Just a quick note for those who might come later to this thread - expect to have to shop around for concrete finishers. We poured the slab inside the walls instead of putting the walls on a mono-slab. The smaller finishing companies in the area (usually just a few guys) didn't want to even tackle the challenge of an interior pour. Luckily my builder does lots of commercial work and brought in a guy with a bit bigger crew (and price) to get it done. The finisher wasn't too happy that it took about 14hrs before they could leave since the concrete was drying so slowly (good for me!), but it seems to have been a pretty good job. Attached are photos of the beginning of the pour, and the next day snapping lines for interior framing. |

Things have progressed on our house since last I updated. Not sure if anyone cares really, but I've updated the shared photo album with pics of the trusses going on, the connections from walls to trusses, and the insulation that was blown. The insulation is not blown directly to the roof deck, but to a layer of laminated, reflective (on the top side) cardboard that is nailed up 2" or so under the roof deck. Lots of labor, but this allowed me to blow 6" of open cell foam under that and create a semi-conditioned attic space. The garage was isolated at it's walls and ceiling from the rest of the house. Had our blower test last week before sheetrock went up (other than garage) and blew a little less than 700cfm50 for a 3000sqft conditioned space. Still on track to be the first certified FORTIFIED home in the state of Arkansas.

Okay, got thrown for a second there.

I normally see ACH50 (where anything under a 6 is tight)
Rather than CFM50 (where anything under 1200 is tight).

Not bad! Not "Passivehaus", but not bad.

Drywall will help that some. And you could probably go leak hunting with a couple cans of spray foam (around windows) and a couple tubes of acoustic sealer.

Looking at the blower-door picture, you have lots of wood-to-wood interfaces (the green lines below in the image), the wood-to-concrete interface (the yellow lines below in the image) and you're probably seeing the bulk of your remaining infiltration through those. Accoustic sealer and a plastic spatula/spreader.


(Click on the image to see the full-sized version: WARNING WILL TAKE YOU OFF THIS PAGE!)




The above image illustrates what I'm talking about.

Like I said, you're good, but you still have LOTS of elbow room to bring down your overall air exchange numbers.  And it's something you could do as a weekend project if you didn't want to pay someone to do it.  Like I said, a couple cans of spray foam, some tubes of sealant and some painter's tape to control the mess on the floor.
It all depends on how anal you want to get.

One REALLY dumb question though.

In a concrete-walled building, why did you opt to do a large stick-frame wall for the entrance?

Mating vertical surfaces like that is usually a *CENSORED!* to air seal well.

Posted By Dilettante on 08 Feb 2018 12:50 AM
One REALLY dumb question though.

In a concrete-walled building, why did you opt to do a large stick-frame wall for the entrance?

Mating vertical surfaces like that is usually a *CENSORED!* to air seal well.

Not sure if you can see, but those were caulked. They used smoke sticks to go around and fill in every spot they could. Even caulked up the multi-plied trusses to about 6’ from the walls. The door you are seeing is from the garage to the living room. The outer shell of the house is fully ICF minus the 18’ garage door that has three 16” LVL beams with a sandwiched 2x4 furring that has insulation in it too. They had it down to around 500 cfm at one point, but something somewhere changed, and we wound up at about 700. Being insulated at (roughly) the roofline means that the cubic footage is quite large. We will get it down a bit after the Sheetrock is up, etc.

I thought I might have one last wrapup of the project. We have been living in the home for a few months and are very happy with the results. The only issues we have been having with the ICFs have been the added humidity that we have in the house as the concrete is curing. Something like 110 cu. yrds. are in the walls and foundation. The Carrier AC system we have has been handling it pretty well, but I do have a supplementary dehumidifier going too when we are out (it's quite loud). We cane in at a HERS rating of 26 which isn't too bad for an under-roof of about 3500 sqft with roughly 3100 sqft of living space. Our 3kWh photovoltaic system is accounting for about half our energy needs, so utility bills are very low. We are also getting the paperwork finalized to become the first IBHS FORTIFIED Gold (High Wind and Hail) home in the state of Arkansas. Actually the first at any level. It involved a bit of extra work, but basically the trusses will shatter before they come off the walls! Attached is a shot with the outside finished, but before I got he yard hydroseeded. Thanks to those who provided feedback along the way! --Mark G.

Love the construction photos you have from your iCloud account. I couldn't help but notice the way you did your wall bracing... 2x4 with an extra 2x4 as a strong back to the side. Were you happy with how they worked, and would you do it that way again?

I'm torn between getting something like a PlumWall and then reselling after we're done, vs Zont's, vs something like you did.

