For example: There is no such thing as ["semi-conditioned space" under the roof?]

What do you call that space under the roof and above the insulated ceiling?

And does the heat loss software consider it to be the same as if it was fully exposed on the exterior?

@ICFHybrid - We haven't factored the attic space as "semi-conditioned".  The eaves are meant for ventilation, and we have a full length 80' ridge vent for venting.  I've been up into the attic a few times this year, once with my thermal gun and I can confirm that it's as chilly there as it is outside, so I doubt there are much difference there.  I too had problems treating it as R60 for 7"-8" EPS, as I know the air infiltration number is a big factor there, and that's why I had instructed the designer not to take the "effective" R-value from the engineering stamped letter but something much more modest.  If someone here wants to take a thermal gun to their ceiling and walls and measure the difference, I can do that here as well for comparison.  So far we're seeing ceiling surface temperature difference of about 4F based on weather conditions of between 10F to 30F (have to confirm that, might be higher or lower than that) between interior walls or interior ceilings and exposed ceilings.  That might be a good finger-in-the-wind type comparison as to the effective performance of the Nudura Ceiling of 1/2" gypsum + 7" EPS + 1/2" gypsum.  Not a definitive type answer, but might be a useful gauge to compare to cellulose or other types of ceiling insulation.  For myself, I'm most interested in the difference to a R40+ cellulose insulation, since cellulose is dirt cheap compared to the Nudura ceiling, and for my next project I might consider a 5" (2x2.5" sheets lapped perpendicular) and then 6-12" of cellulose overtop, in order to reduce costs.

@Rob - I forgot to ask in my last post, how does the radiant ceiling work?  Is it like the warmboard but upside down?  Also, can you share what the costs of the warmboard is, either by the sheet or on a $/sf basis?  I'm wondering what the upcharge is from forced air ducting and air handler, since if you do a radiant ceiling, I would assume potentially a chilled water ceiling would work too, which the Altherma can handle, and that would handle the cooling.  Or would it? I still would need to factor in the PEX and the install costs, as well as the HRV piping and some sort of dehumidification system, but I can do without the air handler and the majority of the ducting.  The bonus is the water temp is much lower, and that brings a (slightly) higher COP on the Altherma, and a lower outdoor ambient cut-off point on the Altherma.  Also, how did the Altherma perform this past summer?

Victor
www.ecobuilthome.ca
A 4350 sqft Net Zero Energy initiative

We are doing radiant cooling in our shop with the altherma, warmboard, and also radiant ceiling. we use a plate and strapping ceiling method but honestly, the warmboard floor seemed to do just as well which contradicts everything I've read which seemed to indicate that floor should have half the cooling output of ceiling.

The Altherma did well in cooling/dehumidification mode. We do not have our BTU/KWH metering up and running yet, so I can't verify COP, but we maintained a roughly 75 degree office with 50% RH and very reasonable electrical usage.

I think if cost effective radiant cooling is a goal, radiant ceiling would be the way to go. a souped up ceiling would be $3 to $5/sq ft in material tops and I dont think we even need to go that high. labor is low. IAQ ductwork only. My scratchings indicate we should be able to do radiant heat/cool in a suitable envelope for about twice a good quality FHA system costs. But it would reduce fan energy to something like 40 watts (UltimateAir unit) and pump energy to the altherma plus a dehumidification coil pump and maybe a radiant system pump if you can't pump primary. Do it smart and your total distribution wattage could be 200 watts or less and half of that is the pump in the altherma we can't easily replace!

Posted By BadgerBoilerMN on 10 Jan 2011 12:20 PM
The only barrier in terminology is between the misinformed and the informed. All the terms Rob has used are accepted on by ICC codes.

For example: There is no such thing as ["semi-conditioned space" under the roof?]

Much time and money can be saved by finding an experienced HVAC designer before starting a new building project.

Junk science is common in the field when salesman get involved.

Since nearly 50% of all HVAC equipment is over-sized, fretting over "bridging" is a bit over-kill for residential applications.

With the Wrightsoft "infiltration" set at "average", the whole heat load is of little value. Online heat load programs of little use to the novice or professional.

In our case the heat loss calc and infiltration that the Town imposed on us did make us over-size the units.  And in our case (and very a-typical) the thermal bridging, when calculated correctly, in combination with the air infiltration, might have eliminated the backup tankless-as-heat, and instead we could have gone with the 6kW backup option on the Altherma, which would have made a very substantial difference in the total system cost.  I guess there's an exception to every rule, and this was it.

