Hey everyone, thanks for all of the information on the site. I'm doing a starter home, new construction project and I want to make some green choices along the way. I've already decided to go geothermal because I don't have access to natural gas. It also allows me to transition to solar power in the future when I can afford it. I would also like to do a rain catchment system for irrigation. I will be doing low VOC paint on the inside too. I'm looking for other ideas (preferably not too expensive)that I can incorporate. I'm just getting started on the home and I've got the floorplan selected and the excavation is done. I tried uploading my floorplan and a picture of the lot but it is too big for the forum. You can see them on my build blog www.ultimatehomestead.com Any ideas are appreciated.

Your website was spelled incorrectly and the link was dead.

Here is the corrected one: ultimatehomestead.com


I assume you are building a wood frame home. What type of insulation are you looking to use (cellulose, spray foam, etc)? Do you have calculated R-Values for the wall, ceiling, etc?

What kind of basement wall? ICF?

Please tell us about your construction methods so we can better help out.

All else being equal, a smaller house is 'greener' (and cheaper) than a big house. Lower ceilings and less windows also help. The 'bones' of a house are going to determine it's true efficiency, so spend your money on a durable, tight, and well-insulated envelope. Put a lot of thought into orientation on the lot and window exposures. There are many facets to the term 'green'. It can mean energy efficiency; it can refer to the impact the building materials themselves have; it can refer to the hated/beloved carbon footprint.

As Lbear said, give us more details about what you are proposing.

Low VOC paint? Isn't that more expensive than regular paint?

"decided to go geothermal" Look into Air source heat pumps, AKA minisplits. Less expensive to install than geothermal but uses the same heat pump technology.

The build site is in North Dakota.

When considering wall and ceiling insulation, consider wet spray applied cellulose w/adhesive in the wall cavities and blown loose fill insulation above the ceiling. Cellulose has a high recycled content and one of, if not the lowest $/R of any building insulation material. Blown loose fill cellulose is pretty cheap and the incremental costs with going R60 vs. R49 or R38 is pretty small. But going with that much attic insulation will require additional ceiling strength beyond 1/2" high strength ceiling board attached to trusses on 2' centers. For R60 cellulose, you would need trusses or rafters or strapping on 16" maximum centers with 1/2" high strength ceiling board or 5/8" drywall. Being that far north, it may be common for trusses to be set on 16" centers due to snow load. Down here in the south, trusses are commonly set on 2' centers.

Due to thermal bridging of wood members in wood framed walls, considering installing ~2" of rigid foam insulation such as polyiso on the outside of the wall studs. Air seal the joints in this rigid foam insulation as your primary air barrier.

Orient the home and windows so that most of the windows are on the south side, and few if any are on the west side.

Consider installing Low E High Solar Heat Gain windows on the south side such as Cardinal LoE-180. Go with the highest R Value / Lowest U value windows in your budget on the north side.

Posted By ICFHybrid on 16 Sep 2013 09:12 AM
The build site is in North Dakota.

And? 

It's possible to size mini-splits for -15F outside design temps, and the cold-temp mini-splits still deliver a COP of nearly 2 running flat-out at those temperatures. Average mid winter temps in ND are in positive single digits to lower double digits, temps at which mini-splits are delivering a COP of 2.1-2.4. Over a whole heating season they'd probably average in the mid-2s.

At ND deep subsoil temps it's not as if you're going to do better than a COP of 2.5-3.0 even with a pretty-good geothermal system that costs 4-5x as much. 

Spending the difference in cost between geo & mini-splits  on air sealing & insulation & better-grade windows to bring the loads down mini-split output range is almost always worthwhile in new construction independently of the subsidy, but especially in areas with near-surface dirt conditions that require you to drill rather than trench-in slinkys for the heat exchangers.

Then there is the competing subsidy and net metered solar electric issues to run the math on.  Sometimes taking the extra power use hit of the lower efficiency of air source heat pumps over geo can be more than made up with rooftop PV panels on an annualized basis at less than the instaled price difference between geo & mini-splits. That's not true everywhere today, but it's becoming more true every day, as PV prices continue to fall.  With subsidy it works in may places, but eventually (probably less than a decade from now) the installed pricing of PV will be under $2/watt even without subsidy. It's already under $2.50/watt in Germany, and it's not because of cheaper system components or labor, but rather it's a less regulatory-encumbered process, with more experienced installation companies & crews. PV installation is growing exponentially in the US, we'll get there too.

