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Net Zero Energy Home - or darn close to it
Last Post 27 May 2009 07:38 AM by slenzen. 13 Replies.
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CHL
New Member
Posts:29
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| 12 May 2009 09:25 PM |
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I'm curious to know what strategies people are pursuing for the lowest net energy homes (not including plug load). And let's please stay away from $15k solar roof installations (credits are great but in northern climes we've got lots of cloudy weather so would have a very long ROI). |
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TerryJ
New Member
Posts:35
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| 12 May 2009 09:35 PM |
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Posted By CHL on 05/12/2009 9:25 PM
I'm curious to know what strategies people are pursuing for the lowest net energy homes (not including plug load). And let's please stay away from $15k solar roof installations (credits are great but in northern climes we've got lots of cloudy weather so would have a very long ROI). Even in northern climates houses can be built to be zero energy using PV & wind etc. Examples are in Edmonton, ON (I'll try to find the link tomorrow) and in upper NY state: http://www.ualberta.ca/~mtyree/SWIEP/Docs/HP125_pg46_Tyree
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TerryJ
New Member
Posts:35
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| 12 May 2009 09:38 PM |
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Riverdale in Edmonton:
http://www.riverdalenetzero.ca/Home.html
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ecobuilder
New Member
Posts:95
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| 13 May 2009 02:08 AM |
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Water filled windows, what the heck is that?
Yes the prototype windows shown have over #3,000 of water in them. The ability to capture heat 
quicker than a traditional Trombe wall but the same principles. Not bad looking either Ay! for more pictures of the house click on the picture.
Below is the short list, with each one being a ten hour conversation at least, maybe even a 3 day workshop. Here in MA we start with the heating loads, maximize inslulation, solar gains, thermal breaks, proper window placement, size, type glazing, orientation. I could go on and on but I won't. If you want to find out more out the approaches I use check out the links below.
Passive design no brainer
Insulate Insulate Insulate, I don't think you can over insulate, but the ROI diminishes pretty quickly over R40 walls and R60 roof
Air seal tight as a drum, blower door during construction
HRV/ERV HRV here in MA cold climate, better control of humidity and indoor air quality
geothermal if you can afford it
solar thermal another no brainer, can be combined to provide some of the heat load
PV if not now plan for the future, the cost came down 50% over the last year, not including tax incentives.
Pictures
http://picasaweb.google.com/TomPittsley/PassiveSolarHomeMiddleboroMA#
videos
http://www.youtube.com/user/eebuilder
Blog
http://tompittsley.blogspot.com/
website
http://www.eebt.org/
Tom Pittsley
ecobuilder@aol.com |
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| "Don't be afraid to go out on a limb. That's where the fruit is." Jackson Brown |
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CTP
New Member
Posts:28
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| 13 May 2009 10:02 AM |
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CHL,
What climate zone are you in? For zones 1-3 and maybe 4 Eco-Panels offers an R-60 panel for walls and roof applications that is only 8.5" thick. This panel virtually negates any thermal transfer under almost any condition and can be sided with many different skins from OSB to FRP. With a maximum dimension of 4X12 this R-60 panel for cold climates can actually achieve an R-64 rating at minimal temperatures. Building a super insulated, tightly sealed structure that is orientated properly is the best place to start in order to achieve the lowest net energy homes. If you have little opportunity for passive solar heat gain, then a passive solar design may incorporate too much window area and can be a big problem for heat loss. Check out our website at www.eco-panels.com to learn more.
Regards,
Craig |
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CHL
New Member
Posts:29
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| 13 May 2009 11:06 AM |
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I agree that extreme insulation is the key and SIPs are the best avenue towards it - of course that's why I'm on this message board. Say you've got the "perfect" thermal envelope - assume the R40 walls and R60 roof (I've heard those numbers before and a couple of people here are reinforcing it - and the slim nature of the urethane panels is very attractive from a total assembly cost perspective) - what then? Windows of course are going to be the next greatest opportunity for heat loss - you've got to balance the positive health effects of natural lighting and "views" as opposed to the thermal bridging. I guess it's just a square foot calculation of U factors and a very subjective value analysis for the amount of windows considered. Links to any studies on how "whole house window selection" can help energy savings would be appreciated - trick is finding a study that isolates it to that point, I think.
