Super-insulated building envelope
- Murus R40 polyurethane core structural insulated panels (SIPs)
- Additional Exterior Layer of R5 Rigid Foam Boad w/ Radiant Barrier
- Alpen "orientation tuned" high performance windows
- Freedom Foam closed cell spray foam insulation in non-SIP Areas.
- Air-tight envelope with continuous mechanical ventilation with energy recovery provided by www.UltimateAir.com
- Oasis Modular Foundation (R10)
- R10 Sub-slab Rigid Insulation
Cost effective modular construction
Southern Exposure
- Passive winter heat gain through high performance South facing windows
- Ideal roof orientation for solar hot water and photovoltaic panels
- Overhangs designed to reduce solar heat gain in summer
Reduced electrical loads
- Energy Star rated appliances
- Extensive use of compact florescent (CFL) and LED lighting
- Energy Star Rated Ceiling Fans
Other Energy Efficient Features
- Ground source heat pump (GSHP) By Climate Master
- Domestic hot water preheated with GSHP desuperheater and evacuated tube solar hot water from Silicon Solar. Both are topped off with a 94% efficient Noritz on demand hot water system.
- Window location designed to provide cross ventilation
Added "Green" Features
- Passive sub-slab ventilation system (in case of radon)
- Extensive use of engineered lumber products (SIPs, OSB, i-Joists)
- Extensive use of pre-finished domestic hardwood flooring
- DRYLOK® Extreme Latex-Base Masonry Waterproofer
- Natural granite countertops by The Stone Cobblers
- 100% domestic hardwood flooring in living areas - by Bellawood
- Eco-Lawn from Wildflower Farm
- MERV 13 Filters
- UV Air Sterilization
- 100% Recycled Asphalt
Insulated Foundations & Thermal performance
Both Oasis and Superior Walls have a stackup where the bulk of the insulation is on the interior space. While this is much better than uninsulated, there is a significant benefit to putting the concrete on the inside of the insulation envelope. There's a good synopsis of ongoing research & analysis on the Oak Ridge Nat'l Labs website:
http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/ind...
Basic results:
[thermal mass inside the insulation] = good
[thermal mass outside the insulation]= less good
The difference between "good" and "less good" varies with season, total R-value, and climate, but it can be significant. They studied 4 different stackups, multiple climates, but in all climates those stackups with interior mass outperform the others. (Click through the various figures. C=concrete, I=insulation in their various stackup labeling.)
Putting the thermal & vapor barrier to the inside also means that the concrete stays exposed to ground moisture, which it tolerates well unless the soil is very acidic and near the water table. A more ideal situation would be a layup where the outside is sprayed on closed cell foam insulation, and the interior finished wall is semipermeable so that the structure dries-to-interior. The concrete can absorb and release quite a bit of moisture, but if the exterior isn't sealed it becomes the transfer conduit, and you're counting on a near-perfect vapor retarder on the inside (hard to do without spraying it on.)
Are there any modular foundation vendors with the stackup reversed, or at least closer to the ORNL's external insulation ideal? (Probably worth looking &/or discussing with the vendors.)
dana
Found it!
These folks have a pour-in place SIP, a concrete/insulation/concrete stackup foundation system that looks like it'll fill the bill to let some interior thermal mass work in your favor as modeled and tested by the Oak Ridge Nat'l Labs:
http://www.thermomass.com/index.html
Seems they spent some time engineering the through-ties to be material & thermlly compatible too- not just a hack!
dana
Solar Thermal
I currently have a 2 panel Steible-Eltron pre-heat setup. Works really well. I used to have an 8-tube evacuated tube Sunda system with a smaller pre-heat tank. It worked ok, but since I installed it in '02 when nobody knew what they were, it should have been done differently.
Basically, tubes cost a bit more than flat-plate, but they give you some flexibility and a bit better performance in super cold temps. You can rotate them by hand if you want to tweak the fin's exposure for the time of year, or even rotate them to shut them down if overheating in summer is an issue. Replacing a tube is done by hand with no tools as well.
If none of those is a concern, spend a bit less and go with a flat-plate. Steible makes a really trick control unit/circulator pump/tank which is fully insulated and very clean. I actually don't have that since I re-used as much of my equipment from the tubes when I installed the plates. Same functionality, just not as pretty in my utility room.
If you go with an on-demand water heater after a setup like this, of course make sure it is a top shelf unit which modulates the flame based on incoming water temp. Many units don't do this, so be careful.
