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!