Been reading a lot on these forums but this is my first post, so please bear with me. We’re about to break ground on our new house, a 2 story Craftsman with unfinished walkout basement up in southern Maine. The basic footprint of the house is 28x30, with an attached 22x22 garage on front (the garage will have unfinished space above it for future bedrooms). After much research on these forums and others, we wanted to do ICF or SIPS for the main house, figuring we wouldn’t be heating the garage or unfinished space. Unfortunately, our dreams didn’t match our limited “starter home” budget. Quotes, from multiple vendors, came back far too high; we decided to save for a year so we could at least afford an ICF basement and then do traditional stick framing 2x6 walls on the rest (spray foam interior and OSB board with Low-E tab housewrap exterior). Our GC is a close family member, who’s interested in green building and enthusiastic about energy savings, but relatively inexperienced due to a lack of interest from clients in our area. Basically, for new construction over $400k, there’s a lot of interest and implementation, but in the starter home crowd, no one wants to spend the money up front. I mention this because the ballparks I’ve seen online for ICF are ~ $13-$18 per sq ft. But we’ve gotten 3 quotes so far and they’re all up over $21 sq ft (for basement only). This would include the door and window bucks (we have 2- 40x44 windows in addition to double doors) but doesn’t include things like parge, vapor barrier, etc. To build the same basement with traditional poured walls and a 3” R-15 rigid foam board outside (plus stick framing the daylight walkout & spray foaming that), we would be saving over $8k. We’d also save money not finishing the int basement, since there’d be no exposed insulation (plus we could insulate the int later when we had more funds). I’ve done heating cost comparisons and it looks like the savings are pretty small between an R-15 and an R-26 in this scenario. Saving the money means we can afford to build now and also afford to put in setups for future energy improvements, like solar tubing on the southern roof and a conduit for PV panels. We could also afford a heat pump over a traditional propane boiler (no natural gas in our area). But after a year of ICF talk – is this the right decision? Would love any feedback people can share – and I do understand the newbies usually get schooled pretty badly, so please go right ahead :) Thanks for your help!

If the money you save will get you into a heat pump instead of on propane, then that is the route to take.

Why are your ICF bids so high? That is a very simple build. Maybe your GC should handle the blocks and concrete and steel and just get a quote from an ICF guy to come out and do the labor on that small portion.

Since you're not planning on finishing the basement, I think you are doing the right thing. There's not much wall area in that foot print, so if you do finish the basement, it won't be that big of a deal to frame out and insulate the inside of the exterior walls. The only thing that would make me do ICF in your shoes, is if you were in a tornado alley. If you are, either do ICF or build a small safe room out of a closet or something in the basement.

I think poured concrete + foam has some advantages over ICF - the thermal mass is exposed and there is one (or two) surfaces you don't have to clad. The foam can even be included in the form.

http://www.certainteed.com/resources/ThermaEZE%20General%20Brochure%2040-96-02D.pdf

http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_0061/0901b80380061a97.pdf?filepath=styrofoam/pdfs/noreg/179-04047.pdf&fromPage=GetDoc

Just as a point of reference the same garage, main house icf with the floor and waterproofing would be about $17-$18000. Your GC should be able with a little guidance  be able to complete the project. It's not rocket science

Thanks for the feedback. We did price out just ICF materials (Logix blocks from a local distributor and our GC's normal guy for concrete & rebar). Came in at about $13k including the below-grade membrane (can't remember if that included the parge for above-grade exposed). Any rate, only 1 ICF builder broke down his price to a materials level, and it turns out he's carrying $7k for labor. He was willing to do just the labor and we'd supply the materials (our costs for rebar & concrete were lower) but with the $ 7k labor, we'd only save a grand or so.

@smartwall - do you mean with the icf basement, we should be in around $17-18k? another option is to have the logix distributor provide "guidance" while we supply materials and GC and his crew do labor. But that makes me nervous when I think about the pouring/bracing handled by an inexperienced crew (as the term "guidance" is a bit vague).

