Posted By geodean on 23 May 2012 08:00 AM

Posted By Boontucky-girl on 22 May 2012 11:56 PM


They also have the electric rate for heating with the GSHP at the correct rate, but the ASHP rate is twice as much. That doesn't make sense to me, since the electric rate is the same regardless of what system I use.

sounds like they are skewing the numbers in favor of geo.

In my AO one company offers electric heating discount for geo, but not all ASHPs qualify.

Posted By joe.ami on 23 May 2012 09:13 AM

Posted By geodean on 23 May 2012 08:00 AM

Posted By Boontucky-girl on 22 May 2012 11:56 PM


They also have the electric rate for heating with the GSHP at the correct rate, but the ASHP rate is twice as much. That doesn't make sense to me, since the electric rate is the same regardless of what system I use.

sounds like they are skewing the numbers in favor of geo.

In my AO one company offers electric heating discount for geo, but not all ASHPs qualify.

"since the electric rate is the same regardless of what system I use."   This is what   I was basing my comments on .

Thanks Geodean. That is my concern. The rate used was 4 cents on the geo, and 8 cents on the ashp. I'll see if I can decipher what they estimate for annual KWH of the ASHP and do the math. If that is true that they are skewing numbers one way vs. the other, it make it harder to trust what they say.

Mike,

Yes, I knew to run both methods are about the same, but the installation costs of one vs. the other was very different. those weren't the only things. I'm not an expert but even I know some things make a difference, like loop spacing, heat loads, flow rates, floor sensors, etc.

Oh, I see what you mean by thermal mass floor. I don't have double bottom plates, and not sure I want gypcrete in the main floor. Not sure either if my floor would hold the weight of lightweight concrete either, specially with tile. i'd love to have stone, but my joists are just slightly above L/480 for the areas where tile is planned. Not to mention that if we do go with granite counter tops, specially on the island, I'd be concerned about deflection and tile cracking with adding concrete weight. I should probably check the load added by extra 3/4" of plywood sleepers all over if we get the radiant upstairs installed.

The quote we got was to install geothermal with a bosh unit, and the cost comparison to the ASHP only says ASHP SEER 16, no model number, brand, or anything... so I can't even google it.
So when it says winter peak electrical demand, that means the geo will pull so many KWH at the peak demand times vs. so many KWH for the ASHP?

Posted By Boontucky-girl on 23 May 2012 06:40 PM
Thanks Geodean. That is my concern. The rate used was 4 cents on the geo, and 8 cents on the ashp. I'll see if I can decipher what they estimate for annual KWH of the ASHP and do the math. If that is true that they are skewing numbers one way vs. the other, it make it harder to trust what they say.

Mike,

Yes, I knew to run both methods are about the same, but the installation costs of one vs. the other was very different. those weren't the only things. I'm not an expert but even I know some things make a difference, like loop spacing, heat loads, flow rates, floor sensors, etc.

Oh, I see what you mean by thermal mass floor. I don't have double bottom plates, and not sure I want gypcrete in the main floor. Not sure either if my floor would hold the weight of lightweight concrete either, specially with tile. i'd love to have stone, but my joists are just slightly above L/480 for the areas where tile is planned. Not to mention that if we do go with granite counter tops, specially on the island, I'd be concerned about deflection and tile cracking with adding concrete weight. I should probably check the load added by extra 3/4" of plywood sleepers all over if we get the radiant upstairs installed.

The quote we got was to install geothermal with a bosh unit, and the cost comparison to the ASHP only says ASHP SEER 16, no model number, brand, or anything... so I can't even google it.
So when it says winter peak electrical demand, that means the geo will pull so many KWH at the peak demand times vs. so many KWH for the ASHP?

It does make ASHP hard to install when they skew the pricing like that. I would call them and ask what the requirements are.

Regardless of what heating system is installed, a closer tube spacing will result in a lower water temp and a better economy. The difference in cost might be 30-35% to go from an 8" spacing to a 5" spacing but the floor will have a more even temp. The problem is that most of the plywood/aluminum plate systems are fixed at 8" or maybe 6" spacing so you take what you can get.

Gypsum cement is supposed to fall within the code requirements without beefing up the joists but each home is different and needs to be looked at individually. IIRC gypcrete is about 14lb/ft2 @1.5".

The bosch is a relabeled Florida Heat Pump and although I have no personal experience with them I am told they are a reasonable unit. 

