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joe.ami
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| 05 Feb 2011 10:10 PM |
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Posted By Como on 05 Feb 2011 09:09 PM
I guess I am surprised, 35 btu sq ft for somewhere pretty cold sounds low for a building with that little insulation.
15 btu with insulation sounds like a lot of work, windows, doors as well as walls and roof? I have to confess I am clueless as to a btu/sq' number for my area as I rely on a load calculation not rule of thumb. J |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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honeychurch
New Member
Posts:18
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| 05 Feb 2011 10:21 PM |
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All I know is the numbers we were quoted in the energy audit. Specifically, the plan is to seal the attic and blow in cellulose to R-50; seal the basement joists with foam; and blow dense pack cellulose into the walls at R-15. Windows on the second floor are all newer vinyl replacements installed by a previous owner; originals on the first floor all have exterior storms and we just put in heavy duty storm doors on the exterior doors which has helped a lot. Is this not enough to get us to the projected 61.4?
I spoke with #3 on Friday and he really explained everything well as far as the pros and cons of 1 system vs 2; he also said we would indeed need a water heater and said 80 gallons sounded right for our family. |
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docjenser
Veteran Member
Posts:1400
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| 05 Feb 2011 10:44 PM |
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Posted By Como on 05 Feb 2011 09:09 PM
I guess I am surprised, 35 btu sq ft for somewhere pretty cold sounds low for a building with that little insulation.
15 btu with insulation sounds like a lot of work, windows, doors as well as walls and roof?
I had the same thought. 64 KBTU/H is a low heatloss for an upgraded old house. Unless they gut everything and spray everything, an old house will always be leakier than a new one.
I would be skeptical of such a "projected" heatloss. May be you can find a compromise and upgrade to 6 tons single unit, should only be marginally more expensive than 5 tons. Tough to judge over the internet. I realized that this does not make things easier. I agree that I would prefer to design a system with one unit and zoning ductwork to save the expenses of 2 units. |
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| www.buffalogeothermalheating.com |
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honeychurch
New Member
Posts:18
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| 05 Feb 2011 11:08 PM |
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I had been informed that the largest residential unit was 5 tons--is that incorrect?
Obviously this would all be easier if I got the insulation done, had another test done and found out what the new heatloss was BEFORE I put in the geothermal system. But all the insulation contractors felt it was best for the geo system/ducting/returns/etc in the attic to be done first, so the new insulation would not be compromised or ruined.
So yes, I could get a new system good for 61.4, but end up with a house at 81.4, and have it be inadequate--or do the insulation, put in the proper system, and then have the insulation fixed/redone? |
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Como
Basic Member
Posts:128
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| 05 Feb 2011 11:10 PM |
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I assume we are talking about Manual J calculations. I get worried when I see these levels of accuracy, much better than rule of thumb but come on.
There are just so many variables that can not be taken into account. Even if you had the most controlled situation, new build manufactured, no two houses are likely to have the same sit eor use dynamics.
Now try and apply modelling to an old building where the precise construction is unknown.
I also have an older building, brick 1897. I have had all sorts of heat loss calcs done, there is a variance of about 20%, which seems fair.
I am doing some re-modelling and found some gaps that neither I nor the insulation contractor knew about. I wonder what else there is.
15 btu, well as a rough guide for an older property that would be really good.
