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12-12-14, 06:49 PM | #1 |
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PassivHaus
So, it seems that the American people who promote the PassiveHouse name (either PassivHaus or other) promote products or techniques that don't meet the specs of the international PassivHaus organization.
Therefore, I am told, that if you want to get a house certified it may take some work to find out who to go to. Here in Canada we can use the European requirements so it isn't an issue here. There are builders certified to the US standards but I don't know if they meet the European standard. Just wondering what anyone else has heard? Last edited by Mikesolar; 12-12-14 at 07:13 PM.. |
12-13-14, 03:19 AM | #2 |
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Have you seen this article?
I don't really understand the PassivHaus standard. They have a Specific Primary Energy Demand of ≤ 120 kWh/m2. Yr which seems to me very generous. Even my house - built in the 1890s- easily meets that. They also have a Specific Heating Demand of ≤ 15 kWh/m2. yr which seems comparatively strict, at least in our climate. My house is nowhere near that. I can't relate the 2 measures. In many climates the energy required for heating is far and away the biggest requirement, but it is a fairly small portion of the allowed total. I must be misunderstanding something I guess. |
12-13-14, 06:00 AM | #3 |
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No one I have talked to pays attention to the 120kwh/m2 only to the 15kw/m2 and if you can get to this level, the biggest load in the house becomes DHW.
I brought this up because I am working on a 3 floor, 380m2 passivHaus and we are struggling to select the heating system. The owners are leaning towards radiant tubing and 40mm of thermal over pour (gypcrete) even though it is a high cost for very little heat output. It does, however, make the heat very even and has other benefits (sound and fire). The option to this is at least 6 heads of ductless (although we have gas on the street, we are not having gas in the house) and an ERV made by Air Pahoda, currently the most efficient one on the market. The ERV was delivered a couple days ago. As we know multi head units are not as efficient as single head units so if we went this route, there would be a lot of infrastructure. so the option is to have one larger heat pump heating a water tank for both DHW and the floors. Total heat and cooling loss is estimated at 7kw (24Mbtu). |
12-13-14, 05:03 PM | #4 |
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Check your math??
-AC
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12-13-14, 05:26 PM | #5 |
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7.000 x 3412btu=23884 btu or, 23.8Mbtu (I know M should be K but look at any boiler spec and it is in Mbtu and this is what I am used to)
Last edited by Mikesolar; 12-13-14 at 05:35 PM.. |
12-13-14, 05:47 PM | #6 | |
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Quote:
is 23884 BTU = 23.8 Mbtu a metric thing? I was under the impression that in metric: 1,000,000 = 1,000 K = 1 M That's the way it is in the world of electric phenomenon, and all other physical phenomenon that I know of. -AC
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12-14-14, 11:33 AM | #7 | |
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Quote:
If this actually is a passive house, the heating need should (by design) be only occasionally required, and when the heat is required, it should be very, very modest. The whole rationale behind Passive House is that no heating system is required at all. That is why it is "passive". For instance, your comment about the heat being very even... if you mean spatially even, like, "the floor will feel warm all over." The floor will not feel warm anywhere, because the heat needs will be so low, that the temperature will never be high enough for bare feet to ever sense warmness. HERE_IS_A_LINK that explains why this is the case. A lot of people who want radiant floors are led by the dream of warm feet in the winter. If your radiant floor got warm enough to feel warm on the feet, AND if it actually is a Passive House, your client will have to throw open windows in the winter to keep the room temp at a comfortable level... This would completely cancel out the work that their ultra high efficiency (and very expensive) HRV is doing. They will be cursing the person who put in radiant floors all the while. -AC
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12-13-14, 05:25 PM | #8 | |
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Quote:
So if your 1890 house is 75 m2 (total wild guess), then your total annual energy use would be 75 * 120 = 900 kWh for the year. Or about 75 kWh per month (total), on average. Of course, there would be seasonal variations. So, your 1890s house has the ability to perform this well? I live in a far less climatically challenging area (Portland Oregon, USA) that you do (Finland), and I am struggling to get my 1890s house any where close to 75kWh per month. In fact, in my least-use months, I'm still using 6 times as much, even after all my work. You must tell me your secrets! -AC_Hacker
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12-14-14, 10:31 AM | #9 | |||
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Quote:
Quote:
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- some ability at basic arithmetic - economies of scale (my house is 724 sq m, not 75, so the PassivHaus target is 7 240 kWh per month; not exactly stringent) - additional wall insulation, inside and out - good attic insulation - well-insulated hot water storage - GSHP for heating - 5 x 20 tube solar collectors There is still much more I can/should/will do to reduce my energy consumption. My approach is for slow but constant improvement. |
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12-14-14, 11:50 AM | #10 |
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And "therein lays the rub" as the bard would say......the floor will not be warm to the touch at all. It will be just above body temp if that. The problem with the ductless in a larger house is distribution and the open/closed door issue. The radiant eliminates this issue, but at a cost. The HP that heats this water will be efficient indeed but seldom used. Most of DHW will be from an oversized drainback solar system which I suspect will account for 80%+ of the load.
I read through the Oregon paper. Most of it is not news to me and I have designed the floor heating with this in mind. The floor will move solar heat to the colder areas but given the high insulation levels, it will all be VERY slow. I suspect that the radiant is not all that necessary but some method of even heating is necessary in a large house. If it were smaller, I might not do it and maybe just do bathrooms and let the HRV move the heat around. Plus...I gave them all the options and the reasons behind them. PassivHaus owners, it seems, really do like to get into the nitty gritty of the house. They are not "passive" owners, haha Last edited by Mikesolar; 12-14-14 at 12:38 PM.. |
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