I've found this site immensly helpful in designing my house, and thought I'd share my experiences.  This might help you, and it might still help me... so in advance, thanks for reading.

I'm building a ranch ICF house with a walkout basement.  Each floor is 1800 sqft, with 9' ceilings.  It has approximately 450 sqft of glass, most of it facing north (on the walkout side), and will use an air-to-air heat pump as the primary heat source (w/ propane fireplace and woodburning stove backups). 

We'll be using raised-heel trusses to permit R-49 formaldahyde-free blown fiberglass insulation to extend to the outer edge of the 6" ICF forms.  We've been told to assess the walls at an R-40 for HVAC purposes (if you add up the materials it comes out to be R-25 or so, but they don't permit air infiltration, which is the real killer in houses  -- this is the primary reason for building with ICFs in the first place).  We're also placing R-7.5 rigid foam underneath our basement slab.  I have no idea what effect this will have, but if it keeps our toes a little warmer, it's money well spent.

Our initial heat loss calculations were done using this free tool  (note that it sizes heating, not cooling):

http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm

It allowed us to make tradeoffs between differing options to get a sense of where our money was best spent.  Additionally, it's numbers seemed to be close to that of other tools I found along the way.  Kudos to the tool's designer: Gary Reysa.

Some interesting things that we found were that Serious Materials vinyl windows came in at around $13,000 with an R-5 (whole window) and lifetime warranty, whereas Pella were about $9,000, with an R-3 (whole window) and 20 year warranty.  We also looked at Anderson, Milgard and Kolbe; all have very good products.  Unfortunately, I can't endorse product here...  but check out these websites:

http://www.seriouswindows.com/html/vinyl.html
http://www.seriousmaterials.com/SeriousWindows_Bro.pdf

Double-hungs tend to be cheaper windows, but casements/picture windows let more light in (because there is no hardware right in the middle) and have better R values. 

We also learned alot about HRVs and ERVs.  Because our house will be so well insulated... it turns out that a 1.5 ton heat pump (smallest you can get without going into mini-splits) might be oversized.  This may result in the AC not running long enough to pull much humidity out of the air.  We are solving this problem by using an ERV.  (ERV's pull humidity out, HRV's don't... and we have to use something because of our airtight walls.)  Because our house will have low humidity as a result of the ERV, we can keep the thermostat higher in the summer, and that should offset it's operating expense. 

The Ultimateair 200DX ERV has an efficiency of 95%... combined with airtight, well-insulated walls/windows, and ample (well-placed) attic inulation, this means very little energy loss.

A free tool to size heating is a good start.

try www.hvac-calc.com which is the software I have used for years. It has an ICF setting so the thermal mass effect is considered, as well as the lower air infiltration factor.

I believe the single use for a project is $50 so you don't have to buy the program for $400.

Ohio.....Wow!! You 'only' need 1 1/2 tons for 3600sf??

There are more efficient windows than the Quantum offering.

You can get a casement in a U-Factor of sub 0.16 quite easily (R-6+)

  We've been told to assess the walls at an R-40 for HVAC purposes (if you add up the materials it comes out to be R-25 or so, but they don't permit air infiltration, who ever told you this is wrong, Free heat calcs are great for experimenting . To size your heating ,ventilating equipment Manual j 8th ed is what you need It will certainly take into account your building materials heat loss/gain through conduction and convection(aka air infiltration)

Thanks for the replies everyone...

I guess the first thing I'll throw out is that I'm not an expert, but am happy to share what I've learned.

As far as I can tell, the "thermal mass effect" is a benefit, but not the biggest one. Here's a good paper on the theoretical mass effect (by itself):

http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/index.html

The left side of the page lets you navigate the article, and the embedded figure links let you see the graphs... The ICF thermal mass effect (by itself) will give you about a 7% energy gain over a similarly insulated stick construction. This is a good benefit... and I believe that ICF construction may be more cost effective than the other two wall configurations the authors suggest.

The solid 6" concrete wall going from footer to truss isn't going to let much air through... by using airtight can lights and a whole bunch of spray foam around every conceiveable penetration... it should be about as airtight as a house can get. In fact it's dangerous to not use and ERV/HRV in an ICF house. Of course, the dryer vent and bathroom fan vents (energy star rated) will be holes... these are unavoidable. But because wind on the side of house will have basically no effect, there is no way for the pressure to fluctuate on the inside of the house. The inside air should stay inside.

BlackHatch is right that more efficient windows can be found; I've actually found one that was R-20 (whole frame). ... but $$$ becomes a problem. For the money, I think we found a good balance of R-value and performance. If anyone has found double glazed windows w/ U values below .20, please let me know. (triple-glazed is out of our price range).

