I'm currently bidding out a project on a 4000 sq ft 2 story house with a basement and full attic. This is a complete rebuilding of the heating, cooling and hot water. The house currently uses a 15 year old oil boiler to heat the house with steam. There is no central air conditioning and since I am a new owner I would like to invest in a complete rebuilding of the heating, cooling and hot water as I renovate the bathrooms and kitchen. I expect to be able to run the ductwork to the 2nd floor directly thru the ceiling from the attic above and the ductwork to the 1st floor thru the floor from the basement below (but we shall see). Having spoken to local contractors on the phone (they will see the house shortly) there were a couple of points that stuck out in my mind and wanted to see whether it agrees with conventional wisdom: 1-Do I go with a split geothermal system or 2 complete systems (one for the 1st floor and another for the 2nd floor)? Also, what would the cost difference be (expressed as a percent is ok given the fact that I don't have a manual j calculation yet)? I would imagine that a split system with the main components in the basement and an air handler in the attic would cheaper and possibly more efficient during the hottest and coldest times, but that 2 separate systems would be neater and more efficient during the lighter loads. In this 2nd case, the system in the attic would have it's own well supply. 2-What should my budget be? I am going for the works - full ductwork, drilling, heat pumps, small auxiliary heat (town gas line accessible already), desuperheater, on demand hot water, backup generator. I was guessing $50k given the expensive nature of the surrounding area, but I've been warned to expect 50% more than that, which kind of through me off, but realized that I'm looking at more equipment than most projects since it's a complete rebuilding of the HVAC (ie, generator, potential 2nd system, on demand hot water). On a side note, I'm considering installing radiant heat in the renovated bathroom and kitchens, but since that part is fairly conventional and will probably reevaluate the decision once I see the estimates, let's set that aside for the moment. I will update as I go through the process.
Hi and welcome, First of all did you know you can do radiant in flor with geo? Secondly the choice between 1 system zoned and 2 seperate systems to me is a no brainer if the money is not crazy different. I advocate 2 seperate systems including the loop fields so that the entire house will never see a total system failure. It has redundancy to buy service people time to respond, and saves you money, think 4th of july weekend service call rates. Your biggest concern in an old house retrofit should be your base line data at this point. At my web site in the geothermal cafe you can read an article I wrote about my personal house entitled "when bad things happen to good houses". Eric
Two systems I agree with Eric with respect to the two seperate systems. With respect to the loop field, why not run both systems on one loop with variable speed circulator pump? I would think the loop temperature would fluctuate less with one large loop to serve the two systems. But as Eric points out, a circululator pump failure could put both systems out of commision. Let me know if you would like one more contractor quotation. I run a drilling company on Long Island and I have a good HVAC partner that I work with.
Split system is simply a seperate compressor and air handler unit (vs a package unit). Generally costs are similar though more labor is required to install the split.If you are going to have a unit in the attic, splits keep the compressor noise in the basement.If possible I am more inclined to go with one unit and duct all from the basement. Usually this will cost less to install and less to maintain.When I have multiple systems, I prefer to share the loop field.It is funny, I have never had a customer worry about a back-up heating system for an oil boiler, but even though a geo has 2 different ways to heat your home (primary and auxiliary) folks ask about a back-up.j
I prefer 2 packaged W/A (water to air) systems tied into a single loopfeild for most 2 story retrofits. It ends up being a clean and robust installation. However if there is a good way to run your ductwork up to the attic, you should be able to save some $ on install costs. If anything is going into the attic, (W/A unit, a split systems airhandler,or ductwork). I would take a serious look at insulating the roof with foam. A 3rd option might be a single W/W (water to water) unit that feeds airhandlers and radiant zones.
