Best way to measure wall/ceiling temperatures
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  1. #1
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    May 2007
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    So Cal
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    Best way to measure wall/ceiling temperatures

    I hope this is the right place to post this question. (I looked, but didn't see a forum that looked more appropriate)

    Given the rediculous electricity rates in CA, I'm trying to do my best to reduce my KWH consumption. Replacing the 30 year old system with a zoned system that lets me only cool the areas of the house that we live in has gone a long way so far, but I'm interested in adding insulation (probably air krete because I already have 1" rockwool in the wall) where needed to control the heat gain as well.

    I bought a temperature gun and was looking for suggestions as to the best way to measure the wall/ceiling temps. Currently with the upstairs off, even though the main upstairs & downstairs areas are open to each other, the temperature separation between downstairs and upstairs can be up to 10 deg F. This doesn't seem the ideal conditions under which to compare wall/ceiling temp. Do you guys recommend trying to have the whole house at the same temperature when measuring? Perhaps just running the fan but not the AC? Any thoughts would be appreciated so I can do an intelligent analysis of what my insulation needs are.

    Thanks,

  2. #2
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    May 2007
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    Upstate SC
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    What model gun did you buy, do you like it, is it accurate, repeatable results? I want to get one to checkmy insulation in the attic by shooting the ceilings and also check around lights to check for temperature increases from air leaks. I know this doesn't answer your question - sorry for the minor threadjack.

  3. #3
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    May 2007
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    So Cal
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    I don't mind you asking at all. I haven't gotten it yet (it got delivered today), but it's the top, non professional model (if you know what I mean). It's supposed to be accurate to +/- 2-3 deg F... I think it depends on the temperature.

    The model is the Raytek (RAYMT6) MT6 Mini Temp Infrared Thermometer. If you see one by Fluke, it's the same (Fluke is the parent company of Raytek). It retails for $99, but I got it for much less than that.

    Best of luck

  4. #4
    Join Date
    Jul 2004
    Location
    Massachusetts
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    Tips on savings with indoor temperatures.

    The first and best way to save in most homes is to first seal all the leaks that allow 'stacking' of the air in the home. This is also referred to as the 'chimney effect and is worse in cold climates. But it's important to understand that for each molecule of air (literally, each molecule) that escapes from a vessel, in this case your home, another molecule must infiltrate to replace it. Nature just doesn't easily tolerate pressure differences so air leaving and entering the structure is one of the greater heat losses over time.

    The second great energy loser is an unsealed duct system that is in an unconditioned space. If you have attic and/or basement ducts and those areas are not supposed to be conditioned spaces, then it's imperative that the ducts be thoroughly sealed to prevent exfiltration and infiltration of air molecules.

    Now for the zone issue. It's interesting to note that zone controls were developed not for the ability to maintain separate temperatures but rather, just the opposite, to equalize separate areas. You are not alone in attempting to maintain separate temperatures but your impact on costs might not be a dramatic as you'd expect. Here's why. In most homes, the walls and ceilings between conditioned spaces are NOT insulated. It's a law of physics that heat will flow from the warmer area to the colder area and the greater the temperature difference, the faster it flows. So if you have two rooms 2 degrees different from each other, there's not too much heat flow. But let's assume you close off a whole room in your otherwise conditioned home. As the room warms up, the walls in the conditioned space do as well and you end up transferring heat from that room into your conditioned space. So really, the greatest savings is when you don't have any temperature differences but rather turn the t-stat UP for cooling or DOWN for heating. You can save substantial amounts of energy for every degree of change.

    I've measured ceilings in 14-foot rooms before and it's amazing how little temperature difference there is between the ceiling and 4 feet off the floor.

    And BTW, don't seal the house too tight or you'll end up with bad IAQ issues.
    If YOU want change, YOU have to first change.

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  5. #5
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    May 2007
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    So Cal
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    Thanks for the tips. I think the reality of how I use my AC might end up saving me money (versus my old non-zoned system), but only time will tell.

    Basically I open up the upstairs windows at night and let the house cool down... Lately it's been getting down to low 70s inside by the morning. I then close up the house for the day as I head off to work. By the time I get home, the upstairs has risen to say maybe 85-86 or so and the downstairs has been cooled to 76. Then when the outside temp gets below the upstairs temp, I open the upstairs windows and let the hot air escape.

    So far, it seems to be working well... certainly much better than when the I had no zones and the upstairs would be 4-6 degrees or so warmer than the downstairs (I had pretty bad duct volume to upstairs before). Again, I would open the upstairs windows once it got cooler outside than upstairs, but I had to wait much later to do that and I was pushing cold air upstairs in addition to downstairs. I can't see it not being more efficient. (Well that and the 19 SEER compressor I got [so the compressor can run either 2 or 4 tons to match the zoned CFM] versus the 30 year old hunk of junk that got removed)

    I don't think I'll have too much trouble with duct leakage as they just reducted the whole house.