I just looked at the floor plan. 

A ~1340' rancher in Harmon Lake with a heat load that calls for 3-tons of geo (at a fairly attractive $25K price tag) at a 99% design temp of about -16F implies a code min building envelope package.   (The average binned hourly January temp in Harmon Lake is about +13F, downright balmy compared to some ND locations.

But you could get a comparable ~30,000 BTU/hr out of a pair of Fujitsu AOU-15RLS2-H  mini-splits at -15F at an installed price of under $10K.

Assuming you're taking the 30% tax credit on the geo, the geo is actually only costing you $17.5K, which leaves more than $7.5K on the table for improving the building envelope. Assuming for the time being that the geo would average a COP of 3.0 for the all-in power use, including pumps & air handlers (not guaranteed, unless the contractor puts it in writing), and the mini-splits deliver an average of 2.2 (it'll probably do better than that), it means to end up using the same annual power you'd need to reduce the heat load by only ~26% with that $7.5K. By the time you do that the load would be within range of a pair of AOU-12RLS2-H, which puts another $0.8-1K on the green-up budget on the building envelope.

Even at the same annual power use, you buy a lot more COMFORT with the more efficient building than you get with the more efficient mechanicals.  How you get there has different costs, and it's worth downloading a copy of BeOpt and using it to cost-optimize the green-up  using real quotes on different aspects.

Dana,


I would think the mini split is the best way to go. I am not a fan of geo thermal (mostly due to complexity and breakdown costs) but do recognize its place in efficient builds. There are great geo thermal systems out there but unfortunately there are also horrendous systems. I've read of plenty of horror stories about them and the constant breakdown and maintenance involved with such systems. If done right, they can be great, but sadly many are not properly designed and installed.

If it was your call, would you go with a ductless mini split or geo thermal?

WOW! Thanks for taking the time everyone. I'll try to answer as many questions as I know the answers to (admittedly not alot).

My overall goal would be above average energy efficiency, water conservation, and overall healthiness of the home to live in. I felt that 1340 sq feet was a good compromise of size and efficiency.

Windows, I am doing low E argon filled dual pain windows throughout. I didn't put any on the north side of the home except the egress windows in the basement. I did move an extra window to the south side of the home for a little bit of additional solar gain (I'll plant a couple deciduous trees to shade them in the summer). On the west side which is the front of the house, I do have a large window but it is shielded from too much summer sun by my porch. Overall, I just went a bit sparse on the windows which I hope I won't regret in the future.

The house will be a 2x6 construction which was bid with R 19 batt insulation which I planned to upgrade to the R21 bats for only a minimal upcharge. It has vaulted ceilings which I know isn't the best for insulating but the Mrs. won on this choice. The basement is just a standard poured concrete basement which will be insulated with a layer of foam and then 2x4 walls with batt insulation. It is very expensive here to get sprayed insulation and would have totally blown my budget so that just wasn't an option unfortunately. I'm researching for a DIY spray foam solution for the floor joists and sill plate areas. The studs will be 16" on center. I looked at adding foam sheeting outside, but having to go 2" with the 2x6's seemed excessive and would require reconfiguring the home. I guess I'm hoping that I can do it myself at some point in the future. I'm kind of locked in to the 2x6 construction and the basement shape at this point. I guess I'm hoping there is some magical way I can still incorporate to break the thermal bridge. I even looked into insulated siding, but that doesn't look like it will really help.

I have to admit I'm a bit ignorant on the mini-splits for a whole home. I've only seen them used in small scale areas and didn't even consider them. My geothermal after state and federal rebates will only be a little over $13K and I still get a property tax exemption on the value of the whole system. In addition, I will have a desuperheater for my water heater which will preheat my water all summer long. I was able to get a reputable company from our area who will provide a 5 year warranty on the geothermal system and they have been quick to respond to warranty/service calls at my current home where they worked. The premium I ended up paying for geothermal over a standard propane system was less than $4k, so I was happy with that.

Thanks again everyone for the advice and time you've put into this.