Here's a link that suggests an R-value for ICF:

http://www.nudura.com/en/NuduraICFFAQ.aspx

...but to be honest, through expermenting with free software mentioned above, the R-value of the wall could change between R-25 and R-50, and the difference is only 1/2 ton of heating capacity. Walls just don't matter much in my climate beyond R-20. The big drivers are windows (nearly a ton differnece between R-3 and R-5), attic insulation, and air infiltration (as in any climate). By controlling those three things, the difference can be astounding.

Here are the inputs I used for the build it solar tool:

-10 design temp
5800 degree days F
celing area: 1800 at R49
walls: 2400 sqft at R40
windows: 450 sqft at R5
floor: 0 at R20
slab: 100 ft at R40
infiltration: .005 (remember I am using a 95% ERV in an airtight house)
volume: 35,000
occupants: 3

The tool also has some disclaimers (it does not factor in solar gain or thermal mass, so the estimate of BTUs/hr should be high).
I found it fascinating how much difference occurs by changing attic insulation from R-20 to R-50 (and this is a cheap addition to the house), by changing windows from R3 to R5, and most especially by assuming that it was stick construction without an ERV (by setting the infiltration to .33).

I did have a couple HVAC people come back and quote me at 2-2.5 tons... but both failed to account for air infiltration or an insulated slab perimeter... and both assumed an attic of R-20. The reason for this is partially because houses are typically sized for AC -- not heat (for humidity control reasons).

This really means that my 1.5 ton estimate is way too big... perhaps a 1-ton unit would be better... but good luck trying to find one of those... and the ERV should help with humidity anyway.

Thanks guys.... but again, I am not an expert, and am only sharing what I have learned in the past six months working with my builder trying to build a good green house.

...oops... I should have also mentioned the HVAC contractors were told R-3 windows when they were developing their quotes. By changing them to R-5, we dropped about a ton in HVAC heating capacity.

One aspect of a well insulated air tight house that I haven't seen much discussion of, and is causing me to have some questions, is the heat generated by bodies and normal living activity. I'm about same as finished with my 2000 sf ICF house. I used 6" Buildblock forms, have an insulated crawl space including XPS under the rat slab, have about R 35 to 40 spray foam on the underside of the roof, and Andersen 400 casement windows. My heat load calculated at about 20,000 Btuh at 20° outside, and 36,000 at 9° outside. I installed a 3 ton Daikin heat pump.

Here's my problem, or potential problem. We're not living in the house yet, but have been working in it all winter. What I have noticed is when the outdoor temp is about 40°+ the body heat from 4 workers, and the power tools and lights we used, along with solar through the front windows, would raise the indoor temp from about 70° to 73° during the day with the heating system not kicking in at all. The windows still have the factory plastic film on them so they aren't totally clear.

What I'm beginning to wonder is if I may have traded a reduced heating bill for an increased air conditioning bill. I may have to run the a/c at a lot lower outdoor temp than one would normally expect to have to to get rid of the normal heat generated by life activities. I haven't made much use yet of the Econo Cool mode of the Ultimate Air ERV so I don't know yet how effective that will be in cooling the house.

Be aware that as you super insulate your house, and get the required heating system size down to a very minimum, you may be holding naturally created heat inside to such a great extent that you will need cooling from March to November!!!

Like I said, there hasn't been much discussion about this, that I've read anyway, and I don't have a long enough history yet to define the issue better, but I really think it's a subject we need to keep in mind. The real kicker is that heat generated by breathing, walking, talking, cooking, watching TV, surfing the 'net, etc., is such a variable it will be hard to place a reliable number on it.

You will want to verify this. My ERV, the same one you're planning on using, does not have a condensate drain. My HVAC installers said the HRVs they usually install do. An ERV moves the humidity from one air stream to the other, the HRV extracts it and dumps it down the drain.

dmaceld, check out:

http://www.airgenerate.com/products/airtap.html

I've often wondered the same thing. That builditsolar website I keep mentioning suggests that between 1800-2500 BTU/hr are from people. That could certainly add up over the course of an 8 hour workday. You would certainly have to use AC over a larger time range to compensate... but in the peak of summer if your house wasn't airtight, you'd be losing your conditioned air to the outside as well. So although the range might be larger (mar-nov), but it won't have to run as long on any given day. You also will be retaining heat in the winter, so your heating bills should be less.

Now, that link I gave you above is quite interesting in my opinion. It allows you to use a heat pump to heat your water using the heat in your house's air. It's like having a very small AC unit on all the time. Of course, body heat and your larger heating system will have to compensate for this in the winter by pulling heat out of the outside air. The basic idea is that the heat pumps are pulling heat from elsewhere (even cold air), not creating it directly, and thus can be more efficient than resistance heat. So if you find your house having an oversized heating system, this might be a good way to compensate. It will also minimize the time that your AC spends running in the summer months.

