2005 West Michigan 43x30 residential build, fairly efficient, I had the rim joists foamed in last winter did help some. Have not finished basement yet. It's a daylight basement so 75% is below ground but 4.5ft * 67ft are not and this portion is 2x6 and insulated/drywalled also housing 3 large windows. With a basement temp of 65f the drywalled portions are 61-63f. vertical foundation walls equal 800sqft, they are anywhere between 50f and 58f depending on depth and orientation, will I see a noticeable reduction in heat load placing foam board on these? I don't intend to do the floor, it is 62-63f. Also if it is noticeable where can I order EPS panels online from a distributor? Box store prices are pretty high aren't they?

A poured concrete foundation is typically ~ R1, losing 1 BTU/hr per square foot of area per degree temperature difference. You have (4.5' x 67'=) ~300 of expose above-grade foundation. When it's 65F inside, +15F outside (still warmer than your 99% outside design temp) the temperature difference is 50F, and you would be losing:

~U1 x 300' x 50F= 15,000 BTU/hr

And that's just for the above grade section! For most houses that is a significant fraction of the whole house heat load.

The other 3/4 of the area losse are less but still significant, probably adding up to at least another 5,000BTU/hr depending on soil type & moisture content, etc.

If you insulate the foundation to the IRC code-min R15, that R1 wall now becomes R16, with a U-factor of 1/R16= 0.0625 reducing the wall losses for the above grade to:

U 0.0625 x 300' x 50F= ~940 BTU/hr @ 15F outside, 65F inside, call it 1200 BTU/hr with the below-grade losses, and still less than 1500 BTU/hr if you keep it at 70F instead.

The greenest & cheapest way to get rigid foam board is from materials salvage outfits, some of which specialize in rigid foam board. Typical fiber faced roofing polyiso runs about R5.5/inch, and 3" would be sufficient for making code minimum.

https://grandrapids.craigslist.org/for/d/iso-and-eps-rigid-board/6385081353.html

https://battlecreek.craigslist.org/search/sss?query=rigid+insulation

1" or 2" rigid foam trapped to the wall with a 2x4 fiber insulated wall can work too.

I would likely use 2" EPS, currently when it's 30f outside the remaining 20000 cubic feet main and upper levels consume ~16k btu/hr with a setpoint of 68... I have two vents cut into trunks in the basement and I leave them open resulting in ~65.0f down there and that is an additional 10000 cubic feet of space. There are no returns in the basement currently, I do intend to finish with 2x4 in front of the board insulation should I put it up in the meantime... finishing could be next month next year or never depending if we keep the house. What I was trying to quantify is would it even be noticeable monthly in the bill? Last billing period was 35 days with a mean temperature of 33f and the usage was 130ccf or 15785btu/hr. Stove, fireplace, water heater, dryer etc everything is gas in the house, only constant pilot is the fireplace. 68f set point most of the time, 62-65 while sleeping, 65 8a-5p during the work week... 2 occupants in house.

Posted By ls3c6 on 18 Dec 2017 04:13 PM
Also if it is noticeable where can I order EPS panels online from a distributor? Box store prices are pretty high aren't they?

This company will cut you the sizes you request so you have minimal cutting on site & they are priced very well. They contract with foam factories all over the USA so they get a much better price than you could (if the factories were to talk with you - which they won't). http://www.universalconstructionfoam.com . Last time I used them their prices were sharp and they cut a lot of different sizes, marked each one, etc so it was like putting together a foam erector set.

Yes, it will be noticeable in your monthly bill.

130ccf/35 days= 3.71 ccf/day, or (/24)= 0.155ccf/hr Assuming 103,700 BTU/ccf that's 16,000 BTU/hr input BTU, but assuming 85% combustion efficiency (use the nameplate DOE BTU out divided by the namelate BTU-in) it's really a heat load of 13,600 BTU/hr @ 33F, and a load of about 25-27,000 BTU/hr at your 99% outside design temp. ( Find a nearby location: https://articles.extension.org/sites/default/files/7.%20Outdoor_Design_Conditions_508.pdf )

If it's a 95% condensing furnace it's a load of about 15K @ 33F.

Heat load is a function of exterior surface area, not volume, and the U-factors of those exterior surfaces. The fully conditioned space above is probably insulated for a much lower U-factor, and much lower heat loss per square foot of exterior surface than your above-grade uninsulated foundation. It's possible that more than half of the buildings heating energy is leaving via the foundation.

