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MN Renovator 01-01-12 04:22 PM

MN Renovator 2012 Hypothetical new house
I'm living in a house I bought in the middle of 2010. I like the house and I've air sealed it pretty well and have a few more gaps that I know about that I'm taking care of this month. I got to thinking about what I'd do if I moved to another place to build a house.

When I do it all over again and eventually build a new place for myself instead of buying the mistakes made by builders and the original owners who chose the place and its location. I want to build it with similar thinking to the Alaska zero energy house but I won't need nearly as much insulation and realistically I don't think I need a huge hot water storage vessel to store summer heat through the entire course of the winter.

I'm thinking that I'd like to go with 12" dense pack cellulose in the above ground walls. I think I'd go with foam overhead and try to get close to R-75 as I can get overhead with a lighter colored metal roof and have livable space in the attic instead of lose that room to being an empty space, all glass larger than 2 feet per side would be on the south side of the house and enough thermal mass built in to do a decent job of slowing the big temperature swings between day and night.

I'd want to go with Fujitsu's 9k 26 SEER 12HSPF ductless minisplit unit installed with a very open upstairs floor plan with living/family room and kitchen upstairs with stairs in a non obstructive location at a corner of the house and bedrooms and theater room in the basement where the temperature stays more stable year round. By going with an open long throw floor plan one ductless minisplit can cover the entire space in regards to air flow.

I think that having a livable conditioned attic or at least accessible storage space and a finished and conditioned basement is key to making a small house work. I'd be looking for a interior floor size of 700sq ft or less, with a 700 sq ft size for each level, I could essentially have almost 2000sq ft of space, attic for suitable storage and bedroom expansion if wanted, kitchen and living space suitable for guests, and theater, office, and bedroom space downstairs with a bathroom on the main floor and basement. I would have the 9k minisplit be the only source of heat and cooling for the house. I think this would work because if my current house can handle staying the same temperature at -20f(-29c) using 26k BTU/hr when it had R11 fiberglass in the walls, plenty of infiltration, an unwrapped skylight, bad directional facing and big windows on the wrong sides of the house I'd imagine a house at 65% the volume and good design with plenty of thermal mass shouldn't need that much. An inside outside difference of 0f(-18c) and 70f(21c) inside is 20k with my current house. 65% of the foundation size as interior size would mathematically be 13k without factoring less windows and better positioned windows or increased insulation. Worst case I fire up a space heater, a toaster oven, a hair dryer, or snuggle in my bed with my heated mattress pad and watch TV on a cold night. 600sq ft floor space would save more and realistically its all I would need and I wouldn't even need the really attic if that complicated things too much but I think that wasting an attic would be wasting a great storage space that I currently use my basement for.

I'd have a small HRV and seal the house to the passive house 0.6 ACH50 standard when it is built, which I would imagine should be that difficult with a small house, a local builder at a 'green expo' said their houses are all 0.6 ACH50 blower door tested with R26 walls, R60 ceiling, and R20 foundation. He was talking about how it doesn't cost them that much to make these improvements over any other house and they average a 46 HERS while energy star requirements bring a HERS rating to 85.

I also had another radical idea, what if I built the house so the main floor was sunk in at the same level that a split-level lower floor is, that would save me from exterior heat and extreme cold exposure through the walls and I'd probably only really need 2x6 construction with less insulation. The house would look weird but if I was retired(not close enough to that yet though) and didn't need to commute to work then I could live far enough out in a rural area where there is farmland and I could have distance from the neighbors and rent the rest of the land to a neighboring farmer so it would look like I was just a farmer with a small house sunk 5 feet into the ground.

Am I way off base with my ideas for building a fairly efficient house? What do you think?

herlichka 01-01-12 08:23 PM

Instead of simply sinking the house 5' into the ground why not consider raising the grades around the house with a series of small terraces? That way, your front door can be at grade, and when you look out the windows you are not looking up. You will find it easier to damproof your foundation, easier to layout your perimeter footing drains, easier to layout your septic system grades, and your electrical meter (if so equipped) would be at a more conventional height. Also, you can choose to backfill the terraces with soils with good drainage characteristics, to help keep the house dry.
If and when you get to the more formal planning stages, my advice is to really study and understand all the systems and components that you want and need, so that when you are getting prices and proposals from contractors you can ask for specific things, such as the exact placement of pipes, vents/inlets, meter bases and so forth. If you don't specify these things, they will often be installed with no consideration for the next contractor's install- for instance a gas meter installed too close to your intended HRV inlet/outlet location. The actual installation crew will usually opt for the easiest/shortest route, and you really have to know what you want beforehand.
The other benefit to this kind of detailed planning is that you can take the site conditions such as sun and wind exposure, summer shade, and even landscaping into consideration, as to how they affect your mechanical systems.

Daox 01-03-12 09:30 AM

I think that setup sounds pretty good. You didn't mention it but I imagine you'd also have a SHW setup for DHW.

