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Joe,
In regards to your statement :
a) The very nature of heat transfer, form cold to warm areas. The system has to account for climatic changes within the structure. Specifically when it is an “oven”, outside colder air will want to migrate in and when it’s a refrigerator, colder air wanting to escape. This we know because of the high pressure created by cold air and low pressure created by warm/hot air.
Maybe I misunderstand what you are saying, but I learned in Physics class that heat moves to cold. Something at a higher temperature (the air) has higher movement at a molecular level, and wants to disperse into an area of less molecular movement.
Is what you are saying that the heat wants to escape out to the cold outside, thus the cold air is being drawn in by a convection current?
I am fascinated by all this and want to learn more. It’s all very relevent to me because I’m doing a major renovation to my home and trying to apply all I learn here in order to have a more fuel efficient and healthy home.
TIA
Phil
Replies
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Venting.....
This subjects gets lots of play here. I guess with the formation of bodies like ASHRAE and Thermal 7 is to assure us that the "thinkers" of this industry are well, thinking and the members and attendees of these bodies are paying attention to the people doing the thinking. My question is, what is it that they actually do?
Do they actually build residential and or commercial structures in different climates and test their exterior envelopes or is their testing done in an controlled environment? If so, who does the building? What systems are put in place for comparison? What materials are tested, fiberglass, cellulose, foams, earth, masonry masses?
Is their purpose to improve or disprove systems that are presently in place or to create entirely new systems. Who funds them? Where do they get their materials from?
Do they determine why a particular system is inadequate or fails, if so, was it materials, installation, design or concept? In my personal experience, most systems fail due to the "improper installation".
I am a proponent of venting and for the last 15 years have employed the standards of this systems ( fiberglass insulation, ridge and soffit vents, (no gables) bathroom vents, poly moisture barriers) with none of the ill effects that others have stated here on this forum. It appears the "modern" course is to construct a monolithic shell that is impervious to any and all outside influences, much like a "rock". This system IMO seems to lack the structure to deal with the truly dynamic nature of the modern living space.
Joseph Fusco
Fusco & Verga Construction Co., Inc.
*Joe, I have a hunch you and I build houses with the same philosophy. Basically, I build them exactly like Fred and some others prefer and then I spend a few extra dollars and vent the d___ attic. This pleases me, the building inspector, the buyer, the shingle manufacturer and with all of that, the house is still warm, energy efficient, and I have no trouble with anyone, which is exactly the way I like it!......
*I'm sure you build the way you derscribe. I'll wager Fred and Gene and others have also. And they have tried other systems and compared them. And they have looked at buildings built by others and the measurements of those other buildings and compared them to measurements of thier own buildings. And I'm sure that is basically the approach of the practioners who convene at these meetings and share their findings. So the only difference between them and you is probably they measure the performance and compare the results.And then there are those who build the same structure with different systems and measure the difference in performance using instruments. The Small Homes Council in Illinois and the NAHB are two organizations that do that.For some "good enough" isn't. They have a need to understand and learn more. Just like those who figured out that using insulation and vapor barriers helped save energy - contrary to the builders who said the way they always had done it was good enough.The difference is in this age of communication the results are spread fast. Ain't it great?
*Bill, while the speed at which we can get information today is great, you may be confusing information and facts. Joesph asks a lot of valid questions I have also wondered about, and while Fred may have some valid points, I would need to know a lot more to accept anything as fact. Tests, like polls and charts can be skewed. You need to know what goes into these tests before you can make sense of what comes out. Respectfully, Barry E
*Barry E - One of my favorite sayings is "figures lie and liars figure" so perhaps we agree on a lot of things. But, I'm not sure I feel a builder has to know all that goes into the tests and research in order to make an informed decision. For instance, what tests or study or research was done to show venting is a good thing and needs to be included in all houses - starting (I think) right after the War? I've looked at what Fred has written and have looked at houses and have looked at what the venting proponents present - nearly all of it from the manufacturer's literature - and conclude its a wrong headed idea. (The most convincing element for me is to look at houses and see that all the snow melts below and around the vents first and over the rafters last.)So I see Fred has made a resolution and I look forward to his fulfilling that (and actually meeting him at Affordable Comfort 99 - I hope - though not expecting the rave personal accolades heaped upon Mike.)
