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Replacement window advice

hifiaudio2 | Posted in General Questions on

I have CRAZY low humidity in my Nashville house right now, the hygrometer is measuring 7% at the moment… The house is about 20 years old and has the original wood windows, which have had rot repaired a few times, etc. I want to replace these with a quality vinyl window to help with efficiency and humidity control. (Some of you may remember other posts of mine when we moved into this house a while back that I added about 8-9″ of open cell to the attic plus encapsulated and foamed the crawlspace. I have the summer humidity under control.. it never goes above around 51% in the crawl, the living area, or the attic, but the winter humidity is WAY too low. I am hoping that replacing the drafty the windows will go a long way to solving this. I have also thought about adding an inline whole house humidifier, but I have seen you guys say that is a bad idea before…. I think….

So, if there a “top choice” in vinyl window brand and model that the experts here love?


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  1. hifiaudio2 | | #1

    Right now the humidity measures 33% in the crawl (the crawl does get some conditioned air from the HVAC), 10% in the main living area (2 story, 6400 sq ft house), and 23% in the attic.

    I was thinking of installing this humidifier....

  2. JC72 | | #2

    I would not opt for the whole house humidifier. It's just a Band-Aid. The better question for your windows is whether to opt for inserts or full-frame replacement.

    I feel you pain as I have a similar problem with my 18 yr old wood frame (out of square) windows.

  3. GBA Editor
    Martin Holladay | | #3

    John Sexton,
    John Clark is 100% right with his advice. You don't want a humidifier. The use of a humidifier may lead to moisture problems in your wall assemblies or roof assembly -- and such problems are often hidden.

    Low indoor humidity during the winter is caused by leaks in your home's thermal envelope. (Escaping air is replaced by outdoor air, which is very dry.) While some homes have leaky windows -- and your house may be one of them -- leaky windows are rarely the culprit when it comes to air leaks. The first two places to look for air leaks are (a) the attic (top-floor ceiling) and (b) the basement or crawl space.

    Here are links to two relevant articles:

    Air Sealing an Attic

    Air-Sealing a Basement

  4. hifiaudio2 | | #4

    OK thanks... but is the attic and crawlspace likely to be the source of air leaks for me since both are foam insulated now?

  5. GBA Editor
    Martin Holladay | | #5

    Foam insulation usually cuts down on air leakage, but there is no guarantee that your insulation contractor addressed all the air leaks unless the contractor was looking for air leaks and verifying the results of the air sealing work with a blower door.

    If your indoor air is very dry, your thermal envelope has major leaks.

    If you aren't sure where the leaks are, the best way to find them is with a blower door.

  6. Expert Member
    Dana Dorsett | | #6

    This is way more than air-leaky windows. If you hate your windows go ahead and replace them, but don't for a second think that it's going to solve a low indoor humidity issue.

    Poorly balanced duct designs or hot air systems that take in ventilation air whenever the air handler is running can drive ventilation rates sky high during cold weather when the outdoor air is dry. Capping or turning off any pre-existing ventilation air intake on the duct system would be the first step.

    Buy a ~$50-100 differential manometer online and start measuring room-to-room pressure differences when the air handler is running, with the doors open/closed etc. An Energy Star house's ducted HVAC would have no more than 3 pascals (0.012 water inches) of room to room pressure difference under all operating conditions. Most cheap manometers have resolution of 0.01", so anything over a 0.01 would probably be a "fail", but as long as it's not over 0.03" isn't likely to be the ultimate dry-air culprit. Start fixing the balance & return paths on the rooms with the highest differences first, work your way down. When you're done fixing all the room to room pressure differences to the sub-0.03" level, start spot-checking room to outdoors pressure differences.

    The % RH without the temperature to which it's relative is kind of meaningless. A measurement of 7% @ 75F would have about the same humidity as 33F air that measured 33% RH. The crawl space probably isn't that cold, and the rooms upstairs may not be that warm, but without the relative temperatures there's no way to assess the difference in absolute (rather than relative) humidity levels.

    A measurement of 7% @ 70F corresponds to a dew point of +6F. That happens to be the absolute LOWEST outdoor dew point measured in Nashville this past week:

    The average dew point has been much higher at +23F, so I suspect measurement error here, unless you have some serious DEhumidifcation equipment running. (What are you using for a hygrometer?) Air infiltration alone (even at fairly high rates) would deliver much higher readings than 7% over the past week. Air with a +23F dew point results in 16% RH @ 70F. The outdoor air dew point right now (3:05 CST, 2 January 2018) in Nashville is +8F, so with truly massive air infiltration rates you might drop to sub 10% RH @ 70F indoors (but it would have to be pretty massive.)

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