Looking for someone who lives in a double envelope home. I am trying to thermally model such a home so I know what method is required to reflect reality.
We are constructing such a home next year and we are looking to figure out how much insulation will be required where, how much ventilation is required, overhang required, etc ... Lots of stuff go into one of these homes for sure.
Currently using WUFI Passive and THERM for the bulk of estimations, not looking for certification but rather just a way to accurately model choices we make to our model. But without an actual house to compare it to it will likely be hard to model accurately.
Well, my house isn't exactly a double envelope, but it's entirely solar heated and the whole north side is what we call the thermal buffer zone, which I think is a similar idea. I'm sorry I don't have any technical specs for you, but I can share my experience from living in it.
The kitchen, bathing room, living room, bedrooms and little study or bedroom are in the south side of the house and as such are solar heated. The northern unheated buffer zone includes corridor, storerooms, stairs, and the two-story dry composting toilet. The upstairs cold corridor also has a washing machine and a handwashing sink outside the dry compost toilet room.
My contractor used only "straw clay" for insulation above the horizontal roof beams, and didn't insulate below the beams; insulated between the heated space and the buffer zone, but didn't insulate the outer walls of the buffer zone; and used single glazing on all the windows in it. Last winter the bottom of the corridor under the stairs did just touch freezing, but the upstairs corridor was a few degrees warmer, and the sink and washing machine had no trouble. This year hopefully the buffer zone will stay warmer, because we've put up white foam insulation mat on all the windows in the buffer zone. I hope to add roof insulation between the beams next year which I hope will also keep the house warmer.
In New Hampshire I think there are local habits and requirements for insulation that will be great. If I try to suggest that much insulation in the roof here people would be shocked and think it sounds completely unreasonable. I wish I could get good northeast US type insulation. Like, a foot thick, or R50. I just wish. My climate is high desert and good 10-15 degrees south of you (10,500 feet high and 34N), so the solar gain in winter is still pretty good, and being made of rammed earth my thermal mass is good. If only I could manage a LOT more insulation I think it would be a lot warmer in winter in this house.
The 3D picture below is not exactly what finally got built. We included an 18 inch overhang over both ground floor and upstairs on the south face, and all the upstairs windows on the south face are half-trombe wall, which in the 3d drawing is only shown on the leftmost window.
I insisted on single glazing on those upstairs south windows but maybe I regret it, because the bedrooms really do get damn chilly in the winter. Down in the low 50s F on January nights last year despite the wool curtains. Maybe even 40s. I don't want homemade double glazing because it gets moisture, dust, and insects inside, but if professionally made double glazing becomes available here I think I'll replace them. The east and west windows in the southern rooms are double glazed, but I wish we'd done double glazing on the windows of the buffer zone, too.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
Location: Cache Valley, zone 4b, Irrigated, 9" rain in badlands.
I built and lived in an envelope house in northern Utah. The inner and outer envelope walls and ceilings were insulated as if they were stand alone houses. An insulated box, inside an insulated box with an airspace between them. There was a single wall on the east and west. A solarium on the south side. A 1 foot wide envelope on the north side, and between ceilings. The entire basement was part of the envelope.
South facing windows were vertical. Made from sliding glass door replacement panels, because they were the most affordable glass. No overhang. There were a few sliding glass doors between the solarium and the inner house.
"beware of envelope home and stick-frame architecture being sold as 'green building'
When examined from an indoor air quality perspective, many sustainable home design schemes are just plain old-fashioned wrong like the envelope home concept. Stick-frame wooden envelope homes allow heated/cooled air to loop around through the structure's walls. A cavity between inner and outer exterior walls is left open to act as a giant ventilation duct drafting passive solar heated air through it. Envelope homes are an extremely bad idea for your indoor air quality since there is absolutely no effective method to clean/sterilize this open 'duct area' between the walls. Mold, mildew, and the occasional dead mouse eventually renders an envelope home the distinction of being a very bad idea indeed. Envelope homes with fiberglass batt insulation are even worse. Impossible to clean without disturbing all that itchy fiberglass dust."
The idea for a double envelope home has been around for a very long time, but few have been built. That's a strong clue, as far as I can tell. I'd add that the extra expense of the second envelope will never pay off. But I'd sure like to hear about your project if you proceed with it.
Here's one in the Philippines at http://kotaronishiki.com/. It's called a passive solar house and utilizes double walls and roof as part of the overall strategy. The homeowner seems to think it's highly effective.
I "grew up" in three improved versions of solar/envelope houses, helped my lifelong architect/builder friend build and design efficient houses over many decades and have been designing the "ultimate" envelope house for the last 10 years (but not building it).
I have learned:
- literally everybody knows for certain that your ideas won't work, and
- almost nobody has actually "mindfully" experienced any such proposed concept-homes.
Well, now that THAT is off my chest, I have learned:
- Thicker walls work (my father's last house had 12" thick exterior walls, double studded with 12" bat fiberglass insulation. His goal was to light a candle in the fall and heat the home all winter in our northern-tier location.)
- Triple-glazing works, especially when combined with exterior screens/shutters for summer heat and interior cellular shades for winter cold.
- Frank Lloyd Wright was right about overhanging eaves (my father's version 2 house had 6-8 ft overhangs blocking summer direct sun but allowing winter horizontal sun fully across the living room to the opposite wall).
- Trombe walls work, especially when the sun hits one side and a wood stove heats the inside.