My calcs were on the basis of -20, 85f delta, we hit -40 last week, only for a few hours and nobody around here remembers it getting that cold. |
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Como
Basic Member
Posts:128
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| 05 Feb 2011 11:16 PM |
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You can not really measure a system, only way to tell is from actual experiance, is it big enough to meet your needs. |
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Como
Basic Member
Posts:128
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| 05 Feb 2011 11:16 PM |
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You can not really measure a system, only way to tell is from actual experiance, is it big enough to meet your needs. |
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docjenser
Veteran Member
Posts:1400
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| 06 Feb 2011 12:02 AM |
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I would be less worried about spikes, a 20 KW supplement heat element makes 70kbtu/h. But I also have a 1927 3800sqf tudor house, and see that the overall performance is not close to what an energy audit predicts on paper. It is just hard to get an old house tight, gaps are everywhere, and heat creeps along spaces you did not know existed. Just because they blow insulation in the wall which has R-15 rating does mean that that house wall will have R-15. 6 ton water to air heatpumps are offered by almost every manufacturer, a 6 ton WF Synergy works flawless in my house. You do not loose much on the comfort side in case it is too large. |
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| www.buffalogeothermalheating.com |
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ICFHybrid
Veteran Member
Posts:3039
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| 06 Feb 2011 01:48 AM |
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So yes, I could get a new system good for 61.4, but end up with a house at 81.4, and have it be inadequate--or do the insulation, put in the proper system, and then have the insulation fixed/redone? You could try this; 1) Get the sealing done/insulation blown in except for the areas in which they expect to mess it up during duct installation. 2) Get a blower door test, taking the opportunity to find and seal obvious leaks. 3) Once the insulation is blown in, the biggest unknown becomes the house infiltration, which you can estimate from the blower test. 4) Do the heat loss calcs to determine heating plant. 5) Install heating plant and ducts. 6) Finish off insulation project. |
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joe.ami
Veteran Member
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| 06 Feb 2011 08:25 AM |
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I am not a fan of designing contrary to the heat loss calc. You do want to make sure everyone does their own calcs and "owns" the results.
J |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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honeychurch
New Member
Posts:18
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| 06 Feb 2011 09:33 AM |
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Company #3, I just found out, also does energy audits--would it be worth having them do one as well so we are all confident in the number we are shooting for/working with? You all have me thinking that 61.4 is a pipe dream! I can also ask about the 6 ton unit (we would be getting the Synergy as well as we have hydronic radiant in the kitchen floor we want to keep).
The insulation situation is complicated. I got 4 estimates (all I could get where I live, no one else would come out). In over 3 weeks, only 2 ever got back to me at all, and we aren't very thrilled with one of those (only quoted half the job, for instance). The one company we are left with is the same one that did the original audit; they are from 80 miles away and indicated they would like to complete the job in one go, even staying overnight in a motel (at our expense, though I did not see that in the final quote--perhaps he changed his mind on that). They are the only ones willing to do the job, it appears.
I can certainly ask him if he would be willing to do everything EXCEPT the blown-in cellulose on the attic floor before the geo is installed, and then finish the attic afterwards. |
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Como
Basic Member
Posts:128
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| 06 Feb 2011 10:05 AM |
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So you would expect the installer to guarantee the that that the system would heat the building down to whatever temperature is selected as a low?
I appreciate that is not quite what you said. |
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honeychurch
New Member
Posts:18
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| 06 Feb 2011 10:17 AM |
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I'm sorry, I don't understand the last comment....I am becoming more confused by the minute!
I would just want to make sure that we have an adequate system for our home, taking into account the insulation improvements, and it appears to do that we have to make most if not all of the improvements before we install the geo to have a better idea of what size unit we actually need. We can't just rely on this 61.4 figure, which is most likely unattainable? |
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Como
Basic Member
Posts:128
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| 06 Feb 2011 10:25 AM |
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You can check your current number, 143,000.
What output is your current system, is it on full time at your lowest designed temperature, does it maintain the building at your required temperature?
From a practical point of view it might not be worth spending the extra to use the system to meet your ultimate low if they occur infrequently and are of short duration.
We have gone to -20, that is relatively unusual, -40 design would just not be affordable, so we will just suck it. If it happens again. |
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ICFHybrid
Veteran Member
Posts:3039
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| 06 Feb 2011 10:35 AM |
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I can certainly ask him if he would be willing to do everything EXCEPT the blown-in cellulose on the attic floor before the geo is installed, and then finish the attic afterwards.
You should do the energy audit, including a blower test after the majority of the insulation has been done. Do the sealing with the assistance of the blower door in place. However you want to do it, the blower door test is going to be the big variable in the heat loss calcs. They might do the test, calculate the infiltration and say "Aha! Exactly as we suspected. We should have just gone ahead and done it the way we planned." But, at least you will have the benefit of knowing that you've proceeded methodically and the unit will be sized correctly. Blower door tests also have a way of revealing major leaks that no one considered previously. |
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Paul Auerbach
New Member
Posts:88
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| 06 Feb 2011 02:03 PM |
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I'm amazed at some of the stuff I'm reading. Honey..., to heat 4000 sq foot home in most instances requires TWO systems - otherwise you may experience stratification. Many geothermal failures are a result of poor heating distribution. Further, noting the age of the home and insulation status, 5 tons is too little capacity. I could understand that heat load in new construction - with use of foam insulation. It might be a good idea to check out the local DX designer/installer.
