I am far from an expert, but like you, I have read a lot here. You can get some idea about light transmission using a photo light meter. They have almost become obsolete in the last years, but they have also come down in price and you might get one on Ebay. I don't have a clue how to use them, but I have seen others talking about using them to get the numbers they want. BB (before bankruptcy) I only used Nikon Cameras and they all did it automatically for lazy me. AH, the Good Ole Days LOL

1eyedJack and the Dawg

I donÂt know about tinted glass, but I looked for info. It would be a shame if you couldn't use those windows.

On this forum, it sounds like folks are concerned some tinted glass is designed to interrupt or block certain wavelengths in the light spectrum. If those blocked wavelengths are the ones that plants need for growth, it might be a problem.

And, this article says the following:
"Unless you intend to grow foliage plants only, avoid heat-mirror or tinted glass-often recommended for sunrooms to reduce heat loss-as it doesn't allow enough light in for your plants. A compromise is low-emission glass, which lets in less light than double-glazed, tempered glass, but has better insulating properties-and provides enough light for flowering plants."

But, National Greenhouse Company offers 1/8" thick bronze-tinted glass as a glazing option.

Also, BC Gardenrooms offers what they call "standard tint" as a glazing option, and they say itÂs "available in a gray, green or bronze with approximately a 15-20% shade. The standard tint is still conducive for plant growth."

I also found a post on another forum where someone briefly mentioned successfully using recycled tinted windows in their greenhouse, but they didnÂt say anything about how dark they were.

My guess is the degree of tint matters. I donÂt know how to measure the tint in your windows (could a glass shop could tell you?) If it looks dark to you, could you mock up a small glassed-in area with some plants, to see if they become etiolated from too much shade?

IÂm no help on thermal mass. If you donÂt get a lot of answers, you might try a new thread with "thermal mass" in the title to get the attention of folks who are more versed in the subject. Also (you probably know this already) you can find a lot of info in older posts by doing a search for "thermal mass" (put it in quotes) in the Greenhouse Forum search box.

Welcome to the forum! :-)

thanks folks... i am thinking of building a cold frame with them to try and figure out what is really going on. it'd be a darn shame if i couldn't use them for a greenhouse because i really hit the motherload with these. i guess i'll just have to wait and see.

Since there are literally hundreds of different coatings on "tinted" glass available, the only real way to evaluate your salvaged glass is to use a PAR meter. This measures the "photosynthetically active radiation" coming through the glass, which is what the plant uses. Relatively simple camera light meters measure the entire spectrum, but would not give you an indication of how much PAR is coming through the tinted glass. These meters are somewhat expensive when purchased new, but perhaps you can find a used one at a reduced price.

Here is a link that might be useful: PAR meter

I do not think you want to buy an expensive par meter. why not simply find someone who has one and use it. one measurement is all you need.

You might try a school or university.

However, I would do a test. a tomato outside and one inside the glass and see how they grow.

I would try new emerging seedlings. They should give a much faster answer. also try some lettuce and peppers etc. just to see if they grow the same.

A big plant would take a long time to show an effect. a new emerging seedling getting its first light would demand good light or not grow well. so you would have a faster answer. I would allow plenty of fresh air around the sides to try to eliminate a heat build up effect. You want the new seedlings to be the same except for the light through that glass.

by the way are the window dimensions in inches or feet. one seems big and one seems small.

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here's the windows.... lots of them. and they are 6.5 feet tall by 3.5 wide.

thank you all for your insight. i think i will have to find someone in the area with a PAR meter, that seems like the best idea. might be hard, but who knows... if i think about it enough, i'll probably manifest one where i would least expect it. that's usually how things happen.

an update.... all your info has been really helpful. although i can't find anyone thus far with a par meter, the general consensus is that the glass is a bronze tint which acts strictly to shade. i spoke to a manufacturer who was pretty confident that the glass will not block any of the visible light wavelengths. she said that there is a possibility that the windows could have a uv filter being that they were commercial windows, but this will not affect my needs. also the bc greenrooms company offers greenhouses with grey and bronze tints to offer some shade. so i am starting to think that these windows might actually be great for the super hot summers we have been experiencing lately. i'm still going to do some asking around, but i am rather optimistic at this point.