And if you have a near perfect thermal envelope, what about the positive thermal impact of the inhabitants? A resting person emits 250btus per hour - and a person in motion can emit three times that much. What about an entire family? Not that I'm thinking that having more kids would reduce my energy bills (funny thought, being a dad), but I wonder if anyone has seen studies of the thermal impacts of home residents? Schools and commercial structures look at this all the time for HVAC sizing BECAUSE IT MATTERS, so it stands to reason if you have an almost perfect thermal envelope you could stand to benefit from a thermal perspective just by being there (assuming you want to warm the environment, which in this case is key). I go back to the old addage for sips - "heat with a candle, cool with an icecube". Perhaps it has not been looked at so much since most structures leak away the energy from any potential residential gain. |
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Dick Mills
Basic Member
Posts:171
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| 13 May 2009 03:36 PM |
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Tom, does anyone manufacture a "water filled window"?
And, CHL, one problem with your "more kids .. lower heating bills" is that the average person only consumes 2500 calories a day. Okay, in the US it might be close to 5000 calories a day for the porkier among us. 2500 calories of energy is only about 10 btus (or 20 btus for the 5 kilocalorie diets). While it is possible in a cold environment that a human can lose a lot of calories, it isn't something that can be sustained - which is why we have to live in climate controlled enclosures. |
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ecobuilder
New Member
Posts:95
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| 14 May 2009 06:10 AM |
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Here is a link to a heat loss calculator I like to use as a first source before doing a complete energy model, but the numbers a pertty accurate. http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htmIt does account for interanal gains from occupants. check it out. it is a great tool, simple to use and after comparing it to the full energy model within a couple of hundred Btu's an hour, heat loss. Tom Pittsley ecobuilder@aol.com www.eebt.org |
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| "Don't be afraid to go out on a limb. That's where the fruit is." Jackson Brown |
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JBACC1103
New Member
Posts:28
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| 15 May 2009 10:21 AM |
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Where is the home? How big is it? What is the budget?
Without generation of some kind, net-zero energy is tough.
You could try solar hot water to radiant heat. Works pretty good, even in cold an/or cloudy weather. I think you would need a seperate system for DHW, that is based on some things I have read about high bacteria counts in systems with DHW and radiant heat used from the same source water.
If you can't afford to do it all, make the home as efficient as possible, with insulation, good windows, good passive solar charistics and non-fuel based heat, then purchase power from your electric company that is 100% renewable(1.5 -2 cents more per kwh where I am). You will still have a bill, but your carbon output will be as low as can be. |
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| It ain't easy being green.... |
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CHL
New Member
Posts:29
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| 17 May 2009 02:05 PM |
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I like the heat loss calculator referenced by ecobuilder. The point of my original post was to try to optimize as much as possible energy efficiencies without going to renewable energy sources. I know for small incremental values (and sometimes the cost is not even more) I can get significant improvements in energy efficiencies - such as with a very tightly sealed and energy efficient building envelope. I want to maximize the efficiency of an investment BEFORE much larger sums are spent on solar arrays on the roof or solar thermal (though I think I'd go solar thermal before PV). Hence the questions about leveraging internal heat gain. General feedback on the priority approach confirms what I've been thinking - after orientation, start with the building envelope, then windows, etc.
On more than one occasion I've seen the scientists at Oak Ridge Nat'l Labs talk about their ZEH Core wall - where heat from major appliances is leveraged for the benefit of the whole house. But I've never seen more detailed information on this except to find diagrams of what they have presented on the web. I know a refrigerator - even a new and high efficiency one - kicks off a lot of heat. Couldn't we be distributing this heat? In a small enough house and well designed home I'm sure we could. The dryer you'd have to be concerned about moist air.... And so on, and so on. |
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Bob I
Basic Member
Posts:121
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| 17 May 2009 07:25 PM |
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Check out Passive House US. Following their guildelines (which are pretty strict) gives you a house that heats for 10% of the energy of a house built to current code. And it works; they've been building them in Europe for years. |
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Bob Irving
RH Irving Homebuilders
Certified Passive House Consultant |
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Dana1
Veteran Member
Posts:1073
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| 18 May 2009 12:44 PM |
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Since heating/cooling accounts for the lions share of home energy use, reducing the load is the single-most important aspect to the net-energy numbers. Insulation is of primary importance at reducing heating & cooling loads, but thermal mass is required in order to stay comfortably cool in summer superinsulated houses without compressor-based mechanical cooling- managing solar gains for optimal winter & summer balance is a lot easier when you have some mass inside the thermal boundary to keep diurnal temperature swings moderated. (Ergo Trombe walls, etc.)
