[Greenbuilding] doing something about condensation on inside of single pane windows

Fri Nov 22 13:55:33 CST 2013

I realize that in phrasing my question I neglected to indicate the dynamic
nature of this problem. In the (near) future, but not this winter, (a) the
space will be heated, and (b) I will have done something about adding
interior storm windows and eventually also exterior. But your suggestions
are all good and appreciated.

The high relative humidity is I think due in part to recent imperfections
in my gas water heater venting regimen which I have now corrected. The
other part is that contrary to many climates ours experiences the highest
humidity levels in the winter. For comparison, in the house, with the
woodstove heating for an hour or two per day, the RH is between 55 and 60%.

I did not have my window maker use insulated glass because I'm sick of them
failing, and I've understood that well sealed storm windows can achieve a
comparable thermal benefit. Upstairs in the house we have the original 120
yr old single pane windows and not very fancy aluminum framed but carefully
caulked storm windows and find it very cozy.

On Fri, Nov 22, 2013 at 9:32 AM, LarenCorie <LarenCorie at axilar.net> wrote:

> From: Reuben Deumling <9watts at gmail.com>
>
>
>  Basement with 2.5" of styrofoam insulation in floor,
>> 10.5" of cellulose in walls, 8" of fiberglass batts in ceiling.
>> Quite a bit of attention spent on air sealing, door gaskets, etc.
>>
>
> Hi Reuben.
>
> The first thing that strikes me is the extreme imbalance
> with all the effort that went into high levels of insulation
> that will have a relatively slow payback in your climate,
> while ignoring the huge heat losses through those single
> glazed windows. For instance. just one 32" x 16" single
> glazed window has much heat loss as near 20 lineal
> feet of you thick cellulose insulated walls.   You could
> cut that by as much as over 60% just adding a second
> layer of glazing.   The cost-effectiveness of curing that
> huge hole in your insulation is vastly greater than that
> of the very high levels of wall insulation. Insulation is
> (usually) most cost effective when used in the most
> poorly insulated area.  A lack of attention to those
> windows is figuratively like a bucket with a hole
> in it, or leaving a door ajar.
>
>
>  temperature dropped to 30F, a lot of condensation
>> suddenly appeared on the inside surfaces of my single
>> glazed wood windows. The interior temps in the presently
>> unheated space remain in the fifties. Relative humidity
>> inside has stayed pretty constant around 75%.
>>
>
>     With 50F air and 75% RH, the dew point is 42F.
> 55F and 75%, DP is 48F. With your single glazing the
> interior glass surface will be about 35F, so of course
> you have condensation.     With R2 glazing, the interior
> surface would have been more like 43+F barely above
> the 50F dew point, with the very high interior RH, but
> above it, nonetheless.  Triple glazing (9/16"-7/8" air
> spaces) would be more in line with the rest of your
> insulation, and would further reduce the risks from
> excess condensation. But, you really need to address
> the high humidity issue (to below 50% in Winter,
> which would make it 25% at 70F.  With the 50F
> 75% the 70F will be 36%, not bad, but it leaves
> you with that very high humidity in your basement
> and inside your walls.  Dew point and condensation
> are not just on your windows. They are also going
> on inside your walls, especially if you have not done
> anything (foam sheathing) to raise the temperature
> of the potential condensation planes.
>
>
> > (1) saran wrap trick on the inside of the windows
>
>   Sure.......two layers (or more) are better than one,
> and since you probably don't spend a lot of  time in
> the cold basement you might just use foam plugs to
> insulate them to R7 or higher.
>
>  (2) desiccant stations (Dri-Z-Air)
>>
>
> I am not knowledgeable about that.
>
>  (3) other?
>>
>
> How are you heating you domestic hot water?
> A heat pump water heater would dehumidify
> the air. Heating the basement would be another
> strategy, though it would probably not be very
> energy efficient..
>
> -Laren Corie-
> Natural Solar Building Design and
> Solar Heating/Natural Cooling/Energy
> Efficiency Consultation Since 1975
> www.ThermalAttic.com  (many new
> photos and pages, coming soon)
>
> Read my Solar house design articles in:
> -Energy Self-Sufficiency Newsletter-
> www.essnmag.com
>
> Home base-LittleHouses YahooGroup
> http://groups.yahoo.com/group/LittleHouses/
>
> Founder-WoodGas - Power from wood
> http://groups.yahoo.com/group/WoodGas
>
> Founder-RefrigeratorAlternatives YahooGroup
> http://groups.yahoo.com/group/RefrigeratorAlternatives
>
>
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