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  1. #1
    Join Date
    Oct 2009

    Question Baseboard - should I reroute feeder pipes?

    I have two bedrooms (copper fin baseboard) over an unheated garage. The pipe supplying the baseboards runs about 20' through the garage, then up into the bedrooms from the back corner to the front for 18' of baseboard, then back into the garage for an L-shaped run back to the starting point. Overall, there's approx. 2-3 times as much pipe in the garage as there is baseboard in the rooms I want to heat, and these rooms get cold for days on end during bad cold spells (northern NJ).

    I think the once-and-for-all solution would be to re-route the pipes to get them out of the garage and up into the bedrooms to the greatest extent possible - that is, put baseboard along all 3 exterior walls around the bedrooms instead of just the farthest one, a full U-shape instead of just an underscore _ .

    A plumber friend of mine is concerned that this would overheat the bedrooms and affect the furnace cycling. Since the bedrooms comprise only 25-30% of the heated floor space, I wouldn't *think* this would adversely affect the furnace cycling, and since they're a separate heat zone, I don't *think* they could overheat. But I don't have any actual experience in this area. What do you think?


  2. #2
    Join Date
    Feb 2008

    Default Re: Baseboard - should I reroute feeder pipes?


    A number of questions come to mind after reading your post.

    I don't know how many times I've read about this particular problem on this forum & elsewhere---"cold room over unheated garage" is a chronic complaint that has many, many possible contributory causes---and likewise an easy solution is not likely.

    Do you intend to do this work (baseboard addition, connection to boiler, insulation, etc.) yourself, or will you hire a heating contractor???

    What are the dimensions of the rooms to be heated, including ceiling height??

    Where is the boiler located & how far is the boiler from the bedrooms & how much footage is in the supply & return pipes??

    How much total glass (windows) are in the bedrooms, dimensions, are they single/double pane/storms???

    Is there any insulation on the supply/return pipes running thru the garage from & to the boiler??

    When you say the bedrooms are on a "separate zone" do you mean there is a t-stat in the bedrooms & either a boiler zone valve or dedicated circulator for the bedrooms??

    How much insulation & type is under the bedroom floors (to keep the cold air from the garage out); along the exterior walls; in the ceiling???---would you say there is a complete 4-sided ENVELOPE of insulation on ALL 4 SIDES OF THESE BEDROOMS to keep the cold out???

    What are the coldest outside temps you get in your area in winter; how low does it get in the bedrooms on a cold nite???

    What is the approx. temperature of the hot water inside the baseboard pipes when the bedroom baseboard elements are heating????---this can be estimated by holding your fingers on the bare copper piping as they are heating up---if you can't keep your fingers on the pipes for more than a second it's about 180 degrees---if you have to remove your fingers after a few seconds, it's 140 degrees---if you can keep your fingers on for a long time, it's less than 120.

    I would agree with your idea to increase the amount of baseboard in the bedrooms to cover all exterior walls---this in itself may make a dramatic improvement---I see no cycling problems with the boiler over this unless the supply/return runs are considerably longer (if the boiler is located ~100 ft. or more from the garage bedrooms some heavy insulation would have to cover the supply/return pipes---your plumber may have been referring to a minority of cases where the garage/bedroom loop is over several hundred feet & water under 130 degrees is looped back to the boiler---this could cause condensation or even a cracked combustion chamber (rare) but a supply bypass pipe can be installed, if needed.

    In many cases extensive insulation, either closed cell foam, cellulose or other has be be blown into the exterior walls, any kneewalls, & underside of the floor & ceiling in hard to heat cases.

    Sometimes the supply/return pipes to & from the boiler have to be insulated with foam coverings, or replaced with double-ganged flexible PEX plastic tubing & put inside insulated-encased culvert pipe to minimize supply/return pipe heat loss.

    Google "cold room over garage" (with & without the quotes); or "cold bedroom over garage", or "cold bedroom over unheated garage".

    Heat Loss Calculation: ---there is a way to estimate how much heat in BTUs/hour is needed to warm the 2 bedrooms (depending on amount of insulation in walls & window size), and also calculate how many BTUs an hour the baseboard elements are putting out---a lot of heat is often allowed to escape from "rooms over an unheated garage", so the strategy is to insulate as much as possible (create an envelope) to keep the heat in the bedroom envelope & assure that adequate heat is coming out of the baseboard elements to heat the rooms.