*Joe, In the beginning there were builders. People built their own houses and builders built everything else. The master builders were the architects. Engineering was done by trial and error. Eventually the profession of architecture separated from building and engineering became a science. Houses were still built by owners. As professional builders became more common in residential construction and houses became commodified as real estate, building codes became necessary. Originally these codes were based on common practice, which was founded in tradition. Tradition could sometimes not accommodate changing practice. For example, when stick framing replaced timber framing carpenters often continued to orient ceiling joists perpendicular to rafters. What worked with a ridge beam and vertical rafter loads, did not work with a ridge board and outward rafter thrust. Neither tradition not trial and error were very accommodating means of dealing with changing technologies. This necessitated methods of a priori evaluation of building methods. This original building science was the domain of architects and engineers, and concerned itself primarily with structure. A major change in building technology occurred with the introduction of mechanical systems, plumbing and heating, and electricity. But, the basic construction methods of housing have been fundamentally unchanged for over a hundred years. What has changed is materials and the nature of the building envelope. Building codes have become universally common, and building tradition and dogma have become codified. Changes in building practice come not through direct introduction by the trades, but by building scientists who control the code approval process. Acceptance of change at a local level is difficult if not impossible. Who are the building scientists? At Thermal VII they were a cross section of government, industry, academia, and the design and building professions. They came with an equally diverse set of interests. What everyone did have in common was an interest in the improvement of the real world thermal performance of buildings. For the most part dogma was left behind. Presentations represented extremely diverse methodologies. Oak Ridge National Laboratory has done extensive hot box testing of whole wall systems. Information is available at their web site. Testing has included studs, corners etc. that are present in real walls, as well as comparisons of carefully and carelessly installed insulation. These tests do tend to confirm that failures are indeed due to improper installation, for the most part. What they do, that simple observation cannot is quantify that failure. When they hot box tested straw bale walls, that have had extravagant claims of insulation value made by proponents, they found that convection currents behind furred drywall negated the insulating effect of the straw, but by using pneumatically applied plaster inside and out, real R-30 values could be achieved. In this case lab testing accomplished what could never have been possible in a real world situation, and the results make computer modeling more accurate. Vented vs. unvented attic performance (in cooling climates) was tested by using two identical tract houses, one vented one not. They were tested for two weeks unoccupied and then monitored occupied. The conclusion was that unvented performed better. The reason being that air handling systems are best kept within the envelope. My own methodology was empirical, intuitive and based in traditional practices. Neither a priori evaluation nor objective testing would be possible, but my proposals for a dynamic interaction of the envelope with the users were very well received by a very diverse group of people. Building scientists are not out to attack what we do. They seem to have a high level of respect for builders and want to contribute to the improvement of building practice in ways that builders cannot.
*Joe,In regards to your statement : a) The very nature of heat transfer, form cold to warm areas. The system has to account for climatic changes within the structure. Specifically when it is an "oven", outside colder air will want to migrate in and when it's a refrigerator, colder air wanting to escape. This we know because of the high pressure created by cold air and low pressure created by warm/hot air. Maybe I misunderstand what you are saying, but I learned in Physics class that heat moves to cold. Something at a higher temperature (the air) has higher movement at a molecular level, and wants to disperse into an area of less molecular movement. Is what you are saying that the heat wants to escape out to the cold outside, thus the cold air is being drawn in by a convection current?I am fascinated by all this and want to learn more. It's all very relevent to me because I'm doing a major renovation to my home and trying to apply all I learn here in order to have a more fuel efficient and healthy home.TIAPhil