Are you considering radiant floor? If so, solar thermal can actually work very well for this too. Baseboard hydronic needs water temps too high, but radiant is perfect. Installing a system like a Tarm:
http://www.woodboilers.com/multi-fuel-furnace.asp
with a large heat storage tank would be the ultimate. The storage tank can have several heat exchangers for different sources.
Radiant floors
I too am wondering if radiant floors don't make sense in this nearly superinsulated structure. It's more efficient to heat the people than to heat the air- in an addtion in my house where we installed radiant floors it's downright cushy (T-shirt comfort!) at 68F, and even at 64F (at shoulder height) it's pretty cozy just lyin' on the rug. With an earth-coupled heat pump designed for low-temp hydronics it should be pretty cheap to run. With the right heat pump design radiant floors can be used for radiant cooling too, as long as the humidity is controlled by other means, like the active ventilation with heat-exchangers.
Hydronic radiant floors are also easy to piggyback onto with other heat sources such as wood boilers & solar thermal setups too- I like this guy's straight-ahead low-cost solar approach: http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.ht...
Building the heat storage tank with high-R insulated concrete forms rather than plywood- wouldn't have cost much more (if any) providing a bit more structural integrity, but it's still a sound design.
The Gouin house probably has much lower heat loss too (the 350BTU/-F degrees cited in the article doesn't sound like a supersulated supertight house unless it's gi-normous.) Run some simulations, but I'm betting an active solar heater half or 2/3 the size in the article would be sufficient here, where the envelope is a tight foam R40 with high performance windows & doors, with passive solar tempering designed in. (Even a 2 ton compressor might be overkill here given that it's built with R40 SIPs- what do the HVAC folks say?)
dana
Radiant Floors
I have considered radiant heat in the past. Although I like the idea, my experience, through estimates, has been that it is not cost effective. In a "stick built" house, it may be cost effective, but for this modular house it just isn't.
I am presently contemplating this idea...
Keep in mind that I am planning to receive millions of free BTUs from the high SHGC front windows. My concern is temperature balance throughout the house. The front rooms will be warm, the back rooms, cool. It is my belief that any centralized system (with limited zoning) will likely have difficulty dealing with this and result in poor temperature balance.
My current thinking is to have have the modular factory install electric baseboard heat (cheap to install). I will then
contract to have a purposely undersized ground source heat pump
installed (using a standing column well). The GSHP will be used to provide an economical "base heat
load" to the entire house. The electric baseboard can then be used for fine
room-to-room temperature control.
Since this is not yet set in stone, I am certainly open to ideas. Just know that I have already priced out a radiant system and the cost/benefit is just not there for this project.
One last note... Notice that I mentioned using a standing column well for the GSHP. One of my ideas is to use solar heated hot water to heat the water entering the heat pump. The heat pump's efficiency rating (COP) can jump into the 5-7 range with some added heat. Also, the efficiency of the solar collectors can increase as well (larger delta T).
Mr. Green Dreams
radiant floors spread heat
Looking at your millions of BTUs of free heat and a concern about the South side of the home being too warm and the North side too cool...
This sounds like a great place for radiant floors and use the liquid to cool the "hot" floors and take the heat to the "cool" North side.
 What kind of pricing were they giving to not frame and insulate a floor and instead put in a slab with Pex coils?
As you have seen, without having experience, a contractor will raise the bid to cover his Fear Factor, but on the face of this, it seems reasonable.
Thanks for letting me contribute my thoughts.
Radiant Floors
I was given a cost of ~$15/sqft for Warmboard radiant floors (http://www.warmboard.com/) (not including the boiler). With 2700+ sqft, we are talking over $40,000. Ouch! Then we still needed to worry about zone control.
Compare that to the cost of electric baseboard installed in the factory for under $1/sqft while giving each room granular temperature control... I simply can't justify the added cost.
Mr. Green Dreams
Seems overpriced.
There are cheaper ways of getting radiant heat- $15/ft (without boiler or controls) seems almost an order of magnitude too high. It's probably worth soliciting other quotes (possibly looking at other methods- say a 2" slab o' concrete with embedded PEX instead of warmboard.) No way should it be costing $40K.
A 95%+ AFUE modulating-condensing LP or gas boiler for a house this well insulated should run you at most $3k, plumbing & zone controls maybe another $3k (4 or 5 zones, including a hot-water heater zone), figure $3-4k to hook it all up, call it $10K. The rest would be in PEX & concrete- another $5k-8k(?), installed. For new-construction like this figure $15-18k. Anything over $20K I'd demand to see the breakdown, 'cuz something is wrong. (Maybe what's wrong is that I'm in the wrong business- could make a killing in the radiant heat biz!)
