Last Updated on July 2, 2025 by Team Ideas24
Every day of the week, someone is busy replacing their ‘old’ timber framed windows with ‘whiz-bang, no maintenance’ windows. And every day, thousands of glasshouse kits are sold. DIYer Cheft, made the connection and built a greenhouse from other people’s trash. One of those is showing how to build a greenhouse from old windows.
This greenhouse project is one of the most inexpensive builds we’ve come across. Although building a greenhouse from old windows is cheaper than buying a quality new kit, you’re still up for the material expenses such as timber for the framing plus the cost of glass. The builder of this greenhouse found a way around this issue by using salvaged windows.
As you can see, the frames and glass in these old windows make perfect building blocks for a greenhouse. You just need to build the frame on which the windows are to be installed on to. You’ll spend very little, if anything, on the windows, depending on where you source them. Craigslist and Gumtree are great sources for these items. You’ll also find lots of timber there so all you have to buy are screws, caulking and latches.
Keep reading below on how to build a DIY greenhouse old windows structure.
Contents
How to Build a DIY Greenhouse Old Windows Project
Materials
- Salvaged Windows
- 4×4 Timber
- 2×4 Timber
- Gravel
- Cinder Blocks
- Screws
- Paint
- Corrugated Sheets
Tools
- Hand Saw
- Hammer
- Power Driver/Drill
- Shovel
- Paint Brush
- Measuring Tape
Steps on How to Build a Greenhouse from Old Windows
Look for old windows and save every one you get. After you have enough to build a small greenhouse, lay them out and play a game trying to make two pairs of “walls” of the same height. Two to three inches won’t matter as you can cover the difference with wood. Smaller holes will need to have glass cut for them or filled with something else. Keep in mind that one end will need a door and the other a hole for a fan as you go through on how to build a greenhouse from old windows.
Using the windows you chose as a guide, construct a frame for each wall. Use good lumber for this, as it is the structure that holds all the weight. I used all 2x4s for the studs and 4x4s for the corner posts. Choose a length that allows at least 14″ of the stud to be placed in the ground for support.
Start placing the walls up, bracing well so they don’t fall over. Be sure to check that they are level.
To avoid certain problems with pesky city building permits when going through how to build a greenhouse from old windows, I built the structure shed height and did not pour a concrete foundation. Instead I buried cinder blocks to stabilize the 4 x 4 corner posts. They keep it from moving an inch.
I used some nicely coated deck screws to affix the windows to the frame. This will allow for easy removal and replacement if any should break. This side facing the camera has the empty window for a fan.
I was able to find someone who needed rocks removed from their yard. Using rocks or stones is good for two reasons: good drainage and heat storage.
This was tricky. I ended up getting siding from an old shed someone had torn down. Any material you use, look for lightweight and waterproof material. Be sure that you have some that will open for ventilation, at least 20-30% of your floor space. You can get by with less if you use a fan for ventilation. Also build the slant roof with at least a 4 degree pitch, otherwise rain may not sheet off well.
I found an old picnic bench table and this fan and shelf in the garbage. I figured I can use them in my greenhouse and save them from a landfill.
Use a good outdoor caulk and seal all the cracks and holes between windows. Paint the wood to protect it from the weather when knowing how to build a greenhouse from old windows.
I was unhappy with having to remove the fan/vent window and having to prop it against something while cooling the greenhouse during the day. The frame was already designed to fit the window into it. I decided to have it slide up and be held in place.
I started by salvaging some hinges from an old entertainment center. They are the kind that sit completely outside the door. Plus these had a unique shape that fit around a right angle. This allowed the wooden “stops” to swing in place and hold the window up while I was venting or when the fan is in place.
Across the frame I nailed some boards to hold the fan window against the frame. Lastly, I found an old pulley and fastened it to the window so I can pull it up easily.
A local community greenhouse was torn down and replaced. I was able to get some great parts. Here is a picture of the new window system. It originally opened the windows on the side of the greenhouse. The wheel turns and rotates the gear attached to the pipe opening the windows. Makes opening and shutting easy. While every window now must be open at the same time, I can control the angle at which they are open.
Also pictured is a gutter claimed from the trash. The hinge side of the roof windows always leaked profusely. The gutter catches the water and stores it in a bucket for easy watering.
Spring Shading: Bought some secondhand rolling shades which are working great when knowing how to build a greenhouse from old windows. They easily roll up and down the south facing wall while not taking up too much room.
Here is the greenhouse in a mild winter. I overwinter many potted perennials inside, and I also build a greenhouse from old windows. To insulate the roof, I stretch a sheet of poly across the top to keep out the drafts.
All the wood is doing well. I hope that, with care, the greenhouse will last over 10 years. It has changed the way I garden, making my backyard much more productive.
Could this be the project that’s perfect for improving your garden? ?
Thanks to cheft for this great project on how to build a greenhouse from old windows.
Energy Efficiency in Your Greenhouse
Building a DIY greenhouse old windows structure is a fantastic way to upcycle materials while creating a nurturing environment for your plants. Ensuring your greenhouse is energy efficient can help reduce costs and environmental impact. Here are some strategies to maximize energy efficiency in your greenhouse.
Utilizing Thermal Mass
One effective way to increase energy efficiency is by incorporating thermal mass into your greenhouse design. Materials like stone, brick, or water barrels can absorb heat during the day and release it slowly at night, maintaining a more stable temperature. When learning how to build a greenhouse from old windows, consider adding these elements to help regulate the internal climate naturally.
DIY Greenhouse Old Windows Project Gallery
Click on any image to start lightbox display. Use your Esc key to close the lightbox.
Passive Solar Heating
Design your greenhouse to maximize sunlight exposure, especially during winter months. Orienting the structure to capture the most sunlight and using old windows with good solar gain properties can significantly reduce the need for additional heating. Implementing passive solar heating techniques is crucial when figuring out how to build a greenhouse from old windows effectively.
Insulation Techniques
Proper insulation is key to retaining heat within your greenhouse. Use bubble wrap or thermal screens to insulate the old windows, especially during colder months. This simple yet effective method helps keep your greenhouse warm without excessive energy consumption. Insulating your greenhouse is an essential step in how to build a greenhouse from old windows for energy efficiency.
Ventilation and Air Circulation
Good ventilation is necessary for maintaining a healthy greenhouse environment, but it should be managed efficiently. Use vents and fans to circulate air, but consider installing automated systems that open and close vents based on temperature and humidity levels. This ensures your greenhouse stays ventilated without losing excessive heat, an important consideration in how to build a greenhouse from old windows.
Energy-Efficient Lighting
While natural light is ideal, supplemental lighting may be necessary, especially during shorter days. Opt for LED grow lights, which are energy-efficient and effective for plant growth. Integrating these lights into your setup when building a greenhouse from old windows can reduce energy use while ensuring your plants receive adequate light.
Water Management
Efficient water use also contributes to energy savings. Install a rainwater collection system to utilize natural resources for watering your plants. Drip irrigation systems can further reduce water waste and ensure consistent moisture levels. This sustainable approach should be part of your plan when you learn how to build a greenhouse from old windows.
Ensuring energy efficiency in your greenhouse from old windows not only helps the environment but also reduces operational costs. Incorporate these strategies into your greenhouse design to create a sustainable and productive growing space.
Conclusion
Knowing how to build a greenhouse from old windows is an affordable and environmentally friendly initiative. This method not only recycles goods but also generates a special and useful area for plant development. If well planned and constructed, your greenhouse will be a useful and sustainable addition to your landscape.
