Archive for April, 2007
It’s So Cool — Naturally!
Sunday, April 29th, 2007One little known method of cooling (and night time warming) a building that requires no electricity, no freon, and no gas, is that of the "wind tower." wind tower This ancient Middle-Eastern technology relies solely on the natural principles of convection and thermodynamics to create a natural "air conditioner". air conditioning
The basic principles behind a traditional Middle-Eastern wind tower are ridiculously simple. (Implementation in a modern building, however, is not.) The tower sticks up above the top of the building some 12′ (twelve feet) or more and is open on anywhere from two to eight different sides. The average in the Middle-East is four sides. Two sides face the wind; two face away from the wind. Inside, the tower is divided into fourths in an X pattern. (An eight sided tower would be divided into eighths, and so on.)
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| Madinat Jumeirah and the Burj al Arab Hotel, United Arab Emirates (The wind towers are the structures sticking up from the top of the building) |
The two sides facing the wind "catch" it. During the day, the hot air is cooled by the thick masonry walls of the tower as it moves downward, into the building. Since cool air is heavier than warm air, the cooled air sinks to the lowest point in the building, forcing the hot air, which is higher up, out the down wind side of the tower. The ventilation and air movement is further facilitated by the pressure differential of the tower itself. Like an airplane wing, the down wind side literally "pulls" the hot air out of the building.
At night, the process reverses. The wind tower, having warmed from removing heat from the outside air all day, is now warmer than the cool night air. As the warm air is pushed into the building on the windward side of the tower, being warmed by the thermal mass of the tower, the cooler air is pulled out of the building by the leeward side of the tower.
This method of heating and cooling buildings heating and cooling buildings, HVAC, heating, cooling is so efficient that the technology is still in use today, even in large hotels like the Madinat Jumeirah and Burj al Arab shown above.
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| Traditional wind tower atop a home in Dubai (As the buildings are made of clay brick, the wooden poles work like rebar in concrete, providing sheer strength to the tower.) |
A study performed by the University of Arizona showed an 18° temperature difference between the inside of a modeled building and the outside temperature during the heat of the day using only the natural convection natural convection currents of a wind tower. Though, in the University of Arizona model study, their building used a solar stack solar stack to vent the hot air, rather than partitioning the wind tower in the traditional manner.
That said, other tests — both computer models and tests performed on functioning buildings with wind towers — show similar results with a traditional single, partitioned tower. Further, those results can be improved by adding other methods of cooling such as a courtyard with a fountain, shading the building during the heat of the day, and underground venting.
With this last technique, pipes are placed underground where the temperature is relatively constant. If properly placed, the ground will change temperature at pipe depth no more than about ±2° from the heat of the day to the cool of the early morning. The pipes are then vented to the outside, some distance away from the building. The wind tower can then draw air cooled by the underground pipes into the building during the day. At night, as the outside air temperature falls below that of the underground pipe, the warmer underground air is drawn into the building, adding to the warmth provided by the thermal mass of the wind tower itself.
Commercial successes like the Mithun Offices/Pier 56 in Seattle and the Hood River Public Library in Hood River Oregon show some of the possible permutations this ancient technology offers us here in the Pacific Northwest. Other modern buildings are, and have been, built using wind tower concepts around the world, further expanding the pool of engineering knowledge about this ancient technology. (See Sustainability Goes Mainstream (Sun, Wind & Veils), by Guy Battle.)
For the home builder, the downside of the wind tower concept is primarily initial cost. Traditional homes around the Middle-East middle-east followed known designs to ensure the success of the heating/cooling wind tower system. Given the harsh conditions, it was, quite literally, a matter of life and death. Experimentation on what worked was not often encouraged. Today, modern homes are individualized. Each one offers a unique set of challenges and possibilites. Because natural convection currents are at the heart of the wind tower system, engineering and modeling is virtually a necessity to make sure that the system will work as designed, meeting the building’s needs.
But given the rising costs of utilities, it could very well be money well spent over the lifetime of the home.
Technorati Tags: wind tower, air conditioning, heating and cooling buildings, HVAC, heating, cooling, natural convection, solar stack, middle-east
Do Yourself Green Pt 1: Door Seals
Tuesday, April 24th, 2007It was pointed out to me the other day that not everybody wants to build a new home in order to "go green." Others don’t have the revenue to do a "green up" remodel of their existing home. But they still would like to participate in "the green revolution" green building, green revolution — as it’s now being called.
And I know it’s true. I’ve worked for a lot of folks you over the years who didn’t have a lot of money, but were trying mightily to figure out how to lower the utility bills and their impact on the environment without busting the budget. environmental impact, lower utility bills
So, I thought I’d start a little series here in Tips & Tricks. do it yourself tips and tricks
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The fact is, there are a lot of things you can do to improve the energy efficiency energy efficiency of your home. Depending on how handy you are, you can do most of them yourself — or with just a little guidance and advice from your friendly contractor contractor — for anywhere from just a few dollars to less than $2,000 (That’ll be our high end for this series) and everywhere in between.
