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turtlelearner

Upper story 10 degrees warmer than basement

turtlelearner
9 years ago

I live in a two story colonial built in 1946, plaster/cement like walls, no insulation in the walls, etc. On the other hand, there is a layer of fiberglass insulation in the attic just above the problem upper story which has been there for years. This 700 sq ft area is semi-ceiled with double pain windows that were installed in the last 15 years. I have a carrier electric forced A/C Unit. I only have 3 air outlets open in the entire house, The problem upper story has one air outlet and two air intakes appropriately placed on opposite sides of the room. The thermostat is on the middle floor where there are two air out lets open and one air inlet. There is a huge air inlet adjacent to the HVAC unit in the basement. Question: What is the right approach? How do I get the biggest bang for my buck? Should I install window air conditioners first ? Should I install a ventless AC unit first? Or should I instead begin insulating?; I could start with the attic by pumping in celulose. I could then plug the leaks I see in the vent system and then insulate the vents. As a last resort, I would pump insulation into the walls. I am not sure how productive Plugging and insulating the vents would be, because I don't have access to anything above the basement level.

Comments (8)

  • jakethewonderdog
    9 years ago

    Wow, there's a lot here... and not really enough information to make solid recommendations - so let me give you some general info:

    Because your basement is underground, it will always be cooler than other rooms in summer.

    You need a a lot of insulation in your attic. I don't know where you are located, but an R 50 isn't unusual. Measure the insulation in your attic and then compare that R value to what you should have for your location. Attic insulation is generally the cheapest and most effective insulation to install. Start there if what you have isn't enough.

    Once you have the insulation in your attic up to snuff, insulate your walls.

    The huge air inlet near the furnace in the basement seems like a bad idea... and potentially a very bad idea. From a cooling standpoint, it means that the HVAC unit doesn't have to pull air from upstairs.

    It's potentially a very bad idea because it could cause carbon monoxide from the furnace to be drawn into the HVAC system. Have a furnace person look at that.

    Don't bother with ventless a/c unit.

  • turtlelearner
    Original Author
    9 years ago

    Thanks for the response!! Turns out, I live in northern Virginia. The charts suggest R38 which means I can add up to 10 more inches. I was told to airseal all penetrations including the scuttle hole entrance prior to adding insulation. I was told to use Mastic tape #1402. Someone suggested that I should airseal any leaks from the non-conditioned attic going down into the walls. Do you agree with that?

  • SaltiDawg
    9 years ago

    OP,

    When you say, " I only have 3 air outlets open in the entire house," does that mean that you have other outlets that are shut?

  • jackfre
    9 years ago

    The general rule of thumb is put your first money into the building envelope, windows, insulation, sealing. Once this is done you will will be able to better determine the proper size equipment for your home. Tightening things up will allow you to use lower capacity equipment. As to the equipment type, I'm a big fan of mini-split heat pumps.

  • homebound
    9 years ago

    Yup, it sounded just like a N. Va 1946 house from your initial description. We're in N. Va, also (S. Arlington). Home built in 1947. You might invest in an energy audit - very helpful info.

    But knowing these homes, I would do the following:
    insulate the walls (you probably have rock lathe). I've opened up a couple of our walls to rewire and found insulation voids because it deteriorated and settled to the bottom of the wall cavities. Proper, complete insulation will make a huge difference.). (You can blow cellulose into the walls, for example).

    Make sure the cavities behind your window casings are insulated (easier to tell in extreme temps). I found several of ours to be empty. Even the window replacement guys like to "forget' this little item during their installs.

    Air-seal, then insulate your rim joist areas in the basement. (Presuming you have a basement - probably so.)

    Use window treatments to block the summer sun.

    Attic: maybe you don't have sufficient ventilation up there. Might be time to enlarge the gable vents and also get a ridge vent installed if you don't have one. This in combo with good insulation in your attic floor, of course. Btw, insulate your attic access door - most aren't.

    Anyhow, that's a start. I wouldn't be worried about the "return" in the basement, but close any basement ceiling registers in the AC months, if you have them. Our basements cool just fine with only the returns. Let the cool air get pushed upstairs.

    One more thing...climb into your attic and make sure all your HVAC ducts and joints are properly insulated throughout. They sometimes leave things incomplete when out of sight, esp. in the hard-to-reach places. If you have recessed lighting upstairs, box over them in the attic (safely), then insulate. Same for your bath fans.

  • energy_rater_la
    9 years ago

    hmmm sounds like my advice with mastic tape...

    "The general rule of thumb is put your first money into the building envelope, windows, insulation, sealing."

    while I totally agree with improving the building envelope...windows
    are one of the absolute last things I recommend.
    with a 15% savings at best...many things come before
    this costly upgrade.

    best of luck.

  • jbmnd93
    9 years ago

    South Arlington c. 1940 here.

    If the problem is temperature difference, change how you program your thermostat on the lower floor. You probably have a cooling function--which controls how often the a.c. produces cold air for the house--and a fan function which controls when the fan moves the air.

    If the fan is set to auto, it will only blow when the downstairs room with the thermostat needs cool air. So the fan only blows in unison with the a.c. The lower room stays a comfortable lower 70s degrees at night while the upper floors collect all the hot air in the house via convection and gets to be a stagnant upper 70s.

    If you want the temperatures equal between floors, set the fan function to on. That way the fan will run all night regardless of whether or when your a.c. conditions the air. Think of it like a Junior Whole House Fan. It won't be a ton of energy because it's just a fan. It's the compressor part of the a.c. function that is the big energy hog.

    With the fan running at night, the air throughout the house will circulate and mix and temperatures will be more even. The a.c. will still condition air when it needs to. The upstairs will be more comfortable.

    Think of it like oil and vinegar. It stays mixed and even while you're stirring, but starts to separate as soon as you stop stirring. So don't stop stirring. Or get a machine to do the stirring for you. For oil and vinegar, that's a blender. For a house, that's the fan function on your thermostat.

  • homebound
    9 years ago

    Jbmnd93,

    Exactly. Good description. Keeping the fan in the "on" position works for many of those townhomes and two-story condos around us, as well.