«The Cob Builders Handbook You Can Hand-Sculpt Your Own Home Table Of Contents: Acknowledgements and Warning INTRODUCTION What is cob? Why build ...»
Glass is magic stuff. It lets the sun's radiation through to heat up the surfaces in the house. Materials that are heavy and dense, like cob or stone are good thermal mass. They absorb the heat and radiate it back. Place your windows so a lot of sun will shine directly onto the flo or. ( See page 58 for more about this.)
Set your windows into the wall in such a way that they will get the winter sun and be protected from the summer sun. Run the house length east/west if you live where you want maximum exposure to the sun, or angle it up to 20° to the east for morning light.
Here's a flexible rule of thumb for a temperate climate. Put roughly 70% of your total glass facing the sun at its highest point in the sky. (This will be south in the northern hemisphere and north in the southern hemisphere.) Put 20% to the east to welcome the sun and start your home heating up quickly after the cool night. Put about 5% to the cold side of the house and 5% to the west where you probably won't want the lowering summer sun shining in after it's been heating up your house all day. Check out your weather and adjust this formula to suit it.
Glass is not very insulative and will let some of the heat and cold in and out of your home. Too much glass will make for extreme indoor temperatures. The local building department will be able to tell you the ideal amount of glass for passive solar heating in your area. This will be a percentage of the floor area, for example: put in as much glass in the wall facing the sun as it takes to equal 15% of your floor's square footage.
Different types of glass have different insulating abilities. Call your local window store to learn more and check out the current prices. If you live in a temperate climate, it is required by code to install double-paned vacuum-sealed windows with at least an R4 insulating value. If you buy double-paned windows, I recommend buying from a reputable company. The windows should be guaranteed for life, but they do leak and fog up sometimes.
111 What about making your own "double-paned" windows? In the old days, people put up storm windows during the seasons of extreme temperatures. These are a separate single pane in a frame that can be removed for cleaning. Unless they're vacuum-sealed, condensation will form between the sheets of glass. Make them so you can remove one of the pieces of glass to clean the insides in case they fog up and grow algae. The insulation value of storm windows is not as good as vacuum-sealed, but the better the seal, the better the insulating ability. Because single pane windows are free or cheap, you may choose to use them if you don't want to buy double-paned windows and if you're not worried about code requirements.
The simplest passive indoor-climate-control system is to make openable windows and open them and the doors when the outside temperature is what you like, and to close them all when it's too hot or too cold, trapping the temperature you want indoors. This is one of the most effective ways of controlling indoor temperature, especially if the temperature varies a lot during the night/day cycle.
Covering the windows with insulating curtains, shutters, or clear plastic helps keep some of the cold from flowing in and the heat from flowing out. If you want to keep the sun's heat out in the summer, shade the windows on the outside so the sun doesn't get in to heat up the indoors. Using a reflective material works best. Hooks to hold up the shades and curtain rods can be built right into the cob, inside and out.
Block off the small gaps around the windows and doors where the heat or cold can get in and out. To make a natural caulking, dip a string in wax (beeswax is more flexible) and push it into the space you want to fill. Strips of inner tubes can also be used to seal cracks. Bigger spaces can be filled with cob.
Another advantage to passive solar design is that nature's light is cheery and good for your eyes. To get the most light out of a window, put it high in the wall unless it's blocked by the eaves or a tree. Place the windows so they let light into the places you want it, like the desk, the kitchen sink, counters, etc.
There's nothing quite as nice as natural light from above. Skylights let in more natural light than wall windows. There are some disadvantages though. Since heat rises, a skylight will let out the heat on a winter's day and may overheat the house on a hot summer day. You can splurge and get one that has double or triple layers of glass for insulation. Plan to cover skylights to keep the summer heat out and/or make them openable to let the heat flow out. They require careful attention when installing or they'll leak.
How to get lots of glass in the sunny side of the house and still support what's above
One way to increase the sun that shines through is to use large windows and angle or bevel the supporting cob-columns away from the glass. This lets in more light when the sun is shining at an angle to the window.
Another way to maximize solar gain is to put two large windows side by side with a wooden board between them and one long lintel over the top of both windows, resting on the cob at either side.
Bay windows are lovely and easy to make. Build the foundation in the shape of the bay you want. You can make cob pillars between the windows to support the arches or lintels above them. You can use pieces of strong wood between the windows as posts for the lintels to rest on. Bay windows are lovely places for window seats.
If you want to have all glass on the sunniest wall, use a post and beam framework instead of cob between the windows, and all the way up to the roof on that wall. Get an imaginative carpenter friend or carpentry book to help if you need to. Where the wood wall and the cob walls meet, use a heavy duty version of the window frame keying system, or use a box key.
A trombe wall is a cob wall with a glass wall in front, to trap the heat. You can build a glass wall in front of a sun-facing cob wall anywhere from 4 inches away, to far enough away to serve as a hallway or sun-room. Close off the sides between the glass wall and the house wall with cob or wood. The low winter sun's rays will penetrate the glass and heat the cob wall during the day, which will radiate the heat into the interior space at night. A dark colored wall will heat up more quickly than a light colored one.
Another option is to put vents on the top and bottom of the house wall to circulate the super heated air from between the wall and the glass into the interior of your home.
With this system, you'll need to set up back flow dampers to stop the warm air from inside the house flowing back into the trombe system.
You can find out more about trombe walls in books on passive solar design.