The Wrightsoft set to average did throw it off significantly by about 25kBTU/h, but as I had mentioned earlier, we are experience much-less-than-calculated heat loss even if we were to completely remove the infiltration loss that was calculated by Wrightsoft.

Online heat loss programs might be of little use to the professional, but it did help us in the very initial stages of the type of heating system we might be able to use.  But I certainly wouldn't want to rely on it like the Bible.  Our designer has over 30 years of experience in the industry, and yet he was uncomfortable with some of the heat loss numbers that were generated in the initial stages, as it looked awfully low.  In hindsight, those numbers were closer to actual then the numbers we used and submitted to the Town.

FWIW.

Victor
www.ecobuilthome.ca
A 4350 sqft Net Zero Energy initiative

@vkykam: Interesting. I'm still curious about the "field-test" on the r-values you mention. Is that pretty much use of the thermal gun and to some extent your observations of energy usage? The engineers who worked on my place showed a lot of interest in continuing to refine their work through real-world observation once it is built and I'm wondering what kind of things might be done towards that end. Have you done any work with thermal imaging or anything that might generate some sort of full-surface record that could be analyzed?

I'm also considering the utility of installing a large network of (primarily) temperature sensors so we could put pulses of temperature or energy into the system and see what comes out the other side, so to speak.

Our local inspectors appear to be more willing to let us make an error by undersizing as long as we appear to know what we are talking about. In terms of comfort, I'm sure we could always fix a problem, but having things undersized may help us follow the full range of capabilities on some of these materials and products.

@Rob - If your experience with the warmboard was that it did just as well for cooling, would you consider doing cooling without any radiant ceiling at all, i.e. warmboard throughout a 2 storey house?  Your climate and mine are very similar, same design temp and almost same HDDs, and I think we're probably as humid as Maine despite our further inland location.  The air handler in a forced air unit might, for the Lifebreath unit that we have, draws 10A for the non-ECM motor; I'll need to look up what the ECM one draws since it's not on their web site for some reason.  In the winter now, we're pushing greater than 75% of the time for the air handler, so that's a potential 650kWh we can scavenge @ 10A draw for the blower.  Would you be able to tell me what the current Warmboard costs are per sheet?  I don't know how much cooling we might need for our next project, but for the current one the heat gain calc shows just over 2 tons, and maybe less since the solar panels will deflect some of the heat away from the attic, and I'd be looking to replicate the same for the next project.  The relatively low cooling load, I'm wondering, if it'll allow me to just use the warmboard for cooling, to try to keep the costs as close to forced air as possible (but still a major upcharge).

@ICFHybrid - We didn't do the engineering on the Nudura ceiling; the field test was done by Nudura 8 or 9 years ago, maybe longer.  We haven't done any thermal imaging yet, and I'm seriously considering it, since I'm curious how the heat loss is from the outside for my section where there's both ICF and SIP.  I'm only suggesting the thermal gun on the ceiling as a finger-in-the-wind type gauge, the thought being that there would be lower temperature difference between ceiling and wall comparing a 7" Nudura EPS ceiling and, say, 15" of cellulose.  It's something that can be done easily and cheaply.

well, my "experience" so far is anecdotal. I will a lot better when I have my BTU metering hooked up so I can verify actual performance. Everything I've read indicates this should not be the case. However, there are some differences between our warmboard and our ceiling that I need to tease out for impact. For example, our ceiling is 16" o.c., alternating light plates with graphite plates, and has significant non-coverage areas while our warmboard is continuous coverage, no blocking features, with wood on top.

My still young understanding of the features indicates that with a wood floor I should not expect much output. So one big X factor here is, what is our real load? I have a calculated load, but it's not verified yet. Next summer I expect to nail down the questions with real observation.

Warmboard itself is usually $6 to $8/sq ft but it does replace the subfloor. with a tile floor I would be comfortable with it for 10 to 12 BTU/sq ft load and with wood floor I'm not really sure. maybe 8 or so. But the whole thing is complicated by the fact that direct solar gain on the floor can raise its ability to cool (purportedly) dramatically, like over 20 BTU/sqft at that time. So..... that might be part of the issue in our office as well. In the end I suspect I may have to have a "gain room" max load vs a "shaded" max load for floors....

Fun stuff.

Well, it's been about 3 and half years after I first asked about air to water heat pumps. Now I'm back on the project that I was first asking about. What are the choices now? Has anythng improved in this this market?