It looks like your 3 ton unit should be able to handle this quite easily. (again, not an expert)

I've also given quite a bit of thought about how to install these... and because they heat water slowly, it might be good to use two large tanks (each 80 gallons or more). The first tank would be good to use with the Airtap as a preheater, the second should only kick on if the water temperature is too low coming in. That way you will never run out of hot water, and the use of resistance or gas should be minimized.

Good call on the 200DX not having a drain... I didn't realize that. I checked the site, and it says it strips about 50% of incoming humidity. It must do this through the filter media (?).

http://www.ultimateair.com/Ultimate_Air/support/faq.aspx#14

I have an Air Tap. Sorry I don't have time to find the thread right now, but you can find it by searching for Air Tap and my posts. I discuss some of the pluses and minuses I've learned about using it.

have you done a blower door test to confirm your air exchange?

it is true icf's are "tight", but the other systems (insulation,doors,windows) may not be.
spray foam is very air tight and will maintain indoor air temp well if installed properly.

have you accounted for the "latent heat" created by cooking, fridge, laundry, shower, ect?

location of windows and shading (overhang, e--lass, ect)is very important when using a program to calculate loads, if you desire accurate results.

mac

Actually, this week we are signing our specs/contract. Hopefully, we will be breaking ground in a couple months.

I'm assuming latent heat to be around 2000 Btu/hr... I'm not sure what our HVAC sub's software assumes.

We've actually had a few things change over the past week; we decided to switch our insulation to R-49 cellulose (instead of blown fiberglass). The cost is about the same (under $2000), and the cellulose has much less air infiltration, and does provide some thermal mass.

http://www.houleinsulation.com/cellulose_vs_fiberglass.html

To prevent drywall sagging issues we are going to have to change the 1/2 drywall ceiling to 1/2 high-abuse board (drywall with glass fibers). Of course, all the penetrations will have to be caulked/foamed to alleviate dust issues.

I talked briefly to our HVAC sub the other day; his MJ8 software says we need 2 1/2 tons of cooling. ...but he said the software is somewhat limited on what can be modeled such as air infiltration, slab insulation, thermal mass, etc. He's agreed to drop us down to a 2 ton condenser with a 2 1/2 ton blower. Right now I'm planning to trust his expertise on this... If we are oversized a bit, my hope is that the ERV can manage humidity.

Has anyone had blower door tests done on ICF houses with sealed attic/wall penetrations? I'm curious what they'd achieve...

dmaceld-- I did look through your posts about the Airtap, and you mention using it in your garage, but I didn't see the pros/cons. Have you had issues with it?

best,
OhioICF

If humidity removal is a concern you will want to reverse your sizes, 2 1/2 ton condenser and 2 ton coil. You're also better to be undersized for a/c than oversized. For a lot of discussion about this go to www.centralair.com, I think. It's the web site of a Houston a/c guru.

I'll write about some Air Tap issues later when I have more time, maybe this evening.

OhioICF,

Thanks for sharing all the great info.

Also using Serious Materials windows, made here in Boulder.

Try 5/8 Drywall for ceilings. Solves sag problem cheaper than 1/2 with fiberglass and adds thermal mass.

We are using 2 layers 5/8" thru out the house both for thermal mass and sound proofing. Also 2 layers feels much more substantial.

We are salvaging any usable scraps from other jobs and using as base layer. On SIPS any piece that is 4'x 1'+ is useable. Will use full sheets on outer layer.  It is amazing how much drywall is tossed on any job.   Another builder puts drywall scraps between the studs of interior bath walls.  Soundproofing, thermal mass and savings on dump fees. 

 

 

 

dmaceld -- that's an interesting idea about reversing the sizes... and makes sense. A colder coil removes more humidity; there would just be less air flowing over it. I'll have to look into this more.

RichColorado -- Today I learned that there is a ICB product "Interior Ceiling Board" that is a 1/2 inch drywall with the strength of 5/8". The price difference to hang the ICB instead of regular 1/2" for 1800 sqft is about $75. I really like the idea of putting scraps in walls; I'm adding that to my spec sheet. Thanks!

I'm getting a copy of some ICF-specific HVAC software from my Nurdura block suppliers. I'll let you all know how that compares with the builditsolar software.

Done right, and this is a real problem, however dont forget the heat of curing is also still adding to your load.

I am so glad some one finally noticed what can be achieved with this type of building, and yes, we have larger cooling systems than heating systems even in Michigan (existing building operating for 7 years now), the issue is that these buildings will simply keep the climate inside closer to sum of all interior heat, less loss, so ensure you put protection on your outside compressors for cold AC operation, otherwise you could, potentially, damage your equipment
Mark Ross

That's what I did when I replaced the a/c unit in the house we had in Louisiana, 2 1/2 ton condenser, 2 ton evaporator. Did a great job removing humidity.