Plug loads count- a LOT. Building a house to PassiveHouse standards you need to manage plug loads in order to not overheat the place. Sure, overventilation with earth-tempered ventiltion air takes less energy than compressors, but it still adds to the power consumption, and doesn't work during periods of peak cooling load. (If it takes less than a kilowatt to keep up on heating-design day, a few stray hundreds of watts represents a cooling load much of the time.) Daylighting without high solar gain can also be key.
ROI is high on solar PV in any climate, but thin-film PV performance is higher than you might think under "bright clouds" conditions. In order to make Net Zero you have to produce more than you use, and energy use will never be zero. PV is a reliable way of getting there. If you make your loads low enough (PassiveHouse style) PV can get you there within the physical footprint of the house, even in foggy-dew coast regions of the Pacific Northwest. But for many 'mericans just their plug loads would swamp the output of 10kw (peak-rated) installations. You don't have to live in the dark, but you can't leave 2 Tivo's, 3 computers & 400 watts of incandescent lights running while putting 3 loads of laundry through an electric dryer every day and keep the PV array physically constrained to a manageable size & cost. (A Tivo uses nearly as much power every year as a high-efficiency refrigerator.) Decimating the background load, then using the highest-efficiency lighting & appliances is far cheaper (& smaller) than ever more PV.
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dmaceld
Advanced Member
Posts:860
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| 25 May 2009 11:05 PM |
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Posted By Dick Mills on 05/13/2009 3:36 PM
And, CHL, one problem with your "more kids .. lower heating bills" is that the average person only consumes 2500 calories a day. Okay, in the US it might be close to 5000 calories a day for the porkier among us. 2500 calories of energy is only about 10 btus (or 20 btus for the 5 kilocalorie diets). Wrong calorie! Food calories are "large calories" or kilocalories. 2500 food calories is about 10,000 Btus.
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| Building house - what a way to spend retirement! It's done! We're living in it! |
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slenzen
Basic Member
Posts:289
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| 27 May 2009 07:38 AM |
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"If you cannot measure it, you cannot improve it."
— Lord Kelvin
How much does it cost to leave your TV on all day? What about turning
your air conditioning 1 degree cooler? Which uses more power every
month — your dishwasher or your washing machine? Is your household more
or less energy efficient than similar homes in your neighborhood?
Its nearly impossible to make informed choices about electricity.
This is a problem but also a huge opportunity for us all to save money
and help the environment by reducing our power usage. Studies show that
access to your household's personal energy information is likely to
save you 5–15% on your monthly bill. Even greater savings are possible
if you use this information to see the value of retiring your old
refrigerator, installing a new air conditioner or insulating your home.
The potential impact of large numbers of people achieving similar
efficiencies is even more exciting. For every six households that save
10% on electricity, for instance, we reduce carbon emissions as much as
taking one conventional car off the road (see sources and calculation).
At Google we're helping enable a future where access to personal
electricity information helps everyone make smarter energy choices.
Google PowerMeter shows consumers their electricity consumption in a
secure Google gadget. Today we are testing the product with utility partners in the US, India and Canada. We plan to expand the rollout of Google PowerMeter later this year.
We think Google PowerMeter offers more useful and actionable feedback
than complicated monthly paper bills that provide little detail on
consumption or how to save energy. But Google PowerMeter is just a
start; it will take a lot of different groups working together to
create what the world really needs: a path to smarter power.
Are there any gadgets that may be some intermediate plug between your appliance and the socket that won't draw anything when your appliance is off? Or perhaps a smart outlet or smart electrical box?
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