Dana 1

There is a moderate to large amount of glass in my plan, as well as a fair sized tower (4th floor) that will be conditioned. I live in Texas, so we do get a lot of solar gain.

They did break the numbers down room by room. I'm not sure what software they use, but they have the Winter temp listed as 22F and the Summer temp at 102F.

They also give a "guarantee" on your average monthly heating/cooling bill. Using my pond for a geothermal HVAC system, the average monthly cost should be $113 (or less) to heat/cool the 8000sqft.

I agree that the 1000sqft/ton might be a fair guess for your average ICF house. I rounded up because want the option to divert some air to my 1200sqft storm shelter (not mentioned in my building plans).

Storm Shelter

Thomas

They also give a "guarantee" on your average monthly heating/cooling bill.

How long does that run for?

The guarantee is for 2 years. They pay any cost over their estimated average, but there are some conditions (they have recommendations and minimum standards in the building process, and you need a separate electric meter for your HVAC equipment). The guarantee is not something I was really interested in, but I think it does show they have some faith in their numbers.

Posted By nd96 on 24 Aug 2012 02:19 AM
Dana 1

There is a moderate to large amount of glass in my plan, as well as a fair sized tower (4th floor) that will be conditioned. I live in Texas, so we do get a lot of solar gain.

They did break the numbers down room by room. I'm not sure what software they use, but they have the Winter temp listed as 22F and the Summer temp at 102F.

They also give a "guarantee" on your average monthly heating/cooling bill. Using my pond for a geothermal HVAC system, the average monthly cost should be $113 (or less) to heat/cool the 8000sqft.

I agree that the 1000sqft/ton might be a fair guess for your average ICF house. I rounded up because want the option to divert some air to my 1200sqft storm shelter (not mentioned in my building plans).

Storm Shelter

Thomas

Like you, I believe my calcs will show 1.5 or 2 tons per floor (2 story ICF, 3200 sqft, south windows, 5000 feet elevation).

but I think it does show they have some faith in their numbers.

Hmmmm. Could it be a sales and marketing tool? Let's say it's a disaster and you actually use DOUBLE that amount. They are on the hook for a maximum of what, 24 months X $113 = $2700? They've probably bought what in effect is an insurance policy for a fraction of that amount using additional profit they built into the price you will pay. That policy bets;
a) That you can't collect because of the "conditions".
b) That you WON'T collect.
c) That the future value of that money is greater than now.

Once they pay off the two year obligation you have to live with it (and pay for it) an additional 12, 15, 18 years or more. If they really had faith in their numbers, the policy would last the life of the unit, or would require them to continue doing work until you hit the targeted performance levels.

"Hmmmm. Could it be a sales and marketing tool?"

Of course. That is the only reason they would do it.

But is slightly better than a simple "Here is our estimate and I hope it works out for you."

Posted By nd96 on 24 Aug 2012 02:19 AM
Dana 1

There is a moderate to large amount of glass in my plan, as well as a fair sized tower (4th floor) that will be conditioned. I live in Texas, so we do get a lot of solar gain.

They did break the numbers down room by room. I'm not sure what software they use, but they have the Winter temp listed as 22F and the Summer temp at 102F.

They also give a "guarantee" on your average monthly heating/cooling bill. Using my pond for a geothermal HVAC system, the average monthly cost should be $113 (or less) to heat/cool the 8000sqft.

I agree that the 1000sqft/ton might be a fair guess for your average ICF house. I rounded up because want the option to divert some air to my 1200sqft storm shelter (not mentioned in my building plans).

Storm Shelter

Thomas

Having a lot of glass will bump the peak loads.

Texas is a big place covering a range of climate/climate-extremes.  I'd need a zip code to narrow in on whether 22F/102F is a 99% number or a 99.5% number or something else.

Or pick a nearby city or two from this list and interpolate.  << Note, on the current design temp listings for Texas there are no cities with 1% design temps as high as 102F, but a few in the 100-101F range. 