I didn't know about ceiling rock until I got bids for my house. One caution, it's a lot harder than wall rock. You know those plastic corkscrew wall anchors? They go into wall rock quite nicely. The other day I broke three of them one after the other trying to get one into ceiling rock. Gave up and just drove the screw directly into the rock!

Air Tap issues.

First one I encountered is the thermostat. The unit comes with a bulb sensor that is part of the coil that goes into the tank. The problem is it only goes down into the tank about 18". Letting it control the Air Tap means that only the water at the top 18 to 24" inches of the tank gets heated to full temperature. When I complained about this to Airgenerate they sent me instructions how to bypass the built-in thermostat and use the water heater thermostat to control the unit. I connected it to the bottom thermostat and the entire 80 gallons gets brought up to set temp, which in my case is 130°. The water heater is not connected to 220 volt power. A person could rearrange the wiring such that the bottom thermostat controls the air tap and the top thermostat switches 220v power to the top element.

In new construction the Uniform Plumbing Code requires a water heater to have a minimum "First Hour Recovery" rating, depending on how many bedrooms are in the house. The Air Tap won't meet that requirement. Neither will any "smart" water heater I have looked at. Therefore I have a second 60 gal water heater in series after the 80 gal heater. Originally I planned to preheat to something like 100 to 120° with the Air Tap and top off to 140° with the second heater. However, the Air Tap will bring the temp up to 130° reasonably well so now the second heater is basically a temperature maintainer and backup. It's also set at 130°.

Heat source for the Air Tap can be an issue. For it to run efficiently the air it extracts heat from should be 50°+. That's no problem in summer. If the unit is in the garage it can help cool the garage, or just suck heat from the hot garage air. If it's in the house it will help cool the house. Winter is another story. You need to supply heat to the Air Tap air somehow, or not use the Air Tap. I planned on my garage wall unit of the Daikin heat pump to bring in that heat at a COP of 3. It turns out the operating efficiency of the heat pump, when only the wall unit is running, is only about 1, same as straight electric resistance heating. For winter I'm considering modifying the Air Tap to bring air from the house space and return the cooled air to the house. The air in the house is heated with the heat pump running at a COP around 3+. In the summer I would have it circulate garage air to help cool the garage. My garage is ICF with insulated roof. This isn't an easy option to execute because codes, and common sense, prohibit any likelihood of garage air from entering the house.

Yeah, I did forget about it, even though it had been mentioned in a thread some months ago! Any handle on how long the half life of the curing heat is? By January the concrete had been in place about 5 months.

I'm considering getting a blower door test. I don't have to have it since I can't get an Energy Star rating. Energy Star Northwest has no criteria to assess/approve using a crawl space as a supply plenum, nor the attic as a return plenum, as I have built.

My windows are tight. The doors may not be. It turns out that it's not so easy to get an air tight seal at the door bottom with a low profile threshold. I built my house pretty much ADA compliant.

The Manual J calc for my house did not include the heat of living activities because it's so difficult to estimate accurately. Be careful how you use the term "latent heat." It has a very specific meaning in the a/c world. It's the heat absorbed or released as water is vaporized or vapor is condensed.

The Manual J program used for my house, Wrightsoft, very accurately accounts for window parameters, including shading.

The HVAC equipment size seems about right. I have a 2,000 sq ft. ICF home -2 levels for a total of 4,000 sq ft and heat it with a 1 1/2 t. Geo in a 5,900 HDD area. I use a sealed combustion fireplace for my back-up on a remote thermostat. I have found that in that Climate Zone that I need the fireplace a few times a year amd did not warrant a larger unit. Air conditioning wise, I need the unit to run maybe 12 days a year. We also have clay walls inside the home that in the early summer will absorb the humidity and act as a "poor mans" air conditioning. We close up the house during the day and air it out at night thus giving up the heat and humidity. I an not a strong supporter of fiberglass, so I used spray foam on the underside of my trusses. This necessitated of course a HRV. I pipe all my bathroom fans back to the HRV and do not directly vent outdoors except the kitchen stove exhaust. I kept my penetrations of the building to a minimum.

Window wise. Since I worked at a University (Building Science) and we conducted window testing I had an opportunity to see all different brands and types. I chose a fiberglass frame window that would expand and contract about the same as the glass, thus the chance of breaking a seal on the thermopane is reduced.

Overhangs is a very important item to consider also and I incorporated a 3 ft overhang on the home and held my window to wall ratio well within 15%. I faced the home due south, thus having the large overhang on the east/ west sides with the less amount of windows on the west wall. I also have skylights on the north roof got light.

As a person working in the construction field ( over 40 Years now), I have seen just about everything and would not build anything other than an ICF home. Love it, love it, love it.

At 5+ months any heat of hydration effect is looooooong gone.  Heat of hydration is not much with 4" or 6" thickness...even with ICF.....and it peaks at day 2 or day 3.  It basically follows the rate of strength gain.

