Collecting Old Windows and Glass for a Straw Bale Greenhouse


One day, while driving back from the Porterville Farmers Market with a good friend of mine who works with a lot of local community projects, we passed a glass shop in downtown Tulare. There were TONS of glass pieces – old windows, doors, you name it – just lying on the side of the building.

I started drooling, and longing, and wishing (loudly) about what a waste it all was, because those would be perfect for my dream greenhouse. My pal pointed out that this particular business owner regularly donates his old glass to groups like the Sustainable Communities Project, that helps people in the community build sustainable features on their property and within the community. Immediately I was like, SHUT THE FRONT DOOR!
I have been daydreaming for literally years now since we first bought our house, of building a greenhouse in the back yard, but the cost of glass panes was just too prohibitive for me to be really proactive about it. Glass is frikkin pricey. And with the advent of Pinterest and DIY mom bloggers like myself taking over the planet, folks at outlets that used to be affordable junk finding ventures (Craigslist, swap meets, yard sales) have caught on and now charge an arm and a leg for what used to fill landfills and cost pennies – old tired, barn wood, pallets, old windows, etc. etc.
I kid you not, finding old windows these days can often cost about as much as buying brand new glass! LAME!
So finding a source of glass – and enough of it to build my dream greenhouse – has got me a bit giddy, to say the least. We stopped in and verified that the glass was indeed up for grabs, and ever since then I have been in blueprint drawing, Pinterest pinning, DIY la la land! Since the supply and type of glass is hit or miss, this has been an ongoing project, where I take a free evening with my parent truck and see what I can load up. Its actually quite fun!
It also gives me time to really plan out how I am going to make this whole thing happen, since I plan on using alternative building materials to build my greenhouse, namely, STRAW BALES!

About Straw Bale Buildings

This straw appears small and light, and most people do not know how really weighty it is. If people knew the true value of this straw, a human revolution could occur, which would become powerful enough to move the country and the world. – Masanobu Fukuoka, The One Straw Revolution
The idea of building anything out of straw can seem laughable, but traditional cultures throughout the world have long recognized the value of straw and grasses a building materials. Straw bale structures in particular share a very American tradition (and I am a freak about recreating, preserving, and exploring American made traditions and cultural aspects!). Once the development of modern baling equipment in the late 1800s made it possible to compress straw and hay into bales, it wasn’t long before pioneers in the Sand Hills of west Nebraska started using bales of meadow hay lie giant blocks, to build everything from churches to houses.
The pioneer’s motivation to build with bales came from a shortage of locally available building materials, but baled hay proved to be equal if not superior to the standard building materials of the time. The tradition of building with baled materials has continued into our present time, with a huge revival in straw bale building in the 1980s, and the straw bale building frenzy is now beginning to spread to the world over.




To clarify, STRAW bales are made from the leftover stems of harvested grain, while HAY bales typically consist of finer stemmed grasses baled green with the seed heads. Hay bales are great for animal feed, and straw bales are typically used for bedding, gardening, or using as seating for outdoor events – they are the leftovers of the grain and grasses world. Basically, almost a kind of waste product.
When used as a building material straw is ridiculously versatile. As long as the bales are protected from moisture, they can be used to create structures that are durable, safe, and will last indefinitely. They are super energy efficient, environmentally safe, simple to work with and inexpensive. Straw bale structures can be traditional or innovative, big or small, light and spacious or cozy and intimate.




The enthusiasm for straw bale buildings for a lot of people (myself included) stems from the possibility and promise that bale construction might help alleviate the desperate global need for adequate and affordable housing. In many places in the world facing severe poverty, bale building can make economic and environmental sense. Bale buildings are ecologically sound, sustainable structures that are easy to build and maintain, that are energy efficient and compatible with renewable energy sources.


Picking Out Usable Window and Glass Pieces

When we look for glass panes, what we are looking for is basically thin, clear, intact glass pieces, with or without a frame. We are keeping it simple and versatile!
Single pane glass is generally 3mm thick, and has and R-Value (the measurement of ‘insulating ability’ of the material) of 0.95, and a U-Value (the measurement of ‘heat loss’ through the material) of 1.05. In the world of greenhouses, this generally means that to keep the greenhouse on the warmer side in winter, it would be a good idea to provide ample insulation in the walls and ceiling and any non-windowed area of the building – which is where the straw bales come in. They have a freakishly high insulation value. But more on that in a future blog post!
Since I plan to use my greenhouse primarily for starting seeds and nurturing young plants, we want to go with clear glass panels (not frosted or opaque), to better deliver direct light instead of giving diffused lighting. The clear covering of glass panes has the advantage of bringing full, direct light to starter trays and better warming the soil, encouraging germinating seeds to sprout and developing vigorous starter plants for transplanting.
If you plan on growing the plants to maturity in your greenhouse, a diffused covering has the advantage of providing even light for balanced foliage growth as well as preventing hot spots within the greenhouse. But this is as simple as buying a can of frosted spray paint at the hardware store.





When checking out the pile of secondhand glass and old windows for a greenhouse project, it is like some kind of funky scavenger hunt, or hobo Christmas, where we paw through the rubbish to find the usable pieces. The things we look for / avoid include:
Tempered Glass – Tempered glass panes are very strong and impact-resistant, and will withstand expansion and contraction during seasonal temperature changes, and they are much more durable and scratch resistant, making them great for greenhouses. BUT! They have a tendency to shatter when you cut them down to size, so much so, that it is generally recommended you don’t even try. Since we want to have a bit more freedom in designing our greenhouse, tempered glass is out for us.
Broken Glass – This one is a no brainer. Avoid glass panes that have huge chunks missing, large cracks, or any dangerous jaggedy portions. No Bueno!
Stress Cracks – Unless a piece is huge and salvageable, avoid pieces that show teeny tiny crack marks inside the glass, usually up in the corners of a piece. Even if it is not fully broken, these are called thermal stress cracks. They typically occur in windows when a thermal gradient causes different parts of the glass to expand by different amounts. At some point, the stress of the expansion may overcome the strength of the glass, causing it to break.
Extremely Thick Glass – Anything past 3mm thick will be a pain in the ass, dangerous, and even impossible to cut without industrial cutting tools. Just give it a pass, unless you want to use it in its entirety without any alterations.
Anyway, we are currently about one or two more trips to the glass shop away from having enough to break ground on this project. I am hoping to have this bad boy up by spring!!

I am crazy excited and will keep you folks up to date on our progress!