Can you build a "green" house in the Adirondacks?

[montcalm]

Golden Rule: Insulate Insulate Insulate -- There are many "modern" approaches here -- I personally like the 2x6 on 24" construction, with 4-6" of external insulation. We have 2x6 on 24", but you can see the thermal bridging everywhere. With 2x12 ceilings (vaulted ceilings) you can see each joist as the snow melts. Someday I'd like to do the caclulation on an an "optimal" house -- my bet say until you get to R50 or so, it's probably better to keep insulating. That said, on grid that does not work out. On-grid, once reasonably insulated, money is better spent on just producing more solar power to offset the loss (efficiency vs horsepower).

There's a rough rule that builders are using now:

It's basically halving, and hopefully I get this right...

R80 for walls, R40 for roof, R20 for subsurface walls/floors, R10 for slabs?, R5 for windows. I believe that is what I recall from actual builders. This in contrast to others I've seen where it's R60 for ceiling, R40 for walls and so on.

I honestly have no idea why they "only" use R40 for the roof, but perhaps they've done the calculations and any addition is not worthwhile, especially if you get a little snow up there which adds R value.


I was also kind of diving off on a tangent on my own home, which I have no intention of going off-grid. I have a grid connection and NG. The incentive to change to geothermal here is minimal and I mentioned that earlier. Solar seems super easy based on what I'm dealing with, and probably will be the only "green" addition I'll do in the near future. There's some issues I'd have to address with appliances to really get anything out of it though. I have an electric dryer, stove and AC. I could switch those to NG and easily meet my AC needs, and probably most of my electrical needs, but what I am really benefiting? Still a majority of my energy is coming from hydrocarbons.

My house was built in the 60s, and is reasonably insulated - I added more about 10 years ago because I was having severe ice damming that I didn't like - still get some, but much better. And I have a cold, cold crawl space that I would have never done, but causes us some issues in the winter. Tried to insulate it but, there's just not enough heat getting in the crawl space from the basement and too long a run on the heat duct - not to mention it's an addition so it's not wanting to stay near the core temp of the house where the thermostat is. I've thought of just putting a small booster (electric) heat system in that room with it's own thermostat to help regulate that room. But of course that won't help my energy needs. A big issue with my home now is drafts and trying to seal them. Seems the best might just to be rebuild my door frames proper. The house has settled considerably and the original construction is a bit tore up - but because the rest of the house is fairly well insulated, I can really feel those drafts like jets of cold air. I'm sure there's a lot more to look into. Anyway, this house is not an easy project and if I did this whole "green" thing I'd start from scratch.

[chairrock]

I have an electric dryer.
.

Get a clothesline, we hang 95% on our covered porch clothes lines. Rarely do we use the electric dryer.

[mooregm]

My take on thermal mass is that you need to be able to control it -- both adding and removing heat. Without control, it dictates your life, not the other way around. There are many approaches here, but personally water makes the most sense to me.

For instance, my basement slab is uninsulated underneath. With a dedicated basement zoned forced air heating I keep my workshop heated comfortably when I'm down there, but the minute I turn off the heat, it dives back towards the low 60s. That thermal mass controls the space -- everything else fights against it. Granted if I were to do it over again, I'd insulate with R30 and put radiant tubes in it to keep it a comfortable ~75*. It works the other way too. If a thermal mass is 80* and there is a warm day, the house will be 80* and you'd have to open all windows to cool it off, and then you are just wasting the stored energy.

On the flip side, my garage is well insulated (walls and foundation) plus a shares a wall and ceiling with heated rooms. I use the thermal mass of the floor to my advantage even though it is not insulated underneath. Without any heat our first year, the lowest the garage got down to was about 40 degrees in late winter. We subsequently added a small forced air zone out there which keeps it heated to 55* (only run at night). This works well and the slab never goes below 50* now. And come spring because the slab stays about 10* warmer than prior years, we have much less sweating/mold issues come humid spring days. Again, the mass of the slab/ground control everything -- we just make it work for the use case. If I were to do a garage again, I think the best situation would be to insulate down several feet, then add back fill and do normal tubes in the radiant floor. Best of both worlds with cheap thermal mass and starting with 80* slab in October, you could run no supplemental heat for weeks at a time of cloudless days and it'd stay plenty warm. Pretty much a load dump. My thought on thermal mass is that it's great in a garage or other space where 10+ degree swings are acceptable. Heat when you can and coast when you cannot.