Welcome! You mention that the current heating and cooling system is 15 year old. Is that the age of the house as well or is the house much older than that? The reason that I ask is in the Greater NYC area the greater the insulation values in the wall the smaller the required geothermal units are. If the house is more than 30 years old, you might want to explore the possibility of adding insulation in easy to get to areas of the house including the attic. That will help cut down on the size of the unit required for the second floor and lower installation costs. To answer you questions: 1. On Long Island, I have installed some systems that use two separate systems for the house and others that use one system. Here are the factors that I consider when determing if one or two units should be installed. What is the load of the space? If the load is greater than 5 or 6 tons, 2 units are typically required for efficiency purposed. What is the intended usage of the space? Depending on the usage of the space, one unit may be better than two or vice versa. Is there a chase to run two ducts (typically 12x12 or larger) into the attic? You need to bring both a supply and return trunk duct into the attic. If there are two closets that line up, are you willing to give up the closet or storage space? Most of the systems that I have installed utilized 2 units for the house. In cases were the customer wanted to save money and there was an easy way to run ductwork from the basement to the attic, there was a significant savings in installing one unit and using a zoning system to allow for two different areas of comfort in the house. 2. Without knowing the load of the house or your exact location, I would say that $50,000 is more likely to little for this installation. Different suburbs of NYC require different types of drilling. If the house is in Westchester, the driller needs to case down to the rock (added cost). If the house is on Long Island, the driller needs to use mud rotary drilling rig. If your on the North Shore of Long Island expect for the driller to hit some cobbles going down, on the south shore expect easier drilling through sand. The drilling costs can vary 10% depending on geology. Of course this is assuming that you are going with a closed loop system (which I highly recommend). As others have mentioned, there are many different ways to design the same system. Having a separate loop field for each unit or separate pumps can help eliminate complete failure of the geothermal systems. If you can report back with what the loads on the first and second floors are, I will be better able to assist you. On a side note, if you are thinking of doing a small area of the house with radiant it might change the recommendation on the equipment. Depending on the area desired for the radiant heating a water to water setup or a triple function unit might be desired. If you can provide us more information on the amount of radiant desired, we can better guide you. Zach
Since you seem to need a larger amount of hot water for hydronic purposes anyway, getting a single water-water hp with a buffer tank feeding the radiant floors and also supplying two air handlers (one for upstairs, one for downstairs) with either hot or chilled water seems to be the logical choice. A 2 pump flowcenter would provide a certain amount of redundancy in case one pump fails. Now you can also have the domestic hot water generated on demand via the w-w heatpump.
Ok, so from what I can tell of the feedback, while 2 separate systems are a little pricier and there are clearly some good alternatives depending on the situation, it sounds like there's some consensus that it's not a bad idea and in some cases may be the simplest. So let's dig down a little deeper. 1-Let's talk about hot water. I have a couple of assumptions. Let start with assumption #1, that I go with a desuperheater and an a tankless hot water heater. Assumption #2 is that the during the summer there's plenty of hot water in the desuperheater and that during the winter there's a little less due to the way it generates hot water, correct? What about spring and fall when the system isn't doing much heating or cooling. Does the desuperheater work well with the tankless hot water all year round or is the hot water experience vary? What's the experience as far a delay for the hot water at the tap and if there is one is a circulator the only way to deal with it? What about a hybrid tankless hot water generator or is that overkill? 2-Let's delve into radiant heat. Would it make sense to use a small gas boiler (the house has a gas line already) to drive the auxillary heat and the radiant heat? It sounds like adding hydronic heat above a certain size would require an additional separate GSHP. Since the radiant is a luxury and could really be used to keep the chill off and I would probably like auxiliary heat anyway would this be an effecient and cost effective way to go vs. an additional GSHP for hydronic heat? PS-the house is in Westchester. I might be interested in PM'ing for an additional quote, but am not able to yet due to by my newbie status.
Depending on the part of Westchester your house is the well driller will most likely need to case down to the rock and drill from there. The few projects that I have experience with in that area have had the rock layer within 50 feet of the surface. The well driller should have a better idea of where the rock is and what is involved in respect to casing the hole so they can drill. To answer your questions: 1. The desuperheater captures heat from the compressor and instead of rejecting it back into the ground loop uses a secondary heat exchanger and pump to transfer the heat into a storage tank. During the summer the desuperheater will produce more hot water than during the winter months. The desuperheater is only active when the unit is running in either heating or cooling modes so during the shoulder months only a small percentage (if any) of your hot water needs will be handled by the desuperheater. The tankless hot water heater will boost the temperature of the water to the desired temperature. You should have no noticeable difference in temperature at the faucets throughout the year. The only way to avoid a delay in the delivery of the hot water at the faucets is to add a recirculation pump to the hot water loop. 2. The auxiliary heating and radiant can be handled off of the boiler, although it typically has a greater first cost than installing electric resistance heaters in the units. If we are only talking about heating a few bathrooms with radiant, a triple function unit might be best for you. If you want to heat the whole house with radiant one larger water to water unit and chilled water air handlers is the better way to go. What percentage of the house do you want to heat via radiant and where is it located? Are you planning on installing a generator? If so, you can reduce the size of the generator by putting in a boiler and only powering the fans of the geothermal unit and the boiler. The downfall to this solution is you will not have air conditioning while on generator power. The next step would be for you to have a load analysis (Manual J) ran on the house so we know the heating and cooling loads that we are dealing with. Zach
If you have NATURAL Gas, and pricey NYC area electricity, then the economics of geo vs NG as a primary heat source need a long and careful look. Gas tariffs (cost per unit heat) are notoriously hard to understand and highly weighted against low volume users. In other words the cost per Btu for gas used just for cooking may be 3x the cost of gas if used for primary house heat and hot water. Consider having an independent energy auditor (someone with no vested interest in either system / fuel type) analyze and walk you through the options. If you have propane, confine its use to grilling steaks and operating a standby genny.