Those 2x6 walls with studs on 16" centers with perfectly installed R19 batt insulation will come in around R14 for the whole wall. Bumping the batts up to R21 might get you close to R15 whole wall.

Rather than 2x6 walls with no external insulation, have you considered 2x4 walls with 2" of rigid foam insulation? The overall width of the wall is roughly the same, but the 2x4 wall with R15 batts, 1/2" structural sheathing, and 2" of external polyiso insulation will net you roughly R22 whole wall. Way more than the 2x6 walls with no external insulation. The external insulation really makes a big difference on wood framed walls, especially on 16" centers. Another thing is that you might be able to find used / reclaimed polyiso insulation cheap. Search Craigslist or check with the Insulation Depot. I found some 4x8x2" sheets of quality used polyiso for ~$6.50 per sheet that way.

Posted By ultimatehomestead on 17 Sep 2013 10:32 PM

The house will be a 2x6 construction which was bid with R 19 batt insulation which I planned to upgrade to the R21 bats for only a minimal upcharge. It has vaulted ceilings which I know isn't the best for insulating but the Mrs. won on this choice.

I would seriously look into blown cellulose within the walls. Fiberglass batts are the absolute worse when it comes to insulation options for wood frame walls. Any air infiltration cuts them down and when it states "R21" they are talking about perfect lab conditions (70F ambient air temps) with NO air infiltration. So in other words, when installed in REAL WORLD walls that see 90F+ temps in the summer and -10F temps in the winter, with air infiltration, you are lucky to see R16 from them. Add thermal bridging from the 2x6 construction and no outside foam, you are hovering around R12 for total wall R-Value. You will get tons of thermal bridging from window and door headers since you can't fit the fiberglass there most of the time.

In a North Dakota climate, you are really under-insulating the wall assembly. Go with blown cellulose, at a minimum. Exterior foam would be a huge benefit to the R-Value. Can they do EIFS out there instead of siding?

In regards to the ceiling insulation, what are you planning to do up there? Fiberglass batts?

At a 25% framing fraction (typical for 16" o.c. framing) a 2x6 with high density R21s and wood or fiber cement siding comes out at a whole-wall R of 14.6 after the thermal bridging of the framing is accounted for. R19s only hit R18 when compressed to 5.5", and at a 25% framing fraction delivers ~R13.6.

But due to the higher air-retardency of the high density batt, it's the preferred solution, if batts are used, since it lowers infiltration & convection losses. Better yet are rock-wool R22s or R23s (but NOT low density fiberglass R22/23). But all batt installations suffer installation errors like compressions, short-trims, & voids. Damp sprayed cellulose goes in cheap compared to dense-packed cellulose or fiberglass blown in mesh, and is FAR more air-retardent than even high density batts. Open cell foam is even more air retardent. Detailing the sheathing as part of your primary air barrier by aiir sealing the sheathing to the studs with acoustic sealant type caulk, and caulking between doubled up top plates as well as between the bottom plate & subfloor, subloor to band joists etc goes pretty quickly, and reduces infiltration and loss of fiber-insulation performance at the wintertime extreme temps dramatically. If using batts or cellulose, air-seal the electrical penetrations in lateral electrical runs with can-foam, and use backer rod and low expansion foam to air seal in the mini-cavities around window & door installations to the exterior sheathing or trim, packing in shredded batt to a fairly high density (firm-mattress level of springiness to the finger push test), filling those micro-cavities completely. The R/inch goes up to R4-4.2 when packing fiberglass like that, but more importantly, it's air-retardency increases dramatically. But you need at least 1.5" of foam + backer-rod on the exterior side of 2x6 framing to fully protect the exterior wood from interior moisture drives.

If it's a trussed attic, use "energy heel" trusses designed to take at least 20" of insulation. Avoid using recessed lighting, which thermally bridge the insulation with a mini-chimney air leak. Air seal the ceiling gypsum at all seams & electrict penetrations with fire rated can-foam as. You may have to tighten up truss spacing &/or use thicker gypsum to handle the dead weight, but dry-blow 20" or more of cellulose up there. The 10 year settled depth will be 18", between R55-R60. The air retardency of cellulose keeps it from losing performance to convection with the attic air the way blown fiberglass does, and unlike high-density batts, it fills in completely, with no seams that become thermal bypass weak points. Cellulose is more opaque to infra-red radiation from hot summertime roof decks too