Joe - my electric co-op offers the seasonal rates for anything HVAC, I could even go with regular electric baseboard heat and outdoor A/C and get the rates. Currently there are no restrictions on one equipment vs. another type. They do limit it only to HVAC equipment. The rebates for installing equipment are slightly better for geo, but not much.

Mike - I'm not too stuck on any particular brand right now, and I haven't seen much for reviews where the complaints are because of a particular equipment. Most of them seem to be about the install/installer. I'm trying to find the right contractor who has good reputation, quality, and service and then consider the brand of equipment they use. But at the same time I do want the right equipment for our needs, which was part of my original question.

The dry sandwich I want for the main floor could be done to whatever spacing. I think for the most part 8" is typical so you don't waste too much plywood when cutting the strips. Closer spacing does mean higher cost in labor, plus additional pipe and I would think that affects loop design.

I have the load rating tables for my joists, so I can look up the load rating for the unsupported spans where tile will go, and add the weight of different assemblies. I'm sure it's on the to-do list somewhere.

Thanks.

Forgot to comment that I do plan to call the HVAC contractor and ask questions about the loads they gave me. The rate difference is one of them. Good point on what different electric companies may allow, since this particular company is probably used to dealing with the neighboring utility company, since that is probably their primary market. They could have different rates based on equipment, compared to mine.

Thanks.

If available in your area, consider shopping for electric suppliers.

Consolidating for a cleaner response about any rate data:

Supplier choices are all going to be deregulated by 2015, already in nearly 10 states, residentially; and 16 and DC now for commercial.  www.chooseutility.com  for example, one group handles 8 or so electric suppliers and in OH to NY to CA, etc. IGS gas and Dominion gas SELL ELECTRICITY , and their territories are on the net .

Still it can be seen today, among claims of an all electric "same rate", - there still are some communities receiving 'penalties' for the required supplemental heating spikes in kwh/ even if just a few hours of spiking with straight electric strip "KW-heaters-back-up". Customers still can be found under 12 cent rates averaging compared to HtP+ Electric supplements averaging over [then] $.14 .
[for some ] -that may drop a '2.5 COP' annual utilization averaging to much closer to 2.2 COPerformance in some -5F below zero in - - - 'gotta have a 68-70-deg home' consideration of then what I simplify as $COP's to $COP's out o' pocket(s).

Which gt?
originally asked-  ? 
You may also find yourself just asking about some more 30 year old proven heat-reclaiming HW heating WHILE in cooling modes for your hot water production. A method of adding a Water:Water GT in with a W:Air has been done - but ask  like, 2 units or 1, and while in cooling, and How many $$ ?
What percentage is reclaimed annually? is a great question/ with what maintenance- SAVINGS that can reasonably be calculated can lead to that  higher gross dollar ROI and 6:1 to 15:1 value added to a home (if real valued equity allows) for each dollar saved in a year  , I have reason to believe.

Other Solar sites put it at 20:1

"That is to say, if a solar system can reduce the electric bill by $1,000 per year, the home is worth about $20,000 more in increased appraisable value. The rational is that if the $1,000 is not spent on electricity, it is available to be spent on a larger mortgage payment [about] ...Risk vs. Reward."

I am not too far from you, in north east Iowa. Here we have a few different power companies, and most offer geo intentives far greater then ASHP incentives or gas furnaces. Some offer reduced rates as well. My power company supplying our new home to build has options that actually make geo cheaper to by then a typical 16 SEER ASHP when combined with the feds credit. Make sure to check into other rebates and discounts your power company offers. Ours has a "new home" package that has several tiers. If you build a home that is 5% better then ES for example, you get 5k in rebates plus a geo rebate which is based on a forumla. With our sized 2 ton system, it would be about 3800 rebate on the geo. This brings the price below a furnace or ASHP quotes including the 30% credit. loads for our 3k sqft house (half below grade) is just over 2 tons total, so we will go with a 2 ton system (vertical closed wells) and 7 kw strip backup.

Where I am I get one choice for electric company. The coop offers $350/ton on geo, and $150/ton on ASHP + $250 for the unit. So the geo is a little better on the coop incentive, but it's still higher in install cost vs. an ASHP. It would be nice to have $3800 on rebates from the local utility. I can get an additional $500 if I have the house professionaly hers rated and is above min. energy star requirements. But not sure how much the hers rating costs around here. So really on the incentinves I don't get much more to push geo vs ASHP when counting the tax credit.

