During some particularly cold nights, I had put up the red heat lamp we'd used for brooding in my chicken's coop. It's a coop that can hold double the amount of chickens that I have so they likely don't keep the coop as warm as it could be. The water that's in there freezes and some of their combs have white on the tips, so I got concerned and added the lamp and kept it on 24 hours. I didn't do it for egg production, just for heat. A few days after I stopped the red light, they started producing more eggs. (I've got 6 chickens and was getting about 4 eggs a day until winter, then about 2-4 eggs a day after winter. My aracauna started laying and I get 4-5 eggs a day now for about a week.) The weather had warmed up and I stopped using the red light. It's cold again and I started to use it again, but I am concerned about it messing with their sleep. I didn't think the red light did that, but if I go out after dark to check for eggs, they'll jump off their roosts and nibble or wander around. They didn't do that without the light. Am I driving them crazy keeping the red light on at night?
From my own experience, the red heat lamp does encourage activity. Last year, I used a red heat lamp to take the edge off the freezing cold. I saw it was causing problems when I put it on a timer to go on and off every hour or so to keep the temperature above freezing. A few hens would get caught down on the floor and couldn't get back up on the perch when the light went off. So I timed the light to come on and stay on during the last few hours before dawn. It seemed to be less upsetting to the hens, but they made an awful mess of things partying during those early hours when the light was on. They also seemed to time their awake hours from when the light came on, and would be ready to go in to roost before it was really dark. This year, I obtained one of those oil-filled space heaters and I set it to the lowest setting. I did away with any augmented light during the shortest winter days. I was quite surprised when they began laying again after molt pretty close to the time they began laying the previous year with supplemented light. In other words, the light or lack of it appeared to make little or no difference in their laying. Since you have lots of space, why don't you try the oil filled space heater? I find it's more effective and far, far safer. Also, I suspect your hens are responding more to the natural lengthening of the days by laying more eggs. I have a hunch they would continue to lay the same if you were to bring back the light on very cold nights.
You can get a 250 watt infrared ceramic heat emitter that does not produce any light. They are found in the reptile section. I think I saw some on Amazon the other day, too, if you don't have any locally. The 60, 100 and 150 watt ones will not do what you are wanting. The 250 watt will replace the bulb you are currently using so far as BTUs is concerned.
