Straw Bale Construction:
About Straw Bale Construction
People have been building homes using straw in many countries around the world for centuries. Reeds and straw have been used for roofing, thatching for walls and even for the ground. This material is used because it is reliable, inexpensive and easy to obtain.
There are straw bale houses in Europe and America that are now over 100 years old and in excellent condition. These were built after the first baling machines were invented in the late 1800s which enabled straw to be formed into compact, easily managed and stored bales. At this time prairie farmers in the sand hills of Nebraska, faced with a shortage of building timber, began an intriguing method of construction using baled meadow grasses which grew in abundance. Straw panel houses in Australia date back to the 1930's, and 12 of those known from the period are still standing today.
Strawbale - Cool in summer, warm in winter
If you can stop the heat of summer days getting into your house by closing up your home early in the morning while it is still cool, you can keep the inside of the house cool, as long as the heat can’t get in through your wall, roof windows etc. That is where a super-insulating straw bale wall comes in handy - it won’t let the heat through.
It is just the opposite in winter when you warm your house with sun allowed in through the windows and trapped in the house or with a slow combustion heater, air heaters, radiators etc. You don’t want the heat to escape - again the straw bale wall will reduce the movement of that heat.
A straw bale wall is made of hundreds of thousands of stalks of straw, each one containing and trapping air. Air is a great insulator so if you can keep it still in the wall, almost no heat can move through it. Even the solid part of the straw itself is quite good insulator but it is interesting to think that a very well compacted bale will give worse insulation than a lighter bale, because the insulation is mainly provided by the air.
The layer of cement render on the inside of the wall stores warmth or coolness so it evens out changes in the air temperature, so if you opened the door letting lots of hot air into the house for a few minutes the cool wall would absorb the heat from the hot air and leave the house much the same temperature as it was before you opened the door.