Good luck! I hope you'll post again about your experiences. Since lots of folks do build using recycled doors and windows, I'm sure this is a question that others will have in the future. You might be able to put some really helpful info in the archived posts for others to find. (Looking through past posts has been a lifesaver for me, that's for sure.) :-)

Please keep us updated on what you find out. They used to use the green colored plexiglas on green houses and they still let in enough light. I'm getting 10-12 4'x8' pieces of tempered glass. I'm not sure if its tinted or not. I plan to make a green house out of it. I would probably only use it in the cooler months unless I could put some shade screen or something over it in the summer and some form of fan or something (110 in the shade here in summer). Would also like to put some kind of misting system in it too. I'm sure some tinting would actually be good in the summer months.

Gemfire

i found a par meter!! the local horticulture research center has one and i am going in on monday to test the glass. i'm very nervous because they seem to think that it might be too shaded, but i am thinking that as long as they don't filter out the red light, i will still be able to design around the shade issue. clear glass on the ceiling and maybe on the south side might be enough to balance out the shade. darn it's hard trying to build a greenhouse for nothing!

OH COOL!!! Let us know what you find out. I hope you can use these windows!! This is interesting!

I came to this forum with the very same question. We scored tinted, mirrored argon gas filled dual pain windows and I too want to use them for a green house or conservatory. Please, I am very interested in any information you may have. Thanks,

the verdict... i went to speak to the folks at the mountain horticultural research center in asheville, nc and they gave me the info i was looking for. we did a par reading this morning at about 10. the ambient reading was 560.4 micromoles/second/metersquared. two readings from behind the glass averaged 476. this indicates about a 15% reduction in photosynthetically active radiation. while it would not be ideal to use glass like this for a large commercial operation, the gentleman i spoke to seemed confident that i could design around the 15% shading for my personal use greenhouse. i plan to use a different material for the ceiling and possibly the east/west sides. this will allow for much more light than if i were to solely use the tinted windows. i still want to build a cold frame this winter as an experiment, but i am pretty sure that this can work.

the par meter provided an instantaneous reading (15 seconds). as a matter of reference, most commercial growers require an average of 15 moles of light/heat energy per day. when we did our calculations, estimating only six hours of sun, my glass would provide between 9 and 10 moles per day. this number is significantly lower than what commercial growers would look for, but i think that my greenhouse location will recieve more than 6 hours a day, even during the winter months. maybe i will have to supplement with some artificial light in the winter, i will only find that out once the greenhouse is operational.

pat tea... i would suggest doing what i did and contact your local horticultural research center to do a par reading. seems that this is the only way to really know what types and amount of light are allowed to pass through your glass. the combination of the tint and your location might not be the best. i live in western nc and it is super sunny here the majority of the time, even in the winter months. we have a naturally long growing season. i don't know if the cloudier weather in the pnw would pose an issue, but that is something you might want to talk to your local researchers about. i spoke to a number of folks before i went to the research center - glass manufacturers, tinting companies, even the greenhouse companies that were referred to in a previous post- and no one really had any solid info to give me, only their personal opinions or another reference. other than getting a par reading done, the only other option seems to be building a cold frame. practically speaking, this would be the best way to experiment, it will just take a full winter to know your results. good luck with it, i hope you can use those windows. free glass rocks!

thanks to everyone for your ideas and suggestions... now on to design ideas. who's got some for me?

This is great information...thanks so much for taking the time to post your results. I've learned a lot from this thread, and I'm sure the info will help many others.

Anything to update? I have a chance to buy a hot tub enclosure but it is tinted. I’d also like to use as a greenhouse, but I’m hesitant.