For primary living spaces, you should not let the thermal mass dictate anything, thus I personally like storage in water since it's incredibly efficient volume-wise, able to be moved easily and works natively with HVAC systems. No issue with freezing if kept inside basement/crawlspace which is should be to capture losses. ~5k gallons is not very big in the grand scheme of a new build. Heated to 115* in a well insulated house using low temperature radiant heated slabs @85* provides 1.25million BTUs -- enough for about a week by itself -- and a few more days if needed when it is around 30* and a well insulated house. There will be storage losses and it can be more complicated than above, but storing water is far cheaper than batteries. Additionally, using a load dump with resistance elements can bring the tank up to ~180* which is enough energy for additional 2 weeks. Though that is practically only possible early and late in the season when there is plenty of sun and less demand for heat -- and it's inefficient resistance heat (heat pumps only work to ~130* under ideal scenarios).

That said, the above 5k gallon tank would cost say ~$5-10k and store ~300kwh of electricity including heat pump conversion factor. A few years ago it was an absolute no brainer cost-wise for batteries. But batteries are now approaching $100/kwh and still declining -- $30k. In a few years it may be closer to even and then I'd say batteries for the win. I'd probably still have some thermal mass for a dump load in say a garage / basement slab / etc.

Windows to me for heating just does not make mathematical sense. Again, we as humans need windows, so include them as needed for light and personal tastes. If possible be smart and use south facing, summer shaded, etc strategies, but I personally would not include windows for primarily heating purposes nor get bent out of shape if they had to all be north facing because say you built on the south side of a lake. Another way to look at it is a common solar panel is ~20% efficient today. And a heap pump has an efficiency factor of say ~4x. Thus one square foot of solar panels (angled properly) can produce the same or more heat as one square foot of window (very bad angle). All without any of the drawbacks of glass -- namely they lose more heat at night then the rest of the house combined!

[montcalm]

Took me a few reads to get (most) everything out of that, but I think I'm there, and it sounds right to me.

I think one thing I was missing was how you were using the water - I thought perhaps you were storing energy in the head, not heat. So, as I understand it now, you're using your heat pump to store energy when you have excess electricity. I was generally think it was an entirely different system of of pumping and generating, but this is interesting. I'd assume you can only get back heat as you have no other way of converting to electricity. But I'd also assume you'd be able to use it for hot water if you had a heat pump hot water tank.

I definitely see what you mean about the thermal mass. I really need to digest it more because it seems it's all about storing as much as you possible can in late summer, early fall.

And as far as windows - passive solar I think was mainly developed for dry, sunny environments where you have large swings between day and nighttime temps i.e. deserts, high altitude arid environments, etc... The more I learn, and it keeps becoming a recurring theme in this thread: it's not all that useful in the NE.

And when you compare a really good R5 window to a R80 wall, then it really makes you put it in perspective.


BTW, thanks again so much for your practical expertise on this subject!

[mooregm]

It sure is a deep rabbit hole! Over time things change and yesterday's "solutions" -- which usually were never really practical solutions to begin with -- do not make sense today. Today's hot items are solar and batteries. It will be interesting to look back in 20 years and see how things shake out.

[montcalm]

It seems like there's going to be a market for rural folks, maybe some limited suburban applications, but cities and industry are still going to need power plants.

We are super close to practical fusion - and by that, I mean I think in the next 10 years some of the systems being built and tested now will actually show some promise. Then it could be another 50-100 years before it's able to be built and distributed on a wide scale... that could make it all obsolete - likely the end of my lifetime and beyond, but perhaps people living in rural areas will still favor the independence of renewables and not having to be tethered to a grid... tough to say...

[montcalm]

I looked through some diagrams and I'm seeing the "buffer" tanks much like you mention you are using now, mooregm. I've not specifically seen any heat pump systems that use those 5K gal tanks - looks more like direct solar, which I could see it could be used either way, just not popular now.

As much as I'm anti-chemical battery, it looks like they are the best solution for large storage with the heat pump, if it makes sense economically. What I mean by this is the tank is prohibitively large, surely has some associated losses with it - there's still a temp gradient, and once you've stored energy in water heat, you're forced to use it as heat. Battery power can be used to run your heat pump anytime as well as all other appliances. With a wood stove backup I think I'd err toward that for heat in the cold months and having electricity available to use for appliances.