It's common for HVAC vendors to add 5F to the cooling design temp and subtract 5F from the heating design temp, then round up to the next size  equipment,  which will sometimes change the equipment sizing by enough to matter.  But with ground source heat pumps every half-ton has both an up-front and operating costs to consider.  (Those costs per ton are probably much lower for you, given you have a pond to work with.) Under-sizing by 10% has an impact on cost, but very little (if any) impact on comfort, since there is usually more than 10% margin built into any of the load calculation software/method, but most contractors are loathe to try to sell that concept to the client, even when they know it to be true. If they push to under-size and it doesn't quite keep up at the 99.9% peak they may have an irate client to contend with. For them it's safer to bump it a bit, for you it's usually better to stand pat at the calculated load or slightly under-size.  (Under California Title 24 it's against code to oversize by more than 15% from the calculated number, but there are always ways to skew the number by tweaking the R & U values or infiltration rates when the contractor gets nervous about the initial result.)

Rounding up to accommodate the storm shelter probably wasn't necessary. The heating & cooling loads of an insulated buried windowless bunker are approximately zero at the subsoil temps in any TX location, unless you're parking a dozen people in there for a day or more and watching the storm rage on a humongous TV.

ND96,

that is a very cool project and one heck of a shelter! Do you have any updated pictures of how it is coming along? Calling that vault door "wind proof" may be a bit of an understatement.. haha

I'd love to see pictures of the home as well.

I have a good amount of personal experience with EnergyWise, they designed a custom program to calculate the results that they provide to their customers. They do the audits and designs for residential and commercial. I have customers that are thrilled with how accurate their energy usage estimates were. Although most do not go the extra mile to install the required equipment to take advantage of the guarantee, just the valuable info that is provided in their report is worth the fee. They can make some simple changes to the design, which can save a large amount of energy in the long run. They have a great background of experience especially with tight homes built with SIPS and ICF, which is where most HVAC guys fall short.

Of course the guarantee is a sales tool, but who can blame a company for employing creative sales and marketing. If you don't as a business owner, you do not succeed in most cases. Heck, we use one too... Quad Lock will pay for the cost of your Energy-Wise audit if you use our product.

Of course the guarantee is a sales tool, but who can blame a company for employing creative sales and marketing.

The point being that it is far more valuable for the customer to utilize some due diligence as opposed to relying on that sort of "guarantee".

Posted By Dana1 on 24 Aug 2012 02:26 PM

Posted By nd96 on 24 Aug 2012 02:19 AM
Dana 1

There is a moderate to large amount of glass in my plan, as well as a fair sized tower (4th floor) that will be conditioned. I live in Texas, so we do get a lot of solar gain.

They did break the numbers down room by room. I'm not sure what software they use, but they have the Winter temp listed as 22F and the Summer temp at 102F.

They also give a "guarantee" on your average monthly heating/cooling bill. Using my pond for a geothermal HVAC system, the average monthly cost should be $113 (or less) to heat/cool the 8000sqft.

I agree that the 1000sqft/ton might be a fair guess for your average ICF house. I rounded up because want the option to divert some air to my 1200sqft storm shelter (not mentioned in my building plans).

Storm Shelter

Thomas

Having a lot of glass will bump the peak loads.

Texas is a big place covering a range of climate/climate-extremes.  I'd need a zip code to narrow in on whether 22F/102F is a 99% number or a 99.5% number or something else.

Or pick a nearby city or two from this list and interpolate.  << Note, on the current design temp listings for Texas there are no cities with 1% design temps as high as 102F, but a few in the 100-101F range. 

It's common for HVAC vendors to add 5F to the cooling design temp and subtract 5F from the heating design temp, then round up to the next size  equipment,  which will sometimes change the equipment sizing by enough to matter.  But with ground source heat pumps every half-ton has both an up-front and operating costs to consider.  (Those costs per ton are probably much lower for you, given you have a pond to work with.) Under-sizing by 10% has an impact on cost, but very little (if any) impact on comfort, since there is usually more than 10% margin built into any of the load calculation software/method, but most contractors are loathe to try to sell that concept to the client, even when they know it to be true. If they push to under-size and it doesn't quite keep up at the 99.9% peak they may have an irate client to contend with. For them it's safer to bump it a bit, for you it's usually better to stand pat at the calculated load or slightly under-size.  (Under California Title 24 it's against code to oversize by more than 15% from the calculated number, but there are always ways to skew the number by tweaking the R & U values or infiltration rates when the contractor gets nervous about the initial result.)

