I am weighing out my options for a heating & cooling system for my ICF home. I am seriously considering a geothermal system but am struggling with cost vs. savings ratio. Here are the stats: * Location: MA * Sq.ft.: 7,000 with basement & garage * Construction: ICF by Quad-lock * Insulation: R-30 closed cell * Heating: In slab radiant loops * Windows: Marvin Integrity * Finish: Oro Coatings Stucco * Status: 75% complete The cost of drilling is outrageous here in the Northeast, so ground loops is my only choice, my question is... what is the best & most energy efficient heat pump on the market that will give me both heating and cooling; I've been told that Waterfurnace E-series heat pumps are good... what do you all think? I am also looking to save as much as possible as we've experienced costly mistakes and delays with our previous ICF builder. Thank you for your help Luftpanzer

Luftpanzer,

I my opinion if you really want to take the guess work out of the decision making process, you may want to contact Energywise Sturctures out of Texas http://www.energywisestructures.com Energywise is a group of former NASA Engineers that are experts in developing Ultra Energy Efficient Homes and ensuring that they envelop of the house is working in harmony with the HVAC. According their website they have successfully designed over 40,000 homes and commercial properties, with several positive testimonials.

For about $1000.00 they will look at your plans and the technology being used in the build. They will conduct an energy analysis and provide you with the best way to ensure optimal energy efficiency. I'm certain that they could do an energy analysis with geothermal and with a conventional HVAC. You could look at both numbers and make a calculation on rate of return.

I think that the law of diminished return will probably show that geothermal will not be the way to go, especially if drilling is extremely expensive. Working with them would take a lot of the guess work out, in my opinion of course.

Hope this helps.

renangle

As a homeowner (not a professional), it is my opinion that any of the known geothermal manufacturers give similar efficiency. The more important part about geothermal is finding a knowledgable installer. If the system is not designed correctly, you will not experience the efficiency that you expect and paid for. If it is designed correctly you will experience the comforts and efficiency which geothermal can deliver (especially if you can do horizontal loops). Some important notes: You should have a detailed Manual J calculation done on your home - not just rule of thumb calcs (I don't know if your builder already has this?) If you want geothermal to provide AC in addition to heating, there are fewer units which give both hot water heat and forced air cooling, so your choices are more limited (and you will have to install ducts). But, like renangle wrote, you will need to do an analysis yourself or have someone do it for you to find if the difference in price of gas + AC vs. geo justifies the added expense of geo.

My husband and I decided to go with geo (we are also in the northeast). One of the main reasons is to relieve ourselves from dependence on changing fuel prices (i.e. gas, oil, etc.). We still have electric to deal with, but that price does not swing as much as the others for us. And, hopefully a solar system in the future will help contend with that dependency. Our payback period is now looking like 10 years... if the price of fuel goes up, that payback period will go down. But we are planning on staying in our home much longer than that. I guess it depends on your own preferences and situation.

I REMOVED A 60.000 BTU PROPANE FURNACE AND INSTALLED A CLOSED LOOP GROUND SOURCE HEAT PUMP FOR OUR 2500 SQFT RANCH.. COST 15.000 WITH A 2500 REBATE FROM THE UTILITY COMPANY, MAKE SURE YOU GET ONE THAT CAN CAN HANDLE 100% OF YOUR HEAT LOAD IN THE WINTER. WATER FURNACE WAS CONSIDERED BUT READ THE WARRANTY COMPLAINTS ON THE WEB.... I WENT WITH ECONAR ... GOOD SYSTEM AND RUNS WELL HERE IN MISSOURI. BEST THING I EVER DID... HAVENT BOUGHT PROPANE IN THREE YEARS. WHEN I CALLED TO CHECK ON THE ECONAR SYSTEM THE MAN THAT OWNS THE COMPANY ANSWERED THE PHONE AND I SPENT ABOUT AN HOUR WITH THE ENGINEER /DESIGNER ON THE PHONE .. GREAT PEOPLE TO WORK WITH..... HIGHLY RECOMMEND THEM....

hmmmmmm, I see energywise has become.......something more.  NASA?   Interesting.

Out of curiosity, how many tons of geo were you quoted in your new home. I would guess between 8 to 12, am I close? It is important to find an HVAC contractor with ICF design experience. Your heating load will dominate, and you must consider whether you plan to heat the radiant floor water with your geo and also your domestic water. Let me know and I will gladly help walk you through the process and help you locate a quality contractor in your area. We have installed over 350 geo systems in the last 9 years Dan

I would recommend giving Lyle Darnell with Energy Dynamics a call. They manufacture GeoComfort (which we are a dealer for)and Hydron Module - two very trusted names in the geothermal business. I agree that conducting a manual J is essential to getting the performance you want from your system. GeoComfort manufactures single systems that handle heating, cooling, radiant flooring, and include the de-superheater that is required to qualify for the 30% tax credit from the federal government. If you are not aware of this, the de-superheater is a component that allows the GSHP to "pre-heat" the water in your water heater. This optimizes the efficiency of your water heater, and can actually cover about 90% of your hot water costs. Bottom line is this: if you are intending to qualify for the federal government's EnergyStar 30% tax credit by installing a GSHP, the system must include a de-superheater. Good luck with your system. Chris Johnson K2 Construction Lincoln, NE

Take a look at www.arit.com They can give you some assistance in your quest for an affordable geothermal solution.

