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  1. #1
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    May 2008
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    Default cold 20' x 16' familyroom - built on slab

    Our familyroom is always cold. Was built by previous owners in
    early 90'. It has baseboard on all 4 walls, and a separate thermostat. It is on a slab, and has a high ceiling (we use a ceiling fan to push down air). Everyone who's been out to look
    at the space as a different idea - blame it on the slab, or maybe something is blocking the piping, etc. etc.

    The last HVAC guy out mentioned that maybe the water is flowing too fast through the loop and since this isn't a large room, the water isn't waiting around long enough to adequately heat the fins in the baseboards. Does this make sense to anyone? His suggestion was to install some kind of value that can be adjusted. He believes if the hot water is slowed down, it will radiate more heat. He said the pipes to and from the space are equally hot - that there should be a heat loss on the return pipe.

    We have a new Buderus boiler, and we're told its more than adequate for the 1,800 sq ft house.

    We're puzzled - if seems no matter what we set the thermostat to,
    it can't keep up .....

  2. #2
    Join Date
    Aug 2007
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    The Great White North
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    Default Re: cold 20' x 16' familyroom - built on slab

    It's possible both the slab and the hot water heat could be related.

    To address the slab --- unless the slab had a layer of rigid foam underneath and along the exterior edges then it will always be cool at the lower level of the room. The slab is a heat sink.
    Whatever heat in the room will always be directed toward the cold floor ---- heat flows to cold --- it's the law of nature.
    The idea of the rigid foam is to provide a thermal break from the cold ground under the slab and the heat within the room. The resistance to thermal transfer this foam provides helps to raise the temperature of the slab and minimizing cold air forming along the lower level of the room.

    Because the slab is drawing heat out this tends to create large stratifications of temperature within the rooms. Usually the human level is cooler and less comfortable because of this.
    Using the ceiling fan is trying to circulate the warmer layer down ---- however --- this probably creates more discomfort from cool drafts because the lower level is colder. Besides when your lower extremites like your feet and legs are cool you will never feel warm.

    I'm no expert on water heat though if the system is not outputting enough heat that would definately impact the comfort.
    But, if the heating output seems to be correct according to calculations of room size , etc. , it may be hampered by the heat sink of the slab.

    Just a thought.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Apr 2008
    Posts
    32

    Default Re: cold 20' x 16' familyroom - built on slab

    I would echo Canuk's comments. We have a similar family room that is not original to our house, and it is the coldest room in our home.

    Have you thought of checking your wall insulation to see if that may be part of the problem? I am convinced that part of our problem is that the former owners cheaped out and/or otherwise half-assed every renovation they did, one of these things being a lack of sufficient insulation in our family room walls.

    Good luck.
    -Daryl, learning how to keep up with an 80 year old house in PA

  4. #4
    Join Date
    Feb 2008
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    554

    Default Re: cold 20' x 16' familyroom - built on slab

    I would agree with the comments of the other posters.

    The thing is, you haven't pinpointed the exact cause of the cold room, despite the fact that it has a separate zone & its own thermostat.

    One thing in your favor is that you have forced hot water heat---there are an amazing number of modifications, add-ons & things you can try to solve the problem.

    Keep calling heating contractors in until you hit on the right one---there are a lot of possibilities.

    Check the exterior walls for insulation by pulling the electric receptacles & shining a light in there to see if you can see any insulation---shove a disassembled steel hanger in there with some glue on the end to see if you come up with any insulation fragments.

    How many windows do you have in this room---what is the total square footage of the windows???---are they in good shape, storms or double pane, or drafty and single pane????

    What part of the country do you live in---do you often experience zero or sub-zero weather???


    Put your finger on the piping when the t-stat is calling for heat---the pipe should get so hot, that you can't leave your finger on it for more than a second (180 degree water)---do this at several spots around the room.

    If the pipes are only lukewarm, or not as hot as expected, check the boiler temperature gauge---it should read aprox. 180 degrees when the system is calling for heat.

    Some new Buderus boilers are designed to operate at 100 degree or 120 degree water temp with an outdoor reset---call the original installer to find out about your system.

    Something just doesn't jibe here---count the # of ft. of baseboard---if you have 50' of baseboard, it should be putting out 560 btu/hr per foot at 180 degrees water temp.

    Thus, 50' X 560 btu/ft = 25,000 btu/hr heat output for a room that would seem to need only 12,500 btu/hr.