Thanks

I finally found one HVAC contr. that does do full manual J! I got quoted a 4 ton unit for my 3800 sq ft house, but contractor did say he doesn't do the full loads unless he gets the job, which i totally understand. I doubt dropping down to a 3 ton unit will be that much savings up front, and not sure how much of a difference in operating costs it is to go from a 4 ton to 3 ton to justify the higher insulation expense (if the loads were to come out that 3 ton was big enough).

I have a question, does adding an extra loop to a geo unit mean it's better? For example a 4 ton unit with 5 loops? 3 ton unit with 4 loops? I have one hvac contractor insisting that it's good insurance and better. True or false?

Another one said (without any heat loads, mind you) that there's no way anything less than a 4 ton would be adequate for my house because of the amount of air that needs to be pushed to the extreme ends of the house (mech room is in the middle). Does that make sense? And that he balances the unit to 0 degrees. What does that mean?

Thanks.

The difference in operating cost is nothing compared to the difference in upfront cost. If the 3 ton is slightly undersized at the heating design temp it means the operating cost would be slightly higher if resistance electricity is used to make up the difference, but that's usually a small adder to the operating cost (especially in cheap-electricity land.)

In my neck of the woods GSHP runs about $8-9000/ton. Dropping from 4 to 3 tons of GSHP would likely yield substantial savings, saving that would take DECADES of auxilliary power use on a slightly undersized system to make up. But clearly YMMV.

At 4 tons for a 3800' house it feels like a "1000'/ton" sizing rule of thumb for cooling, which is usually about right for newer-better construction. But with R60+ attics and way-better-than-code windows even that can rule of thumb can yield substantial oversizing.

Paying for the Manual-J up front will usually save more than any fee charged for that service just in well-drilling & loop sizing if it shrinks the design by a half ton or more from a WAG or rule-of-thumb approach to sizing.

It is uttter nonsense, complete balderdash, that an extra ton of capacity is needed for the sole purpose of pushing air to ends of the house. If needed, a 2 ton system can push every bit of its airflow to a room 100' away if the Manual J calls for it. That's not ideal, but it is doable. It simply takes a bit of attention to duct design, test and balance.

I hesitate to mention this, but some brands allow 3 ton systems to be ordered with a more powerful blower, the same blower standard with 4 tons and up. The reason I hesitate is that option is yet another crutch for poor duct design. The only time that option is acceptable is when existing ducts or building assemblies housing ducts do not allow the ducts to be properly sized.

I concur with Dana. The best ton of the capacity is the one not needed, bought, installed or operated for the life of the building. An investment in insulation or upgraded windows that staves off an extra ton of geo pays off up front and down the road.

If possible, pay for the Man J calc up front with the understanding that the payment will be credited toward the system if purchased. You want a room-by-room Man J, not just a block load. The room by room result will drive duct design. Once the Man J is done, (assuming it is computerized) substitutions can be quickly made to guage the effect of various insulation options.

I've gotten 3 bids for geo, 4 ton Hydron modules between 22K and 24K before credits. These are combo units that would do forced air upstairs and replace electric boiler for radiant in the basement. I asked one what would it be to go to 3 ton if heat loads show 4 ton is oversized, and they said be $1700 less.

Hard to justify to spend an extra $6K on insulation to save $1700! Even to justify a payback of 5 yrs on extra $$ for insulation, we'd have to save $70/mo on a 3 ton compared to the 4 ton, and I doubt that would happen. I feel like we should stick to the $8K bid for an ASHP, leave the bsmt radiant on the electric boiler and save the extra $16K for geo. Very disappointed right now.

If you need to see a 5 year payback to invest in anything, note that in that time frame you can't even make a financial argument for code minimum insulation levels, let alone a ground source heat pump. Just the cost of going code-min won't usually show a positive net-present-value under 2 decades without significant (possibly unrealistic) energy price inflation &/or unrealistic discount rates.

Can you point to an investment of ANY type breaks even (after taxes!) in 5 years? That's about a 15% annualized after-tax return!

Got junk-bonds? No, those are only paying in the 7-8% range (and that in pre-tax dollars)... lessee... hmmm...

How's about mortgage-default-swap derivatives?

