Designing the Dream: Up on the roof
Let’s talk about roofs. You want your roof to drain water as efficiently as possible from the
House. Wood can resist getting wet and drying again, but it can’t get wet and stay wet without generating dormant bacteria, mold and mildew – in short, rot. Keep that water moving. Put it down, move it.
Make your roof work for you, not against you
Where the water from the roof reaches the ground, be aware of how it is directed away from the building. If the drain runs to a patio on the uphill side of the house, how will the drain escape? If you ignore that now, it could mean flooding during summer cloudbursts, and a formidable
glacier cum ice rink in winter. On the other hand, you can take advantage of runoff by directing a gutter downspout to water your trees and shrubs. For every 2 square feet of roof, 1 inch of rain will produce 1 gallon of water. It is a great resource in this arid climate. Colorado law prohibits us from:
catch water in a cistern, but we can divert it if it runs off the roof, and the water police can’t do anything about it. Your roof protects your house against snow, hail, rain and in the San Luis Valley especially against sun and wind. Metal roofs last a long time, let the snow fall well and withstand our raging spring winds better than most other types of roofs. They will also shed embers in the event of a wildfire. Composite roofs last almost as long and come in a variety of styles. Asphalt shingles and rolled roofing are less expensive but will not last as long. “Flat” roofs (each roof must have a certain slope to drain), commonly used on Southwestern style homes, must be carefully and professionally designed and installed so as not to leak. Because snow can build up, they must be structurally stronger than pitched roofs. For simplicity, durability and fire resistance, I would go for metal on a pitched roof. Of course,
another option that will do double duty is the new solar shingles that will keep your home dry while producing electricity. I recently read about green too
(vegetable) roofs that come as a pre-planted panel.
What will they think next?
Place a small gable roof (called a cricket), or at least a sloped snow deflector, over doorways where the snow will pour, especially on the north side. They will save you a lot of snow shoveling by diverting snow to both sides of the entrance. Gutters don’t work on the north side; they will freeze with ice and snow. It’s not as critical in the south as the sun will often melt small amounts of snow in front of the entrance during the day, while in the north that dumped snow will melt and refreeze into an impenetrable barrier if not removed. . Another advantage of a roof, if it protrudes over an entrance, is that it can provide protection over your head so that you (or your visitors) don’t have to stand outside the door in the rain looking for keys or waiting to be let in. Are you planning an addition for the future, when there is more money? Plan it now so you can make all your roofs work together. At the very least, you will become aware of where headroom, ridge height or slope may be a particular concern, and you can plan accordingly. A well-designed roof overhang protects the windows from the hot blazing sun in the summer and allows the house to fill with warm sunshine in the winter. I’m sure you can appreciate shade from a canopy on a hot August afternoon. A well-ventilated roof, by shading the house, helps keep it cool in the same way. In winter, a well-ventilated roof over a well-insulated living space keeps your home dry and warm by keeping the house’s escaping heat from melting snow on the roof,
There are different types of roof ventilation, which you can find by Googling “roof ventilation”. Here I have shown soffit/ridge ventilation. While the warm air in the attic escapes through the ridge vent, fresh air is drawn in through the soffit. I also show here the advantage of a cricket over the doorway, especially useful on the north side of the building in winter. NSdrawing the NSBelt
On the roof that can form ice dams if the runoff reaches cold eaves. That can cause ice to build up under the roofing material and cause leakage. The recommended amount of ventilation is 1:300 net free airflow, ie for every 300 square feet of attic space, you should have 1 square foot of open airflow in both the intake and exhaust vents. (Net free airflow means the size of your vent minus any louvers, screens, etc.) It’s vital to have both intake and exhaust vents. As with windows, if the old, stale air has nowhere to escape, the new, fresh air can’t get in.
What will it look like?
More complex roof styles are admittedly more expensive, but the size and slope of your roof will affect you aesthetically as long as you live there. Once you’ve decided how to drain and vent your roof, take a look at it in side view to see how it fits with the rest of the house. How do the proportions and slope of the roof interact with the mass of the house and the height of the walls? Bad proportions can make for an ugly house. Neither you nor your neighbors want that.
Roof slope is measured in rise:run. In other words, how many feet does it rise over a given horizontal distance (usually 12′)? The house in our drawing has a slope of 10:12. The roof rises 10′ over a span of 12′. The minimum slope for many roofing materials is 3:12, but check with the roofing materials manufacturer for their recommended minimum slope – you don’t want water to get under your roofing and seep into the house. Remember, go down, move it out.
What is the right choice?
It should be noted here that I have not done a careful study of the carbon footprint of different materials. My priorities for this house are that it has low energy consumption, is easily accessible, is suitable for the San Luis Valley environment, takes full advantage of passive solar energy and views, is low maintenance and is moderately priced. The market price of materials still doesn’t accurately reflect their carbon footprint, and the price of everything seems to be in flux. So I’m going for a solid house that will last me through the ups and downs of the near and longer future.