Concrete strength gain and heat of hydration is minimal after 56 days for normal concrete mixes......the curve is quite flat at that point.

Bruce

Cure times are a lot longer in an icf to ultimate strength, and the heat remains higher with a more complete cure.

.....and why would this be different than, say, a concrete cylinder from a testing lab's curing room?

Concrete hydration is a chemical reaction (exothermic) and the amount of heat produced by this reaction is mostly a function of the amount and gradation of the cement in the mix.  The insulated forms will keep it warmer for a few days longer.

The curing curves for ICFs and the same concrete in a slab or column will be virtually the same shape (rate of gain), with the ICFs having a slightly higher ultimate strength because of better curing.  This is a small % and should not be factored into the mix design.

One of the potential benefits of ICF (for those who think in terms of decades, scores of years or centuries) is that being encapsulated in styrofoam may prevent or minimize carbonation, which deteriorates concrete over time from the surface inward. 

Bruce

Bruce:

Thermocouples proove that during winter (reporting done in North Bay, Ontario, Canada), in an unheated ICF concrete structure, placed in the fall, by mid winter, the temperatures of the core are still upwards of 50 degrees.  Additionally, if concrete "dries" instead of curing, then it will stop hydrating.  A good example of this, is the mass of the Hoover Dam, which still has a very high internal temperature to date and has been monitored from date of construction.

dmaceld,

yes, latent heat is the heat required to be removed to condense water vapor(to get it out of the house)

most people don't realize the amount of water vapor they put in the house.
showering without exhaust fan, boiling water on stove, air drying clothes ,and water form defrost cycle on fridge, ironing(steam), ect

in a dry climate it may not be as important.....but in Florida, we spend a lot of energy to remove water form our homes.

sounds like you are getting a lot of solar gain how much south glass exposed in summer vs winter?
mac

OK... here's some more data. My Nudura block supplier let me try out his Portland Cement Association HVAC sizing software (4.0).

Overall, I found the software very easy to use. It assesses the location, orientation, and geometry of the house, the window placement, window shading, wall construction, amount above/below grade and several other parameters. The only shortcomings that I found were I wish it asked for the type of attic insulation (for thermal mass reasons, as well as air infiltration); I also wish that it did not use a default air infiltration rate based on wall construction... or at least allowed one to select an ERV/HRV option. I believe our "effective" infiltration rate will be less than the default specified by the tool because our fresh air will be going through a heat exchanger. That said; it's a very good tool, and should continue to improve.

My house, as described in the first few posts in this chain (3600 sqft walkout ranch w/ 6" block and now a R49 cellulose attic), was tested for two different options using 70 degrees as both the heating and cooling setpoints:

1) windows with U=.33, and SHGC=.5
This resulted in requirements of 25,000 BTU/hr heating and 19,000 BTU/hr cooling with 9% of the cooling load being "latent."

2) windows with U=.21, and SHGC=.3
This resulted in requirements of 22,000 BTU/hr heating and 17,000 BTU/hr cooling with 12% of the cooling load being "latent."

I thought this was very interesting... but raises more questions than answers:
--For $4000, are the better windows worth it?
--If not, would a 1.5 ton unit be able to adequately heat an Ohio house with the lesser window selection?
--At what point should one start sizing for heating rather than cooling?
--The program assumed infiltration per ASHRAE standards, how much of this would be temperature corrected by an ERV (lessening the heating/cooling load)?
--How should the condenser be paired with an Air Handler for a 35,000 cubic foot house?... the 1.5 ton blower might not be strong enough... but like dmaceld pointed out earlier, a larger blower might not get the humidity out well enough.

...lot's to think about...
I'd love to hear your thoughts...

how much wood can you split?
1.5 ton might work "most of the time"

mac

Agreed... Well, that's why we're putting in a woodstove (sort of).

If you need an 8 ton unit, going to a 7.5 or 8.5 ton unit probably wouldn't amount to anything... but switching from a 1.5 to 2 ton is a 25% change. Maybe a 2 ton condenser with a 2 ton variable speed blower is the answer(?).

6.5 btu/hr/square foot of house in heating sounds very, very low.  I live in Ohio, with a winter design temp of 12 degrees F in cincy. This represents a min of 18.3 btu/hr of straight loss, for every square foot of window area for the windows at the U value you have entered.  With an average 10% window area, this translates to a window loss load of 6,588 BTU without any air infiltration being considered.  Three doors, that are well built, in raw loss translates to another 1,008 Btu, if you have a patio door, you are looking at another 700 Btu per 5' wide slider, with 3 panes of glass.  now the wood burner...thats a standard at best case of very close to 1000 btu/hr.  with your walls, even at 2 Btu/hr, you have to have roughly 2,400 lineal feet at the very lest for 4,800 Btu/hr, and your roof raw loads will be 2 Btu/hr/ft with 1800 square feet at 3,600 Btu/hr for a total of 17,696 Btu/hr raw loads, with no infiltration, lineal footage of crack for openings, other openings, basement slab loads, garages in the building, roof penetrations such as light fixtures, dryer or exhaust vents for bathrooms (they typically rate around 300-400 btu/hr)any missed openings or icf wall foam omitted, rafter edge loss, or leakage through conducted areas.  All of this is assuming you are in cincy area, anywhere north of dayton, and your equipment will be too small, if it is even large enough for the lower part of the state. 