Curt, I agree with you. We worked together on a project were the customer decided not to go with geothermal. With natural gas prices at a 10 year low, geothermal might not be the best option for some NY homeowners. When customers do not have Natural Gas available or they believe the prices will rise significantly over the next decade geothermal still makes sense to them. NY has a high electricity cost, high cost of living and high drilling costs. Those three things make detract from the economics in installing geothermal. Zach
So Zach makes an interesting point about the economics of a geothermal system vs. gas heat. For me, it's a 'big picture' economic argument. I do believe that at some point, gas prices will go up and I am putting in ductwork for air conditioning and updating the heating regardless. I would also argue that this being a 2 level older house with a full attic and basement (and beautiful details throughout and closet space I would prefer not lose) that currently has oil based single pipe steam heat situated in the basement, a 2 system geothermal with forced air (with the attic system serving the 2nd floor and the basement system serving the 1st floor) would actually be a cleaner install than the alternatives: -replacing the oil boiler with a gas based steam boiler, putting an A/C system in the attic and one in the basement (and all the inefficiencies of steam) -replacing the steam heat with gas-based forced air and running ductwork from the basement throughout both levels with 1 (or 2) AC system(s) serving the house -and just to nip the inevitable third option - converting the steam heat to hydronic - this option would be too messy given that it is a single pipe system Does this argument hold water? PS - I will delve into ongoing economics next, but realized as I wrote this post that simplicity and ongoing maintenance of the system is an economic issue that a plays a factor in the decision
I'm not sure which argument you are referring to, but hot water vs steam does require 2 pipe config. Geo hydronic requires more radiation than higher temp HW or steam systems, however, houses built 100 years ago are often way over radiated as people would sleep with their windows open to avoid dying in their sleep (as little was known about CO and folks weren't waking up in the morning). In our area, NG still costs more to operate than geo, but pay-back horizons are distant. Without the existing tax credits I expect we wouldn't have much interest where NG is available.
Just wanted to post an update. System has been running for a few months now (though we just finished insulating a few weeks ago). Though, not without it's bumps along the way, so far so good. System has been performing up to expectations (which were not low), and I estimate that we have reduced our heating costs about 50%-70% (cooling TBD, but I expectations are high). Started the Welserver installation, but only have a few sensors running right now, though data is really useful and am working on adding more. I hope to post in testimonials when in a few months when the system is a little more broken in. Overall, I would say my takeaways are the following: -Insulation was probably the most important part of the project. Not just for the obvious reasons, but because planning the insulation installation in the walls before moving in allowed me to accomplish the one part on insulation that all my new neighbors regret not thinking of and don't want to be bothered with now. -I was concerned about putting the air handler in the attic (outside the envelope) because of larger sizing of equipment and energy waste, I believe that putting R-55 of insulation in the attic mitigated a lot of those issues. Putting the R-55 attic insulation in was the last part of the project and it made a huge difference. The 2nd floor system hardly runs now and we probably could've gotten away with a 3-ton system instead of a 4-ton system for the 2nd floor. Besides, the attic insulation covers a good percentage of the ductwork, but not the air handler. Also, with all that insulation, the 2nd floor system is whisper quiet. -This project was a good fit for the house because there was no A/C, the heating system was oil-based and old, and we were sanding the floors (and thus patching holes was not a big issue) and painting the walls (although patching the holes left by injected insulation was more costly than expected). Had any of these factors not existed, I think it would have added to the project cost which would have affected the economics, complicating the payback. In the end, I was able to take a 90 year old inefficient house that used thousands of gallons of oil every year and make it comfortable for the future. Thanks everyone on the forum for your help in making this happen.
Glad things are going well. Atta boys are always a plus. Thanks for the update, lots of posters here get lost in their project and never up date their progress. It is a good thing I was MIA in 2/2012 or you would have gotten my water to water goe heat pump rant and a big bunch on how the steam system and HV a/c could do the job. warm regards, Mark
