Author Topic: Passive House (or perhaps passive-aggressive house actually?)  (Read 4148 times)

Money Badger

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Since MMM is a big fan of "thermal mass" for housing and some of the concepts implicit to a net energy positive house, wondering if anyone on MMM has built or lives in a home that is fully following global (namely European) Passive House standards to ensure the construction returns net consumer energy to the grid the majority (if not entire) time?    What were the pitfalls...  what were the joys of such an endeavor??    Does the passive house deliver the monthly payback in all seasons, or just the extremes of summer and winter???

Looking at the available tech, it seems a solar+inverter+battery system for a true "nearly off the grid passive house" s going to be in the $30K ish range total.    So a payback of < 10 years means saving $3K plus interest per year...


AdiposeFinn

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Re: Passive House (or perhaps passive-aggressive house actually?)
« Reply #1 on: July 10, 2016, 12:42:52 PM »
Building a true Passive House will be very expensive and if you live in a mild, temperate climate it will be a huge overkill. The window package alone will be at least $30K and probably have to be imported from Europe. Unless you have a ton of money to burn I would look for other solutions like the Pretty Good House (PGH) standard. http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/pretty-good-house
 
BTW: You don't mention what climate you live in or the style of house you are trying to achieve.

If it were me I would build a house that is net-zero (or close) and follows the cheaper PGH standard. Then when solar panels double in efficiency and halve in cost, I would put solar panels up to get to net-zero.

There are just too many variables to answer your question. Go to the library and start reading every article in Fine Homebuilding  on Passive House and net-zero houses. Then when you get a better idea of the trade offs and costs, consult with an architect in your area.
« Last Edit: July 10, 2016, 12:47:48 PM by AdiposeFinn »

human

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Re: Passive House (or perhaps passive-aggressive house actually?)
« Reply #2 on: July 10, 2016, 01:39:55 PM »
There's a series of articles called a pretty good house over on greenbuildingadisor. IIRC the focus is more on roi and keeping costs down. The focus is insulation and sealing.

Vic99

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Re: Passive House (or perhaps passive-aggressive house actually?)
« Reply #3 on: July 10, 2016, 02:35:44 PM »
I like this whole idea and if I were buildling from scratch I would be net zero or something really close, but I live in a 1920 built 1600 sq ft Dutch Gambrel.  Took me 10 years to get to ave insulation for New England, added grid-tied solar, and a wood burning stove for ~95% of our heat.  I like my house and land and am not moving.

Unless you are away from the appropriate infrastructure, going solar with battery storage (off grid) doesn't make sense if you already are grid tied.  Although I don't know much about the batteries that Tesla is developing, traditionally batteries double the cost of solar.   Batteries are billed to last 5-20 years before needing replacement, but most go 5-7 years because you have to make sure you don't do too deep of a discharge.  It really kills battery life and efficiency if you drain down too much too often.  Although lots of us on this forum are about optimization and efficiency, do you really need another thing like babying batteries to prolong there life to keep track of?

 Many states offer some kind of incentive to be grid-tied with solar.  Here in MA we get a credit for all the power we make in excess and sell back to the grid to temporarily and intermittently power our neighbors houses.  We also get to create and sell SRECs (Solar Renewable Energy Credits).  You make 1 per MW of solar produced.  I make 6.5/ year.  Currently they are selling ~$425/SREC here.

Four years ago I paid ~31k for a 6.4 kW system with installation that also included an upgrade from 100 amp to a 200 amp system.  This covers ~98% of my electricity and I charge a Chevy Volt (although I do get about 1/4 of the volt's energy from charging at work).

Plenty of other solar threads here.  If you go solar, get as big as you can afford.

Lots to say on insulation, but depends on your climate.  Air sealing is probably the cheapest and most effective activity you could do in this department.

Good luck

BudgetSlasher

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Re: Passive House (or perhaps passive-aggressive house actually?)
« Reply #4 on: July 10, 2016, 03:31:06 PM »
To preface this post, most of this is based on my research and/or planning for projects over the next few years.

Since MMM is a big fan of "thermal mass" for housing and some of the concepts implicit to a net energy positive house, wondering if anyone on MMM has built or lives in a home that is fully following global (namely European) Passive House standards to ensure the construction returns net consumer energy to the grid the majority (if not entire) time? 

I thought the goal was net-zero not net-positive. Where I live there is net metering with credits that carry over for 12 months before expiring. Which means going from net-zero to net-positive is a money losing investment. Actually going net-zero is money losing too, because there is a monthly minimum bill (covering the first 50 kwh); so as long as you are connected to the grid [financially] you should take advantage of those first 50 kwh.

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What were the pitfalls...  what were the joys of such an endeavor??    Does the passive house deliver the monthly payback in all seasons, or just the extremes of summer and winter???

I have only lightly looked into passive house and I have pulled some good ideas from it, but if you are dealing with an existing structure you probably will not be able to justify upgrading to a true a passivhaus and I have not looked into the balance on building. Still what you see in a passive house can give good ideas for upgrades in a remodel.