My goal with this series will be not only to give you some guidance and good-old practical do-it-yourself help, but also to play the roll of "myth buster." There’s as much hype (masked as advice, of course) out there in the green building field as there is anywhere else. Not all of it is true, not all of it is effective, not all of it is even good for you.
So, with all that said and now out of the way, let’s start the series. Today:
Sealing up the doors
door seals
You would be amazed at how much heat leaves a building through the doors and windows, even though the doors and windows are closed! doors and windows
The simple fact is: If your house is more than a few years old, your doors frames are probably no longer square. At the best of times you can slide a piece of paper between the door and the stop. On older homes the gap is often wider in some places than others. More opportunity for air flow around the door and stop, letting either hot air out or cold air in. You can lower your heating costs by between 15% and 40% simply by sealing up your doors and windows! And, it only costs about $17/per door to do.
Fortunately, the fix is simple. You can buy door seal kits, also called "weather stripping" at the hardware store. There are two basic types. weather stripping
- Self adhesive foam. You simply clean the door stop well, cut the seals to the right length, peel the backing and stick them in place. The down side is: The soft foam usually deteriorates in a few years, making it necessary to replace the seal.
- Tacked in place. These seals are basically a long piece of rubber or metal tape. The soft rubber side is installed tight against the door stop. The thin tape lays either against the jam or against the stop (depending on style). The tape often has precut holes in it for the miniature finishing nails that hold the seal tightly in place. This type of seal is usually of a higher quality and will last for years.
Note that: If your door is so far out of plumb that it drags against the jam, you should plumb-up the door before installing the seals. If you don’t know how, ask your contractor to help you.
To install you’ll need big scissors or a sharp knife, a tape measure, and a hammer. A pair of needle nose pliers is handy too.
- Measure the three sides of your door jam and cut your weather stripping into those lengths. Don’t assume your jam is square. Cut and measure each piece individually.
- Making sure the seal rests in the groove between the jam and the stop, tack it into place with the miniature nails the manufacturer provided. The top jam seal should touch both side jams. The side jam seals should be snug against the top jam seal and just touch the threshold at the bottom. Or if your seal is the type that is screwed into the face of the stop, make sure the “fat” part of the bead just touches the stop.
- If you have trouble with the little nails, use a pair of needle nose pliers to hold them while while you’re getting them started.
Your door will probably be a bit more difficult to close once the seal is in place as the door has to literally "crush" the seal in order to latch. This is normal. In fact, it’s what you want!
Now, while you’re at it, you may as well install a nice tight door sweep too. A door sweep is an aluminum strip with a soft rubber foot at the bottom. The foot sweeps across the floor without damaging it. When the door is closed it presses up against the threshold and floor creating a much better seal at the bottom of the door. door sweep
To install you’ll need a screwdriver, tin snips, and perhaps a drill. (It depends on whether your sweep comes with self tapping wood screws or regular wood screws.) If you need to drill pilot holes, make sure you use a bit of the size recommended by the sweep manufacturer.
- Measure the width of your door at the bottom. Don’t assume the door is square and measure at chest level because it’s easier. Measure at the bottom where the sweep will actually be fit.
- Cut your sweep exactly that width. I try make my cuts so that the little screw holes are evenly spaced from the ends of the door.
- Now the hard part. Line up your sweep along the bottom of the door. It should just touch the floor when the door is closed.
- Mark the door with a pencil on the hinge and knob side along the top of the sweep.
- Mark you pilot holes if necessary. Set the sweep aside and drill your holes. Don’t go too deep. If you want, you can mark the depth on your drill bit with a bit of tape to make sure you don’t go too far. (A bit won’t hurt, but you sure don’t want to drill a hole completely through your door!)
- Line your sweep back up on your pencil marks and your holes.
- Starting at the center, sink the screws and you’re done!
Tip: The holes in most sweeps are oblong. Drill your pilot hole in the middle of the oblong hole. That gives you a total of about ¼" adjustment in the sweep even after you’ve drilled and set the screws. Simply loosen the screws, move the sweep, and re-tightening as needed to get the sweep even with the floor.
Finally, if you need more guidance on how to do this job, ask for help at your favorite hardware store. Or, you can search around the web. There are lots of do-it-yourself sites, some with more graphical help than I have time to provide (sorry!). Finally, you can email mail me at michael@altbuildingservices.com and I’ll try to help.
Next time: Window seals!
Technorati Tags: green building, green revolution, environmental impact, lower utility bills, do it yourself tips and tricks, energy efficiency, contractor, door seals, doors and windows, weather stripping, door sweep
Left Loose it Leaks
Tuesday, April 17th, 2007A light day, today. Mostly paperwork with one little service call that started out drawing on the oldest of components to the old business: appliance repair.appliance repair
A lovely young mother of a newborn called me because her dishwasher seemed to be spontaneously leaking all over her kitchen floor. And, she said, her garbage disposal wasn’t working either.garbage dispsal, dishwasher
As it turned out, there was nothing wrong with the dishwasher. There was also nothing seriously wrong with the garbage disposal. Grease buildup had gummed things up to the point that it didn’t want to work. A bit of hot water and a bit of working with “the special wrench” and it was back in operation — if only for a short time. It is old and is heating up just from running, so it’s an appliance that’s on its last leg. But for now, it works.