Didn't Arit go belly-up

Since you have radiant heating, you may count on achieving COF of 4. That is, getting 4 units of energy for every unit of electricity to feed into ground sourced heat pump.

Geothermal heat pump would give you more (COF ~5), but as you have figured out, cost of drilling is too expensive.

Good points from everyone - thanks for sharing. Looks like installer is just as important as brand (Climate Master , ECONAR , etc.)

Insulation: R-30 closed cell

That must be walls. It's hard to believe R-30 meets code in MA for overheads. How did you get to the R-30?

Looks like no expense was spared in this build. What did you do for underslab insulation?

You realize the OP was more than 2 years ago, and that it was his only post to date, right?

R30 (center cavity) does in fact meet MA code-min for cathedralized ceilings, which would take ~5" of closed cell. It's a pretty expensivey and low-performance way to treat an otherwise higher-R house though.

I can't say that R30 in ccSPF at an installed cost north of $5 per square foot makes most financial sense though, since a better-performing R30 can be done for half that using a combination of rigid foam panel above the roof deck and fiber below (with better thermal breaking over the rafters/trusses), or ~2/3 the cost using a combination of rigid foam above, open cell below. An R50 cathedral-ceiling is achievable within a $5/foot budget using other methods & materials than closed cell spray foam.

You realize the OP was more than 2 years ago, and that it was his only post to date, right?

I've got to stop posting before I've had a cup of coffee.

R30 (center cavity) does in fact meet MA code-min for cathedralized ceilings,

Do building codes let cathedralized ceilings off easier than conventional roof assemblies?

a better-performing R30 can be done for half that using a combination of rigid foam panel above the roof deck and fiber below

I'm still looking for a better assembly than what is on the drawing board for me right now. In Western Washington I have 2 X 12 purlins and rafters at 2:12, then 1/2" sheathing, high temp peel-and-stick and standing seam metal roofing. A couple inches of sprayfoam underneath and then batts or blown-in to fill out the cavity. There is about 60 squares of roof up there. I keep thinking about having some circulation underneath the metal panels to relieve moisture during 10 months of the year and heat during the hot weeks and some way to relieve the thermal bridging......

"Do building codes let cathedralized ceilings off easier than conventional roof assemblies? "

Indeed they do! In MA code-min is currently R38 for conventional roofs, R30 for cathedralized ceiling.

"I'm still looking for a better assembly than what is on the drawing board for me right now."

There may be a Hunter/Atlas vented panel solution to your hot metal-roof problem. With 2 inches of iso above the roof deck replacing the interior-side SPF you have a higher center cavity R and an even higher whole-assembly R.

http://www.hpanels.com/index.php?option=com_content&view=category&layout=blog&id=40&Itemid=54

http://www.hpanels.com/images/stories/pdfs/lit_prod_color/english/Cool-Vent-II.pdf

http://www.atlasroofing.com/tabbed.php?section_url=51

http://www.atlasroofing.com/tabbed.php?section_url=51&tab=5

Clipping from somebody else's blog with edits (http://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-minimum-thickness-rigid-foam-sheathing ):

Section R806.4 of the 2009 IRC allows builders to insulate unvented rafter bays with a combination of air-impermeable insulation (for example, closed-cell spray polyurethane foam) and air-permeable insulation (for example, cellulose), as long as the thickness of the air-impermeable insulation that is “applied in direct contact with the underside of the structural roof sheathing” meets the minimum R-values required for condensation control shown in Table R806.4. These values are:

Climate Zones 1-3 — R-5
>Climate Zone 4C — R-10<<<<<<<<<<<<<<<<<<< this is western WA.
Climate Zones 4A and 4B — R-15
Climate Zone 5 — R-20
Climate Zone 6 — R-25
Climate Zone 7 — R-30
Climate Zone 8 — R-35

-------------end edited clippage----------

If R10 SPF gets you there on the interior, surely R13-R16 in panelized foam gets you there if applied on the exterior, since exterior moisture drives are essentially eliminated, and the wintertime interior drives are fairly low in western WA.

