirect-fired units need fans, controls, and sometimes pumps. That load sits on temporary generator power with everything else in the trailer. Size the genset for starting watts, not just the heater’s nameplate. The construction generator sizing guide walks that math.
Fuel is the other half. Diesel heat plus diesel power means two burn rates on one site. Plan deliveries the way you would for a long-running genset. Our fuel management guide covers how that actually gets scheduled.
If you want heat on site before the first real cold front, contact us at (866) 448-1594. We’ll match the fire type to the space and size the BTUs against the generator, not against a guess.
FAQ
What is an indirect fired heater?
An indirect-fired heater burns fuel inside a heat exchanger. Hot, clean air gets ducted into the space. Exhaust leaves through a flue. Use it for occupied trailers, tents, and finish work where fumes and CO would be a problem.
What is a direct fired heater?
A direct-fired heater (torpedo or salamander) mixes the flame with the air it blows. It heats fast and uses less fuel. Keep it in open or unoccupied areas. Don’t zip people into a tent with one.
How much does it cost to rent a heater?
Rental cost moves with BTU size, fuel type, how long you keep it, and whether delivery and fuel are in the rate. Indirect-fired units cost more than a cheap torpedo. They also keep the space occupiable. Ask for a flat monthly number that includes the generator if the heater needs one.
Do I need heat before the first freeze?
Yes, if you have night work, occupied trailers, or finishes that hate 45°F. The official freeze date is a climate average, not your schedule. North Texas can still see an October freeze in the record book.