That leaves — The Leak!
Which was comprised of one loose fitting and one missing gasket seal. Actually, the seal wasn’t missing, it was on the back side of the nut.
So here’s a new adage for the home handyman: “LEFT loose it leaks. Do it RIGHT it’s tight.”
And of course: Don’t forget the seals. They belong BETWEEN the nut and the male threads, not behind the nut.do it yourself, plumbing, plumbing leaks tips and tricks
Technorati Tags: appliance repair, garbage dispsal, dishwasher, do it yourself, plumbing, plumbing leaks tips and tricks
Building Green: Cost v. Benefit
Monday, April 16th, 2007As an article in the July 2006 issue of Eco-Structure Magazine pointed out: "The question has changed from `should we go green’ to `how do we do it.’" (See Concrete Points to Green in the above issue.)
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As the graph at left shows (and will be explained below), the cost to benefit ratio of going green is no longer at issue. It’s the `how’ that is the rub, because the `how’ of green building is not a simple question to answer. As we shall see in this short article, there are many variables at play, and they all interact to produce an ultimate cost/benefit to the owner, each affecting the overall efficiency of the building.
According to a New York Times article, green building methodologies once added as much as 20% to the cost of construction, no matter how one chose to go about it. Today the availability of green materials and building systems have dropped that cost to a much more manageable level.1 But that doesn’t mean it doesn’t add cost. As Mother Earth News pointed out in an article a few months ago: ". . . efficiency may come with a higher price tag — whether it’s a new home with the latest technology or an existing home remodeled with energy improvements, such as added insulation or a more efficient furnace." In 2003 a California study entitled "Managing the Cost of Green Buildings" reported the cost premium for achieving LEEDS ratings at 2.5% for Certified, 3.5% for Silver, 5% for Gold, and 8.5% for Platinum. Though they did note that the costs have been declining in recent years.2
If one examines utilizing green building techniques solely from an economic perspective, then the additional initial construction and design expenses should result in lower operating costs for the building. And in fact green buildings do just that. Sometimes they achieve dramatically lower costs.
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A prime example: The Reilly
Home. General contractor Bill Rielly built his own 6,300 square foot home in Hyde Park, New York. The HVAC system is tied into geothermal vents. The photovoltic cells on the roof generate the electricity. He hasn’t paid an electric bill since moving in, in November of 2005! (Here in California the utility company would be required to buy surplus electricity back, further reducing the operating cost of the building.)
So how much can be saved in relation to how much is spent? In economic terms this is called "Life Cycle Costing" (LCC) and, if you’re an economist or statistician, LCC is a relatively straight forward process.
In the accompanying charts, Q* shows the point at which energy cost savings and LCC reach optimum. To the right of this point, savings vis a vis expenditures decline remarkably. In all three charts it pays to increase the level of investment to increase energy savings if the level of investment is to the left of Q*. It rapidly becomes less and less cost efective to increase the level of investment as the investment amount moves further and further to the right of Q*.3
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Obviously, while specific dollar amounts will change over time, and will be unique to each project, current models show that the relationship between the various variables: Investment Costs versus Total LCC, Operating Costs, and/or Operating Savings, for instance, all remain relatively constant.
The trick for the designer or architect and builder is in trying to fit the variables together so that the project lands precisely where you intended it to relative to Q*. If you have the money and are very environmentally oriented, you might want everything to be as efficient and evironmentally friendly as possible. Your project would end up on far the far right hand side of the charts, squeezeing every penny of efficiency per dollar invested in your project.
Or you might not have enough money in the budget to reach Q*, but you want to get as close as possible. For you, your design team will have to work hard to find the best compromises in efficency per dollar invested.
Public entities might choose to evaluate bids based on the cost to achieve Q*, rather than on the standard formula of accepting the lowest qualified bid.
In the final analysis, it is clear that building green is already cost effective when compared to traditional building methods, and is therefore a wise use of investment dollars — for private home builders and government agencies both. It is also clear that the cost/benefit value of green building is only going to increase over time. The costs associated with green building and design continue to fall as manufacturers scale up production, and as techology and sources of green materials improve. At the same time, the cost of gas, electricity, and heating oil continue to rise. No wonder green building is the hottest topic in the construction industry.
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1. The New York Question: how Green Is My Tower, New York Times, Robin Pogrebin, 4/16/2006.
2. Geof Syphers, Mara Baum, Darren Bouton, Wesley Sullens. "Managing the Cost of Green buildings.” KEMA. October 2003.
3. RS Means, Green Building: Project Planning & Cost Estimating, 2nd Edition.(Reed Construction Data, Kingston MA, 2006), pp. 303-6. Charts included in this article are my own adaptations of those published on the listed pages.
