Big Warm Door-Wall




About: BongoDrummer is co-founder of Flowering Elbow. He loves to learn about, share, invent, and make things, particularly from waste materials. Check out his youtube channel:


As part of the Flowering Elbow workshop we wanted a big entrance, the kind of size you get at garages, that you can drive vehicles through, throw open on sunny days to bring the outside in, and provide epic purge ventilation when you have blown up your experimental whatever. The problem was we also wanted it to be very well insulated so no one inside would freeze on winter days, and we would have very low energy requirements for heating. This ruled out the usual steel roll-up doors.

The Big Door-Wall

It is basically constructed of a big softwood frame (mortice 'n' tenon joinery), with a ply outer layer, sandwiching 100mm of celotex style PIR insulation (u-value of about 0.18). Above the 3 across ply sheets, is a large multi-wall polycarbonate window, to let in some light. Polycarb worked for this because it was lightweight and had an excellent u-value (a good insulator). 
A few sets of rollerblade wheels rolling in a strip of old angle iron recessed into the concrete floor allow it to slide, while a few wheels on the top keep it vertical. To prevent the roller blade wheels developing flat spots, when the door is locked the whole thing is lifted a 1/2 a millimetre off the ground....

The lock is an RFID Arduino based system, that controls two motors at either end of the door (I have attached the Arduino sketch so you can download it if interested) . One Motor was a scrap treadmill incline control motor (it is geared to turn a ACME thread, slowly but with a great deal of torque). The other is made from an old skipped battery drill, an angle grinder gearbox, and the tread and nut from an old F-clamp. Safety micro-switches from scrapped microwaves provide the limit switches for both locking-lifting motors.

Small vid of us testing the drill/grinder lock/lift: 

Flexible brush seals defend the bottom on both front and back, and the top of the door from draughts. The door jambs are sealed with old bike innertubes  filled with foam and a bubble seal fabricated from old wetsuit material,       

All in all quite a fun project. 

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Instructables Design Competition

Participated in the
Instructables Design Competition

Hack It! Contest

Participated in the
Hack It! Contest

Be the First to Share


    • Furniture Contest

      Furniture Contest
    • Reuse Contest

      Reuse Contest
    • Made with Math Contest

      Made with Math Contest

    7 Discussions

    Straw bale building are a valid building option. However at current prices I think firbreglass insulation is cheaper

    The price of straw varies with the growing conditions, so depending on when and where you are getting it, this may be true. Bear in mind comparisons like this are not too straightforward, in that for straw bale construction, the insulation is also the structural building blocks (so you don't need an existing structure to stick your insulation in/on).
    Also, straw bales are thick - total wall thickness usually ends up about 500mm 450 of which is straw - u-value of about 0.13 W/m2K. which is perfectly reasonable. 

    One last point: while the thermal performance of straw bale construction/insulation varies a bit, depending on detailing, type of straw, compression of bales etc. It varies no where near as much as standard modern building materials/practices, which when tested, time and again show up a plethora of thermal bridges, insulation voids, uninsulated headers, etc.

    OK, so that's as much to do with the practice of building as anything else. Another cool thing about straw bale - we had keen volunteers helping us, working for nothing but a meal and the chance to learn about a sustainable material... It probably remains quicker and easier employ professionals  and build and 'standard' (if you have the cash) but where the fun in that ;) 

    Hay ShutterBugger, No. At least not as yet, and the walls were uncovered for at least 4 months before we got the clay plaster on. During that time we were quite vigilant: didn't leave any loose straw unbagged or against the wall etc. (it is the loose stuff the little critters like to nest in - the tightly packed bales, not so much).
    One important benefit of the clay plaster is that it really seals up the surface of the straw, so we don't really need to worry any more.


    7 years ago on Introduction

    Amongst other things, the walls are straw bale (hay is very different and wouldn't work). They give excellent insulation, and are plastered over with three coats of clay plaster to give good fire resistance and thermal mass. You can see lots more info and details of the 'walling' process on our blog (