Thanks
Rob

Posted By robisinwa on 11 Jun 2018 10:53 PM
Love the construction photos you have from your iCloud account. I couldn't help but notice the way you did your wall bracing... 2x4 with an extra 2x4 as a strong back to the side. Were you happy with how they worked, and would you do it that way again?

I'm torn between getting something like a PlumWall and then reselling after we're done, vs Zont's, vs something like you did.

Thanks
Rob

ICF is very rare around here, so the ad hoc bracing was the only real way we could do anything. Used a string along the top edge to straighten the walls and a spinning laser level to level the top course. We had some small blowouts and bulges, but nothing catastrophic. We also lucked out in that the concrete pump guy was new, so he went slow since he hadn’t pumped walls before. More “experienced” pumpers might pump too fast so they can get on to the next job. That can really cause issues. Also make sure they don’t overwater the concrete to make it flow faster. You want the rebar to be able to slow it a little before it hits the footers. The one thing my builder said he would have done better was the window and door bracing. You can see in the pictures the 2x4s that went across the outside of the windows. Make sure they are 18-24” on either side of the window - especially if you have ICF blocks that end close to the window bucks. There were a couple of courses that has small < 12” sections near the windows. Those weak sections were where all our issues were.

We used a Flir thermal camera that attached to our cell phone to look for cold spots last winter after the drywall was up but before mud.

It worked really well. I just drilled a small hole and filled the cold area with spray foam. Along with spray foaming good around everything before drywall.

We had a BD test last month and got .79 ACH on a ICF house that was 3700 sqft ranch with walkout.

We also thought about turning on the attic fan on a cool night to look for cold spots with the camera but didn't need to.

Very nice house you have, great build.

Posted By newbostonconst on 12 Jun 2018 10:41 AM
We used a Flir thermal camera that attached to our cell phone to look for cold spots last winter after the drywall was up but before mud.

It worked really well. I just drilled a small hole and filled the cold area with spray foam. Along with spray foaming good around everything before drywall.

We had a BD test last month and got .79 ACH on a ICF house that was 3700 sqft ranch with walkout.

We also thought about turning on the attic fan on a cool night to look for cold spots with the camera but didn't need to.

Very nice house you have, great build.

Thanks. Sounds like a really tight house! Our final ACH50 was 1.3. Not great, but I'm pretty sure that it came down to our bathroom vents not having great backdraft valves and the integral apartment (see plans) not having a dryer attached. That meant LOTS of leakage around the exterior flaps for that. We also have a fresh air pipe into our HVAC air handler that was probably sucking a bit in too. It's still one of the tightest houses in Arkansas the HERS rater has come across in 30 yrs. Which goes to show how inefficient homes can be here I guess! I know a good chunk of our estimated energy usage is for the electrically heated master bath floors. The definition of "inefficient", but the wife needs her toasty toes coming out of the shower!

Sorry to bump a dead thread, but considering how much time/money I spent getting this certification, I had to show it off to someone! I actually had to contact IBHS directly as there were no evaluators here in Arkansas. I was able to work with a very experienced evaluator in Florida to provide all the needed documentation. Using ICF helped fulfill lots of requirements just because of how the the walls are tied into the foundations. Having no gables made it easier too. Getting the porches right was the big item that needed a lot fo preplanning.

If you are building along the coast, or in Tornado Alley, you can get some good insurance benefits from certification. Hopefully if more in my state do this, the insurance companies will know how to calculate discounts.

Great job....and thanks for turning us on to this certification.

No. Don't apologize. Look at the thread as an ongoing, if rarely updated, blog.

And this info is great!

Also missed the original post back in June.

HERS score of 26 after solar is pretty decent!
With about 6-7 points taken off for the solar (so your pre-renewables was about 33, still EXCELLENT).
Not quite "Passive House", but it makes a code-built house look like a screen porch and makes most of the leaky legacy homes out there look like a gazebo.
And your array looks fairly right-sized for your home.
So your energy bills should be nearly nonexistent.

Awesome job!

Posted By Dilettante on 20 Oct 2018 06:42 AM
Awesome job!

Thanks. Without the electric heated floor in the bathroom, the HERS probably would have been lower. Even only using it a few hours a day it uses 5-10kW a day in the fall and winter. This summer we were doing about 400-500kW a month from the power company ($50-$60) after I send them 120-170kW from the PV array.

The main issue, if one could call it that, is that the house retains heat and humidity so much. Just having 3 people in 2500sqft can raise the temp 1-2 degrees during the evening. That and all this concrete is still curing, releasing lots of water into the air. I’ve only seen the house below 50% humidity once or twice. It hovers around 60% even with a dehumidifier going strong. Of course right now I love it. In the past 8 days of the outside weather being 20-35 degrees below the house temperature, the interior temp has only dropped 3-4 degrees total.