2" of EPS is only a bit more than half of code minimum, but will bring the walls up to about R9, or U 0.11, from U1.

At an average outdoor temp of 33F, 65F indoors (at 32F delta) the above grade U-1 wall loses

U1 x 300' x 32F= 9600 BTU/hr. (plus below-grade losses) That's more than 2/3 the 13,600 BTU/hr @ 30F number, close to 2/3 the 15K number!

If it's a concrete block foundation rather than poured concrete the above grade foundation losses would be lower than 9.6K, but still more than 5K @ 33F.

Bump that foundation to U0.11 with a couple inches of EPS and it's:

U0.11 x 300' x 32F=1,056 BTU/hr. (plus the now substantially reduced below-grade losses.) That's knocking about 8K off the 13-15K total load @ 33F.

When you build out the 2x4 studwall and install unfaced or kraft faced R13 the "after EPS" numbers will be cut by about half, and meet current IRC code.

The heat loss out the slab is pretty much a constant, except near the walkout side, and slab-edge insulation of R10 down to 2' below grade would meet current code. That inserts an offset to the otherwise fairly linear increase in total house load with falling temperatures, and it's not clear just how much of the 13-15K @ 33F can be attributed to the slab.

Putting an inch of EPS under the studwall's bottom plate will provide a thermal and capillary break from the slab, reducing the peak moisture content of the framing both winter & summer.

Okay hold on a sec.

You're saying the basement is unfinished. But then you're telling me that a portion (for the above ground exposure) *IS* finished?

So, half your wall, from the top down, and the portion underneath is just bare wall?

Or are you saying you have a drywalled-in basement (floor the ceiling) and you want to throw foam ON TOP of that?

Sorry if I'm coming across dense on this. Just trying to get a good picture of the situation.

A pic of one of the walls would probably be the fastest way to illuminate the situation.

I guess I'm not clear on that either. How many of that 800 square feet of the R1 uninsulated foundation is above-grade?

If the average wall surface temp is 50F and the room temp is 65F, it's about 8 BTU per square foot of loss, x 800'= 6400 BTU/hr.

If the average wall temp is 55F in a 65F room the losses are about 5 BTU per square foot, x 800' = 4000 BTU/hr

Either number is a sizeble fraction of the measured 13,600 - 15,000 BTU/hr. Insulating with 2" of EPS will reduce that by about 85-90%, adding R13 batts to the eventual studwall will would make it a 90-95% reduction in those losses.

The above grade portion of the concrete will drop WELL below 50F when it's cold out, but below grade it'll start out in the mid-50s , dropping to the low 50s by the end of the winter.

Posted By Dilettante on 18 Dec 2017 06:35 PM
Okay hold on a sec.

You're saying the basement is unfinished. But then you're telling me that a portion (for the above ground exposure) *IS* finished?

So, half your wall, from the top down, and the portion underneath is just bare wall?

Or are you saying you have a drywalled-in basement (floor the ceiling) and you want to throw foam ON TOP of that?

Sorry if I'm coming across dense on this. Just trying to get a good picture of the situation.

A pic of one of the walls would probably be the fastest way to illuminate the situation.

Yeah the basement is currently 8ft high about 3/4 of it is poured concrete and a fair amount is below grade, the backside of the house/basement is "daylight" so the first ~40" from the floor is concrete, above that is wood framing and windows are placed in that where it meets the framing for the rest of the vertical structure. Anywhere there's wood they insulated/drywalled per code, but didn't touch any concrete. I'm just looking to cover the exposed concrete which equates to 800sqft in this entire space with foam before finishing it and mainly right now, just to reduce heating bill and make comfort better down there as I do have some workout stuff and a projector/home theatre going on. The ceiling is joist and osb, no finishing of any sort down there except there's a door on the staircase that leads down there and they drywall/insulated the wood portions above grade because I think they were required to... same with the garage, the common wall to the house is drywalled/insulated but nowhere else. I've already had the rim joists foamed in, they were batted when I bought it I didn't notice much/any difference with that.

Insulating the R2-R3 rim joists + sheathing & siding won't make NEARLY as much difference as insulating and equivalent area of R1-ish above-grade portion of the foundation wall. It's still worth doing, and air-sealing the rim joist & foundation sill makes a real difference in the air infiltration losses (not measured in U-factor numbers.)