[Zach]

I lived in a passive solar house in Maine till I was 15, and it worked quite well. We had more sunny days in the winter there than we do here, but it was not the desert by any means. We had 2" polyisocyanurate (if that is the spelling) foil faced panels that we put into the windows at dark in the winter and took out in the morning. They had tasteful duct tape to cover up the edges, and contact paper on the inside. The wood stove in the basement provided the rest of the heat. It would get hot inside on sunny days in the winter, and at night it would get cold sometimes if we didn't start a fire on borderline temperature nights, but it was not uncomfortable. I would like to build a passive solar house again someday, when time and money permit. It's not a perfect solution by any means, but it is helpful.

[montcalm]

There are perfectly functional passive solar houses around the state, not sure how many in the Adirondacks, but I know I've watched videos on earthship builds in Ontario, Canada - which may be more similar or harsher than the Adirondacks.

The houses I know of in NY I believe all had wood heat as the primary source. They were also built into embankments on their north wall much like an earthship uses - almost all passive solar designs I've seen use the basic premise of the earthship but whereas the earthship was designed to be totally self-sustainable in water as well as energy, most of the houses in the NE forgo the water aspect as it's so easy to drill a well. But the desert models use a much more sophisticated system of water catchment and water recycling that wastes absolutely no water - every bit is used from drinking, to washing, to flushing toilets then finally to watering the green house and then watering the outside garden.

I also think they were designed around a desert environment in that they possibly aren't able to regulate (easily) long, cold winters. Deserts can be quite cold, and that's where the thermal mass comes in to try to smooth out those daily ups and downs as well as the seasonal swells.

Also a true earthship has a break between the greenhouse and the living space that is insulated - there are (sometimes) less windows (but also adjustable circulation vents) that allow you to bridge how much of this intermediate room you want in your living space, or how much you want to isolate it.

These designs don't really use much insulation at all, and absolutely no thermal break between the thermal mass and the living space, which is what mooregm is not a fan of - I get his perspective. You wind up with a space that is highly regulated, but not necessarily exactly where you want, and when you need to add heat, you are constantly sinking it right into your thermal mass.

[John H Swanson]

My take on thermal mass is that you need to be able to control it -- both adding and removing heat. Without control, it dictates your life, not the other way around. There are many approaches here, but personally water makes the most sense to me.

Two points come to mind.

Water is easy but prone to bacterial growth, freezing and leakage. Additives can help with this.

I read an interesting book decades ago titled "double envelope houses" or something like that. It presented solar houses that used two heat sinks - one above and one below ground. The concept was to use one to add heat to the living space and one to remove heat from the living space depending upon the needs. This concept is probably of interest to you. I thought it pretty smart but then became more anamoured (sp?) with super insulation. As I previously mentioned I would still use a solar collection panel to pipe hot air into the living space but keep it isolated to avoid the work of opening and closing off many large shutters. One could create an air circulation system that uses the cool sub-grade heat sink to cool the living space but it might be fraught with problems (radon, mold, vermin) compared to a heat pump system that figuratively does the same thing. And of course a 100F day could be spend in the basement.

Separately on the subject of insulation I read an article that discussed the merits of attic insulation and how much. It discussed adding more insulation (+6") to an already insulated (~8") attic. It presented the heat loss calculation for the entire attic and the heat loss from the area of the uninsulated pull down steps. Eye opening. I had already built a box over my pulldown steps and I went out and added 6" of fiberglass to the top of that 2" polyiso box. Then I used the IR meter to search out other warm spots in the attic on a bitter cold day. With the outside air at 10F (NJ) most of the attic floor was in the low 30F but there were spots up to 39F that got some attention.

And of course vigilantly focussing on sealing heated air escaping through gaps is of paramount importance.

[montcalm]

I know the question came up earlier on my part, but I read last night propylene glycol is often an additive used to both increase heat transfer, but also prevent freezing (or evaporation).

It is used as a food additive, so is non-toxic, at least in small doses. WTBS, you don't want it to mix with potable water, as it still would be a pollutant, so you have to add a some extra clap trap to keep it isolated.

[montcalm]

On a side note - I'll try to find that presentation from the building company with the 80/40/20/10/5 thing. I'd like to try to understand the physics of that.

Also, I'm a bit skeptical on the whole R80 wall. Some calculations I looked at for a 12" double 2x4 with a thermal break wall would be on the order of R50. But I didn't look too hard to figure out how good that estimate was.

[montcalm]

Another side tangent here, but I believe in my environment, I could easily use a air-sourced heat pump.