Rounding up to accommodate the storm shelter probably wasn't necessary. The heating & cooling loads of an insulated buried windowless bunker are approximately zero at the subsoil temps in any TX location, unless you're parking a dozen people in there for a day or more and watching the storm rage on a humongous TV.

Dana 1
I appreciate all your thoughts. My zip is 75407 (near Dallas). I agree that I probably didn't need to change the unit size for the storm shelter. Ground temps 15 feet down here are about 68F (+/- 4 deg depending on the time of year). With the big screen TV and a few people down in the man cave, it might need just a little cooling, but it mostly needs airflow to keep the air fresh and keep humidity down.

My preference is to get 2 identical sized HVAC units. The only DIY geothermal units I found on line came in whole numbers (3 ton, 4 ton or 5 ton). So my option is to size down 1.5 ton to two 4-ton units, or size up 0.5 ton to two 5-ton units. As there is only a $300 difference between the 4 and 5 ton units I'm looking at, my current thinking is to size up. I know an undersized unit may be better to help control humidity levels, so that is a consideration.

I'm a big DIY guy and plan on playing general contractor for the new house. Next weekend I will be laying 2600ft of 2" HDPE in the pond. Let me know if anyone is interested in helping out.

BrianBaron
I haven't done too much to the storm shelter since that thread. I just finished the hatch on the ladder (outdoor) end of the structure. The other end of the storm shelter will connect to the house by a spiral staircase, so I need to wait until the house is built to finish it. I'll also finish out the inside of the storm shelter at that time. When we break ground for the house (hopefully in 2-3 months), I may start a new thread here if I have enough time.

Thomas

The Dallas FW airport data indicate 24F/98F as the 99%/1% outside design temperatures. Carswell AFB or Denton's design temps would both be 22F/99F.

So using 22F/102F doesn't appear to be significant thumb on the scale, it's at most a pinky on the cooling design temp.

But at least they weren't using 108For 110F, even though it hits those temps more often than we'd like: http://weatherspark.com/#!dashboard;q=75407 Bumping the 1% design temp 3 degrees may make sense if last summer's extreme averages becomes the norm rather than the exceptional year.

I know an undersized unit may be better to help control humidity levels, so that is a consideration.

I think that this aspect has been over emphasized. I have oversized AC and the only time humidity bothers me is when it's 78F and 90+% humidity outside. But since it doesn't run at all at that temp, no AC unit will fix that (unless it can operate as a dehumidifier).

I don't blame contractors for exceeding 1% designs - they don't want to receive several calls per year per customer about the AC not keeping up. And that's assuming that the load calculations are perfect; but they are far from it.

I don't blame contractors for exceeding 1% designs - they don't want to receive several calls per year per customer about the AC not keeping up

I do blame them. It's not a professional attitude to "force" oversizing on a client just because you don't want to get calls during hot periods. Besides, what a great marketing and customer service opportunity.

The "new" ACCA 99% & 1% design temps are different from the previously published numbers primarily due to a definition change- the numbers currently used are essentially what USED to be called the 97.5th and 2.5th percentile numbers.

By the older definitions used by the ACCA the 99% design temp for Dallas was +18F (rather than 24F) the 1% was 100F (rather than 98F).

The older ASHRAE values used +20F as the 99% number and 92F dry-bulb @ 76F wet-bulb for a 1% number, which is arguably too low for summer weather conditions of this past decade.

The contractor may have relevant data for Princeton TX and Dallas/FW indicating that would make 102F a true 1% (new definition) design temp rather than 98F or 100F. Even if the true 1% number is 98F this is in not going to make a relevant difference if the equipment is sized no more than 15% up from the calculated load on the higher number. You don't get even 5% granularity on heat pump equipment sizes, and there's greater than 5% statistical "noise" error in the calculate heat transfer efficiency of the pond/ground/well loops in most GSHP designs. For me it's only a red flag when the design temps used are 10F away from published designs and they upsize it from there.

