We are looking at a new building that is heated with overhead gas powered infra-fed radiant heaters. My current shop has a large single fan-forced gas heater. What are the differences between these two heat sources? How long, for example, does it take to warm a space with the radiant heaters? Are they comfortable to stand under? Do either of these heat sources have any impact on building humidity? I have heard that my current fan-forced gas heater adds moisture to the air. I don't know where I heard that. It might be just the movie in my own head.
From contributor J:
Water vapor is a byproduct of natural gas combustion, but that should be vented outside; your current furnace shouldn't add moisture to the air unless it's equipped with a humidifier.
I used to work in a shop that had overhead gas-fired radiant heat. I remember it as being like standing in direct sun on a chilly morning; the parts of you that have a direct line of sight to the heater feel warm, while the parts of you that are "shaded" feel cool, until the air finally warms up. If you leave the shop cold overnight, then such a system might provide some sensation of warmth very quickly, but it would be awhile before the air temperature got to where it was supposed to be. To the extent that you keep the shop reasonably warm all the time (to facilitate finish curing, glue drying, wood stability and such), I'm not sure there'd be much benefit to this over forced air.
I don't know how a forced air heater could add moisture to the air unless it brings in exterior air. They usually are re-circulating air within the building, so humidity would be constant.
Two potential kinds of damage come to mind. If lumber were directly exposed to intense radiant heat, it might cup towards the side facing the heater. Hopefully you can keep things moving through the shop briskly enough that this never becomes an issue.
The other potential issue would be if you allowed the building to cool off significantly at night (assuming you don't have three shifts going). Sticks inside a big pile might never get fully warmed, so they might take on extra moisture.
We also have a couple of shop built humidifiers that we sometimes use. With two of them we can control the humidity in 10,000 sf. If I had the choice and the ceiling height, I would go with the radiant, as you just don't get that drying effect.
Comment from contributor B:
I've worked in non-wood shops that have had both. Radiant makes for a building that is workable fairly soon, but areas under benches, inside cabinets, and drawers take a long time to get warm. I always wanted heavy boots and thick socks in the radiant heated building. The shop with the overhead gas heaters always had dust control problems. It would create dust in one corner, and it would make it to the other corner minutes later.
The nicest shop for heat that I've been to had hot water in the floor. Dust was less of a problem, and feet were toasty so you could wear sneakers which made walking around and over all the stuff less clumsy.
For example, the paint booth was just a corner with heavy plastic to the floor, a fairly small exhaust fan, and one of those hang-from-the-ceiling dust collector boxes to provide make up air from the room to the cabinet. The exhaust was at the bottom of the room. The net effect was that filtered, somewhat warmer, air from the room filled the paint booth and was pushed to the floor and exited outside when the booth was in use, and crept out under the plastic when the exhaust fan was off. The shop had a couple of big slow ceiling fans to reduce air layering, but with the floor heat it didn't matter much.
The downside was that you didn't change the temperature of the shop in a hurry. It took about six hours for the slab to heat up. The original slab was not insulated, so the shot was heating eight inches of concrete and a couple feet of earth.
This became a problem in spring and fall when the temperature swings outside were substantial. The slab basically keeps the inside warmer than the outside. A sudden spring warm spell has you working with the main door open. Similarly a cold snap meant the shop was chilly for a day while the heat brought the slab to a higher temperature.