    Google "heat loss calculation" to get several HLCs, or use the manual one below---baseboard puts out ~590 BTUs/hour when the supply water is 180 degrees---but ~400 BTU/hr when the supply water is 120 degrees---if your total room dimensions are 20' X 15' = 300 sq.ft. X 60 (heat factor/est.BTUs needed/sq.ft.) = 18,000 btu/hr to heat the rooms---18' of baseboard at 560 btu/ft.(assuming supply pipe cooling) = 10,080 btu/hr baseboard output.---in this theoretical case you're only getting ~half the btu/hr you need from the baseboard---with 35' of baseboard: 560 btu/ft. X 35 = 19,600 btu/hr baseboard output---enough to heat the room.

    Insulation, glass & water temp among other factors have to be considered, but you get the basic idea.

    Please post back.

    Last edited by NashuaTech; 10-14-2009 at 11:59 AM.

  3. #3
    Join Date
    Oct 2009

    Default Re: Baseboard - should I reroute feeder pipes?

    ***! Thanks, NashuaTech. I'll answer your questions as best I can.

    Who would do the work - there's a plumber I trust, I was thinking of him.

    Room dimensions - that end of the house over the garage, including a stairwell, hallway, and storeroom which presently have *no* baseboard or *any* method of being heated other than air movement from somewhere else, is about 20 x 25. The bedrooms together are about 20 x 15, 8' ceilings, with total 4 good-sized double-hung windows, single-pane with storms (1 north, 2 east, 1 south). The hallway has a glass sliding door facing south, no storm. That whole end of the house is significantly shaded, including some big evergreens.

    "Separate zone" - there is a thermostat in one of the bedrooms, but I don't know about a boiler zone valve or dedicated circulating pump.

    Boiler-to-garage distance - I'd guess 30 feet, mostly through a suspended ceiling in the finished part of the basement. That doesn't count the run through the garage itself. That pipe probably isn't insulated, but runs between a heated area above and suspended ceiling panels that look like fiberglass on the backside.

    Insulation on the feeder pipes in the garage - they're so close to the floor joists and the outside walls, there's very little room for insulation. My dad put foam cylinders anywhere they would fit, and wound strips of fiberglass, not very thick, like bandages around the rest. Both types of insulation have suffered rodent damage.

    Insulation of the bedrooms - Wall and attic insulation unknown. Bedrooms enclosed (from a screen porch) early 1970s, wood siding, probably standard 2x4 wooden studs. Because the whole garage section was an add-on, the only attic access to the this part is through what used to be a gable-end opening in the original end wall, that's maybe 2' square? I don't consider myself claustrophobic, but I won't crawl through that. My dad had put 2 layers of 3.5" fiberglass between all the floor joists, but I ripped that out a few weeks ago because various sections had mildew and/or evidence of past rodent infestation, and/or were falling down of their own accord, plus every single vapor barrier was on the cold side (replacing that is the subject of a separate post in the Insulation section).

    Coldest outside temps - between 0 and 10 degrees F, teens more common. Temp in bedrooms during these spells - 60, not counting the heat generated by my dad berating me for "overworking the furnace."

    Don't know the temp of the water in the baseboards.

    Also, one detail I left out of my original post: in the garage, just before what I presume is the return pipe exits the garage heading back toward the furnace, there's some kind of heater unit with louvers and presumably a fan. The thing is stuffed with fiberglass, probably by my dad; the electrical connection is unhooked; and nearby there's a round back-of-thermostat plate with no thermostat attached. I admit I have no understanding of how one loop of pipe can have two separate thermostats directing it, and I don't know if it was disconnected before we moved in or just afterwards.

    You've given me an idea, though. The unheated storeroom that I mentioned has sheetrock on the exterior wall, but was never spackled or otherwise finished. If I can move enough shelving away from the wall, I can probably pull off a piece of sheetrock to find out what the wall insulation is, at least. I'll work on the rest of your suggestions and calculations.

    And, yes, the unheated hall/stairs/storeroom is between the bedrooms and the rest of the house. So, of the six sides of the bedroom space, the north, east, and south sides are exterior walls, and the top, bottom, and west sides face areas of the house that are themselves unheated. I think I could have designed this better myself.


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