room cold. how to proceed?

Discussion in 'HVAC Heating & Cooling' started by richb2, Nov 22, 2010.

  1. richb2

    richb2 New Member

    Messages:
    59
    Location:
    New York
    My bedroom is about 14 x 16 or so and has only one wall that is connected to the rest of the house. There is a window in each of the three freestanding walls. Each window is pretty old and although we did have storm windows added to the outside about 15 years ago, I feel that they are leaky. I can hear cars driving by. The outside of the building is made from rubble stone, maybe 12 inches think. The walls and ceiling is plaster. Above the room is attic and I know that there is insulation on the floor of that section of the attic. The floor is wood and below this section of the house is another bedroom downstairs. The wood floor is always cold. I am thinking that there is no insulation in the walls between the stone exterior and the plaster interior. If I feel the plaster walls with my hand, in the winter they are usually quite cold. There are baseboard hot water radiators on those 3 walls.

    What is the best way to work on the heating for this room? I was thinking that the first crack at it would be to replace the 3 windows with efficient (tax deduction) ones. If that doesn't work, I could put in radiant heat under the floor since I have an extra existing connection on a radiant heat fitting in the boiler. In this case I would need someone to demolish the plaster cieling of bedroom below mine, put in the radiant heating, and then have someone come back to sheet rock the ceiling again. Or perhaps the answer is to have the plaster walls to my room demolished and for insulation to be installed, and then sheet rocked again. We are in NJ.

    I need to be cost effective since money is definately an issue. Any recommendations?
  2. Dana

    Dana In the trades

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    Location:
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    Is this a rubble-stone veneer over a studwall structural wall on which plaster & lath are applied? A masonry cavity wall? If it's plaster & lath on studs, and the exterior sheathing is in good shape it's possilbe to insulate it by blowing cellose (or fiberglass) from the interior through a hole drilled in each cavity vastly reducing the amount of repair necessary compared to a full-out demolition. If possible have them "dense pack" the cellulose to over 3lbs/cubic foot to eliminate settling over time, and reduce air infiltration to an absolute minimum. (Have them quote it both dense-packed vs. standard density dry, blown. It's ~50% more material and 25% more labor to dense pack it, but it's usualy worht it.)

    If the wood floor is always cold, odds are there air leaks through the joist passing from one side of the house to the other. Depending on how the house is constructed there may be lower cost ways of dealing with that.

    Is this room on it's own zone, or part of a larger zone? Retrofiting radiant could get real expensive real fast, and would not be subsidised the way insulation is. It's nice & all, but installing bigger or more radiation in the room will be substantially less expensive than radiant floors. (Replacing some of the fin-tube baseboard with radiators could make real difference.)

    Insulate first (including the floor, if there's a breezy "thermal bypass" going on through the joists) then see if it really needs anything further on the heating system front. Weatherization & insulation is often subsidized these days to the point where it costs less to have the pros do it than to buy the material yourself. Regardless of fiber type, blown works better than batts, but high-density cellulose restricts air flow better than all but the most expensive new-school ultra-fine fiberglass, (eg. JM Spider, Certainteed Optima.), and those would need to be packed to at least 1.8lbs/ft^3 to even compare. (1lb density Spider or Optima is also a standard installation, but has higher infiltration & convection than standard density non-dense-packed cellulose.)
  3. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    I'd say stop air infiltration first and then use elec. heaters to get the desired indoor temp with a given outdoor temp. The heater power times the duty cycle gives you how many BTU/hr you need.

    E.g., room temp. = 72F, nighttime outdoor temp = 40F, and a two 1 kw heaters on 100% of the time = 2000 w = 7,000 BTU/hr and let's say this is enough to maintain this temp. difference.
    Then this 7,000 BTU/hr loss has to be made up with better insulation or more heat added or both.

    For other inside/outside temp. differences the arithmetic is easy.

    The rule of thumb is 10 w per sq. ft. of floor area but the tolerance on this value might be +/- 50% or more.
    Last edited: Nov 22, 2010
  4. richb2

    richb2 New Member

    Messages:
    59
    Location:
    New York
    >>Is this a rubble-stone veneer over a studwall structural wall on which plaster & lath are applied? A masonry cavity wall? If it's plaster & lath on studs, and the exterior sheathing is in good shape it's possilbe to insulate it by blowing cellose (or fiberglass) from the interior through a hole drilled in each cavity vastly reducing the amount of repair necessary compared to a full-out demolition.

    No the stone is structural. I suspect that holes coul dbe drilled in the plaster and cellose blown in. I doubt that there is any air leakage between the stones or under the floor. I think that the windows and maybe in the closets is only only possible place for leakage.

    The room does have it's own thermostat. I could just set the thermostat to say 72. But I actually sleep near on of the windows and it is cold over there. Perhaps the answer is windows and blown cellose? It is only because I can hear traffic going by that i think that there are gaps in the windows.
  5. Dana

    Dana In the trades

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    Location:
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    What's holding up the plaster?

    Without somesort of cavity to fill, with sheathing and a gap between the sheathing & stone ANY sort of insulating can be problematic. I need a better detailed description of the wall stackup, not just he exterior & interior layers, and info on how the structural wood interfaces with the structural stone to advise properly.

    Sealing & insulating around the windows is probably necessary, but may not be sufficient.
  6. richb2

    richb2 New Member

    Messages:
    59
    Location:
    New York
    The plaster is on metal lathe. Between the plaster and the inside of the stone structure is a pocket of maybe a few inches.
  7. Dana

    Dana In the trades

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    Location:
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    The cavity between the plaster and the stone is essential for condensation control- don't fill it. In a more temperate climate (such as in the UK or much of low-lying western Europ) you could get away with blowing it full of expanded polystyrene beads or rock-wool, but in the NJ climate that approach almost always creates rot conditions where the structural timber meets the stone.

    Your best bet is to air seal it as best you can and insulating around the window frames (low expansion foam- never fiberglass). If there's only a few inches of insulation in the attic, blow in "stabilized" celluose on top of whatever is there to a total depth of at least 12-15".

    Near the ends of the floor joists insulation contractors can stop the flow of air in joist-cavites by drilling a 2" hole in the ceiling about a foot from the ends of each bay, inserting a woven bag, and dense-packing cellulose into the bag. It has to be sufficienty far from the end to not interfere with the vertical flow of air in the plaster-stone cavity. The wall cavity is probably vented either into the vented attci or to the great outdoors at the eaves, and it's important that it continue to do so, but at the moment any sort of wind-pressure from one side of the house to the other is washing cold exterior air under the floor, a classic "thermal bypass". With the ends of the joist bays blocked by bags of dense cellulose those air flows are reduced by 99%, and the floor will be noticably warmer in winter.

    Find an insulation contractor that does both air-sealing and dense-pack cellulose, and have them assess it for you, and discuss the concerns about keeping the wall cavity open vertically. With weatherization subsidies you'd likely be able to block the bypasses and bring the attic R up to snuff for lower cost than doing it yourself, and the contractors would be able to advise on what money would be available to you.
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