Harmon Lake is on the warm edge of US climate zones 6 & 7. In zone 6 you can use as little as 2" of exterior polyiso foam and be able to skip the interior vapor retarders, in zone 7 it takes 2.5". (See: http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_7_sec002_par025.htm ) If you add 2" of exterior polyiso (R15), since it is not thermally bridged by the framing, you more than double the R-value of the wall area, cutting the heat load of the walls in half. The material cost of virgin-stock polyiso is about 10 cents per R per square foot, so R15 cost about $1.50/square foot + installation & scrap rates, call it $2-2.5/foot, installed. It's definitely a cost-adder, but it's HUGE mid-winter comfort boost, and combined with the R60-ish attic probably peels a ton or more off your geothermal or ductless compressor sizing. If you got thinner than 2.5" on the foam there is still significant benefit (even an inch of iso cuts the heat loss of the wall area by almost a third) but you then have to use a "smart" interior vapor retarder such as Intello Plus or Certainteed MemBrain to protect the sheathing from excessive wintertime moisture accumulation, but (unlike cheap polyethylene) still allows the assembly to dry toward the interior. When you go too thin on exterior foam the air sealing of the interior becomes critically important too- a square inch of air leak is worth a whole wall's worth of vapor diffusion through latex paint even without the vapor retarder, and air leakage can render the vapor retarder moot.

A primer on exterior foam techniques can be found here:

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-install-rigid-foam-sheathing

http://www.greenbuildingadvisor.com/video-how-install-rigid-foam-insulation-outside-house

http://www.buildingscience.com/documents/guides-and-manuals/gm-guide-insulating-sheathing

Argon filled low-E can range in U-factor anywhere from U0.28 to U0.35. On the south side you'll want to use high solar gain (rated as SGHC in the specs) even if it means going somewhat higher U (but no higher than U-0.34.) On the east & particularly the west side it's better to go with a low SGHC window, with a U-factor no more than U0.28. It's possible to get low SGHC double-panes with U-factors in the U0.22-0.24 range, that are still far cheaper and more durable than U0.15-U0.20 triple-panes

When you decide just how far you're going to go with the building envelope, then it's time to re-calculate the heating & cooling loads. If you set up a spreadsheet with room-by-room with I=B=R style heat loss calculations you can track the load by adjusting the U-factors of the wall/window/ceiling as you make the changes. Since that methodology won't include infiltration & ventilation factors or internal sources like plug-loads and warm human/canine/feline residents you'll have to make some fudge-factor adjustments at the end, but it still works out pretty close- within the noise of Manual-J measurement error. The U-factor of a wall or ceiling assembly is simply 1/R using "whole-wall R". The units are BTU/hour per square foot per degree of temperature difference. The tempearture difference appropriate for sizing the heating system in a Harmon Lake climate would be interior-temp minus the 99% outdoor temp (which is about -15F to -17F), which is about 85F degrees. Eg: With your ~R14-ish whole-wall value for batt wall the U-factor of the wall is 1/14= U0.071 BTU/degree-foot, so at 85F delta the heat loss per square foot of wall at the 99% design temp is about 0.071 x 85F= 6.04 BTU/hr per square foot. With 2" of exterior iso that becomes an R27 ish wall, with a 1/27= 0.037 U factor, which loses 85 F x U0.037= 3.15 BTU per hour per square foot. With batts-only a 12 x 18' room with 9' R38 (U0.27) ceilings (probably code-min, but might be R49) and 18' of exterior wall, and 30 square feet of U0.35 (probably code max low-E argon) window has a heat load of about

Windows: U0.35 x 30' x 85F = 893 BTU/hr

Walls: U0.071 x ((9' x 18') - 30') x 85F= 798 BTU/hr

Ceiling: U0.027 x (12'x 18') x 85F= 496 BTU/hr

Which adds up to 2187 BTU/hr.

If you bump the attic to R60 (U0.017), bump the windows to U0.28, and add 2" R13 iso to the walls (now R27, or U0.037), those numbers drop to:

Windows 893 x (U0.28/U0.35)= 714 BTU/hr

Walls: 798 x (U0.037/U0.071)= 416 BTU/hr

Ceiling: 496 x (U0.017/U0.027)= 312 BTU/hr

Which adds up to 1442 BTU/hr, only (1442/2187=) 66% of the code-min, a 1/3 reduction. If you went with 2.5" of foam to skip the interior vapor retarder and add resiliend that 416 BTU/hr number drops to about 370BTU/hr, not a big change from 2", but it adds resilience.