If anyone wants HVAC details, PM me with your questions.

Rather than PM it, just drop it here.

What IS your HVAC setup?

I'd think, had you gone with an HRV/ERV that you'd see better dehumidification than that.

ditto........

If you're still sitting at 50% relative humidity indoors, you may need to add a more powerful dehumidifier and may actually be contributing to the lengthier drying time.

Optimal drying of concrete occurs at 30% RH between 65 and 70 dregrees F.

Full dry-in for slabs and walls SHOULD be approximately 1 month per inch (or so) of thickness. You're sneaking up on 11 months right now. So unless your walls or slab are a foot thick, you're lagging on drying time.

I'd think, had you gone with an HRV/ERV that you'd see better dehumidification than that.

60%RH @ 70F is a dew point of 55F. In Arkansas that means an HRV/ERV will only dehumidify the house from early October through through the end of April, since only then will the outdoor dew points be below 55F more than half the time.

https://weatherspark.com/m/10887/10/Average-Weather-in-October-in-Little-Rock-Arkansas-United-States#Sections-Humidity

https://weatherspark.com/m/10887/5/Average-Weather-in-May-in-Little-Rock-Arkansas-United-States#Sections-Humidity

As Dana1 pointed out, Arkansas is very humid where I am (even more so than Little Rock). 55% is almost always lower than the outside RH. Also, because of how we are insulated, none of the walls cure to the outside - it's all into conditioned or semi-conditioned space (attic). That and 110 cubic yards of concrete is a lot. There are some places around the edges of the walls where the footers and slab meet that are a few feet deep and a few feet wide. The 3500sqft slab is also 6" instead of 4".

The HVAC setup is split into two systems - main house, and in-law suite. The 550sqft in-law has a single cartridge Carrier split-air system that is only used when someone is using it (about 1/4 of the time). We have a single supply from the central HVAC in the closet, and a return in the corner of the bedroom. Not enough to condition the space, but enough to keep the air quality acceptable even when the split air isn't on. The central HVAC system is a Carrier Infinity 18 SEER heat pump with a 5 stage compressor connected to a variable speed Carrier FE4 air handler in the attic. It's run by the Infinity communicating thermostat which is, unfortunately, the only thermostat that can handle all the functions of the compressor and air handler. Its user interface and reporting are years behind Nest and Ecobee, but I would be crippling the system if I went with one of those because the "brains" of the system are in the thermostat, not on a board on the air handler. I do know we keep the temp quite a bit higher than others though. During the summer, we kept it at 80 unless we were doing a bit of work inside, then we dropped it to 77. In the winter, we keep it at around 72 with offsets for us all being at work, etc. The dehumidifier will keep the system running (but not turn it on) if we have above 57% RH. I found if I put it down to 55% or so, it never turned off, so we deal with the extra 2%. We do have a portable 70 pint dehumidifier that we run quite a bit. It helps, but 2500sqft means it can't get everything everywhere.

Another important component are the ceiling fans. We have 5 in the main house and 2 in the in-law suite. In the living room and master bedroom, we have Haiku 60" fans. They are monster air movers and dead quiet. At low speed they move 1000 cfm. Seems ludicrous, but having slept beneath one for months now, I believe it. Expensive, but so much better than the Hunters we have elsewhere. It means we can keep the thermostat higher, and still feel comfortable.

The thermostat has some reporting features (last 2 days, last 2 months, last 2 years). it tells me I've done:

• August: 282 kWh
• September: 155 kWh
• YTD (March to now): 1738kWh (1259 cooling, 361 heatpump heating, 118 electric heat) A big chunk of that was actually at the very start when it was running continuously for a few weeks. Also we had workers finishing the house for much of March and into April, so we kept the temps better for them.

Since people seem to like photos, I've added several more to the shared iCloud album.

Edit: I forgot to mention that the master bath has a continuously running Panasonic exhaust fan that does a silent 50cfm to the outside that ramps up to 110cfm when someone is in the room for more than a few minutes (motion sensor). The air handler also has a goodly sized fresh air intake. Our consulting company, HVAC subcontractor, and HERS rater went back and forth for a week or so making sure that we had enough air exchange to not have a "sick house". We had a _very_ good HVAC guy who has done lots of commercial and residential specializing in energy efficiency, so I'm reasonably comfortable that we have the right system.

This is fantastic. Any chance of an update how it's all worked out?

We are just north of you in Arkansas (Amity) and would love to do something like this. [/I] I would be interested to know the vendors/builder you used so we could contact them.

Thanks!