Center cavity with ~R13 vented panel foam on the exterior and R38-R43 on the interior you'd have 23-25% of the total R on the exterior of the roof sheathing- which is considerably BETTER than the ~16% requirement for on UNvented walls zone 4C. While roof are not just tilted walls- walls get only a tiny fraction of the direct rainwater that roofs do, a roof with a vented nailer deck pretty much IS "just a tilted wall", and moisture won't accumulate in either the roof deck (due to the high exerior R limiting condensing hours) or the nailer deck (due to the cross venting.)

There are variations to the theme, and you may be able to build your own venting/purling scheme on top of unvented nailbase, or some other approach. But as long as you have ~R13 or more above the roof deck and some amount of air between the metal and the rigid foam, you can probably sell this. Pay attention to fastener spacings & type, but the mechanicals have been mostly worked out:

http://www.hpanels.com/images/stories/pdfs/Fastening_Pattern_Guides/Cool-Vent_Application_Guide.pdf

http://www.hpanels.com/images/stories/pdfs/tech_bulls/Fasteners.pdf

Assuming 2x12 rafters, the whole-assembly R with R13 foam and R38-R42 cavity fill comes in around R45, which is about dead-center on the recommendations BSC has for high-R "compact roof" assembly in zone-4. See table 2- p10:

http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones

Great resources, thank you for the time you put into that, Dana.

It looks like the Hunter products are brought to us by Carlisle CM. I was recently looking at some possible uses of GeoFoam only to find that they, too are a Carlisle company. Looks like Carlisle is going places with foam of all kinds. I have become even more interested in foam during the course of this build. Over 5500 sf of shell is now up and every stick of wood that has been used so far resides in a salvage pile; not in the structure, save for some treated window bucks. Much of it has already been used twice, or even three times. Of course, that will begin to change when the stick portion of this "hybrid" structure starts on Monday, but it is pretty interesting where you can get in residential construction without wood; just plastic (foam), steel and concrete.

Does using a couple inches of spray foam on the inside of the wall sheathing and an inch or two of rigid foam on the outside of the sheathing violate the issues of having two vapor barriers? Energy modeling of walls gave a 9% improvement using exterior rigid foam, which on this structure results in an (expected) savings of about $81/year. Cost of rigid foam and installation put payback out at 50 or even 100 years, if I recall, so we decided against it. However, if I now decide to add the foam, I am wondering if I will create a new problem given the existence of the interior spray foam.

Similarly, the roof construction is alluringly simple as it exists. Obviously, R806.4 was our guide. Two inches of spray-in foam under roof sheathing, plywood sheathing, peel-and-stick membrane on the deck and steel roofing above. If I add rigid foam exterior to the sheathing (in order to decrease the thermal bridging of the rafters) will I be creating a dual vapor barrier issue there? That concern was what got me to thinking about ventilated foam products, and I haven't priced them yet, but I am sure they don't come cheap. The goal here is to build simply and sensibly. Living in Western Washington for any amount of time gives you an uncomfortable feeling about tight layers of any kind, except maybe, GoreTex :-)

Steel decks.....hmmmm....something new to consider.

At 2" most 2-lb ccSPF is only semi-impermeable, in the neighborhood of 0.6-0.7 perms, and not considered a true vapor barrier, (asphalted kraft facers are ~0.4 perms, and also only a vapor retarder as compared sub-0.1 perm materials like sheet poly or foil facers.) If you want to give it more drying capacity you can use the R5/inch 2lb Icycene product (MD-R-200) which runs 1.33 perms even at 3".

On the exterior wall sheathing foam, if using XPS anything under 2" is sufficiently high-perm to allow seasonal drying, and it doesn't matter if the interior of the sheathing has high or low-perm foam. GeoFoam EPS is probably even more permeable, if it comes without facers. Low density Type-I EPS typically runs ~5 perms @ 1", which becomes ~2.5 @ 2" , 1.2 @ 4" etc. Higher density EPS might be as low as 2 perms @ 1", or 1, perm at 2", which means you can go up to about 4" with any density EPS and still have at least 0.5 perms of drying capacity. EPS with foil or vinyl facers can be true vapor barriers, and you'd have to pay attention where/how you use it.

Products like Grace Ice & Water are true vapor barriers, so anything low-perm stuff you put above that doesn't matter, as long as you don't create a sandwich around moisture susceptible wood. Fiber facers on iso are under 1 perm, but also usually only semi-impermeable. Foil facers are true vapor barriers, but with an air gap between any rigid insulation and the steel, it's unlikely that true deluge conditions could persist long enough to saturate the iso itself (as sometimes happens under failed flat-roofs.)

Doing our own vented structure rather than vented panels takes more labor, but is the cheaper way to go if you have fairly simple roof lines. Cut up with a bunch of dormers & valleys it's sometimes worth biting the bullet on vented panels and just git-'r-dun. Time is money.

(BTW: I lived a coupla decades in W-WA, and definitely know what clammy-cool winters are all about. ;-) I love the Cascades, and usually visit the relatives every summer, often for a little July ski-mountaneering daytrips.)