Doing it in concrete also adds significant thermal mass to the house, which will help with any solar gain imbalance issues as well. The only downside to it is that the floors don't have much "give" to them- they feel firmer if you're prone to falling.
If you wanted to design it yourself, SlantFin has downloadable freeware tools. You'd have to cheat a bit on their exposed-walls factors (R40 SIP isn't a menu option. :-) ) but you could get close if you used the lowest loss-factors for any and all of the plug-in options for windows, walls, ceilings, etc. Try it: http://www.slantfin.com/heat-loss-software.html
That could get you roughly the size of the boiler (I'm guessing 60K BTU/h on the coldest day of the year, could be lower) and the heat demands for individual rooms. Other places have rules of thumb about how many feet of PEX of what diameter & flow rate would get you there, but it HAS to be smaller/less schtuff overall than any conventional stick-built system. Radiantec up in VT (http://www.radiantec.com/index.php ) has a lot of useful information on design and DIY tips on their website- they may be willing to quote doing your project too.
Whomever gave you a $15/ft number couldn't have done the math on what it actually takes to heat a superinsulated house- they had to be just plunking down how many square feet, assuming it was 100% warmboard and running with it. There are much cheaper and more appropriate ways to go on this. This guy did a really nice (wood subfloor, not concrete) solar-radiant retrofit on his (much less efficient) house in MT for about $4K worth of goods, and that's including the guts of the solar panels.
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/House.htm
You could build floors like his (but designed for YOUR heating load, which is substantially lower than his) over a standard plywood subfloor for well under $10K, probably under $5K. If you do it as a single zone and use an 87% efficient sub-$1000 modulating/condensing Rinnai on-demand hot water heater as the heat source your entire heating system could be literally an order of magnitude lower than $40K.
Shop it around- radiant heat is pretty flexible.
dana
On the other hand...
Thinking it over, going with hydronic baseboards has to be cheaper than even the best-case radiant floors, yet remains flexible enough to use small woodstove boilers in conjunction with (or in lieu of) super-efficient LP/gas boilers. It'll be more expensive than electric baseboards to install, but is greener & more efficient than electric heat to use.
The only real downside going with hydronic baseboards is that it pretty much precludes a solar input option except during the sunniest of times, and would require evacuated tubes (or evacuated tubes in series with flat panels) to deliver a high enough temperature with any efficiency at all. This would be both more expensive and perhaps not the most effective use of the solar resource. The only all-electric heating option that makes any "greensense" would be a ground-source heat pump (also carries a hefty hardware + installation price tag, even for a 1-2 ton unit.) But a heat pump (hydronic or air output) may be coupled with an efficient low temp solar-assist (if and only if designed well).
dana
Heating systems must be engineered to work efficiently
Designing a solar-hydronic assist to a heat pump's input loop is not a trivial task to do efficiently (I'm not sure it'll be easy to raise the COP by more than 1 with simple hacks). If the output of the heat pump is hydronic not forced air it may be easier to parallel up, run low-temp solar HW at longer duty cycles, switching over to the heat pump if/when the solar isn't keeping up. It would involve custom controls, but need not be unduly complex. (Hydronic output heat pumps are more amenable to zone controls too, which may partially solve the sunny vs. northerly room imbalance problem.)
Heat pump driven hydronic baseboards generally don't work in conventional houses (they're more often used with radiant floors) but in a superinsulated house like this it can. You'd probably need to be using higher-temp solar HW than efficiently attainable with flat panels during cold weather (say ~150-160F) but well within the efficient operating range of evacuated tubes (or with flat panels pre-heating in series with evacuated tubes) This would clearly have to be designed by a competent HVAC & solar engineers.
Rebalancing the temperature distribution between the sunny spaces and the rest of the house is THE fundamental design problem with passive solar houses. The solutions tend to be design specific though. Moving relatively low-temp air mechanically creates a wind-chill effect, makes it seem drafty. Building-integrated thermal air panels can work, if the return path is reasonable, and the forced-draft is above 100F. If the sun-spaces have sufficient thermal mass they don't overheat, so the imbalance is less perceptible. There are high effective-thermal-mass phase change wallboards under development, but so far none commercially available.
Thinking outside the box for a bit, the same plates & tubing used in radiant floors has been applied to walls as well. If interior partition walls have sufficient surface area the same technology could be applied there, making the whole wall into a low-temp radiator. It may be difficult to heat large rooms this way, but not-so-tough in rooms where the ratio of interior-wall area to floor area is greater than 2/1. (It's a somewhat harder design problem than baseboards or radiant floors/ceilings, to be sure...)
dana