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Venting st. gl.
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 Posted: Wed May 14th, 2014 04:28 pm
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Krueger
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Although this topic has been discussed previously, a recent trip to the Hackley Library in Muskegon, Michigan (adjacent to Lake Michigan) prompts a re-discussion. In the more recent past, there seems to be more studios venting to the inside, rather than the outside, and there seems to be several methods to do this. The one I personally viewed was interesting....a public library that is open 6 days a week has different heating/cooling requirements than does a church only used a couple days a week. Here, the library initially asked for proposals from 10 studios but they had to come to the library, not just make a proposal from photos....only 6 came, responded with bids, which were narrowed down to 2. The library wanted to install NEW thermopane glazed windows on the exterior, as the wind off Lake Michigan is very strong all year. That meant the stained glass would have to be vented to the interior. The selected studio, Shenandoah Studio, Front Royal, Virginia used small round plastic vents, 1 at each corner in narrow windows and 2 at each corner in larger/wider windows....It has been several years since the windows were done and the library is very pleased with the outcome....no condensation, no drafts, cracked glass replaced (all Kokomo and available), some releading.......

Here are 3 photos of some of the windows.....there are probably close to 45 windows total, about 10 of which are interior "dividers" between rooms, at the top of book stacks

https://www.flickr.com/photos/eridony/3029178248/in/photostream/

The middle photo (ornamental) the vents are visible......

Barbara Krueger
Michigan



 Posted: Thu May 15th, 2014 02:43 am
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Vic
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I doubt that those tiny vent plugs are doing anything, they are too small to allow significant air flow in those "large" windows. I'd say that the IG units are the reason why there is no condensation. As long as the IG units work, all is good
Vic



 Posted: Thu May 15th, 2014 06:36 pm
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gil
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I think that Vic hit the nail on the head. The vents are so small, relative to size of the windows, that they might just as well not be there.

Tom



 Posted: Fri May 16th, 2014 02:04 pm
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Courage
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I agree with Vic and and Tom, I can tell you that two small vents to the interior does not work here in South Louisiana with our humid, hot, and now cool climate... very strange weather.

Cindy



 Posted: Fri May 23rd, 2014 05:22 pm
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jjkrol
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I thought I would share a situation we experienced as a possible answer to the age old question of venting inside vs. outside.

We performed a full restoration of all the windows in this particular church.  Brick structure, wood frames and medium to large facility.  We then applied full new storm glazing on all windows.  We used Sussman frames and vented all horizontal members with three vents including the bottom and top.  I decided to take the two windows in the sacristy and put the vents to the interior since they had a full sash frame as a test.  Since they were using the same furnace (new geothermal) throughout the church, I assumed the air quality would not be sufficiently different between the windows. 

Winter came.  I had never had windows actually ice up, but the tower windows did so badly.  The water was coming out the bottom vents and dripping below.  The remainder of the windows were badly fogged.  Since I had never had this happen before I immediately suspected the new geothermal furnace.  I had never installed storm glazing with a geothermal system. 

Fortunately I am friends with an HVAC engineer.  He came to the church with his instrumentation and came to the conclusion that the church was pulling humidity from the basement which had a dirt floor, ground water flow was toward the foundation and not away from the foundation, and the new heat system was pulling its air from the basement.  Humidity levels in the church were as high as 80% in the tower where the worst icing was happening.  Despite heat drying air, the air was still over fifty percent in the church nave.  The church is rectifying the situation this summer, but it gave me a chance to observe the venting systems. 

I could definitely observe the airflow from the outside of the church through the storm glazing vents as clear "V" shapes.  I knew they were working.  On the window with the interior venting I could not see any clear spots.  Both types of vented window were just as fogged where the "V" shapes were not clearing it up.  This was a good lesson as to how much humidity actually passes through a stained glass window.  It also tells me that churches with high humidity levels, be they artificially made by humidifier or by large amounts of people, are better vented to the outside.



 Posted: Sat May 24th, 2014 03:21 am
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Vic
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one thing that you didn't say was on what surface was the fogging on.Front of stained glass, back of stained glass or inside of protection glass.
Totally eliminating moisture/condensation build up may not always be possible. But, you do want to keep it off the stained glass.

Last edited on Sat May 24th, 2014 03:22 am by Vic



 Posted: Mon May 26th, 2014 01:28 am
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jjkrol
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Fogging and icing were on the storm glazing.  Absolutely keep it off the stained glass!  That is a given. 

My point was that with the excessive humidity in the church, both windows vented in opposite directions were doing almost the same thing.  I took this as an extreme lab condition to test the two theories.  The outside venting was slightly more effective in this situation.  It was, however, a very slight difference.



 Posted: Tue May 27th, 2014 04:45 pm
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Krueger
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Some years ago I was asked to view a church with significant condensation on their stained glass windows.....come to find out they had (1) recently installed a new heating system, and (2) had also installed all new wood pews......I suggested they wait 6 months to let everything even out.....and contact the heating contractor.....it was not a stained glass problem.

