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Old 05-29-12, 05:09 AM   #1
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Default In question of Passivehaus

EnerPHit

We already have many older houses. When should we give up and call the bulldozer? Is 0.6 ACH@50 actually going to save you ANY money at all? Or maybe cost more than you'll save over a thousand years? I'm being quite serious with the thousand year remark. I constantly do ROI calcs and for anything real serious we're usually talking about a time span which is MUCH longer than the usual human life. In a retrofit do you drop over 100K to only get CLOSE to PHI standards or do spend 50K or less and "simply" go with "absolutely fantastic"?

My personal opinion is that PHI standards are an absolutely great goal. Just don't beat yourself up when you can't make them. It's honestly pretty hard to get below 1ACH 50 in new construction. It can be done ...... but you have to be OK with using tapes and foams which aren't going to last 50 or 100 years. In 30 years your passivehaus is at 1.7 ACH@50. But you did get to have the PH inspector come and give his seal and you also did get to pay for it.

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Old 05-29-12, 06:08 AM   #2
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There were three things that brought my into thinking that passive house can actually be affordable. There is the Minnesota passive house that is at the Minnesota State Fair, talked with the guys there about the costs and the additional costs of the passive elements are partially offset by not installing a standard HVAC setup and further by the utility costs. They don't really have a good web site with info and pictures or I'd try to link it, sorry.

The second was the 100k house project, they built affordable low energy houses and then eventually went all in for a passive house, it is a great read to show the extra steps needed to reach passive. They do show lots of details like installing a thick plastic barrier to prevent air from below the slab from interfering with the 50 pascals, lots of things I didn't think of.

The final, and my favorite is the CLAM affordable passive house. I watch this video and it shows a lot of detail of what was done to seal up the structure (11CFM at 40pascals prior to windows) and .35ach50 after full construction. This one made me realize that you don't need a concrete stucco or metal clad building to seal air and brought plenty of ideas together for me in case I ever build a new house myself.

Even if you did slink to a 1.7ACH50, that's still very good. There is a Duluth, MN house project that didn't meet the Passivehaus standard because their ACH was at 1 but the house is still effectively passive, even in a climate that has a design temp around the -20f region that has plenty of wind from Lake Superior.

The ACH standard seems tough to meet and I see the limits myself for payoff periods with my own retrofit. It seems that the airsealing that I've been able to do was cheap and anything that I can't do involving tearing down walls would cost more than what I could reasonably make back. I find that Passivhaus standard seems to always be focused on reducing the heating need of a house and adds more windows than would probably be needed which creates a high cooling load unless the proper overhand is built in, which I rarely see being done. For my house think that blocking most of the light in the summer will reduce my energy use the most over doing anything else that I haven't done yet, more so than heating costs with my current equipment setup. Likely not if I swapped out my air conditioner with a more efficient one but the swapout of the air conditioner and furnace is I can't see ever paying off because it would take a very long time to rack up even a $7000 energy bill at this point. $300 of insulation, easy to make that pay itself off.
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Old 05-31-12, 04:39 PM   #3
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EnerPHit

...When should we give up and call the bulldozer? Is 0.6 ACH@50 actually going to save you ANY money at all? Or maybe cost more than you'll save over a thousand years?
Glad you included the link... but did you actually read the original article? There is way more information there... maybe 10x more.

It can be frustrating, but there are highly detailed trainings on how to achieve PH standards on new construction and also how to achieve the reduced standards on retrofit.

The difference in cost for new construction between code and PH is pretty small, when you subtract the elaborate heating system that will not be needed. And the payback is short.

Retrofit is a different matter in the USA... at least for now.

Our energy costs are held low because we spend so much (1/2 of the federal budget) on the military, guarding 'our oil that happens to be in other countries'?. How long will we be able to sustain the extravagant military? How long will the oil hold out?

Europeans, who have 2X+ energy costs are much more motivated than we are.

Sometimes I think that we are like flies caught in amber, in as much that we hold to pay-back models that ignore the rapid rise in energy costs. Fracking will save us some, in the shorter term, but the environmental cost will catch up to us.

I think that whatever we have to do to use less energy is the right thing to do.

Thanks for leading me to that article in Construct Ireland Magazine. It's a keeper.

-AC
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Old 05-31-12, 08:14 PM   #4
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My point was that the line between passivehaus and regular super house is pretty small but very hard to achieve. At the level of a good super insulated house the HVAC system will be about the same size. I'm just not a fan of all the tapes and foams needed for .6 ach 50.
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Old 06-01-12, 11:06 AM   #5
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My point was that the line between passivehaus and regular super house is pretty small but very hard to achieve...
I do understand that point of view.

But I still think that casual ROI calculation methods, that we all tend to do when we go about making well-thought decisions, need to be updated...

Something like this from an entirely different thread:

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...Running the calculations it will take 20 years for the lights ROI. But that is at todays dollar. The next time we have an increase in the cost of energy that ROI time will shorten...
...that way of looking at things may not lend itself to intuition very well, but it is certainly on the right track.

And there was another very interesting post in another thread (which I can't find right now) wherein the poster was trying to decide whether to insulate, and how much insulation to put in their house. The person posting was comparing the alternative of putting the insulation money into a savings account (money presumably at no risk, and a known rate of return) to the alternative of reaping the benefits of insulation and enjoying the money not spent on energy costs. In the comparison, the money not spent was treated as being equivalent to interest earned in a savings account.