Posted By ICFHybrid on 04 Apr 2012 01:23 AM
If the money you save will get you into a heat pump instead of on propane, then that is the route to take.

Why are your ICF bids so high? That is a very simple build. Maybe your GC should handle the blocks and concrete and steel and just get a quote from an ICF guy to come out and do the labor on that small portion.

Or even if the savings doesn't cover the cost, at current southern ME electricity & propane prices even if the heat pump only averaged a coefficient of performance (COP) of 2 (typical average for a ducted air-source heat pump in that location), it would be cheaper (roughly half-price) to heat with an air-source heat pump than with condensing propane. If you went with a high-efficiency ductless air source heat pump you'd get a COP of roughly 2.5 (saving ~20-25% on heating costs over a typical ducted-air system.)

That does seem a bit pricy for ICF, but many things can affect the cost. If a project is too SMALL it can add quite a bit to the per square foot numbers.

If you go with the exterior-foam approach it may be cheaper still to go with 4" of type-I EPS than 3" of XPS, especially if you can use reclaimed goods from re-roofing projects.   There are multiple sources for such goods in MA at 25-30% the cost of virgin stock. (eg. The Insulation Depot, in Framingham).   EPS does at least as well as XPS on below-grade applications in terms of long term water absorption/degradation.  Ants and termites will tunnel through either, but backfilling with sand inhibits termites, and a metal Z-flashing that extends over the top edge of the foam and under the foundation sill keeps them from finding an unobserved  route to the wood (they have to bore out to daylight to make the path around the metal.)

The most important guidance is the pour. A GC should be able to do the build. Plumb,level. square is the theme. The pour is the critical part and even some "pros" leave something to be desired when it comes to pouring a fully consolidated wall.  My question is with 3" foam on the outside of the foundation, will the foam stick out past the wall of the exterior of the house.   The 17-18 grand is the price around my neck of the woods for everything based upon some assumptions without knowing all the details.

BTW: A traditional 2x6 with spray foam cavity fill may meet code min, but after factoring in the thermal bridging of the framing it's still only an R14 wall. If you went with blown cellulose on the cavity fill and 2" of EPS on the exterior of the OSB you'd have an R22 wall for about the same cost (or less if using reclaimed goods.)

You can also use 2" of reclaimed roofing iso over the OSB instead of EPS for less than the cost of virgin-stock EPS and get ~ R26 out of it. Detailing the OSB as the primary air-barrier with mastic-sealed seams and spray foam-sealed edges, and it'll be as-tight or tigther than a spray-foam cavity fill. Detailing the housewrap as an air barrier is also recommended (caulking between sheets at the overlaps is more reliable than housewrap-tape alone, etc.)

With 2" of foam over the OSB and 4" on the exterior of the foundation you'd have to cantilever the studwall off the foundation by ~1.5" to get planes to align (assuming 1/2" OSB sheathing) but that does not present a structural issue- 2x4 walls have a half-inch less timber bearing directly on the foundation than a 2x6 hanging 1.5" off the concrete and over the foam.

Furthermore...

If you're not already keyed into it, there's a DOE program for subsidizing U0.20 windows, which is a substantial reduction in heat loss relative to code-min U0.35 windows. A mininumum buy used to be 20 windows, but that restriction has been eliminated.

See: http://www1.eere.energy.gov/buildings/windowsvolumepurchase/news_detail.html?news_id=18210

For weather history and heating design temp purposes, what's your ZIP code?

Sorry for the delay - things have been a little crazy. We're building near Portland, zip is 04101. Going to check out some pricing from the Insulation Depot this week and see what we can do about adding rigid foam on the exterior to bump up the r-value. Also going to check out that window link now.

I think we're pretty set on doing the basement with rigid foam for cost reasons, and using the savings for a more efficient heating system. Our hvac vendor gave us a (very affordable) quote that involved a split system - using a heat pump for the 1st fl great room and 2nd fl master bdrm, but also using a high-efficiency propane boiler to do hydronic radiant in tiled areas and small radiators in the guest room, study, etc. I'm not sure we'd need both systems with the woodstove... any thoughts?