Barbara in Michigan



 Posted: Wed May 28th, 2014 11:29 pm
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jjkrol
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Yes, Barbara.  This is a good lesson for all.

If what you have been doing is attaining great results and suddenly there is a change, it is probably not what you have done.

To have a friend who is a degreed HVAC engineer go to the sight and issue a report to the pastor went a long way to alleviate concerns that it was our problem.  If I did not have this relationship, I would have still hired a very reputable engineer in the field to analyze the situation. 

It is all to the reputation of the studio that proper steps of research had to be done even though I knew it was not my problem.  Even the perception of a problem can cause a lot of ill will.  The reputation of a lot of artists and craftsmen in the studio is at risk, not just my own.






 Posted: Thu May 29th, 2014 06:43 pm
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Rebecca
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jjkrol wrote:
I thought I would share a situation we experienced as a possible answer to the age old question of venting inside vs. outside.


... Despite heat drying air, the air was still over fifty percent in the church nave. 
...


This is a bit misleading. Heat doesn't dry air. Warm air can hold more moisture than cool air. If you have warm air with a high moisture content and the air is cooled sufficiently, you will have condensation - some of the moisture will turn to liquid form. If you draw this liquid moisture off and re-heat the air, it will have less moisture than it did before it was cooled. What is confusing is that we measure moisture in air with "relative humidity." We compare the amount of moisture in air at a certain temperature to the maximum amount of moisture that air will hold at THAT temperature. So if we take cool air at a certain relative humidity and warm that air, the relative humidity of the air will go down, but the actual amount of moisture (water vapor) in the air will remain the same. (In a controlled environment.)

Rebecca



 Posted: Thu May 29th, 2014 08:56 pm
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Vic
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" If you have warm air with a high moisture content and the air is cooled sufficiently, you will have condensation"

So in JJKROL's Church. If you vent to the inside, you are allowing warm/high RH air to come into the cavity and come in contact with the cooler surface of the protection glass forming condensation on the protection glass.
If you vent to the outside, you allow cold air in the cavity and come in contact with the warm surface of the stained glass, getting condensation on the stained glass.



 Posted: Thu May 29th, 2014 10:21 pm
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jjkrol
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Rebecca, I believe your critique is correct.  This is why I pulled in the big talent with the ones with the scientific instruments.

Vic,  I had the exact feeling as you have said about venting to the outside.   That is until this church where for the first time I had the opportunity to vent one window on the inside and the other on the outside in a very extreme situation.  The relative humidity was the same on the inside of both windows and the fogging of the storm glazing was exactly the same on both windows with no condensation on the stained glass on either window.  The only noticeable difference was the six inch "V" shaped airflow noticeable on the outside vented windows. 

I was very surprised that either direction did not lead to condensation on the stained glass, especially the windows with the venting on the outside, and in both situations the condensation was on the storm glazing.  Try to figure that one out!



 Posted: Fri May 30th, 2014 03:13 am
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Vic
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is there a chance of inside air "leaking" through the wall cavity? Meaning between the exterior wall surface (sheathing) and the interior wall covering (like plaster board). If so, warm air is still meeting the colder air on the storm glazing



 Posted: Fri May 30th, 2014 10:48 am
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jjkrol
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All the frames were painted which means for us, they were scraped, any holes filled, coat of primer and two finish coats.  The panels themselves are sealed into the rabbits.  I do not see how air would leak into the space as there is no exposed brick, plaster or other substance since the aluminum storm glazing was fastened to the wood also.  There was a four inch air gap between the stained glass panels and the storm glazing.

This means, from inside to outside, we have stained glass, sealant, primer, two finish coats, aluminum, glazing tape, glass and final sealants around glass and perimeter aluminum.