I think you may want to look a little more at the heating and cooling loads, (get a professional HVAC engineer to do it there are many out there that can do proper heat loads for these buildings), because I have yet to see a house with less than 12-14 btu/square foot in Ohio.

If you are as well built as you claim, then your cooling loads would be a lot higher than heating loads.  EG we have a little 2200 square foot in central Michigan (this includes the basement), with a full ICF roof on it, that needs 1.5 tons of cooling, and there are practically no south facing windows in it.  however the two that are there, do overheat the place in the summer.  And the windows...they are the best.  Maybe eldon can post here on this.  Personally, I made the same mistake....twice.

Oh yeah, I forgot about loss from wind, which is actually fairly high.

Mark Ross

markross -- awesome post; there is a lot here to think about. Your numbers do make sense to me... The 17,696 BTU/hr sounds about right for the raw loads... appliance and bodies will offset some of the leakage, but it's a little too close for comfort for me... and for that reason, I think I'm giving up on the 1.5 ton idea. It was a nice thought while it lasted... but just doesn't seem feasible anymore.

The good thing about this is even if we fall short slightly with a 2 ton unit, we can still light a gas or wood fire to supplement the heat pump. 99% of the time, we should be covered just fine.

...and we are right by Dayton. Small world.

I am not saying my reply is the answer, nor is it right, I have done a few heat loss's and work in wright soft for my own projects only now.  I just have found, that if you break it all down, its easier to understand, however you need the information to start with.

Dayton gets a lot more snow than we do here, its funny what a 40min drive will do for weather.

BTW I am originally from Northern Canada, I just live down here now.  However, it is a small world.

Nice texting "ya-all"

The house is at 45 to the world so there's no directly south facing glass. I've got two 6/4 x 6/0 windows facing SW that are pretty much 100% exposed to the sun in mid winter, and about 30% exposed in mid summer. I've got a pretty good overhang above them, a bedroom wing to the SE of them, and a porch to the NW of them. There's two 5/0 x 6/0 windows on the SW wall shaded by the porch. They have 0 sun in the summer and about 30% sun in the winter. Two bedroom windows face SW with no shade but they're only 2/8 x 5/0.

I can't remember, and I'm too tired to look, if window sizes are normally stated H x W, or W x H. The above are W x H.

Do you have a link to the study?  I would like to see the temperature curves.

It is clear that hydration will continue as long as there is availble moisture and silicates. There is enough microscopic water in a good mix to allow it to gain strength almost indefinitely (the curve gets really flat), even more so if it is not subject to surface drying.

One of my projects in the past had a 16,000cy, 10' thick mat and pumped concrete 1000' vertically, so that got me very interested in concrete technology.  After almost 30 years, they tell me that the mat is still a bit warm, too.

If you like concrete stuff, you might find this link interesting:
<http://www.cement.org/tech/pdfs/pl972.pdf>

Bruce
(sorry for hijacking the HVAC, Window and insulation thread)

I have been told that concrete has something like a 100 year lifetime, 50 yrs getting stronger and then 50 yrs getting weaker and deteriorating. This is probably more likely in thin structures such as walls and slabs than in huge masses like dams.

When I visited Grand Coulee dam in Washington during a college field trip, ala 1966, we were told that the piping for running cooling water through the dam had been removed only a few years before that. I don't remember when the dam was built but I think it was the '30s.

As I stated in my previous posts, we've got a 3600 sqft house (1 story ranch w/ walkout basement) built w/ ICFs all the way up to R-49 cellulose in the attic w/ raised heel trusses. We're using an ERV for ventilation. Most of our windows face North (due to the lot topology).

I ran the portland cement HVAC sizer for ICF houses: it says I need 1.5 tons cooling, 2 tons heating.
I consulted my local HVAC installers that used Wrightsoft: it says I need 1.5 tons cooling, 4 tons heating.

Bottom line: we selected a 2 ton condenser w/ 2 ton variable-speed blower. When it gets really cold, we won't want the heat pump running anyway; we'll be using resistance heaters. This works out to about 6.5 BTU/sqft. Let the experiment begin...

We're also putting in a direct vent fireplace and a woodstove for emergencies. I'll be sure to let you all know how this system performs.

Now that it is summer and I assume you are living in your house, how is your system performing?

