We had another request for some info - but way south of Maine:
I live in Spartanburg, SC where most of the time it's in the 40's & 50's during the winter days and in the 30's at night. It does dip in the mid to upper 20's at night but not very often. I would really like to build an earth shelter. My plans are similar to yours except my front garage corner will not angle away from the front but will angle towards the front, giving me a workshop inside against the back wall. Planning on 3 bedroom, 2 bath. It'll come in somewhere around 2700 sq.ft. not including garage/shop. Plenty of south facing windows where the bedrooms & living room will be. Also planning on radiant floor heating to the bathrooms, kitchen & TV room using Thermomax. What's the square footage of yours & how much heat is generated thru the windows? Winter? Summer? Are all those windows a big source of heat leakage? Do you have any sort of ventilator installed or mainly rely on opening the windows?
Wow, with those temps, there are times I think we should head south.... Here is the answer - most of the items were mentioned in a blog post during construction.
Your questions are all good ones. Our house is around 1900 sq. ft. Two bedrooms, two baths and a study in the 'kink'. We wanted to get our house size down to something easy to maintain and clean, etc. The ten large, fixed windows are 46"X72" each. They are a commodity item used in sliders and commercial store fronts. We paid around $125 per window, which is way less expensive than a ready to hang window unit. These come with just a rubber or butyl liner around the edge, you have to build your own jams. So, how much they leak sort of depends on how well that is done. Mine aren't done yet, just some caulking most of the way around them. I think we most notice the radiant losses at night, like standing next to any large window. Thermal drapes would stop a lot of that, but I don't know if we will get those. We also have four casement windows for ventilation and fire escape code. The large window glass is clear with no inert gas between the panes. That may not be the correct thing for your climate. I chose clear due to the higher light transmission compared to low-E coatings. A really important aspect of windows is your overhang width. 26"-28" is considered optimal for this latitude - just under 45 degrees. Yours would be different. You definitely want to keep direct summer sun out of your rooms. The heat gain in winter is phenomenal, if anything, it can be too much on a crystal clear day in Jan.-Feb. We have some roll-up bamboo blinds we lower once in a while. The house will go up to 80 degrees no matter the temperature outside on a clear inter day. We crack a few windows open as needed. The temperature drops back to low to mid 70's by early evening. We have only lived here one summer, we did use fans to stir the air during warm spells. I suspect there is a fair amount of radiant heat gain through the windows in summer even though they are shaded by the overhang. Of course, heat in Maine is relative. We get so used to moderate temps that 85 deg. is a scorcher here. It rarely hits ninety, maybe 6 days per summer, sometimes it never hits 90 all summer. In any case, summer is short here, so we just put up with it. Based on our experience and trying to guess about your climate, I think you would make different choices on windows. We optimize for winter here. I wish I had a more technical answer. It pays to read up and talk to people in your local area. We were able to visit three homes of this style before committing to the design, that really helped to frame our expectations. Ventilation in these homes is very important. For the first 6-12 months they are loaded with residual moisture in the concrete. We have interior plaster and it also takes a while to really dry out. For ventilation we have an outside air inlet for the wood burner, a high capacity kitchen range hood fan than vents to the outside and four fans in the ceiling that exhaust into the attic space. There are attic exhaust fans at each gable end of the house that are controlled by a thermostat switch. The four ceiling exhaust fans are on individual switches. The attic exhaust fans turn on around early afternoon on hot summer days. They pull air through the soffit vents to cool the attic space. The four ceiling exhaust fans are used only in summer. We open windows in the evening and let them pull fresh, cooler air into the house. That air pressurizes the attic space and pushes air out through the soffit vents. With so little air infiltration through exterior walls, getting air in is really something to plan for. Are you planning on air conditioning? I think it would be a good idea just to control summer humidity. You don't want to have moisture build up through condensation, which will happen in rooms that are on the 'back' side of the house. The earth berm will keep those walls and floor pretty cool compared to the outside temperature. For heat, we have a radiant heat system installed that rarely gets used - thank goodness, given the price of propane. I ran a couple zones for about 4 hours twice this winter during an extended cloudy period. We burn just under two cords of wood in the fireplace stove. It is a Tulikivi soap stone masonry type stove. There are over three tons of soap stone in it, once it is warm, it radiates heat for the next 20 hours or so. We usually burn it once per day but skip a day now and then depending on sunshine. For the bedrooms and bathroom in the far end of the house, which don't receive much heat from the wood burner, we use electric heaters to take the chill off during cloudy spells. That is less expensive than running the radiant heat - go figure. I really think our house would never go below the mid-fifties with no added heat, just the sun. I haven't tested it since sitting around in a house that is in the low sixty range isn't comfortable. A regular framed house around here will freeze up solid in about 2 days with no heat. Given the cost of a radiant heat system and your climate, it must be hard to choose. I think our radiant heat was really not a good use of the money, it works just fine, but is not really needed. When you consider we can go for weeks at a time here where our high temperature for the day is well below freezing, and we hardly use the radiant heat, your climate may not need any sort of central heat in a solar house. Maybe electric heat combined with an air conditioning system would be better in SC? Our water heater is a zone on the boiler, someday I might get into a solar pre-heat set up. We have a propane range/electric oven combination. For hot tap water and stovetop cooking we use about four and one-half gallons of propane per week. A flow through on demand water heater might save a little, but our tank is well insulated and the boiler hardly ever runs unless someone is using hot water. One thing that takes getting used to is how earth sheltered homes don't fluctuate in temperature very much and certainly not quickly. We can go to bed after being too lazy to make a fire in the Tulikivi with a temperature of 68 or 69 degrees; it will be 64-66 degrees the next morning with no heat on anywhere. That's with an outside temperature in the low teens. It really demonstrates what thermal mass does. Well, I hope I answered your questions helpfully. Good luck with your project. We really like our house, and the higher fuel goes, the more we like it! I would be glad to answer other questions you may have. Have you considered earth sheltered roofs? I have never been sure which is better - bermed walls and regular roof or go all the way and have an earth covered house with just the southern side exposed. While I was cleaning the record amounts of snow and ice off my roof this winter, I was sure the sod roof would have been the way to go - Ha! Regards