The upfront cost of a high-efficiency propane boiler for the tiny-load zones could be a real budget buster.  With tiny micro-zones like that it'll prematurely wear out the boiler as well since the mininum-fire output of even the tiniest propane boilers will be many times overkill for those very low loads.

A more appropriate and cheaper solution would be to use a condensing propane hot water heater with a heat exchanger to run the hydronic zones, or an electric-boiler.  (At the trajectory of propane & electricity prices in ME the cost-per-BTU isn't that different now, and may cross over to favor electricity soon.)  

According to the EIA residential retail electricity is averaging ~15 cents/ kwh there, which is ~$4.40 per 100KBTU of heat delivered inside the house.  The state average price for propane is currently $3.16/gallon LP burned in a 95% boiler is $3.65 per 100KBTU delivered inside the- house, or about ~17% less than resistance-electricity. (At an average COP of 2.5 the heating with the ductless is $1.76 per 100KBTU.)  The price of propane tracks the world price per barrel of oil (about half the propane supply is from oil refining, the rest largely from natural gas processing) and fairly volatile, but the ten year trend is turning up, and as world demand for oil shows no sign of moderating, that trend is getting steeper.  Electricity is a regulated market with multiple source fuel/energy  inputs, and tracks a flatter more predictable curve.  You may be better off doing your domestic hot water with electricity as well.  

A 5-10 kilowatt electric boiler is about a grand up front, and the installation costs are small compared to any propane-boiler.  It's unlikely you'd need anything over 10kw, and even 5kwh may be more than enough.  A 5kw unit would be enough to support about half the heat load at my house at +2F outdoor temps (the 99th percentile heating design temp  for Portland) , and I'm living in 1923 antique that's well below current code on R-values, with ~2400' of fully conditioned space + 1500' of semi-conditioned (~65F in winter) basement.  Even if propane continued to be cheaper than resistance electric, with most of the heat load being handled by the ductless heat pump it would take decades to make up the upfront cost difference.  Spending the difference in installed cost on better air-sealing, thicker exterior foam, or U0.20 windows would likely be a better long-term investment.

Here in Minneapolis we us high efficiency condensing water heater for combi domestic water and space heating easily handling the smallest of micro-zones with a sub-assembly featuring weather sensitive controls but this is with natural gas.

If electricity can be had a discount, a modulating electric boiler with outdoor reset (ODR) is the thing.

Dana in right, insulate first.

Thanks again for the feedback. Ideally would like to do more ext rigid foam but the installation costs from the framing crew are going to start to affect us. So might have to settle for addl insulation inside and deal with the thermal bridging. Going to focus on making sure the ext is sealed very tightly and I'm hoping for a small boost from the low e tab housewrap. Also looking into the possibility of doing airtight drywall if we add batts in over the spray foam.

Starting research the U.22 windows ( doing mostly DH), it appears most Maine distributors carry lines that reach the rating by using triple glazed glass, with a low SHGC. We planned the house with some passive solar benefits, so we're looking for something with a higher SHGC and (just a personal thing) a high VT (that blue "sad" look is a downer when it gets dark out at 4pm in the winter... love seeing 'warm' sunshine). Cardinal makes a low e 180 with i81 coating that supposedly achieves a U.22 with the other ratings where I want them - any experience with these or which manufacturers utilize this glass?

@ BadgerBoilerMN - those combi units are what I'm looking into. Our DHW was already planned as a tankless gas unit... I've read differing things - can you convert LP units to natural gas later on? (hoping for gas in the next 5-10 years) We're hoping to do solar tubing by 2016 for the tax credit, so we could tie this system. Our plumber usually works with Viessman for boilers and Rinnai for DWH... Rinnai sells 1 combi unit, so I also started looking at Bosch. Any recommendations? I'm about to delve into a few threads on here where you and Dana posted on this topic.

To be, sure on south facing glass high SHGC is important, but it's also important to model that.