From first-person experience (no calculations necessary) When I insulated the mostly below grade foundation walls in my 1.5 story bungalow to ~R15 with continuous foam, the fuel use dropped about 15-20%. It seems like your house would likely see similar or even better reductions.

Posted By Dana1 on 18 Dec 2017 06:51 PM
Insulating the R2-R3 rim joists + sheathing & siding won't make NEARLY as much difference as insulating and equivalent area of R1-ish above-grade portion of the foundation wall. It's still worth doing, and air-sealing the rim joist & foundation sill makes a real difference in the air infiltration losses (not measured in U-factor numbers.)

The framing is 2x6 and they filled the pockets nicely with spray foam, my main compliant there was the cantilever for the fireplace... I think it did help keep it 65 down there instead of lower 60s but I didn't notice much/any reduction of the bill vs the batts that were originally in those pockets.

Also I inspected the interior with a FLIR camera, good uniformity in the insulation and wall temps, there are many can lights but they have foam trims, i'm sure there's some infiltration and as always "things could be better" but i'm not going to start ripping out drywall especially since it's a 1.5 story house and it's 20ft height above the living room and hallway/staircase.

Posted By ls3c6 on 18 Dec 2017 06:57 PM

Posted By Dana1 on 18 Dec 2017 06:51 PM
Insulating the R2-R3 rim joists + sheathing & siding won't make NEARLY as much difference as insulating and equivalent area of R1-ish above-grade portion of the foundation wall. It's still worth doing, and air-sealing the rim joist & foundation sill makes a real difference in the air infiltration losses (not measured in U-factor numbers.)

The framing is 2x6 and they filled the pockets nicely with spray foam, my main compliant there was the cantilever for the fireplace... I think it did help keep it 65 down there instead of lower 60s but I didn't notice much/any reduction of the bill vs the batts that were originally in those pockets.

The reason that you didn't notice much of a difference it that the remaining losses were still primarily out the foundation.

If you leave the barn door open it's hard to notice the difference when you close the side window, even though closing the window is still important.

Posted By Dana1 on 18 Dec 2017 07:16 PM

Posted By ls3c6 on 18 Dec 2017 06:57 PM

Posted By Dana1 on 18 Dec 2017 06:51 PM
Insulating the R2-R3 rim joists + sheathing & siding won't make NEARLY as much difference as insulating and equivalent area of R1-ish above-grade portion of the foundation wall. It's still worth doing, and air-sealing the rim joist & foundation sill makes a real difference in the air infiltration losses (not measured in U-factor numbers.)

The framing is 2x6 and they filled the pockets nicely with spray foam, my main compliant there was the cantilever for the fireplace... I think it did help keep it 65 down there instead of lower 60s but I didn't notice much/any reduction of the bill vs the batts that were originally in those pockets.

The reason that you didn't notice much of a difference it that the remaining losses were still primarily out the foundation.

If you leave the barn door open it's hard to notice the difference when you close the side window, even though closing the window is still important.

Well i'm just an I.T. guy with a love for numbers, my last house was built in 2001 it was a basic bilevel 960sqft per level and previous owner had finished it with 2x4 in the basement and used just batts, that house compared to friends that had identical bilevels with little or no basement finish was excellent on BTU consumption comparatively. This one is much larger at 20000 cu/ft main levels and 10000 cu/ft basement and it uses about 40% more fuel than the bilevel did. It is sounding like I was ignoring the foundation walls as part of the equation of severe overall loss. You're giving me hope that $300 some adhesive and a saturday will make a measurable difference with the benefit of hopefully getting the basement closer to 68f to match the main level without too much HVAC run trouble in the future.

If you're a real lover of the numbers, you could build yourself an I=B=R heat loss spreadsheet and measure up the whole thing to figure out where the heat it going:

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-perform-heat-loss-calculation-part-1

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-perform-heat-loss-calculation-part-2

Bottom line, paraphrasing a Bill Clinton era campaign theme, " It's the cold surfaces, stupid!". A surface colder than the room air is taking heat out, and it's proportional to the temperature difference.