 Posted: Fri May 30th, 2014 05:54 pm
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Kal Tiki
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I have been standing on the sidelines waiting for the discussion to shake out a bit and get all the info. It's very interesting to see how different designs of protective glazing work well or fail. I'm in a similar environment (Boston) as Michigan so let me throw my two cents worth in.
 Any type of protective glazing creates a micro environment that can be very different than the general environment of the church. Obviously the isothermal glazing would work drastically different on the north and south sides just because of the Sun exposure. Even with the rising damp from the basement producing 80% humidity north and south sides will be quite different. And the specific environment of the stained glass and protective glazing changes drastically with the seasons. Up north here we can be below 0 for a week in winter and above 90 for a week in summer.
 Some of the earliest work in iso thermal glazing was done by Tony Jutte in Holland where the environment is quite different than Michigan. He understood and tested the glazing for basic air movement principles that most HVAC mechanics understand. You can only get a larger volume of air moving through the space of the sg and protective glazing with openings the same size in the top and the bottom. I seem to remember he was saying that you needed a minimum opening of at least 3/4" away from the window and across the whole bottom otherwise turbulence would slow the air flow.  And you would also need an equal amount of square inches opening at the top of the window.  The little midget louvers just don't provide close to the airflow needed for exterior venting or interior for that matter.
 To complicate matters in isothermal glazing in the northern climates is the extreme cold in winters. If the exterior glazing is a single layer and you have 80% humidity in the church then in practical terms you have designed the perfect dehumidifier with the water condensing between the layers. I don't believe it is possible to build the perfect single layer glass isothermal glazing system in northern climates without insulated glass. There will be times when condensation occurs with single layer. This will happen especially on the north side of the building where there will be less chimney air flow effect whereas the south side will be driven by the low angled sun of winter.
 The example of iso thermal venting presented at the AGG Conference in Pittsburgh conceded that condensation would occur and allowed for water to drain at the bottom through aquarium stone. However, if there is enough room for water to drain then there is also enough space for cold air to be drawn up during the chimney effect which could be a potential problem in itself. The basic principle of completely sealing the window off from the outside environment is isothermal glazings greatest characteristic. But in order to truly seal the stained glass off from the exterior environment in northern climates double layer insulated glass units would ideally be used.
 Of course cost is an issue and very few wood or stone openings have an easy way to apply insulated glass. Isn't the issue really to do what is right for the window and provide the best long term solution? In addition to fully protecting the window from the environment there would be additional heat and air conditioning savings.
 I started my rant talking about specific micro environments. That also includes even small specific areas in the space between the protective glazing and the stained glass. Sometimes the condensation might be in an upper or lower corner only. Sometimes all over. But sometimes we also see things done completely wrong and there is no problem. I am always amazed when I see some windows on the south side of a church with sealed single layer of plate glass that has been there for 100 years and it looks fine. These individual examples of micro environments delight in confusing the issue. It is best to look at the conclusive failures, like the Michigan example that spurred this thread, as baselines for how to look beyond budget constraints and wishful single layer solutions and really look at all of the environmental issues of the interior and exterior of the church and what is the real solution for the properly functioning isothermal glazing for the next 100 year life of the window.  Dan Maher
 



 Posted: Fri May 30th, 2014 09:40 pm
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Vic
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It's also important to remember that isothermal glazing studies and techniques where done in Europe and the UK. While they may have weather similar to ours, many of their Churches are NOT the same as ours. Isothermal glazing was mainly developed to protect Medieval stained glass. These windows were/are living in unheated and unairconditioned stone buildings. A totally different environment then most of our Churches.
Ton (correct spelling)Jutte has for years been discussing "sick" buildings. Concluding that vented protection glazing is a waste of time if the general environment of the building is poor. I was with him and David Frazer in a Church in Brooklyn a number of years ago. We were there to figure out how to glaze and vent the stained glass. After a few minutes Ton wanted to go up to the attic. His conclusion, properly vent the building first. Then come back in a few months and look at the stained glass.



 Posted: Fri May 30th, 2014 09:53 pm
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Kal Tiki
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I agree Vic. If you have a sick building even the best designed system may not work. There are fewer churches with dirt basements but in my earlier years I would often walk into a church and see the efflorescence around the stone. I would ask if they had a dirt basement and they would always be surprised I asked, and most time they would say yes. Also seemed to be a correlation between the dirt basement, rising damp, and plaster blooms at the edges of the lead.



 Posted: Sun Jun 1st, 2014 04:44 am
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jjkrol
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I should know that venting would carry into quite the pool of varied techniques. 

Please remember that my whole point all along is that we do not have problems with our venting and our church windows as a general rule.  This was an isolated case that I thought I would share.  It is the case of a "sick building" as someone said earlier.  It was such a flip flop as to what our outcomes usually are that I knew it was not our storm glazing vents. 

I think there will always be questions on venting as long as there are multitudes of different church environments and we need to adapt to those variances.  The important outcome as I see it is twofold, if it has been working well in the past then it is most likely not the venting and the search needs to go beyond the glass.  The second point is do not be too afraid to call in a professional in their field like my friendly engineer in HVAC.

Last edited on Sun Jun 1st, 2014 04:45 am by jjkrol



 Posted: Sun Jun 1st, 2014 12:39 pm
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Vic
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Since this happened over the winter. Has the Church done anything to fix the problem?
If you go through another winter under the same conditions, it would be interesting if you fully seal a window (no vents) and see what happens.



 Posted: Sun Jun 1st, 2014 10:28 pm
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jjkrol
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The church is supposed to do landscaping to keep the water from flowing toward the building to limit the exposure to moisture in the basement.  The current landscaping was definitely allowing water to flow to a brick and then stone foundation. 

Vic, it would help me if you would develop your thought process more as to sealing the vents and why you think that helpful.  There is an "however" in the worst bell tower windows.  These windows were the only windows surface mounted to the brick due to design, which meant that these were the only ones that had brick exposed between the storm glazing and the stained glass window.  The bell tower had the highest humidity readings approaching eighty percent.

Last edited on Sun Jun 1st, 2014 10:30 pm by jjkrol



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