- Thermal switches for fans controlling semi-passive cooling of root cellars with outside night air work.
- Attic exhaust fans controlling intake of cool night air resolves the "fresh air" paradox of excessive insulation and vapor barriers.
- Envelope structures aren't all the same; hallways or sunrooms or enclosed porches as envelopes are good, sealed and inaccessible envelopes are not. (Use Hawaiian lanais as a model.)
- Tinted, IR/UV filtering window films are effective when used with consideration of the direction that you wish heat to travel or be reflected (and must switch directions between summer and winter).
- Outer envelope walls with "easy" ventilation options are good (all-window walls made of sliding glass doors are ideal for some sections).
- Completely wood framed structures, including basement walls and floors are good (this idea courtesy of a WSU wood technology professor who showed me several farm homes built entirely of wood frame construction).
- Sub-basement plenums with heat- or cold-storing rocks and controlled by ventilation fans are good.
- Plenums using floor joist space are better than ductwork for ventilation.
- Maintaining day/night room temperature "steady" is better than allowing cooling at night.
- Plastic vapor barriers between ceiling rafters and sheetrock make the screws eventually slip and cause the sheetrock to crash down on unsuspecting people reading magazines (this tip is not related to "efficiency").
- Experiment with an "envelope" garage or shop buildings to validate your design with your locale.
- My theoretical two-story Great Room octagon is all-glass with a 4' wide sunroom/porch made entirely of sliding-glass doors around the entire 360 degrees circumference. A mezzanine level provides an 8' wide "eave" for shade during summers so that zero sun hits the inner room yet winter sun can penetrate far into the room. The outer envelope is effectively an open screened porch in summer and a closed heat-trap in the winter. All glass walls have cellular top-down/bottom-up shades for controllable/directional insulation for all seasons. Note: This home is on an elevated and forested river-bank, so privacy is only an issue for intruders who penetrate the wild-rose thorns and juniper "fence line". Also, a biochar-producing steel fireplace/stove is set between the inner space and the outer envelope, contributing to carbon sequestration of my forest slash piles and ambiance, as well as creating soil amendments. The food-forest only has plums and apricots so far with two tomato plants and chives. But the compost pile is ripening... Oh, and a simple composting plastic-bucket toilet from Walmart works, using only peat moss (to convince relatives before you get rid of the septic-tank and drain field).
I'm retired military and retired IT and am bound by my legacy of genetic environmentalism with a twist of Eagle Scout-itis thrown in. Having moved 37 times in 47 years of marriage, I'm ready to settle down... Though my current south-facing glass-walled great room along the river bank is "tolerable" for the time being...
When I was in Afghanistan the tent housing used the double envelope structure to limit solar gain and improve the efficiency of the heat and AC, but that was government housing intended to be temporary
After much research, 33 years in the construction business, growing up in Europe , the need to build a non toxic home, and lots of courses on building, we decided to build a concrete house in Hope, Maine for our daughter. We are using Comfort Block a Genest Concrete product made in Sanford Maine. They are based on a German design. The house is small, 24'x35'. The walls are 9' high and it took three guys in their 60's three and a half days to put up the walls. The insulation is already embedded in the block. The electrical channels inside and outside are part of the blocks as well. They even have weep holes in case water ever does get in there. We used triple pane windows from Pinnacle Windows. If you call Genest, tell them that Crystal sent you. They have a spec house you can look at that isn't far from NH and you are welcome to come to Hope. What I like about it too is that we used stucco on the exterior and plaster on the interior. If you have more time than money that is the way to go. My husband and I did it ourselves and, frankly, we think the stucco looks professional even though we are amateurs. The plaster on the inside was more difficult but that is because our daughter wanted us to use NH 3.5 lime plaster. It is very pretty and durable but much more time consuming and difficult to use than the products that Genest recommend.
My brothers, who are also in construction, like the double wood walls but, unless every step along the way is done perfectly, there is too much opportunity for water to get in there and get trapped. We saw way too many 10 year old houses that were built by other contractors that were completely rotted out. A well designed and well built concrete house will last for centuries.
Check out Monolithic Dome Homes at: https://www.monolithic.org/homes These structures start with a "?rubberized canvas?" which is inflated after which an approx. 4" layer of foam is blown on the inside of the expanded half-sphere. After that process is completed and foam is cured re-bar hangers are inserted and then re-bar fitted vertically and horizontally on about a 9-12" grid. After the re-bar is set a light-weight concrete mixture is sprayed on the inside of the foam insulation to around a 3"to 4" thick layer.
Check out the web site for a TON of information about all of the How's and Why's, however, with the weatherproof "skin" and the insulation on the outside these homes are very good at maintaining temperatures, so good that the company usually tries to dissuade people from building fireplaces because of overheating possibilities.
I took time to review the information on the Monolithic Dome site and some things are hard to find on your first Navigation through the site. SO, I have added some specific links below to get you the the HOME area and to actually see Homes that have been built.
This link offers views of various builds of Dome Home plus much general information about designs, acquisition, financing, insuring, etc. The links further down are on the page, but may not be noticed for specific OFF-GRID LIVING ideas. ENJOY!
My aunt lives in Maine in a double envelope house. the original farmhouse was box in box, the later other side (a second house) used passive thermals to warm the whole house. Only a couple of days during the coldest part of the year do they use heating for the house. I can give you more details if you contact me
Companion Planting Guide by World Permaculture Association