Bruce

Bruce,

Unfortunately we're not in yet (probably 6 months out)... the banking process was slower than expected. I will certainly post what I observe though.

Cheers!

Thanks for asking. Here's a, hopefully not too long winded, rundown of results so far!

We moved into the house in April, the wife & I and two dogs. Generated body heat isn't near as great as when we were working in the house. Because of the overhang I have above the living room windows, and because the front porch shades the dining room windows, the summer time solar gain is less than it was during the spring. Heat gain picks up late in the day when the sun is more directly shining at the windows. The AC usually kicks in during the afternoon. Since the Daikin has a variable speed compressor and a variable speed condenser fan in cooling mode it moves out of the house only the amount of heat required to keep the temp constant. The indoor temp doesn't move up and down very much at all, maybe 3 to 4° at most. Much of the time, even when the outdoor temp gets into the low 90's, the air coming off the condenser was hardly any warmer than the outdoor air, and the fan was running at low speed! Note that the Daikin circulates air constantly, not just during cooling/heating times.

Interestingly, when we've been gone for a couple of days, the house will be at about 74° with the controller set at 75°. After we've been home for a couple of hours the temp will rise to about 75°, without touching the controller. All I can figure is our body heat causes the rise and it takes a little more rise to cause the controller to increase the cooling rate. Then the temp stays pretty close to 75° unless the heat gain picks up fast.

One thing I learned fairly soon after we moved in, is the Daikin remote temp sensor on the hallway wall just above the Daikin controller, and the Honeywell thermostat which I have wired into the ERV to control the Econo cool mode, are sensitive to the temperature of the wall! The air temp in the hallway would swing up and down upwards of 4° either way from what the sensor and thermostat were sensing. Subsequently, in both heat and cool mode the Daikin and the ERV weren't responding anywhere nearly as quickly as they needed to for room temp changes! Right now the Honewell is mounted about 1/2" off the wall, and the Daikin temp sensor is hanging loose from the box and a couple of inches away from the wall. Now the system responds to the air temp changes much better. Because the ERV feeds fresh air directly into the Daikin air handler return duct we installed their optional remote temp sensor in the hallway. Normally the air handler senses the return air temp with an in-unit sensor and uses that temp, compared to the controller set point, to control the rate of cooling or heating. The fresh air from the ERV causes the return air temp to not be a reliable indicator of the room air temp.

Another interesting phenomenom, to me anyway, is the living room air can be at 75 or 76°, but it feels downright uncomfortably cool when I'm lying in the recliner under a ceiling fan running at low speed! I'm sure that's because the room air temp is quite uniform from floor to ceiling since the air handler is running all the time, and the supply registers are in the floor and the return grills are in the ceiling. No 85° air at the 13' peak of the ceiling in this house!!

I have the ERV connected to the Honewell thermostat so that when the outdoor air is in the 60's, or cooler, and the indoor air is above the cooling set point, the heat exchange wheel turns off. That's on the 1st stage cooling set point. The second stage set point will put the ERV into 'boost' mode, meaning it runs full speed. There's also a thermostat in the incoming air to keep from going into boost mode unless the incoming air is 70 or cooler. I have the cooling set point at 73°, 2° cooler than the Daikin set point. What this does is cools the house down to 73 using cool outdoor air, if the outdoor air is below 70. This actually is the case during much of the summer here, 95 day time, 60 night time.

My garage is ICF with Icynene on the underside of the roof. On cool nights if I crack open the overhead doors and open a window the garage will cool down nearly to the cool night air temp. If it's closed up all day with outdoor temps into the upper 90's, the temp will climb about 5 to 6° is all. I'm considering installing a thermostatically controlled ventilation fan in the garage to cool it down every night whenever possible. Talk about nice to work in during a hot day, 90 outside, 70 inside! Even having a door open it doesn't heat up real fast in there. I have a 9000 Btuh wall unit in the garage. It will cool the garage down rather nicely. The garage was over 80 at 2:30 this afternoon so I turned the air on. It's now 5:50 PM. The temp is 76 and outside it's 97.

Our May 20 to June 19 power bill shows 1838 Kwh used, but that's for everything, cooling, cooking, heated shower walls, and hot water (I take long showers!). Money wise it's more than I was hoping for, but then I was looking at heating and cooling only when I was planning this house.

Right now it's 97 outside, 75 inside, and the AC is running comfortably blowing fairly warm air from the condenser.

I hope this has been a little bit informative, and not just a bunch of dribble!

Here's another thing to keep in mind...  When using a air-to-air heatpump, AC in the spring and fall should be very cheap because the units will be operating more efficiently.  The inside to outiside temperature difference is working to your benefit... so the electric bills shouldn't be nearly as bad as your AC running in the summer.