With hard-coat indium tin-oxide low-E float glass on both panes it's possible to hit the mid to low-0.2s with a double pane, and it's definitely not blue. With dry-air fill it ends up under U0.25 but with argon-fill would bring it down to ~U0.20. (Argon is cheap stuff- they shouldn't be charging a whole lot extra for it, but hard quote tells all.)

The "i" in "i81" is for indium, which is a non-blue hard coat low-E. I may or may not have seen Cardinal's lineup, but hard-coat low-E is pretty neutral, doesn't have the blue-haze thing going on at all. I'm not sure what their high-SHGC LoE180 soft coat looks like. Their web page description of LoE180 reads:

"The glass is coated with a microscopically thin, optically transparent layer of silver sandwiched between layers of anti-reflective metal oxide coatings. A protective coating is applied to assure durability and long life. The coating is virtually invisible to the eye – it’s just like looking through clear glass."

Which is different from their LoE i81 description:

"LoĒ-i81 is sputtered onto the indoor lite, the #4 surface, thus reflecting escaping heat back into the room and lowering U-factors. Coupled with our LoĒ² or LoĒ³ glass and argon fill, this double-pane unit delivers performance much better than clear triple-pane – a center of glass U-factor of just 0.20 compared to 0.35 with clear triple-pane."

Without exterior foam you'll need to use an interior vapor retarder &/or rainscreened siding (= back-ventilated, with gap between the siding and sheathing) to protect it from wintertime moisture drives. You might look into using aergel stud strips (http://www.thermablok.com/ ) if you intend to apply the thermal breaks from the interior. Unlike exterior foam it won't thermally break the band joists & floor/ceiling joists, but it's better than nothing.

All tankless-based combi systems are all extreme-overkill for a low load house heated primarily by a ductless heat pump. Even if the design day heat load of your house is 30,000BTU/hr (probably won't be that high) the heat load of your micro-zones are probably going to be under 3000BTU/hr each, and it'll short-cycle. The min-fire on the Rinnai combi is 35KBTU/hr, which is likely to be higher than your whole-house heat load- not a good fit. The min-output on the smallest Bosch combi-heater running LP is 39,900BTU/hr, which is even worse.

Too much burner, at min-fire leads to higher wear & tear on the unit, and lower net efficiency (it throws away a fixed amount of heat with every ignition cycle & flue purge, whether it was drawing a pint of hot water for a hand washing, or heating up a radiant slab floor, and it all adds up to "not appropriate for the load".

The easiest way around the problem is to use a tank-type HW heater, using the thermal mass of the water in the tank to limit the number of burns required. A condensing unit such as the Vertex or Polaris is far preferable to a standard tank heater for several reasons- you can ruin a non-condensing tank heater in one heating season using it to run low-temp floors if you're not careful with the design & set up.)

The Vertex has purpose-built ports on the sides designed for space heating applications, and even the smaller-burner version should be able to handle your zone loads (or even your whole house load.) with margin to spare, as long as you don't forget to close the windows & doors. ;-) The manual (http://www.hotwater.com/Resources/Literature/Instruction-Manuals/Residential-Gas/Vertex-Manual-197423/ ) shows an "open" system using it to run an air-handler, but for radiant floors you'd want to isolate that with a plate type heat exchanger, using 2 pumps- one for the tank side, the other for the heating system side of the heat exchanger. This isn't rocket-science hydronics, but most plumbers aren't rocket scientists either, and if they've never done one it, using a hydronic heating design service (maybe even BadgerBoilerMN ) to spec it out for them may save time & money in the end.

The Polaris has a longer and generally good history in radiant floor applications, and is similarly ported with heating-system taps:

http://www.americanwaterheater.com/products/pdf/NRGSS00908.pdf

Again, the smallest version would likely serve your needs, but has a bigger burner than the smallest Vertex.