There is a reason why the IRC finally got around to requiring foundation insulation, but I believe it wasn't until IRC 2003 before that was the case (it might have been 1999.) Even now it's grossly mis-interpreted or ignored by many builders (and inspectors.) I see many new houses going in with foundation insulation on the exterior only that stops at at grade level, with NOTHING between grade level and the insulated studwall above, the very section where the foundation heat losses are the greatest.

Posted By Dana1 on 18 Dec 2017 07:53 PM
If you're a real lover of the numbers, you could build yourself an I=B=R heat loss spreadsheet and measure up the whole thing to figure out where the heat it going:

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-perform-heat-loss-calculation-part-1

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-perform-heat-loss-calculation-part-2

Bottom line, paraphrasing a Bill Clinton era campaign theme, " It's the cold surfaces, stupid!". A surface colder than the room air is taking heat out, and it's proportional to the temperature difference.

There is a reason why the IRC finally got around to requiring foundation insulation, but I believe it wasn't until IRC 2003 before that was the case (it might have been 1999.) Even now it's grossly mis-interpreted or ignored by many builders (and inspectors.) I see many new houses going in with foundation insulation on the exterior only that stops at at grade level, with NOTHING between grade level and the insulated studwall above, the very section where the foundation heat losses are the greatest.

Yeah this house was built in 2004, they did well to put 2x6s in and at least batts in the joists, airloc cans, wrap etc they "tried" but as far as I can tell the foundation is fully uninsulated on the exterior.

Took some pics, concrete is pretty uniform in temperature on various surfaces but very bad in corners like 48f See pictures https://myalbum.com/album/EMk0Tp27fKLd

Okay, the pictures help me ENORMOUSLY.

Yes. You're bleeding heat out of the foundation walls and floor.

You're probably ALSO experiencing stack effect through the uninsulated joist bays into the floor above.

What I'd do if money weren't an object.

1: Foamboard the entire wall to a uniform surface (or as close as possible). 1" on the closest surface should be fine.
2: 2x4 frame walls, leaving cutoout areas for major plumbing/electrical penetrations. Drop in batt insulation. With a product like Roxul, that'd give you an R15 from the batt and R5 from the board, giving you R20 a rough from the concrete portion (as always, small losses through the wood) and +R20 to whatever value the above ground 2x6 wall is providing. Once done, sheetrock it.
If you don't want to do the whole wall, and think the upper wall is sufficient, you can build the lower wall as a bench instead.

3: Insulate the floor. It's going to continue to be a heatsink otherwise.
4: INSULATE YOUR DUCTWORK! And while you're doing that, have them do a leak check on it and reseal where necessary.
5: Insulate those joist bays and sheetrock what you can.

You don't have to do all, or even MOST of this stuff.
Insulating the walls and floor will probably give you the greatest ROI.
Insulating the ductwork, even though it's not likely insulated elsewhere, will help eliminate heat bleeding from the system in the cooler basement, raising efficiency slightly.

Oh, and you may want to see if you can replace that 1" wood "shim" in the pocket beam.

I don't know why the hell ANYONE does that. All the other areas you're told NEVER to put untreated wood on bare concrete.
Yet someone comes in and puts a pocket beam in there, supported by a piece of untreated wood...

I'd recommend at LEAST trying to find a good piece of dry, treated wood. And if you wanna be PARANOID about it, drive a nail in, dunk it in sealer/stain and let it dry for a couple days before swapping out.

at this stage it's unlikely i'll do anything else than foam board the verticals, can I expect much from that? I'd like to find a contractor to complete the finish but for some reason finding reliable and knowledgeable guys is near impossible for me.

I was going to leave the joist pockets empty I thought that was a no no to insulate due to humidity etc? I would also like to remove that entire beam and replace with metal but again, finding contractors is near impossible for me, I was going to leave the floor as is since it's at least 62f

Okay, if you just foam-board the concrete walls, that'll cut down (but not eliminate) heat loss into the foundation, as the slab will continue to act as a heat sink.

With the joist pockets, remember, both the basement and the floor above it are technically conditioned space. Especially once you insulate the walls.

The problem is that the intervening floor is an uncontrolled thermal exchange zone. Ideally, all thermal exchange should happen through your HVAC system with only minimal adds from migration and stack effect.

Insulating those joist bays should allow greater thermal retention in the basement, meaning your HVAC system shouldn't have to work as hard to maintain it at a given temperature.