04-25-12, 10:12 AM | #31 | ||
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The way these gadgets I know of were created was with a rubber flap at the bottom and a fan using a small PV panel to open the flap with negative pressure. I don't think people used thermostats.
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04-25-12, 11:22 AM | #32 |
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I could manage it manually too but it seems fairly easy to modify a standard relay driven electronic thermostat to open and close the circuit. I could do it manually, takes a little bit of diligence but in reality I'm trying to maintain a 10 degree temp swing and if it drops low I don't mind. Makes it easy for me to control. I'd imagine that when it is 20 degrees outside during the hottest part of a MN January day, I won't have much worry about the house overheating. I could always use something like this to cycle outside air directly through the solar air heater to bring in outside fresh air. I'll leave it at that before things the topic gets too far off track with the solar air stuff to respect the OP's thread.
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04-25-12, 03:11 PM | #33 | |
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It sounds like the following do not seem satisfactory for your needs:
So it would be interesting to know if the research you have done has turned up anything promising, that will satisfy your needs? Have you done any original development work to create a working solution that actually will meet your needs? I don't think that it is very likely that if you had an electrically-powered HRV, and the grid went down in the night, that you would suffocate. But if you were able to get your house so tight that that a night-time grid failure did cause your untimely death due to suffocation, it would really be something to be proud of. You would have established a new upper-limit of house tightness, and that would give you some serious bragging credits! They might refer to the incident as, "The Drake Mistake" long into the future. -AC
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04-25-12, 03:50 PM | #34 | ||
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AC_Hacker, that was the best thing I've read all day.
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04-25-12, 06:37 PM | #35 |
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My intentions of this discussion weren't to upset anyone or imply that the direction any other wishes to take are wrong. If so I apologize. But fact many people HAVE died from CO2 in UN air tight spaces. Nearly myself(while awake) in an ice house when younger.
I can't see how a set ACH can be assigned to all spaces and all lifestyles in that space. If it is an average what is the range of that average if one wished to make do all thing needed to achieve the low end. Standard are revised all the time so they are not absolute. The DIY HRV thread seems to show I'm not the only one not satisfied with commercial HRV's. I don't think I dis'd earth tube but if I did one is one of my major options(at least for minimal night ACH as I will trenching 150' out of hill side for gravity footing drainage and line for possible future HP pump and dump, have oversized well and wetland at bottom of hill and is allowed). I calculate that it is not long enough nor deep enough the whole run to be able to pretemper incoming air for worst case winter so it will need another source as well. A second 150' run could be laid in the trench needed for gravity sewer line to septic mound. Earth tubes have a potential for toxic mold though it is minimized if only used in winter. So one is not decided on method yet. Day time solar tempered fresh air not difficult 80% of the time. In college I all but heated my two room brown stone apartment with a 4x8 DIY soda can solar collector in Duluth, MN. Granted there was a very large swing from mid 90's to low 50's but preheating fresh air shouldn't be undoable. Over heating thru solar will not be an issue for me as any overload of heat can be dumped into the half of or home that will be a large three season space if we don't want to heat it for use in winter. Fresh air is the last unresolved piece of my construction project and a very important one which is why I want as best a solution as I can find. I find "frosting" and HRV performance because of it troubling. That they are "coded" into new construction doesn't make them perfect or the best method. I have designed and built many high tech and elaborate systems in my life and what I have learned the most from them is that those that required the least were the most overall successful. MN Ren, Don't worry about going off topic your last post made me consider the potential of my mostly unheated cabin space as a large area of tempered air for nighttime. It as it stands is passive solar and well insulated enough to rarely freeze even when unheated. Dumping overflow heat from from even more aggressively passive/super insulated space hold even higher temp tempered air. It may have some VOC's in it but it won't have any O2/CO2 issues. I purposing installed leakier slider windows in it to allow enough fresh air for safe wood stove(w/ make up air) combustion. A daytime solar collector can feed this space as well(one has never been needed yet as wood stove provides more than enough free heat). If it turns out that this spaced is used often another night time fresh air source will be needed. I am working on calculating potential daily non toilet grey water volume and how many btu's could be recycled to preheat night time air also. With near free well water/septic sewer svg water isn't less important, sending heated water btu's down is. Solar%20air%20heat%20-%20Wikipedia,%20the%20free%20encyclopedia.webarchi ve Solar%20Buildings%20-%20Transpired%20Air%20Collectors,%20Ventilation%20 Preheating%20SolarWall%20News.webarchive These site are info on low temp transpired solar air preheating which might be another option. I am a critical consumer. And I don't see Big Tech as the best answer to low demand. No offense to anyone. |
04-26-12, 01:18 AM | #36 | ||
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In general, for homes ASHRAE starts with 0.35 ACH and then adds extra air for more people and more activity, etc. I'm sure that if you spent some time searching it out you could find the details on the base-line ACH value and also the adjustment factors... it's out there in the google-plex of web pages. Quote:
Best, -AC
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04-26-12, 09:33 AM | #37 |
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Sorry for the bad addresses I tried coping the address line from each website that I have saved on my desk. Searching for "transpired air collectors" or "preheating fresh air" should find them.
I have not had a blower test done on our current home but after an full gut remodel, insulation upgrade and air sealing effort just to the point of needing an HRV. Heating with a gas furnace on an 8 degree night mid day double setback(8 hrs ea) our furnace rarely comes on more than once during setback periods except on coldest/windiest winter periods. It would make sense to me that if we were having a .35ACH or higher than we would have to be heating enough air to replace the whole house every three hours or more than twice each set back requiring the furnace to run much more than it does. Calculating exact furnace Btu consumption is not easy as we have several gas appl the are run year round are on a yearly leveled payment plan and rates change(increase) every year. After thirty years of clean living in this space with no ill effects humidity(sweating windows even on low E windows) from a few too many green plants(I got carried away raising orchids a couple of years). So unless I'm misunderstanding .35 ACH, a full house air change every three hours, it seems high. One day last winter(when my wife was gone) I opened the house for till it felt about ambient with outside(one full ACH), furnace off, then closed up and turned furnace on. It ran for nearly an hour to reheat space. Much more than it already does to heat what should be 2 full AC's. Not scientific but I've also seen a lot of good looking numbers "crunched" that don't reflect reality. Somewhere the two should match up to me. |
04-26-12, 09:57 AM | #38 | ||
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HRV's come with a control unit that allows you to adjust the fan speed. And don't forget that you may have a .25 ACH turn around but you are only loosing 40% of that heat if your unit is 6% efficient.
I have seen so many people in even leaky old houses get HRV's and say that they don't know how they ever lived without them that I can't ignore their benefits.
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04-26-12, 08:33 PM | #39 |
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Our house was built in 2002 as an energy efficient house. The builder recently bought a blower door and tested it on our house. It came to 1.0 ACH50. That correlates roughly to 0.05 ACHnat (actual ACH under normal weather conditions).
We built the house with an HRV. I set the unit on its lowest speed, about 35 CFM. That's a little less than normally recommended for a 1320 SF house, but it has worked well for us. The air gets noticeably stuffy if we turn it off. We had six people and a small dog in the house for several months, and 35 CFM was sufficient. The return air comes from the bathrooms, the supply air goes into the cold air return. |
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04-26-12, 10:15 PM | #40 |
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Running an HRV at it lowest capacity would be the best operation to result in the least frosty if it was to happen. Have you had frosting issues? Do you run continuous or metered/timed?
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