What are you calling a payback? If you mean will it reduce your costs in all seasons the answer is yes; if you mean will I get cold hard cash, the answer will depend on your local solar (I assume that is your main point here) interconnect agreement. If your question is will I have a net-positive electric flow at all times; well it depends, the further south you are the more stable solar generation is year-round, up north to have a surplus in the winter you would be massively over producing in the summer, it will also depend on your seasonal energy use.

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Looking at the available tech, it seems a solar+inverter+battery system for a true "nearly off the grid passive house" s going to be in the $30K ish range total.    So a payback of < 10 years means saving $3K plus interest per year...

I am considering going solar in the next few years; however, before I do I am doing what I can to minimize power use and thus the size of a system needed. To me 3k a year savings on an electric bill seems like a high electricity bill, but I have fossil fuel heating/DHW and no cooling, so location and what is electric in your house could change that.

If you are only going to be "nearly off the grid" why invest in batteries? As I discussed above, at least here, the utility acts as the battery providing credits that are good for 12 months and we rarely suffer a power outage that is more than just a blip; plus batteries wear out faster than a solar array and will have to be replaced.

Vic99

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Re: Passive House (or perhaps passive-aggressive house actually?)
« Reply #5 on: July 11, 2016, 12:57:47 AM »
Budgetslasher said, "wer will depend on your local solar (I assume that is your main point here) interconnect agreement. If your question is will I have a net-positive electric flow at all times; well it depends, the further south you are the more stable solar generation is year-round, up north to have a surplus in the winter you would be massively over producing in the summer, it will also depend on your seasonal energy use. "

I mostly don't dispute that.  However, it is worth noting that solar panel effeciency increases with cooler temps.  My panels max out production more or less under 20 F.  Of course day length, and snow before it melts off are bigger factors than gains from cool temps.

My best total production month is March.

slugsworth

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Re: Passive House (or perhaps passive-aggressive house actually?)
« Reply #6 on: July 15, 2016, 05:25:11 PM »
This has become a big deal in Seattle/Portland/I-5 corridor with an active "Passive Haus" design community and a number of net-zero and net-positive buildings.  If I was going to build new, I would consider it.

I saw a mother-in law unit that was modeled at a $30/yr annual heating load (cooling is still fairly uncommon here) so I think that even a larger passive house would require a fairly modest PV system in this climate to be net-zero. . . I don't see a reason for batteries as they have a big carbon footprint and don't do much in an area that is well connected to the grid.

205guy

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Re: Passive House (or perhaps passive-aggressive house actually?)
« Reply #7 on: July 26, 2016, 07:29:18 PM »
I have friends in Hawaii with grid-tied solar, and that essentially makes their house net-positive. They get enough over-production to cover their grid usage and charge an electric car (same as he other commenter with a volt, they charge a bit at work too). No heating (no insulation), and they get by with ceiling fans and no A/C--house design is all about post-and-pier and airflow, not thermal mass. Hot water is solar too, with electrical backup. I guess they do use a bit of gas for cooking, I'll have to ask about that. As you can imagine, it's easierto be net-zero or net-positive there with the mild weather.

One thing I've done myself is to add a small solar array and batteries to my regular house. This is not grid-tied, it's a separate 12 VDC system. this is only for lights, all appliances still run off of the 110 AC. I installed cable lighting with 12 VDC LEDs in all my house, so I have really bright lights, like halogen, without the incandescent heat or CFL colors and flicker. I had an electrician install the inverter and wire the batteries, then I ran my own cables through the attic, down to some DC switches, and strung the lights. I also added some 12-to-5 VDC USBcharging ports for phones and tablets. It saves a bit of electricity, though not enough to be really be cost effective because batteries are expensive (but not insanely expensive because ey are not sized to run a fridge or a well pump). But in the end, I also have nicer lighting and backup for storm outages, etc.

Money Badger

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Re: Passive House (or perhaps passive-aggressive house actually?)
« Reply #8 on: August 20, 2016, 06:08:11 AM »
Very helpful comments and insights all...   Some observations locally...

Solar/PV companies in my state (Georgia) focus mostly on industrial users who have people that do the math, file the paperwork and have good accountants to write off the capital expense, file forms, etc.    However, they also market to residential as well and have very detailed financial models to show the benefit over time, depreciation of the system, total annual net benefits, etc.

There are good net metering rates for my co-op utility that make solar more attractive if a residential solar system achieves net positive generation.

Local builders with true energy efficiency credentials are scarce.   But there are local meet-up groups on the subject where good ones can be found through word of mouth...   The good builders / remodelers don't need to advertise.

The comments about PGH standard were very helpful...   The Germans passivehaus of course, goes to the engineering extreme.   The true value proposition is in the middle of the options somewhere...

So overall, quite encouraged and as we consider downsizing our nest... will continue the efficiency quest!