The lifecycle of insulation is long at least 4-5x longer than a GSHP, but if you insist on short-term (or fully up-front) payback none of it makes sense. To make rational decisions you need to do the full financial analyses and compare lifecycle costs. If you don't plan to hang around in this place for another couple of decades the numbers probably not going to work for you unless you anticipate very high energy-cost inflation in your local market. At some point the cost of energy saved by insulation becomes more expensive than the lifecycle cost of photovoltatics & air-source heat pumps (even at today's prices & efficiencies, let alone what the PV cost & heat pump efficiencies may be in 25 years, well within the lifecycle of insulation), which is a growing criticism of the PassiveHouse approach.

Even the smallest bare-bones GSHP system has a minimum cost independent of tonnage, (be it $8K or $20K): Any system has to be designed, plumbed, wired, & drilled/dug, and some of those cost barely change with system size. In my neighborhood I suspect drilling is the lion's share of cost, and drilling through granite comes at a substantial per-ton premium. But clearly YMMV.

Even though your total system costs for GSHP are much lower than mine (by a third) for equivalent systems, your power costs are also less than half mine, so from a strictly financial point of view you're right, the lower cost ASHP system is likely to have a lower total lifecycle cost than a GSHP system (even after the GSHP subsidy). Even though the ASHP may use 50% more power, if power is cheap it never catches up. In a 5 year time frame that would ABSOLUTELY be the case.

With insulation and high-performance windows you're paying as much for comfort as you are for energy use. When it's 0F outside the difference between a code-min wall and an R20+ (whole-wall) is something you can easily feel, since the temp of the interior wall is significantly higher on the high-R wall, making for a higher average radiant temperature. It's harder to tell the difference between R20 & R40 walls, but still possible. The comfort difference between U0.30 windows and U0.20 windows is even more striking (but so is the price, eh? ;-) )

Hi Dana1 - yes, you are right in up front/short term payback is hard to rationally compare the payback. But even at 10 yrs, still hard to say let's spend $6K more to save $1700 up front. I do believe that comfort is worth it, but when the budget gets slashed in half because the house didn't appraise as expected, it's very tough. And I'm talking just numbers. I just feel like I keep hitting my head on a brick wall and very frustrated.

Yes, .3 windows were definitely more expensive... but when we installed them we really believed the house would appraise high enough to justify it and cover the expense of them. Appraisal was horrible. Will cost more to build than we can sell for. So to finish the house with the higher insulation, all radiant heat, and decent flooring/trim we couldn't even turn around and sell it. Can't even get a loan to pay for what it will cost to finish. So in my case I don't really have much to help me push insulation costs since that goes behind the wall and avg. homebuyer wouldn't care. They'd care about utility bills but with GSHP and cheap rates higher insulation won't make that much of a difference on that. Not that I'm planning on selling. We wanted to build our dream home and stay here till we retire. But not sure how to get higher insulation fit in the budget when we have the not dream budget.

But not sure how to get higher insulation fit in the budget when we have the not dream budget.

Less house.

While building a home you only get one shot at the energy details. Other amenities can be added later. We built in 2007 and faced budget issues. We chose to give up a metal roof and hardwood floors (figured we could have them later) in order to keep sprayfoam, good windows, and geo.

Less house is a fair point. We are students of the "not so big house" way of thinking - no formal dining room, minimize bedroom sizes, reasonable ceiling heights.

Why not upgrade insulation and go ASHP?

Posted By joe.ami on 08 Sep 2012 06:29 AM
Why not upgrade insulation and go ASHP?

Into kicking over hornet's nests, are we?

In the land of cheap electricity, that's probably a reasonable thing to do in the face of the declining home valuation. The marginal upfront cost (even subsidized), for the GSHP system may have less of a financial rationale than the ASHP + electric boiler solution if you're paying 7 cents/kwh rather than 20 cents/kwh. The lifecycle of the insulation is 5x that of a heating system, and the performance difference between ASHP &  GSHP may never "pay off" over the life of the equipment if electricity stays cheap. 

Insulation is boring and lo-tech, highest-efficiency heating equipment is more exciting, but none of it changes the resale value of the house very much (not that you're selling). Insulation & better-class windows buy more comfort than higher efficiency heating systems do, at equivalent power use & interior temperatures.

In the unlikely event that electricity prices somehow triple during your tenure, making running the radiant floor in the basement with the electric boiler prohibitive, you can always do the math on heating that zone with a mini-split which would cut the power use on that zone by well over half, but giving up the cozy toes barefoot cush factor when it's below 0F outside.