IIRC BadgerBoilerMN prefers the Polaris (probably due to familiarity with the unit leading to assurance/comfort on the designer's part), but the Vertex has been out there for handful of years now, without tales of woe from the combi-heat builders. They're great units, but command a premium over the Vertex. Amazon.com pricing on the smallest Polaris is $2800 + shipping:

http://www.amazon.com/dp/B0033Z70C0/ref=asc_df_B0033Z70C01971641?smid=A1BLSSVV3AOXMD&tag=dealtmp680155-20&linkCode=asn&creative=395105&creativeASIN=B0033Z70C0

Whereas the smaller Vertex runs about $1700 in the NG version just about everywhere (I'm not sure what the up-charge is for an LP version, if any.)

As for converting any appliance from propane to natural gas, it's probably not in the cards, unless they sell a kit specifically for that purpose that passed all safety & code requirements.

I do like the Polaris water heater for the micro-zone applications so aptly described by my esteemed colleague. However, one might note that the Vertex is remarkably like the Polaris with a couple of exceptions. First, the Polaris has been manufactured since 1987 and sports a stainless steel tank and flue. The Vertex by contrast is built like a standard glass lined tank-type water heater with the important exception of fully sealed and condensing combustion. Like the Polaris the fuel savings should be in the 40 to 50% range with a life expectancy in the 10 to 20 year range. Closer to 10 for the Vertex and 20 for the Polaris. Where domestic water quality is an issue the more expensive Polaris is the clear choice. They share burner, blower, ignitor and gas valve and both are field convertible from NG to propane and back (qualified personnel only). The similarities should be no surprise since both are owned by A.O.Smith. We are certified to design, service and install both Polaris and Vertex. With a $1000.00 plus discount for the Vertex, the choice in most cases is one of budget and investment strategy than performance or efficiency. We are happy to help skilled homeowners and licensed contractors with water heater based heating systems that conform to accepted industry standards in the US and Canada. Name your poison.

Thanks Morgan- it's good to know that they support field conversion without running afoul of the inspectors!

Thanks all again ! Good reading.
in a small app how would an inexpensive Rheem ' instant ' (usu not approved)
in-this-case-as-done last year:
How would this stack up: -Modulating to 30% start, smallest heater on a small 20 gal buffer tank, by pass Series+Parallel piping as part of the only header run without special mixing control/ 33w circulator will run it nicely, swing ck to buffer, re-circ for small zone/cycling tolerance. OEM Tech approved use, as long as 30-deg dT hits instant DHW heater unit, so the boiler is in a secondary at out to zones.
Bigger APPS:
I have only used 4 IBCboilers.com IBC Technologies, Canada
but do not know how a modulating 20-115 boiler stacks up, installed for ~ 6000, new headers and pump, retrofit.
....

Let me get this straight. You want to get off the space shuttle and jump on a pedal bike? Tank-"less" water heater with a buffer "tank"? What are you trying to do again?

~ 6500-5500 installed The IBCboilers.com can easily modulate 20-115, with a little 25 gal tan, but goes to HW  or other applications, well designed programmable control and sensors for 3 pumps and zones built in, differential programming, all .

IT is not called a tankless, but IS just capable at 5 deg diff to 30 deg diff handle directly ICE melt to radiant high mass slabs on cold starts to HW Priority on demand .

The Rheem at a 1500 purchase and always wanting at least 30-deg differences, was regulated to not fire until a 35 deg diff to run between a 95 and 130 range by interferrence,  NO tank was used , only but a 33 watt recirc...

The household HW recovery was ~ 3.1/2 GPM continuous as Priority from 52 deg well.

IF anyway to fit:
Of course then a 3-to-4 staging GT for Priority HW only to an inexpensive HX on the side, would offer more with Cooling in 100% RECLAIM as well,  and but as GeoThermal, the entire system is called in having supplemental gas or electric boiler - complete on a contract if tax credit are for the qualified buyer.

GT HEAT and Warm Air if wanted HVAC + Full Sized DeSuperheating and Priority HW
 HW SYSTEM BUILD as GT, reservoir and finishing tank,
or one tank with coil (more costly replacement,  unless lifetime)
 Cooling and DeHumidification
 SYSTEM BUILD COMPLETE with up to 4zoning, OEM board inside with many features, inclusive

JP

www.GEOPros.org