Similar improvements around the house takes the size of the geo from three tons to two, which may or may not reduce it's after-subsidy cost to that of mini-splits, but your comfort levels soar, your operating costs are cut by a third (or more, since your outdoor temperature balance point for heating/cooling is under 60F), and the resilience of the structure to moisture goes up (provided you have enough exterior foam for wintertime dew point control, or use a smart vapor retarder if you're cheating it a bit.

Notice also that windows are now literally half the total heat load. Keeping south facing windows up to about 8-10% of the floor area of those rooms is worth it since you gain more heat than you lose, but if you can shrink the size of the west facing windows 25-30% the whole-house peak cooling loads drop by 15-20%, and you also get the benefit of lower heating loads (though a very modest increase in heating season energy use, due to the loss of that solar gain.)

I've ignored the slab & foundation losses, but in any ND climate it's worth putting 2-3" (R8-R12) of EPS (the bead-board stuff of cheap coolers and coffee cups) under the slab, and insulating any foundation walls to at least R10.  See Table 2, p.10 of this document, and read the whole first chapter. You are on the zone 6/7 boundary, and those R-values are all "whole-wall", not center cavity.  Note that the 2.5" iso + 2x6 wall solution is only R30- there's a long term rationale for more, but R30 is about 2x your code-min wall.

BTW: On any new construction it's worth adjusting the roof pitches & orientation for optimal photovoltaic solar gain, particularly for homes heated with heat pumps. Even if you don't install PV right away, the cost is poised to hit the sub-$2/watt range (unsubsidised) within the next decade, at which point it's lifecycle cost per kwh is well under the retail cost of electricity in most markets.

This is a fact that is driving utilities and state regulators a bit crazy, since if simply net-metered at retail it shoves a large fraction of the grid infrastructure costs onto the other ratepayers, so expect some real changes, but the solar-tsunmami is coming- it's too cheap & attractive to pass up. Farming your roof acreage for kilowatt-hours might be done by you, your utility, or yet a third party, the details of which will vary, but any of which will likely work out well financially for YOU, provided you designed the roof pitches such that you get reasonable annual yield out of the PV.

In re-reading parts of the thread if the all-in cost on the geo is ~$13K and you can get to talk to at least 3 satisfied customers willing to share their mid-winter billing and contractor-experience, that's probably the right HVAC solution, with a few tweaks:

The desuperheater buys you nearly nothing in that climate and isn't worth the added complexity. An AirTap or Stiebel-Eltron heat pump water heater located inside of the conditioned space is a better expenditure of the desuperheater money. A heat pump water heater will lower the cooling load, while adding some to the heating load, but the net efficiency of geo + HPWH is going to be about the same as a deseuperheater based solution that's more complicated and expensive, taking up even more space.

It may be oversized for the actual loads if you make at least some improvements to the building envelope. Crude heat load WAGs on code min constuction might have an allowance for 8000-10000 BTU/hr or more attributed to air infiltration, but if you get serious about air sealing that drops to 2000BTU/hr or even less, which is about a half ton of compressor and ground heat exchanger you'll never need.

For the most cost-effective envelope upgrades:

Start with defining and implementing the primary air-barrier that stretches from the sub-slab poly to attic floor, detailing each floor to wall, wall to window & door, and wall to ceiling transition. It's the cheapest performance upgrade you can buy.

At a minimum an inch of exterior iso (+ smart vapor-retarder on the interior if less than 2") is always going to be worth it in that climate, (bringing the whole-wall R north of R20 make sense even in climate zone 5 if you intend to live there!) If thickness is a problem dropping back to 2x4/R13 framing and adding 2" of exterior iso is an ~R22-23 whole wall, in the same wall thickness as a 2x6 framing package, and plenty of dew-point margin (no interior vapor retarder needed or wanted!) If you bump it up to R15 rock wool or HD fiberglass in the 2x4 cavities so much the better, you'll be at about R24 whole-wall. (I prefer this to a 2x6 + 1" iso on both performance and resilience grounds.)

