I have been doing a lot of research on green homes, i.e. net zero homes in an attempt to make it a practical conversion from a typical suburban home in a northern climate. I'm not an expert at green homes at all, but I want to put down some thoughts, maybe others will correlate or correct.
The typical net zero home usually involves making the outer surface area of the home as minimal as possible (i.e. a box). then adding tons of high-quality insulation, careful for cracks, triple-pain windows. Having most windows pointing toward the equator, some east and west, and very little towards the poles, basically only enough to let natural light in. Then, efficient appliances, hot water heating, and lighting. Then, since everything is so sealed, they have an air exchanger so no one suffocates unless the electricity goes out, then, since electricity is needed, they load the top of the house with solar panels and install a battery cabinet.
The typical wofati is a cave with glass windows facing toward the equator. Some have earth-battery tunnels (a fan and tunnels into the earth).
The typical northern house, especially older and suburban is a box. Sometimes there's an additional room. Ours has one. Until it can be insulated to mimic a wofati, it is curtained off with the understanding that is a great storage area.
Windows facing the equator is different in each house. Ours was chosen for lots of natural light (for plants and humans in winter). Most are facing the equator, however, there are plenty facing the pole. This can be fixed by exchanging, plastic/rubber overlays, shutters, window quilts, heavy curtains in some sort of combo (taking into consideration the need for natural light). For instance, we have a balcony door facing the pole that's all window and another door in the house that's facing the equator that's mostly solid. A quick switcheroo would correct that.
With solarenergy, you need a surface for absorption, which means dark colors and thermal masses. By painting the swath the window light travels across during winter a darker color, especially having the material being a thermal mass, you can absorb the energy from winter better. Paint is not too expensive, 20-30 a can. Cement board ($10), cement coloring ($, and a bag of fine cement ($15) = a thermal mass. You can also use cob, which some people can locate for free. And, pick up some black furniture or furniture covers ($20) or black rug.
Insulation in a suburban home is usually nothing special. Probably a going over with an energy audit to find holes and get the insulation up to 30R across the board would be a good idea. Most old insulation jobs are not up to code, and with the pressure differential between inside and outside any insulation gap jets cold air in and hot air out. Most net zero homes have an R of 60 or more, but I read there's a certain drop-off in value at a certain point on the insulation front, so 60R + might be over-kill.
Another thing to consider is thermal bridging. If insulation is installed inside the home, like they are experimenting with in the U.K., then this might be helped, but even still I'm not sure it's a huge difference, so in my house I'm going to do about everything else first.
Window thickness in most homes is double-pain, some with additional storm windows. However, the more panes, the less light (the more refracting), so I'm not sure this is worth it on the equator facing. On the pole facing, this might be good, but a much more expensive than the ones mentioned above.
Most older houses in northern climates have a basement. This is for storage, safety, and as a temperature regulator. For this reason I prefer a deeper, less finished basement. For those that aren't deep or are really finished, perhaps some wall venting or burying the house up to whatever it can take structurally is a good option. I found that our house was, for whatever reason, about 2 ft higher out of the ground than necessary, which was also causing the slope and rain to go towards the basement. Dirt was all that was necessary to correct that. Where the structure is not as strong, perhaps a retaining wall can help.
Lighting and appliance efficiency. We are slowly eeking towards LED and lizard-lamps (that contain mercury and thereby help with vitamin D deficiency). Most people do that because most people can't seem to remember to turn off the lights when they leave the room. I considered sensors to regulate this, and maybe will in the future, but there are some more important (in my opinion) efficiency issues.
1: managing your heat vents. Don't heat rooms your not in. Don't close all your vents but, why heat the guest room or mud room?
2. adjust your heat intakes. Some furnace intakes are in odd places that don't make sense. One of ours is right under a window that if we close the curtain,it sucks the cold air we are trying to hide behind the curtain into the house. We will be moving that vent about 1 foot into the room by building it into a simple bench.
3. Separate out lights and fans you don't need. Sometimes a whole bunch of light is on one switch, when you only need one. In our case our bathroom fans are attached to the bathroom light. So, if it's a cold night and you want to see your teeth as you brush them you are forced to turn on a fan that sucks the hot air out of the house.
4. Heater choice. If wood is abundant, use this for general heating. It has a 270%+ efficiency (heats on chopping, hauling, & burning). However, most suburban homes are large. Instead of fully heating the house, heat your house to barely passable and then heat yourself or the space you are in. Space heaters do rooms. Heated blankets and pads do people/things. Use a bit of elastic and a few nails to keep room doors closed so the space heater doesn't attempt to heat the whole house. Have warm blankets, robes, pjs, slippers, socks, etc. So people are comfortable with less heat. Place a heat lamp above the dining room table, cook instead of ordering in or microwaving a meal. A soup pot or stew humidifies and heats. Get a fuzzy pet and train them to sit on your cold feet or lap. Share your house, have guests. Have hot tea or coffee.
Also, use windbreaks by placement in your yard of things like garages, sheds, wood stacks, thickets.
After that, then there's solar, wind, and human power to help with the remaining energy needs.