I like the idea of sinking the house for additional insulation, but you wouldn't be able to get the southern window space (unless you dug out around it) that you could with a house above grade. You also may have water/ice issues with steps leading down to your front door.

Piwoslaw 01-03-12 10:24 AM

A good idea is to build on the southern slope of a hill. That way you still have maximum solar gain from the exposed South, but the back and sides can be partially dug into the mountainside. IMO the soil isn't actually an insulator, but acts as thermal mass, reducing the temperature gradient through the (buried) walls during winter. You can get away with less insulation, but you have to make sure everything is protected against water. Also, building on the sunny side of a hill puts you in the windshadow of any chilly winds from the North.

Ryland 01-03-12 06:36 PM

Sounds like a decent design to me as well.
I'm a fan of saving money and energy on windows that don't open, sure you want enough windows that open that you get some cross ventilation, but having some pitcher windows that are triple pane can save a lot on window cost and they have fewer seals to leak.
I also got to check out the house that has the ground tempering of incoming fresh air via a ground loop of pex instead of using earth tubes, it's a slick system that takes care of the cooling needs of the house in the summer as well.
I worked for a number of years building straw bale houses and found that when working with other contractors that you have to assume that they are going to treat your project as a normal house so any details that might not be standard you need to be clear about and get in writing that they realize these details are there, we had issues with the footings for our walls being to narrower for a 20" thick straw wall, truss companies wanting to sell us trusses that didn't have space for R70 attic insulation and foundations that didn't have the amount of insulation that we specified.
In my own house and in others I've had to deal with insulation contractors that skimped on insulation in really extreme ways too.

I really like the idea of building up the soil around the house if you don't happen to own a south facing slope, I hate houses that you have to go up or down steps to get to the main floor/kitchen, 2-3 steps going up is ok, but hauling groceries in gets old and as you age it becomes more of an issue.

AC_Hacker 01-03-12 08:13 PM

As long as the house is still imaginary...

The solar orientation should be primary, and then taking advantage of favorable site conditions. Everything already said about insulation is just great.

But a design feature that really intrigues me, that you don't see so much anymore is the idea of a 'core room'. I just made that term up, but the idea is a room that has rooms or hallways that surround it on all sides if possible, protecting it from extremes of weather.

I have one such room in my house, it has only one outside wall. The rest of the walls, and floor and ceiling, have a room on the other side. And this room is the warmest room in the winter, and the coolest room in the summer. It is also the quietest room at any time.. it is the best for taking a nap.

Another very handy idea is an actual, functioning pantry. My house had one that had been remodeled into a bathroom long before I moved in, and I didn't realize that it was ever a pantry until I removed the unnecessary bathroom... Then the logic of a small windowless room on the corner of the house that got the least sun, became clear.

In Oregon, 120 years ago, pantries were built into every house, for storing food, because you could not assume the uninterrupted availability of food.

120 years ago, in Oregon, people in the city planted nut and fruit trees around their houses, for the same reason.

I don't think it is unreasoning paranoia to think that we may live to see similar conditions again...


MN Renovator 01-04-12 02:12 PM

herlichka, Sinking the house is probably a bad idea now that I think of it and Daox brought up the front door which I didn't think about. I don't think I'd raise grade. The thought was to reduce the need for insulation by having the ground shield the house against the temperature extremes. In the end, finding a builder to do this in an attractive way, or even a water-safe way may be extremely difficult.

Daox, I'm not sure if I would go with SHW. This summer I managed 4 therms of gas for two differnt months usage between the hot water and stove. I take showers and cook stuff so I'd imagine that if I had SHW, I'd actually have to use more water than I do for it to be worth it. I think that for the limited roof space that I'd rather have as much PV I can have up there which would have the added benefit of blocking sun from the roof which would be light in color and no asphalt shingles. I'm not looking to go with spendy panels to get higher output per panel but something on the affordable side from a reputable company who has a warranty worth something. It looks like a 2 to 3kw setup would balance my electrical usage but with more insulation and properly placed windows. I forgot to mention that I wanted a 2kw-3kw system. Ideally I'd probably put as much up there that I can fit, if somehow 4kw of panels managed to work, I'd be happy too if I'm on-grid and feed back and cash in the excess.

Piwoslaw, Soil might not be an insulator but the slab and walls of my basement are warmer than the upstairs of my house right now so I'd imagine that the soil temperature would save some energy in the winter and more energy in the summer since the exterior exposure wouldn't be the outside temperature. The solar gain is going to be whatever size glass I install. If the southern wall is 5 feet tall and the window is 4 feet tall and as wide as that side of the house then I'd imagine that there would be plenty of solar gain.