Going R60 or better on blown cellulose in the attic is pretty cheap performance too, even if you need to tighten the spacing on the trusses to manage the dead-load of 1.5- 2 feet of cellulose.

Then it's a matter of chasing down the thermal bridging in other places. Air sealing & insulating the foundation sill to the concrete is critical, as is insulating the foundation itself. IRC 2012 calls out R15 for basement walls R10 for slabs & slab-edge.

Posted By Dana1 on 18 Sep 2013 11:51 AM


Argon filled low-E can range in U-factor anywhere from U0.28 to U0.35. On the south side you'll want to use high solar gain (rated as SGHC in the specs) even if it means going somewhat higher U (but no higher than U-0.34.) On the east & particularly the west side it's better to go with a low SGHC window, with a U-factor no more than U0.28. It's possible to get low SGHC double-panes with U-factors in the U0.22-0.24 range, that are still far cheaper and more durable than U0.15-U0.20 triple-panes

Dana, don't you think he will be better off with a SHGC of > 0.45 on the southern side? In such a climate passive solar would be beneficial.

NFRC rates window U-Values as a total sum of the glazing and framing. The framing being the "weak link" in the equation. Cardinal Glass is the default glazing for most calculations but Guardian Glass offers different options when it comes to SHGC and U-Values.

I personally think it would be a good effort spent to bid out triple panes. One would be surprised in some cases that the cost is negligible and in some cases, even less than double panes.

Posted By Dana1 on 18 Sep 2013 05:18 PM
At a minimum an inch of exterior iso (+ smart vapor-retarder on the interior if less than 2") is always going to be worth it in that climate, (bringing the whole-wall R north of R20 make sense even in climate zone 5 if you intend to live there!)

According to 2009 IECC the southern part of North Dakota is climate zone 6 and the northern parts are climate zones 7 & 8.

2009 IECC North Dakota

If he is building in the northern part of the state (Zones 7 & 8), his current build approach will not make code, in my estimates. He will also have a hard time if he is located in the southern part of the state (Zone 6).

No offense to the OP, but I believe the approach to this build is backwards. Instead of focusing on the "bones" of the home build, you began to focus on the interior accessories like the stove, microwave, etc. While there is nothing wrong with getting appliances that are low energy use, the most important factor here in the structure of the home and how it will be built and what insulation techniques will be used. The design of the home is essential and will provide the best bang-for-buck in terms of "building green." Low VOC paint and the appliances are important but it's the cart before the horse approach.

If I were you, and you plan on living in this home for some time, I would totally revamp everything. Dana gave out some really good info. Some of it may be really technical but the key factor is that you want to change your stance on the "no foam" for the exterior. You really should put some foam insulation on the exterior walls to reduce thermal bridging and bump up your R-Value on your walls.

I'm in Zone4 and I wouldn't go below a true R-23 for my walls. If I was up in Zone 6-8, I would surely push that into the R-30 or higher range with 5" of cellulose within the walls and 2" of foam on the exterior walls, if doing wood frame. If ICF, I would get the additional EPS on the exterior walls to bump the wall R-Value into the upper 30's or 40's. For my Zone4 roof I am at R-60+ and if I were in Zone 6-8, I would definitely push that into the R-80+ area.
 
Are there any green energy builders up there in North Dakota? I think you would be best served with someone who knows the field. Not just any GC but someone who knows how to build high-R homes and build them tight.

This is a great thread. Dana- I ran the same formulas on my ICF home, and the windows were more than half of the total BTU's. Because we're in a mild climate (SC), I figured I'd skip the floor insulation since it is over an insulated basement. But using a winter temperature of 55 F (in the basement), the heat loss through the floor was more than the walls, windows, and ceiling combined! I guess I'll be insulating the floor after all. The whole house comes in around 10K BTU without any adjustments for infiltration, ventilation, etc. Any idea how much to fudge for those factors, assuming decent tight construction? I've done a lot of detail work around the doors and windows, and am going to seal the ceiling with foam before dry cellulose.

At ND deep subsoil temps it's not as if you're going to do better than a COP of 2.5-3.0 even with a pretty-good geothermal system that costs 4-5x as much.

If you can't put it in ND, then where can you put it?