    I would imagine as I more tightly seal the downstairs, I'll get less stack effect and thus the upstairs won't get quite as hot.

    Anyway, I totally agree that there will be some 'bleeding' of heat from the unconditioned space to the conditioned space, but it can't cause more of a load on the AC than attempting to cool the entire house. The way I run things right now, I basically just put off cooling the unused upstairs until we can open the windows and let the breeze do it.

    Thanks,

  6. #6
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    Jun 2002
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    Merrimack Valley, MA
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    Quote Originally Posted by glewis29 View Post
    I don't mind you asking at all. I haven't gotten it yet (it got delivered today), but it's the top, non professional model (if you know what I mean). It's supposed to be accurate to +/- 2-3 deg F... I think it depends on the temperature.

    The model is the Raytek (RAYMT6) MT6 Mini Temp Infrared Thermometer. If you see one by Fluke, it's the same (Fluke is the parent company of Raytek). It retails for $99, but I got it for much less than that.

    Best of luck
    I'd be curious how the gun works for you. I've toyed with getting such a device to pinpoint issues in my 31 year old home. I think I'd have better luck in the winter up hear in New England, but there's nothing like a nice visual to tell the story. Perhaps post a picture or two of the result?

  7. #7
    Join Date
    May 2007
    Location
    So Cal
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    I'll be sure to reply back with the details of how it worked for me. For the price, I felt it was worth buy the toy... err... I mean tool.

  8. #8
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    May 2007
    Location
    Upstate SC
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    GLewis29, I saw that brand and about got it, but went for the Mastercool (MAS52224-A)- no real reason I picked it over the one you got. Let's compare accuracies/repeatability info. Mine's due in the first few days in July. I asked over on the pro's tool message board at this site for recommendations, but no one had any and my thread morphed into two old friends catching up on old times. I didn't care because I probably couldn't afford their recomendations anyway.

  9. #9
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    Apr 2002
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    11,808
    raytech, every reading will be "point 0" or "point 5"
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  10. #10
    Join Date
    May 2007
    Location
    So Cal
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    Ok, just got it and dang.... that's freakin' cool.

    Here's some initial observations. Measured my AC return register at ~75*F and my main exhaust register at ~50*F. So it seems like the AC is cooling fine. I went around and measured basically every surface in the house (including the wife's lovelies...she wasn't too happy about that. )

    Part of my ceiling has had the original 2" rockwool replaced with 6" fiberglass. Two areas right next to each other, one with the old and one with the new were 2-4* difference.

    I measured the West wall which is gettin sun and the North wall which is in the shade in the same corner of a room at the same height and the West wall was 4* hotter. At the moment, this wall gets sun from about 1pm to 8pm. I think that'll be the first candidate for the Air Krete.

    Right now it's 85*F upstairs and 77*F downstairs and 82*F outside. Most of the upstair walls are well hotter than the room (85-91*F range)

    Like Carnak said the readings are on the half degree, but for what I'm doing, relative readings are what's important to me.

    I'm hoping tomorrow I can monitor it throughout the day to establish a basepoint before I get the West wall filled with foam.

  11. #11
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    May 2007
    Location
    So Cal
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    Just a heads up in case anyone was curious. I did some samples on Saturday in between yard work. I determined a couple things.

    First off, the temperature gun isn't extremely accurate, but it does allow one to get a general feel for which areas are giving off heat to the area.

    Second, I set the thermostat in all 4 zones of the house to 76. It wasn't a terribly hot day with the high being somewhere in the 85-90 range and from about 12 to 6pm, the AC stayed on, cycling between 2 and 4 tons. This is a lot more than other hotter days I've had where I let the upstairs get hot and only cooled the bottom zones. Also, the bottom zones never got above 74. The cool air coming from upstairs was enough to keep the downstairs cool too.

    I also determined that the main heat gains in order came from the attic walls (but not the attic floor), the ceiling, and the upstairs west and east wall (when the sun is on them).

    I figure if I can fix some of the heat gain to the upstairs, it'll help with the balance issues to the downstairs.

    All in all, I'd say it was well worth the cost for what I learned.

  12. #12
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    Apr 2002
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    Maybe if you are going inside and outside taking readings, let the gun sort of adjust to the ambient temp first.

    What can happen when all that cool air falls downstairs is it can suck in outdoor air into the upper levels. Maybe around openings in ceilings or down/through wall cavities.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  13. #13
    Join Date
    Apr 2002
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    11,808
    backdraft a bit on cheap bathroom fans, the path of least resistance
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

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