Because of the variable speed compressor in the Daikin vs a fixed speed compressor in the typical American heat pump, the efficiency differences are probably not as great during seasonal temp swings. In cooling mode the Daikin efficiency increases on the order of 15% when outdoor temp drops from 90 to 50 w/ the indoor at 75°. In heating mode its efficiency increases about 20% when outdoor temp rises from 20 to 50° with the indoor at 70. These are from the published engineering data from Daikin and for a connected indoor unit capacity load equal to 100% of the outdoor unit capacity. They publish figures for indoor loads of 50% to 130% of the outdoor unit capacity.

Another aspect of my system I just last night became fully aware of is the thermal storage of my crawl space. Since I use the crawl space as the supply plenum the rat slab and building structure get cooled to under 70 with the system in cooling mode. What I just observed is the living space temp continues to drop in the late evening even after the controller has turned cooling mode off. Because the air handler is running constantly the house air continues to circulate through the cool crawl space and continues to drop in temp. Right now at 11:15 PM it's 70° outside, the controller is set at 75°, AC has turned off, and the house temp in the hallway is 73°.

dmaceld,

These websites might be of interest:

www.ourcoolhouse.com and http://www.welserver.com/index.htm

They have a nice webpage that shows some of their greenbuilding thoughts, and are all about energy monitoring.

cheers.

dmaceld,
I noticed in your last post you mentioned using your crawl space as a supply plenum.
Tell me a little more about that and how that works for you.

Will do in a few days when I get back from making a motorcycle trip on some North Idaho roads.

It's working great so far. Haven't been through a winter season yet so don't know yet if it'll work as planned, although it should.

Because the ICF walls go from footing to roof the perimeter is sealed, naturally! I put 2" foil covered rigid insulation on the top and sides of the perimeter footing. The entire crawl is covered with poly with the poly draped over all the interior footings. I then put 3/4" blue board over the entire crawl and covered it with about 2" of concrete. So far, in A/C mode, there has undoubtedly been very little heat exchange with the earth below as the crawl space temp varies from about 64° to 74°. I believe the slab is acting as a cool thermal storage as the house temp continues to drop after the A/C unit has shut off.

I used the Daikin 36,000 Btuh duct mounted ceiling unit in the crawl. I have three short runs of ducts, about 6' to 15' long, to direct the air flow toward the thee ends of 'T' of the living room & bedroom floor plan. Floor registers are located around the perimeter the same as if it were a ducted system. The one variation is that the register must, by IRC, have an 'ash pan' hanging under it. This is to catch dust, cigarette butts, who knows what all, and keep them from spreading around the crawl space. I think it's a code requirement will very little, if any, real benefit.

Along with using the crawl for the supply I'm using the attic for the return. I have return grills in the ceiling scattered around the perimeter of the house. There's one large duct from the attic down do the air handler in the crawl. The fresh air duct from the ERV feeds into the return duct.

Because of all the supply registers and return grills, and the fact the air handler fan runs continuously, there are no drafts anywhere in the house and the whole house is at a pretty uniform temperature. The one exception will most likely be that the living room and dining room will be somewhat warmer during spring and fall from solar gain. But this would occur with a ducted system also.

The only comfort issue I've identified so far is the floor temp. The floor temp is near the same temp as the air in the crawl space so during cooling mode it is uncomfortably cool to bare feet. But I believe we may be getting the benefit of radiant cooling from the floor.

Everything should work pretty much the opposite during winter heating. I'm hoping that the floor will be somewhat warm so that I will have a quasi radiant heated floor. But what little heating experience I had this past late winter and spring showed the floor didn't get much above the room temp. But that could be because I relied on my pellet stove for most of the heat back then.

One thing I concluded fairly soon after we moved in is thermostat set back isn't a great idea. The mass of the entire structure, including exterior walls, interior walls, floors, furniture, appliances, tile walls and floor, and the crawl space concrete creates a tremendous amount of thermal inertia. The house air is circulating around or past almost all of it. Coupled with a heat pump that is putting out air only a few degrees above or below the set point there was a severe time lag in raising or lowering the temperature of the entire structure. I also found out that the thermostats are sensitive to wall temperature, to the extent they weren't responding quickly to air temp changes.

Sorry if I've bored you with more info than you wanted. Ask away if there's anything more you want to know.

dmaceld,
Not boring at all. Just the opposite. Please keep us updated. I am very interested to see how the system works over the winter.

I wonder if it would be possible to reverse the flow for the a/c, using the attic as supply plenum and crawlspace as the return?  Then return to your original setup for heating purposes.  Very interesting concept.

You have a valid concern, but something occured to me. You said you are concerned about the heat from 4 workers, lights and tools, etc. When your house is done, will there be workers and tools buzzing around creating heat? I know firsthand how much heat just one of those lights can create when doing construction. I would imagine that other than maybe an occassional workout on the treadmill or random house project that heat source would go away would it not? Just a thought.