When the alternatives are viewed from that perspective, the correct choice stands out quite clearly.

-AC
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Old 06-02-12, 10:08 AM   #6
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Default ROI & Performance

There have been some very excellent postings and work toward our homes envelope performance. No mater what heating/cooling sorce we use, we need to keep that energy as long as we can. But at what lengths do we go. Bull-dozer or retro-fit. Is the ROI the goal, what about comfort is that the goal? Do we need a project for our hands and sence of well being? Would our log cabin of 120 yrs old just need a little maintance. The very best thing about our being eco-renovators is anything we do improves our lives.
The passive house is a great inspiration. Alot of the technecs and materials have been around for a long time. The carefull attention to detail is the holy grail. We can do this, and save some hard earned cash.
Myself I've learned alot here. I've saved a lot of money and my family is more comfortable. ROI , yes,, comfort, yes ,, work satifaction,yes. 0.3 ACH@50 not even close but I'm not going to put down the spray foam can any time soon.

Of late I've been in the shop installing the condensate line for the home made GSHP air handler for the air condition season coming up. Also installing 1" copper for the addition of solar hot water to the south wall. Solar hot water had worked so well for the house.(haven't paid for any domestic hot water in two months) This leads me to the shops insulation. The shop is insulated Ok but R20 ceiling & wall, could be a whole lot better and the steel siding is starting to show its age. Hmm, I'm thinking, remove steel and install foam and stucco to exterior as well as one south wall of glass & copper fin. This would help air-seal the envelope as well as add much desired insulation. The other improvement considered, was heated concrete floor. We will have to pick and choose the under-takings. ROI with the further improvements. Ha, I believe with the homemade GSHP heating the shop this winter didn't cost me $400.00 in electrical costs, far cry from oil heating $2800.00 or more. From this point the ROI maybe only in resale value in the distant future or if electrical cost go up exponetially. Comfort, some windy cold nights I start work in the morn. with a shop temp of 14 Deg C. That would get better but not entirely nessisary. Something to improve greatly Eco-renovator style, you bett.

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Old 06-02-12, 12:19 PM   #7
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...Is the ROI the goal, what about comfort is that the goal? Do we need a project for our hands and sence of well being? Would our log cabin of 120 yrs old just need a little maintance? The very best thing about our being eco-renovators is anything we do improves our lives...
Great thinking.

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Old 06-02-12, 12:40 PM   #8
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The retrofit passivhaus (aka EnerPHit) stuff is well beyond me. I can't come up with how the ROI would pay off to tear down lots of drywall, add studs, insulation, and redrywall, replace windows, etc would pay off, even over an extended period but the insulation that I've added where I can do far and air sealing has done tons. It's clear to me though that I've got a long way to go for air sealing because I can watch the humidity rise on a high dew point day at a fairly fast rate even though I've got no latent loads in the house(time between showers, cooking, etc) and on a day with a matching indoor/outdoor dew point the relative humidity is solid. To me that's the universal indicator of air leakage. I'll do what I can to seal the place but outside of tearing apart the half of my basement to get at the sill plates that I can't reach, I can only go so far. I suppose I can seal off the finished area gaps from the unfinished part of the basement the best I can and hope for the best.

If I was going to tear down all the drywall and basically rebuild the envelope from the inside, I'd rather sell this house and build one that better fits my needs and go as super house as I feel fits my needs. For me I don't mind a little air leakage as S-F suggests and would like to be sure insulation cavities are sealed the best they can be and use well performing windows and thick offset stud walls with cellulose and do the best with air sealing as the house is built and hope I can track down a reputable contractor that can give me some sort of guarantee on airtightness.

There's that weird point that you reach where installing a solar heat system with lots of storage or going with baseboard heaters and using ductless mini-splits is cheaper than going the conventional ductwork natural gas HVAC route. I'd include a flex-ducted Recovery Ventilator as the only ducting in the house. If I get to that point, I'd be plenty satisfied and would like the ductless mini-splits for their dry function and variable capacity, not to mention heating without baseboard almost 100% of the time. I'd probably just skip the baseboard and use the little space heater I already have if I need the backup heat.

I won't get to that point retrofitting my house, even though I could keep it to temp with the smallest variable speed motor natural gas furnace that is sold today for homes and I suppose if natural gas gets expensive enough I'll toss in a mini-split as my current furnace is a 76% efficient clunker and my AC is 8.5 SEER, a 95% efficient furnace doesn't have the ROI for me when my heating bill has never been over $70 last winter and was less this winter. Electric bill has never hit $100 and only once went over $70. I think I'm doing pretty well already considering I have R19 walls and quite a bit of leak. I don't mind temp swings as much though, so usage and bills will change when someone else moves in.
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Old 06-02-12, 03:23 PM   #9
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...we spend so much (1/2 of the federal budget) on the military...
All I'll say is that the military budget is $0.7 trillion out of the total federal budget of $3.8 trillion. Defense spending is 5% of our GDP. Heath care, pensions, and welfare are $2.3 trillion.
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Old 06-02-12, 03:52 PM   #10
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