New to the forum, looking for advice. I am building a walk out basement with ICFs in the near future. I am looking at two companies, both offer either an r22 or r30 system. I am in Western NY, so we have a number of heating days and not many cooling days. I do plan to put in-slab radiant heating in the basement. Being that this is a basement, and the tempurature of the earth remaining more constant, I am not sure if it is worth the extra money to bump up to R30. It would add $1300 to the cost of the forms which is a 23% cost increase. I plan to have only 3' of basement wall exposed over grade on 3 sides and 9' or less on the walk out side. Any/all input is helpful. Thank you

How much snow cover around the house? What's your frost depth? Both will affect how cold the outside of the basement wall below grade can be. Have your HVAC guy run the numbers. If you go for a 10 year payback you would only have to save $130/year to justify the R30. But I would guess, without knowing the design parameters and energy costs, the extra probably isn't worth it.

Frost depth is 42" plus. We get a good amount of snow, average is like 100" in the nearest city but I think my area will get a little less than that, maybe 60-80". Snow tends to stay for most of the winter, it doesn't melt off till April lol

It is an easy pay back calculation if you know the exposed wall square footage.

Is this a log/icf/or stick home on the top?

If you went build block you could do Global Block(R30) on the exposed walls and regular Build Block(R22) forms on the rest. I just finishing my house which is a ranch with a walkout. I did regular build block on the bottom and global block on the top. Those two forms interchange.

Global Block R30 forms are actually cheaper then the R22 blocks and Global uses a third less concrete. Thus cost savings.

It makes no sense to go with R30 basement if above-grade walls are lower performance than that.  Code min is R15.    At R22 you're already at a level sufficient for going Net Zero Energy with an array that fits on top of the house if you built the rest of the house comparably higher  than code-min performance.  The odds are pretty good that  from an ROI point of view the  $1300 difference in cost for the extra R8 of mostly below-grade level EPS will be better spent on ~400 watts of rooftop solar photovoltaic panel.

What does the rest of the house look like for construction type, air tightness & R values, etc?

How are you heating & cooling the place? (fuel & equipment efficiency)

Western NY is a big place, partly in US Climate zone 5, some in zone 6- which zone are you in?



For roughly what it takes to hit Net Zero see table 2, p.10 of this document.  Even in Zone 6 they're suggesting you can get there with R20 continuous foundation insulation.  And that analysis was done in 2009, when rooftop PV was typically 13-15% efficiency compared to the now-typical ~18-20%, and cost north of $7/watt (installed) compared to today's $3-3.50 (before any tax or other subsidies are applied), and the better class heat pumps were running HSPF 10-11, compared to today's better class units in the HSPF 12-14 range.

If you did all the above grade wall with ICFs too and you're in Zone 5 you can probably get to Net Zero now with R22s, at current vintage PV & heat pump efficiency. In zone 6 you might still need R30-ish whole-wall numbers for the majority of exposed wall, but maybe not.

[edited to add]

I noticed in one of your other threads that you're in Livonia.  All of Livingston County is US zone 5.

The house will be a real log home with natural, un-milled logs. I can only roughly estimate the R value of the walls because the diameter of each log changes and will be different. We have some butts that are 25" around while some tops are like 14". The book on lumber I have estimates about .93 r value per inch so, on average, the wood may be like an r 18. Then the gaps between the wood will be stuffed with insulation but I am not sure. So figure an R 16? for walls. Air tightness I'm sure will be low but thermal mass of the logs will be very high.

Roof will be 12" of eps foam which is r 52 if i remember right.

Heating with a Propane boiler with radiant in floor heating.

To meet IRC 20120 and newer code-min in zone 5 requires a "whole-wall R" of about R17, and air tightness of less than 3 air changes per hour at 50 pascals pressure (3ACH/50), which may be hard to hit with a log home. The thermal mass of soft wood species is high, but I'm not sure if it quite qualifies as a "mass wall" under IRC definitions.

My brother lives in a house built with ~14" douglas fir logs. It's not an energy pig, but it's performance isn't super-great,a and multiple attempts at air sealing haven't proved effective over the long term. The seasonal dimensional changes of the wood seems to thwart air sealing reliability.

Sawing the logs in half and installing 2" of EPS between the halves, along with an EPDM membrane to make it air tight is probably the only way to get real air tightness and spectacular thermal performance out of a 14" log wall. There would be details to attend to around air-sealing the EPDM to the roof's air barrier, but nothing like what it would take to air seal chinked log walls. To get code-min performance out of it you could use OSB for the wall's air barrier rather than EPDM + EPS. That's a lot of odd-ball milling though- not sure who (if anybody) is set up to split logs that way.

The 12" of continuous EPS above the roof deck would meet code min with margin, in fact you could get there with 9" (R38 continuous insulation plus R1 for the roof deck itself plus R1 in air films is about R40, or U0.025. A code-max U-factor would be U0.026 per TABLE 1102.1.4 (about halfway down the page) :

http://codes.iccsafe.org/app/book/content/2015-I-Codes/2015%20IRC%20HTML/Chapter%2011.html

With 12" of EPS above the roof deck you'd be down around U0.020 which is great!

Unless you have a private source for ultra-cheap propane, a propane boiler is going to be significantly more expensive to heat with than an air source heat pump, even at NY style electricity prices. Run a room by room Manual-J type heat load calculation on the place (hire an engineer or energy nerd for this, not an HVAC contractor), with the amount of available floor area per room, which will tell how much heat per square foot you need to get out of the floor. There are a number of reversible air source hydronic chilllers out there now (Chilltrix even has modulating version), but it takes a bit of system design work to get it right, and low output temperatures to get the full efficiency out of it. But without the room by room and whole house load numbers it's hard to make good recommendations.

There are icf systems out there that can increase the r-value without an increase in price. I sell one that has 6.5 inches of 1.5 lb foam for $3.25 per sq ft. for comparison.

That's $3.25 just the foam , not the installation, the rebar, and concrete. It's still an expensive way to build an ~R28 wall.

But it's FAR easier to make air tight, and would reduce the water temperature demands (and ultimate cost) for the radiant heating going into that place than building it out of 14-20" logs, guaranteed to be air-leaky enough to at least double the heat load.

But it has a different aesthetic, to be sure.

Rebar $400, concrete $6400, pump $650, installation $2500, Helix[floor] $360. 6 " core, 1600 sq ft 8'high wall, footing and floor poured in one shot. 4 hours done. And $5200 for the form.

We lived in a log cabin in our early years. It was wonderful initially, but I soon got tired of dusting and vacuuming all the logs...and I even eventually got tired of looking at all the logs... As Dana indicated, it will be very challenging to maintain low air infiltration. While the thermal mass did help regulate interior temperature, it was a low energy performance home compared to our subsequent ICF homes. There were lots of other negative issues too like sagging/shifting structure and high preservation maintenance. Perhaps they have applied new construction methods to log homes these days and these things are less problematic. I still love staying in a log cabin for several days of vacation, but I sure wouldn’t want to own one again...especially as we get older and eventually wouldn’t be able to keep up with the annual maintenance requirements.

I was originally bound to do ICF but I eventually realized it would cost me way more than just doing a double wall insulated with lots of rock wool because I had a cheap source of rock wool. I might have considered building a log cabin if I had timber on my property giving me a cheap source of logs...otherwise no way because of the sealing issue. Best to first evaluate the cost per wall r value before becoming fixated on how you will build. You might get better answers to your questions on a dedicated log cabin forum than on a green building forum like this one where most of the people care about high performance construction.

http://www.loghomeu.com/