Good luck. Done right you won't regret installing geothermal...
Paul
www.TotalGreenUS.com
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engineer
Veteran Member
Posts:2749
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| 06 Feb 2011 08:45 PM |
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I wasn't at all amazed by this thread...until now!
Two units are needed to avoid stratification? That's news to me. A single unit can handle up to 3 floors with proper zoning and duct sizing.
If the design heat loss comes down to 61.4 kBtu per the renovation plan, then a nominal 5 ton unit is right on. A 6 ton would get closer to meeting all load, but at a higher first cost, more noise and less zoning flexibility.
"Poor heating distribution" will compromise ANY HVAC system regardless of type.
Let's not get into a water / DX war.
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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docjenser
Veteran Member
Posts:1400
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| 07 Feb 2011 12:39 AM |
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Posted By engineer on 06 Feb 2011 08:45 PM
I wasn't at all amazed by this thread...until now!
Two units are needed to avoid stratification? That's news to me. A single unit can handle up to 3 floors with proper zoning and duct sizing.
If the design heat loss comes down to 61.4 kBtu per the renovation plan, then a nominal 5 ton unit is right on. A 6 ton would get closer to meeting all load, but at a higher first cost, more noise and less zoning flexibility.
"Poor heating distribution" will compromise ANY HVAC system regardless of type.
Let's not get into a water / DX war.
You are right on, if the heatloss is indeed 61.4 kBTU/H, which I questions given the other specs of the house. But again, it is just a thought based on the experience I have with older homes, without having seen the house. This is a opinion without knowing all the facts, over the internet, but that heatloss is a number we get with our BIN data for new built 4000 sqf house. I don't think you are going to get there with an old building. |
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| www.buffalogeothermalheating.com |
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joe.ami
Veteran Member
Posts:4377
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| 07 Feb 2011 07:32 AM |
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Posted By Paul Auerbach on 06 Feb 2011 02:03 PM
I'm amazed at some of the stuff I'm reading. Honey..., to heat 4000 sq foot home in most instances requires TWO systems - otherwise you may experience stratification. Many geothermal failures are a result of poor heating distribution. Further, noting the age of the home and insulation status, 5 tons is too little capacity. I could understand that heat load in new construction - with use of foam insulation. It might be a good idea to check out the local DX designer/installer.
Good luck. Done right you won't regret installing geothermal...
Paul
www.TotalGreenUS.com
Paul, What? Must have 2 systems for 4000 SQ' to avoid stratification (in most instances)? No. Good duct design matters. Are you also suggesting a "DX" guy will understand the project better? As always, I'll suggest that references trump brand or type. Guys: location is listed as central PA, not mid MI or upstate NY. I think heat load could be a little lower than we expect. Further a 5 ton for a 60mbh heating load is heavy with a little aux use, you are easily going to heat 1/2 again as much. The main thing is to see the installers man j calcs (not insulator's). They are the ones that will be responsible for the results. j |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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docjenser
Veteran Member
Posts:1400
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| 07 Feb 2011 11:15 AM |
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Posted By joe.ami on 07 Feb 2011 07:32 AM
Guys: location is listed as central PA, not mid MI or upstate NY. I think heat load could be a little lower than we expect. Further a 5 ton for a 60mbh heating load is heavy with a little aux use, you are easily going to heat 1/2 again as much.
The main thing is to see the installers man j calcs (not insulator's). They are the ones that will be responsible for the results.
j
Again, I question the load calc (or projection), Western NY actually has milder climate then central PA, since we have the lakes around. BIN data does not show big spikes. I agree, get the load calcs from the installers, and ask them to give you a guarantee. Like I said, 15 BTU/sqf is a good value for a new built, I question wether you can achieve this. |
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| www.buffalogeothermalheating.com |
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