Just want to run something by you guys to see your thoughts on the subject. Earlier this year I discovered that closing off the back room in the mobile home for extended periods (4-5 days) results in a fairly stable low temp about like the inside of a cool fridge. Obviously the door closed, towel/sheet blocking and effectively cutting off about 120 square feet of shack for the wood stove to heat. This predictably makes it easier for the wood stove to keep the rest of the place warm. Now, when it's chilly, I'll close the back room at night, and crack it a few hours after morning warm up to blend the air to slowly bring the temp up back there. Now, here's where I got to thinking. Can I block off the duct running into this back room without harming the furnace or creating some kind of goofy pressure within the ducting? Not as a permanent fix, just on cooler nights. The reason I ask, is because even with the room closed, cold air rolls back in the duct (very slight but you can see it with a cigarette. Another reason I want to see if it's alright, is because if you run the furnace in the morning, you now have to incorporate all that cold air from the back room (this is a cool room even with the door open slightly) into the mix, and the furnace runs forever. If all other registers in the place are open, would blocking the line in the last ten feet mess things up? Would I see higher pressure from it struggling to get air out? Would it maybe boost air coming out all the other vents, and warm the rest of the place quicker/with less effort like the wood stove does? Any and all thoughts appreciated.
I started to answer this and ended up with a short story for print. Mobile homes are known for not so great duct systems. Closing off the register in the bedroom will accomplish the same thing as plugging the ductwork. Once the outlet is restricted, the sire will stop flowing to that outlet. (It may result in a slightly higher pressurized duct system, but 100 cfm should not make or break any properly designed system.) By rights, there should be a cold air return register in the bedroom also. This may very well be the source of the "cold air that rolls back into the duct" you mentioned. Blocking that off may solve that problem. But for "not a permanent fix, just on cooler nights" I would block off in the bedroom and NOT the ductwork. No matter where you block off that bedroom, you are inviting the cold into your house and instead of combating your home sitting on a cold source, you have now allowed it to gain a foothold in your dwelling. Sounds like a better skirting system or improving the one you have on the mobile home is needed?
I have to agree with yooper, if one room is causing an issue, it is the result of a bigger problem.......the room is the result we need to fix the cause.
I can say that many moons ago when I was in school for HVAC we did a lab project on the thermodynamics of closing off a room to "save" money on heating and cooling. It didn't end up really being all that beneficial. Like yooperdave mentioned you have invited old man winter right into your home. There likely isn't nearly the insulation separating the rest of the house from that room that there is separating your exterior wall from the outside. Better insulation at the skirt is where I'd focus my attention as well.
I don't think there are much gains to cooling off a room inside an insulation envelope. A couple of degrees for sleeping maybe, but I doubt it saves fuel.
just make sure your water lines are truly inside, most run them next to the ductwork . They were not built with a wood stove heating the place in mind. make positively sure your bellyskirt is in one piece no openings in it from what ever including rodents. That comprises it's intended purpose and can allow pipes to freeze fast. Got T shirt. That belly skirt also acts as a ground moisture block , seeing as most of the flooring is chip board , you do not want that exposed to ground moisture.
So after giving it a go this morning, I have a few thoughts. You can be amazed or in disbelief or unimpressed it doesn't matter much, I just know what I observed. It was bad for a first test, as usually if I run the furnace, I'd like a fire to have been cooking along for 30-40 minutes. Anyways, threw wood in stove and cranked furnace. Furnace seemed to heat the place noticeably quicker by itself (before fire raging). Seemed to have more pull on the furnace door (or room doors) and may be blowing harder out of vents. Not sure if good or not but seems to be what was happening. Also could feel cold air from back room pulling much harder through side and bottom of bedroom door with furnace running. I notice nothing to this extreme running wood stove only, just like a leaky outer door. The trailer warmed up a whole bunch, and the back room with door closed came up a degree or two. I realize there's no free lunch, and you pay now or pay later, but that's okay. That's part of my goal, and once the place warms up, I can crack the door slightly and cold air bleeds out and warm air rolls in. I mention having found the room unheated holds a steady fridge temperature. This is actually a bonus for deer season, as I aged my deer to perfection. This is not in my view the trailers fault, or the skirtings fault, it's a good thing for when the weather is too cold to use the shed. It's also a 1970's mobile home, so not exactly the best insulation even when new. The back of the trailer has always been the coolest room, in the days of oil heat only, but maybe more so now with mostly wood heat. Again, not the trailers fault that I'm heating the whole place with a glorified space heater.
70's trailer, yep water lines run next to duct work to keep from freezing, having had a 1980 unit with exactly the same heat distribution problem. mentioned the belly skirt deal because I did freeze lines, and it was not a fun project repairing 3 different leaks which is when I found out how bad a shape my belly skirt was in. They put plastic like a drop cloth type over the particle board flooring in the heated side but nothing on the bottom. so because of the leaks which were spraying on the particle board I had to replace various sections of that as well. Ah well that's what happens when you get nailed by a divorce and all your assets are frozen. Cica 2001