If your large trombe wall will cover the sunny side of the house, it's OK to put windows in the cob sides of the trombe system so you can see out and enjoy the natural light. If you make the windows operable, opening in, you can clean the glass on the insides of the trombe wall and outsides of the windows. Set up a shade or plant deciduous trees, artichokes, tomatoes, or something to protect the wall from the unwanted summer sun's heat.
Ventilation Observe the sunshine, wind and the climate carefully at your site before deciding where to put the windows.
A very simple vent can be made out of a bucket with its end cut off. Any sort of tube buried in the wall will serve the same purpose. These can have removable or permanent screens attached to the outside of the vent to keep critters out. I've seen bright colored cloth tied onto the outside end of the tube or bucket to give a pretty light and keep the mosquitoes out. When the vent needs to be blocked off, put the lid on the bucket or just stuff a blanket or something in it. These buckets can second as storage places.
You may want screens on the window openings to keep insects out of your house. I like to have removable ones because I don't need them in the winter, and I love to look outside without anything interrupting my vision.
Make extra ventilation in the 'moist' rooms like the kitchen and the bathroom. This will help keep them drier. You may want to put a vent over the stove to let out cooking smells and grease.
Make good latches to secure your windows and doors, so the wind doesn't fling them around when they're open, and so they won't rattle or leak when they're closed.
Views Imagine your life in the house as thoroughly as you can. Where will you sit to eat and to study? Where do you stand to do the dishes? What view do you want to look at while doing the things you do in your home? Where will you need natural light? What do you want to see from your bed?
Remember, windows allow people to see into the house as well as out. When visitors approach the house, what do you want them to see? If you have neighbors close by, think about where their windows are and how you want your windows to relate.
Where do you want privacy?
When you've built the walls up to the height of the bottom of the window, have a friend hold the window up in different places so you can see where you like it best.
Because it's so exciting to put windows into the walls, the tendency is to put them in too low; in the wall. Observe window heights in finished homes to help you "see" what you want. Stand and sit in the house while your friends are holding up the windows to check if the height is right. Consider this carefully before you place the windows.
Try to imagine the finished building. Look at it from the outside as well as the inside before you make your decision. You may want to get more than one friend to hold up other windows, so you can get a look at how they all relate to each other.
Noise Cob walls block sound amazingly well. Windows will let noise in and out a lot more than the walls will. If you live near something noisy, you may want to minimize the windows facing the direction of the noise.
Magic windows Centuries ago, people sometimes used window placement to mark a certain day of the year. You can put a window where the sun will shine through it on your birthday, a solstice, or on the equinoxes, and onto a special spot on the opposite wall. This is tricky to figure out, unless you can capture the moment as you're building. Anybody know how the people in the old days figured it out?
Some glass safety tips
If you can get it, use safety glass in the most vulnerable places: skylights, large windows, and doors. (Safety glass is the kind used in cars, that's laminated so that it breaks into small pebbly bits instead of big dangerous shards.) Transport and store sheet glass in an upright position. Put it in a safe place, where the wind or someone walking by won't knock it over.
116 Have a lot of respect for the danger of being cut with glass. Wear leather gloves and shoes when handling it. Never carry glass around after drinking alcohol!
Be extra careful when handling or storing broken glass. If you have broken glass that's still hanging onto its frame, it may be safer to take it out of the frame before moving it. When you are embedding broken glass in cob, put tape around the sharp edges and wear gloves. Be extra aware of your precious hands while you are massaging the cob onto the wall around the glass. Cobbing with cuts is not so fun.
When you put big pieces of glass into the walls, put some long strips of bright colored tape onto the glass to prevent yourself and others from accidentally trying to walk through it.
Getting rid of unwanted windows Too many windows is easier to deal with than too few, so be generous. Later you can cob over any window you want to get rid of. It's harder to knock out a piece of the wall and add a window than it is to cob over one.
Replacing broken glass If one of the windows that's buried in the cob breaks, you'll have to chip the cob away, get a new piece of glass, and cob it in again. Cob sticks to cob well. Read the sections on applying new cob to dry cob (pages 91).
Fun window ideas Bottles for windows Bottles and jars can be buried into the wall to make fun mini-windows. They are more insulating than a single pane window because they already have two "panes" or sides.
Colored ones will light up with color when the sun shines through them. When you're outdoors at night, the light from inside will look lovely where it shines through the colored glass.
If the parts of the bottles and jars that are buried in the cob are white, they reflect a lot more light than if they're right up against the dark cob. The outsides can be painted white, or wrapped with wide white tape where they will be touching the cob. Leave the exposed parts uncovered so the light can shine through the bottles.
With a little imagination and a lot of colored bottles, pieces of glass, ashtrays, and stuff from second hand stores, you can make amazing stained glass/cob "windows".
Bottles and jars can be cobbed in sideways to the wall too, tapering the width of the cob wall in toward the glass.
view from above light passing through Big gallon-sized jars and buckets can be buried with their mouths open to the inside or outside of the house to be used for storage. You can use their lids to close them.
Glass from cars Windshields and the rear windows from cars are often cheap or free and make interesting windows buried into cob. All car windows are made out of nice thick safety glass. You could even bury a whole car door into a cob wall, leaving the window handle and the window exposed for an openable window.
ROOFS There's lots of information about roofs out there, so I will give a very basic explanation and tell you about the eccentricities of attaching a roof to a cob building.
I'll also briefly describe some 'out of the ordinary' roof systems.
The roof is absolutely vital to the longevity of the walls in any type of home and is often the weak point, requiring maintenance and rebuilding. The roof passes the weight down to whatever is below, then onto the walls, down to the foundation and the ground. It is worth putting time, attention and good quality materials into your precious roof.