    Unless you have NO insulation in the exterior walls & 200 sq.ft. of drafty window glass. and a 25' ceiling, 12,500 btu/hr baseboard heat output should be sufficient to heat the room, which would equate to 22' of baseboard with a water temp of 180 degrees (560 X 22' = 12,300 btu/hr).

    In other words, you already have TWICE the amount of baseboard in there (if 50') than you need, assuming the boiler is putting out 180 degree water.

    (For these calculations a heat loss for the room of 40 btu/sq.ft. is assumed until additional info is given: 20' X 16' = 320 sq.ft. X 40 btu/sq.ft. = 12,800 btu/hr assumed heat loss that has to be replaced to keep the room warm).


    Please post back with additional info.
    Last edited by NashuaTech; 02-20-2010 at 06:56 PM.

  5. #5
    Join Date
    May 2008
    Location
    New England
    Posts
    118

    Default Re: cold 20' x 16' familyroom - built on slab

    The ceiling is 8 1/2' @ center peak - all beadboard. There are 24' feet of baseboard (4 different sections) - broken up because of fireplace on south wall (attached 2-car garage is on other side of this wall), sliders on the east wall, "open entry" to main house on other (this wall also houses the backside of another fireplace & chimney in main house), and the front door and 5'x 3' window on west wall (which is front of house). There's also a sky light on southside.

    Anderson windows and slider which were installed during initial
    construction. Had an energy audit performed 3 years ago and they didn't detect any major leaks in this room.

    The pipe is very hot to touch.

    Located in New England, so gets cold.

    Have someone coming out tomorrow (yup, on a Sunday) and he wants to take temperature of water - on the return. He's equating water flow to walking on hot coals - if one walks fast, the coals don't feel hot. But when one slows down, the coals feel hotter. Even though the coals never change temperature. He's also mentioned replacing baseboard, and putting in larger units - to cast off more heat.

  6. #6
    Join Date
    Jan 2010
    Location
    Northern Virginia
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    1,131

    Default Re: cold 20' x 16' familyroom - built on slab

    A quick fix would be to insert a ball valve on the return line; throttle down the return flow and the water stays in the rads longer. If it doesn't seem to work, just let it open and it's right back to the previous state. Would a gate valve be better than a ball valve?
    S_M
    Remove not the ancient landmark, which your fathers have set.

  7. #7
    Join Date
    May 2008
    Location
    New England
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    118

    Default Re: cold 20' x 16' familyroom - built on slab

    The HVAC guy coming out later today, mentioned a "3-way valve". Said it was something homeowners could adjust themselves to slow the flow of the hot water through the loop. Is that the same as ball valve or gate valve?

    Another HVAC guy suggested installing a "chill chaser" in the room.

  8. #8
    Join Date
    Feb 2008
    Posts
    554

    Default Re: cold 20' x 16' familyroom - built on slab

    I'm finding it hard to pinpoint which way to go on this deal---it's not the type of thing that can be solved over the internet----there seems to be some big heat losses with the slab floor, the fireplace, the open entry to the room, the lack of insulation.

    I would definitely have some cellulose insulation blown into all the exterior walls, & even the wall between the room & the garage---for a few hundred $$$ this would make a big difference.

    You have the option to add additional convectors (radiators, high output baseboard, steel panel radiators, fan-driven convectors, etc.) to increase the heat output of the hot water, which seems to be adequate now according to your "touch test".

    I remain unconvinced that the problem is that the "water is moving too fast" in the piping---more heat is produced with HW moving at 4 gallons per minute, than at 1 gallon per minute---the essential thing is to have sufficient convectors/radiators so their metal can absorb & distribute the heat into the room.

    A 3-way valve can mean several things---one version is used on radiant systems to mix 180 degree water with colder water; another version could refer to a multi-speed circulator that can be adjusted for water flow---I think that route would be a waste of money, but who knows.
    Last edited by NashuaTech; 02-21-2010 at 04:25 PM.

  9. #9
    Join Date
    May 2008
    Location
    New England
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    118

    Default Re: cold 20' x 16' familyroom - built on slab

    > another version could refer to a multi-speed circulator that can be adjusted for water flow

    yup, that's the one he is recommending. runs about $100. said if that doesn't work could install high output baseboard. also suggested thermal "scan" to detect heat loss. since we didn't put this addition on, have no idea what was and wasn't done w/insulation. do know the previous owners didn't use the room much (they never had cable installed for TV, had little furniture in it, & never use fireplace).

    BTW, there was about a 5 degree temperature difference in water "going out", and "returning".

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