For summer, here's my thoughts:
The thermal mass, basement, and insulation will still benefit you. The trick is shading out the sun using pergolas or arbors and trees on the equator side. The sun coming in here during summer has been calculated to approximate me using the wood stove all day full blast. Simply blocking that out will result in a strong reduction in air conditioning needs.
Most old houses here are set up so that they can catch a nice breeze. Use this by opening the basement windows and attic windows, top-down.
Also, go outside a lot. Humans do have SOME ability to adapt to their climate, so going outside will help your body compensate and then not feel so hot or cold. (accept perhaps when I'm fighting a bug, but I think that happens less when you get down and dirty with your local soil microbes).
Use fans as necessary. Fans can even be solar powered. Roof vents are possible...but I found that the houses here really don't make them necessary. Cold drinks and frozen stuff also help. Kiddy pool. Out-door kitchen.
In summary, though the net-zero homes are pretty cool, I think that homes that exist now can certainly get a lot closer to net zero than they are with very little money to get there, and any money put in should pay for it's self in barely any time. I don't think zero will be achieved, but zero now usually is only with the help of lots of solar panels which we are not compensating for their manufacturing costs.
You can sometimes find them used for a good price.
Our current project was the most inefficient house in the county. A drafty 100+ year old two story farm house. We tear out the plaster/lathe of the old wall, install a second wall with a 4" space between the two walls, new wiring/plumbing and vapor barrier, then blow the thing full of cellulose. The new wall structure is a foot thick and gives us a solid r-50.
We replace the windows with triple pane low E, and we do bubble wrap in the winter, and some insulated curtains. We're about 1/2 done, and the results have been very promising so far.
If you don't use icky building materials that offgas a bunch of icky solvents, the potential indoor air pollution because the house is tight is pretty minimal. But there are real advantages of HRV (Heat Recovery Ventillation). If the electric goes out, you can crack a window or two and not worry about suffocating or build up of indoor air pollutants to unhealthy levels.
I think extensive retrofits take 2.5 or 3 times the time and 40% more money than building from scratch. I'm not suggesting you don't do it, and that is the path I chose as well. But don't underestimate the cost in time and money.
I'm at still learning about this, so excuse my ignorance, but it seems like the super insulated house is a lot more work than need be. Couldn't you use the old house and lathe as an outer shell and just insulate in the walls that exist and then put another set 4" in on the inside rather than a year out? Doesn't the difference in materials help hear from traveling? Isn't the gaps in the existing insulation more important than just generally more insulation? Also, it seems that the rate of heat gain has to just be less than the rate of heat loss. So:
A 30ft tall by 30ft tall house with r30, true r30, would have a heat loss from a 30 degree temp difference of 1 watt/ sq ft, calculated for the house and converted to BTUs that would be 16,320 BTUs. If I calculated this right, that is like a cooking fire and person cooking, which makes me think it's the air leaks from the spots not insulated that are the issue rather than adding more insulation to insulated places. Am I making sense?
I am with you on everything except the basement part. My experience, based only in Maine, is that they are damp and drafty. A much better situation is a slab. I have a super-insulated house and live on a concrete slab. It works well because it is warm in winter and cool in the summer. In this state anyway, I am not alone in this thinking and a lot of very energy efficient homes are based on slabs. My father can attest that having his basement home burn to the ground, then replacing it with a slab home was the best thing he ever did.
Note I said slab. Mine happens to be concrete, but if a person dislikes that building material, other substitutions could be made.
There is a guy here who hosts a radio show on heating and cooling and he built a net zero shed using solar passive gain and super insulation. With a concrete slab he was able to keep his shed above freezing with no additional heat. And this was a shed with no heat emanating from electric motors and life either. He said today, with modern building materials it would be quite easy to live in a non-heated building in Maine, if done proper.
For me, radiant has been an interesting journey. Passive solar gain completely screws up radiant heating so I went a 100% super insulated home, a decision I am not convinced 100% was the right one, but not convinced 100% it was the wrong one either. The one mistake I did make was in in adding radiant heat to a mudroom. I assumed that since it was small and super-insulated it would easily heat, but that was DEAD WRONG. I never thought that I actually needed MORE PEX because the concrete slab was so small in size (9x13) it provided little radiating surface to sufficiently heat the room.
My house is now entirely heated by wood instead of propane, and we let the fire go out during the day and at night, yet even at -10 below zero (f) the other night, it only got down to 64 degrees. Chilly, but not unbearable, and this is a 3000 square foot home, so its no tiny house by any means. Right now I am burning softwood slabs that come off the sawmill because I have so much of them and it burns about 2 arm loads of slabs per day which really is not much.
I would not call my own home a net zero home, but it is pretty close I would say. I am not sure what the figures would be if I used hot water solar panels to collect the solar gain I am missing by having super-insulated walls instead of windows.
One thing that was not mentioned, and maybe outside this threads intent though, is a Green Switch. I wished my home had this and have thought really hard of installing one. In an existing home this is problematic.
For those that do not know what a green switch is, it is simply a switch located by the main entrance that you shut off when you leave your home. This kills all power to all but essential appliances like heaters, refrigerators and freezers. It really saves money because electricity is not being wasted on appliances that are not running, but not completely shut down neither, and even wiring resistant loss. It really adds up to electrical savings.
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