I really need to do the math here, but I *think* I only spend about $1200* a year on utilities - that's gas and electric. My furnace and water heater are fairly new - but I could probably get off the gas and switch to a heat pump WH when I need to upgrade. Furnace might be a while. I'm thinking if I do add solar panels I'll switch as much to electric power as I can, and that it would probably be worthwhile to upgrade my 60 year old panel.


*last year was $980. I'm pretty sure it's been as high as $1500, using the same appliances but when our local energy supplier was sub-contracting energy suppliers - it was very confusing and it was far more expensive, then it just magically disappeared.

For reference we have about 1300sf of heated space, a slab of 3 season room and garage attached. 600sf of full unfinished basement, unheated, non-insulated. 5 people in the house.

I use the basement all year as storage on one side, shop on the other. It stays around high 50s/60s all year. In the summer I don't do anything, in the winter, I sometimes wear a sweater if I'm down there for a long time. It has old terrible windows which could definitely be improved, and probably keep it a little warmer in the winter.

[montcalm]

I did some estimates for my own home just to see how easy it is to get net zero.

It's not very. I'm pretty average in terms of energy use per sf. Last year my monthly average was 600kWh.

I used a local solar supplier to make an estimate on my house. They gave me 17 panels @ 5.7kW. So backcalculating they are recommending 330W panels, which I'd definitely be in for because my roof area is minimal. They use google photos to estimate panels. I estimate I could fit 13 on my south roof, lying flat. Perhaps if they were tilted and up on a frame we could get another row and hit 17. They gave an annual output estimate for 17 panels at 6120 kWh. That's the tricky one - I'm hoping that's based on some actual solar data for this region. But either way, that's below my yearly electric usage - and that's not my entire energy usage, that's just electric. I still have hot water and heat on NG. So all-in-all, it's perhaps not as easy as one might think to simply add horsepower.

[montcalm]

I'd like to bring this back to focus...

As much as I love the idea of earthships and that kind of design, I just don't think they work well in this environment. I've watched a number of video tours of current builds in different environments and they all rely on a woodstove (which is OK - more on that later) but I'm not loving the idea of minimal insulation. I'm actually thinking now, based on previous posts (which then led me down other paths of research) that superinsulated + basement slab thermal mass seems like the way to go. There are still a few things I'm skeptical about, but here's my basic requirement:

1000-1200 sf of living space + 600-1200 sf of unfinished basement, insulated, with radiant tubes. Basement size would depend on site and whether I needed to do two-story. I'd prefer single story, perhaps with a small loft in one area.

I don't know that I'd do the large water tank. Maybe now it works, but I'd rather rely on the grid a little bit than invest in that. But my mind may change if I buy land without grid access.

The radiant basement seems like you get it for free, so why not? If I do a garage, I'd do that too, but a heated garage would not be a direct requirement off the bat. Insulation recommendations I see are for R20 in basements, but I'd check that over see how much benefit there might be for more...

I think I'm convinced on minimizing windows and focusing on insulation. With the temperatures in the toughest months I think every bit of thermal resistance will be the winner. I'll likely design the window scheme around the site with an emphasis on south facing (just for sanity of getting some natural light during the dark winter).

I like the idea of double wall, 2x4 construction with the thermal break. Whatever R value that comes to be I'm sure will be sufficient - R40 min.

The questionable area I get into here is secondary heat. I'd like wood. It's cheap, easily accessible in the ADKs and if I use this for a vacation home at first it may likely ONLY have this heat source at first, but be setup to add a heat pump. I'll likely have the well and lines put in during build, and add the system later.

Anyway, my experience with wood, and especially woodstoves is that they tend to overheat the heck out of a place when you run them. I'd imagine on a small, super insulated home this could be hard to control. I was thinking a small stove in the basement with forced air might be the best. Hopefully just a small fire at night would keep it warm until morning. Gonna have to do some figuring here....

Electric - I'd hook up the grid if it was available, start with just panels, then add batteries and see how far I go. If I use it seasonally I don't really want the batteries because I'd assume them getting cool is not going to be favorable. If no grid is available, then I'll think harder, but I'd like to lean on wood for any inadequacies in energy needs and minimize the batteries.

Seasonal use - my wife has summers off, so it may be occupied through summer vacation from school. My hope for solar would be to fulfill that at first - shouldn't be too hard. Winter use would be on weekends, so minimal electricity and wood heat. I hate to say the "g" word, but maybe in the cards for part time. Spring and fall would be sporadic, but I'd assume solar demands could be met for the amount of time we'd be there.