On a big glassy house like nd96's the effect of a 4 degrees difference outside design temp on the calculated peak cooling load is far less significant than the U-factors and SGHC values and ventilation rate specified.

Posted By ICFHybrid on 27 Aug 2012 01:02 PM

I don't blame contractors for exceeding 1% designs - they don't want to receive several calls per year per customer about the AC not keeping up

I do blame them. It's not a professional attitude to "force" oversizing on a client just because you don't want to get calls during hot periods. Besides, what a great marketing and customer service opportunity.

Considering we had 40 consectutive days of 100+ temps last summer, I don't blame them for going slightly above the "textbook" number of 98/99.

The textbook is always changing- the ACCA uses the averages for the most recent 25 years for their spec- IIRC ASHRAE uses 50 years for theirs. Either way, in the face of the undeniable shift in weather of the past decade relative to the prior 5 decades, if only 10 year data were used a 1% number for Dallas or Denton could easily hit 102F or even higher.

And who knows how the trend over the past 10 years projects forward for the next 20 or the lifecycle of the equipment? Jim Hansen seems convinced this is just the beginning of a big step-function on the summer temperature averages, with even wilder excursions on the extremes.

OK, those are all good reasons. If you could present your customer with solid data showing projections of future need, you would definitely be doing a service to the client.

Should we be improving envelopes in anticipation of a substantially different future?

Posted By ICFHybrid on 27 Aug 2012 05:00 PM
OK, those are all good reasons. If you could present your customer with solid data showing projections of future need, you would definitely be doing a service to the client.

Should we be improving envelopes in anticipation of a substantially different future?

That's the $64,000 (in building envelope upgrades) question, isn't it?

That tends to be the PassivHaus take, but from a  building code point of view the 25 year net-present-value of avoided utility costs tend to dominate the discussion, with some allowance for energy price inflation (the numbers of which are always wrong, but you have to at least try), but only the most recent 25 year weather history is ever factored in, with the presumption that the next 25 year will be similar enough. The weather/climate assumptions on that basis worked for most of the 20th century, but there's reason to believe it might not for this century, but the models aren't sufficiently robust to build it into construction codes.

Critics of PassivHaus (notably some of the Building Science Corp folks) will point out that at some R/U value the avoided energy cost of the upgrades become more expensive than the lifecycle cost of photovoltaic electricity used in heat pump technology RIGHT NOW! And as the PV-power costs continue to fall and as heat pump efficiency increase, PassiveHaus levels of building performance become even less economic.  In 2010 BSC released this document of building performance recommendations to put a stake in the ground on economic rationality. They are looking at a middle-ground, fully acknowledging that local costs and builder/buyer interests will vary.   The recommendations are quite conservative from a 100 year building lifecycle cost point of view- still economic at 25 years if implemented in a lowest-cost fashion, but a bit beyond current code-min for most locations (and quite a bit for some.)  

In some cases, with optimal roof orientation for PV, houses built to those recommended R/U values could be retrofitted to Net Zero Energy levels with PV and heat pumps, especially if some care is taken to enhance the solar heat gains or rejection. But most Net Zero houses would use 25-30% higher R-values than the recommendations in Table 2, and somewhat better windows.

The vast majority of the houses that will be around in 2050 are already built, and most of that housing stock is nowhere near current code-min.  There's a great deal of work to be done on existing housing to both reduce energy use and keep them comfortable if the climate shifts more rapidly than it has to date.  Given the time scales relative to how long most US homeowner stay in the same place, getting there will take more than waiting for a market reaction to increases in energy pricing (though that is proving to be an impetus at $3.50 propane or $4 heating oil.)

Besides, what a great marketing and customer service opportunity.

Pissed off, overheated customer: This #$&^* system can't keep us cool again.
Contractor: That's intentional. Can I sell you a second system? Or a duct cleaning?
Customer: You will be hearing from my lawyer. Click.

Posted By BrianBaron on 24 Aug 2012 03:43 PM
ND96,

Quad Lock will pay for the cost of your Energy-Wise audit if you use our product.

I'll tell Darren F you said that... ;)