I have been trying to get an answer to this for a while but to no avail.
In NYC many brownstones are heated with single-pipe steam heating. Often the apts are too hot and people open windows to cool them down. If, instead of opening the window, I put insulation on the heating pipes, does the steam heater output less heat and consequently use less oil?
This is a great question.
The answer is, ‘Yes, but not much.’ You are right to think that insulating those pipes will make the system more efficient, leading to lower fuel consumption, and it will cool down your apartment. However, the amount of energy saved will depend on the amount of heat lost from the pipes you are insulating and therefore how much heat you are saving by insulating them. The amount of heat saved depends on the amount of surface area insulated. Radiators are designed to lose a lot of heat; that’s how they heat up rooms. So they give off a lot more heat than the pipe you’d be insulating and the total effect of insulating the pipe will be small compared to the amount of energy used by the whole system. So if it’s not a great effort, definitely go ahead and insulate those pipes. They will save you energy and cool your apartment down a little, but it’s not necessarily worth a whole lot of effort or expense.
A better idea is to turn off some (or maybe even all) of your radiators. There should be a valve on the pipe leading into the radiator and if you close that valve, steam will stop flowing to the radiator and will instead flow past to other radiators in the building. In this way, you will keep all the heat the radiator would have given off (and the radiator is much better at giving off heat than the pipes) in the system. I have three radiators in my 1BR apt and three hot water pipes that pass through to other apts. Up until this cold snap, I had only one radiator on and relied on the hot water pipes to heat up certain spaces in the apartment. The apartment was still nice and warm, but not so warm I couldn’t sleep at night. Even after it got cold I’ve only turned on one other radiator, and it was more for my cat than myself as I was still fairly comfortable. One note about this though, is to make sure you turn the valve all the way off, or all the way on again if necessary. A half closed valve may cause a bottleneck above which water returning from the radiator can collect. This can trap steam in the radiator. The steam will build up pressure until it pushes through the water, causing the clanging sound you hear in older steam heat systems. Hope this is useful. Steven Lenard GreenHomeNYC