Ryland, I've found that the only weather I can open my windows in my climate is in the seasons where my electric bill is not dominated by the air conditioner because of the humidity. In the summer we sometimes get nice cool 60 degree nights but those are the nights where the dew point during the day was above the indoor temperature so opening the windows would raise the humidity quite a bit. I probably won't open windows too much and so a large picture window with two smaller side windows would probably do the trick. I've been reading that triple pane windows don't save much over double pane windows with a large enough gap because triple pane windows don't have a large enough gap between the panes to insulate as well as someone would think. I'll buy the windows based on the U-factor and in the end will probably get triple pane. I'm assuming triple pane doesn't affect the solar gain, does it? I want the southern windows to pull in the heat and in the summer have a proper overhang to block the sun. At the MN state fair this year there was a display showing passive house design, they used a ground tempering and since Minnesota needs it, the setup had a condenser to cool the incoming air. I think the building's entire air conditioning setup may have been to cool the incoming air exchange. What R value is a 20" straw bale wall assembly? I've been doing my own insulation in my house, and still working on a few details but I will be finished up once I can crawl in the 27" high upper attic without freezing. My current house has two steps to go up to get in. I like it because the ground level is the kitchen and living room and if I have someone over in a wheelchair it is much to not have to climb them up or down in a split-level house setting where the door greets you with a choice of stairs up and down. Some day I will convince my family to have grandma over at my place so we don't have to carry her up and down stairs. I could even make a simple plywood ramp too.

AC_Hacker, Most of what I saw about insulation was either learned searching for it, seeing it on the Building Science articles Building Science Information from this site, and quite of bit of the actual numbers and quantities came from members this site or a few of the energy auditors that are also in HVAC at the hvac-talk site. It just bugs me that I can't post there without my thread being closed because of their no DIY policy even though I wasn't saying anything about installing my own equipment. For what it's worth, this spring I'll be putting in a good half dozen or so fruit trees, 4 apple trees, 2 pear trees of different varieties. I never thought about nut trees, I don't know which ones would survive here but I'll take a look in spring. I like the idea of having food trees because they take nearly no effort once they are established to get food from them.

I like the idea of a 'core room' The problem with that idea is if the house is small, putting a room in the middle with no exterior walls might not really work. I think a good idea would be to have the master walk-in closet with a door seperating the outside from the inside and not intentionally conditioning that walk-in closet. I've seen zero energy houses that use a closed off area for entry ways that aren't conditioned and have the interior of those insulated from the outside as well as between that entry room and the outside. I don't think I need to go to that extreme since I don't ever leave the door open long at all and it adds sq ft and construction costs. If the inside is insulated enough such as 12" of cellulose I'd imagine its going to be quiet inside. Once I air sealed my bedroom I could crank my laptop volume as loud as it would go, which is fairly loud and couldn't tell there was music playing outside. I put the laptop downstairs where I hadn't air sealed yet and I could name the music that was playing on random. One thing I'd like to mention though is avoiding hallways. My plan is to not use them, if the house is designed without hallways and having the rooms on the outer walls then the only thing that resembles a hallway would be any stairs separating levels.

Ryland 01-04-12 07:21 PM

According to an environmental engineer who's house I worked on years back, you get enough more solar gain from non-low e glass on the south side of your house that the extra heat that you get makes up for the extra heat loss that you will see at night, if you then have insulated window shades you can close you can keep even more of that heat in then even the best window by it's self, if I was building the house from scratch I would install the outside insulated window shutters.

MN Renovator 01-04-12 11:29 PM

I like the idea of outside insulated window shutters, I'd imagine that having those on the front of a house would be considered an eyesore to many, along with awnings(which is why I'll have a carefully designed overhang). Hopefully I don't get angry picky neighbors when I build my next place. I've already got a neighbor who acts funny ever since he asked me about the 60 bags of cellulose insulation I had in my garage last year, apparently saving energy and money makes us all strange. Some tie it into their political assumptions too, which gets some people worked up now that elections are on everyones mind. I'm trying to think of how to add thermal mass to the house, in a design phase, I don't see why I wouldn't be able to 'build it in'. I figure the thermal mass should smooth out the excess heat and then let go of it when its cooler. I'm thinking of doing something other than having a 'Water jug masterpiece' for thermal mass. I think people who come over would look at me funny for that one.

I'll definitely have the insulated window shades, maybe a matching set to cover the wall containing the 'CulligaPicaso'.

AC_Hacker 01-05-12 02:16 AM


Originally Posted by MN Renovator (Post 18844)
I'm trying to think of how to add thermal mass to the house, in a design phase, I don't see why I wouldn't be able to 'build it in'...

A hydronic slab floor would certainly provide the mass you are looking for.

I saw a great article a few years back, in which a house was designed so that winter sun fell onto a substantial amount of the concrete floor, and the heat radiated out in the evening, along with heat from hot water in the slab.

I have a friend who built a very successful passive solar house near Portland Oregon, an area not known for its sunny winters. The house was long, East/West, and narrow, North/South. It had the usual overhang to shield against summer sun, was backed into an earth berm on the North side. Had an abundance of windows along its South face, an insulated concrete floor to store heat (no hydronics) and something like R-60 in the roof. It has a wood stove in the living room that supplies heat to the whole house... there's a free-standing stone wall behind the wood stove to capture and slowly release heat from the stove.

He says he burns a bit less than a cord of wood per year. That's his only heat, other than the sun.

A very pleasant house...


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