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Hot Water Radiator Heat vs. Forced Air Heat


We are faced with a dilemna in our 75 year old house. We have hot water radiator heat system in the main house (3 floors) and it works wonderfully. We have an in-law suite in our basement where oddly enough heat was never installed even though we experience bitterly cold winters.

The original owner had the house for over 70 years and the basement remained unfinished. Newer owners only lived here for one year and made several errors when renovating throughout the home. One being not installing heat in the basement apartment, not installing insulation in the basement and opting for electric space heaters instead of getting the job done right.

We have received various suggestions for heat in the basement apartment from licensed HVAC pros we have interviewed. They are:

1) Hot water baseboard radiators. Extended from the existing gas hot water boiler (35-40 years old).

2) Add new forced air gas furnace and create duct-work for in-law suite.

Our concerns are the following:

1) Price. Some contractors have said that gas forced air heat total cost is more expensive (purchase + installation) and we are better to stick with baseboard hot water radiator system in the basement. Others have said that in the long run, gas forced air will be more effective and more cost efficient than hot water heat - plus easier and less invasive to install than baseboard radiator system (a few of the walls/baseboards are concrete).

2)Noise factor. A newer model Gibson was suggested by 1 contractor. He stated that the older models were noisy but the newer ones are very quiet. A few suggested a Frigidaire system.

3) Effectiveness or inadvertent problems with addition of radiator baseboard heat in basement possibly stressing old school radiator heat system in main house, or we need to purchase a new boiler to handle larger heating system. (A few HVAC guys said we would need a new boiler and others have said that even though it's old it's fine.)

Even with all the varying advice from HVAC pros we are left wondering: Which system would be better in the long run?

In case this info is needed: The main house has two floors which total 3,300 square feeet. Our attic which is full-sized is approximately an additional 1,200 sq ft. The in-law suite is 1,500 square feet. At this time, gas is only used for boiler and hot water heater which is going to be changed to larger unit (40 gallon presently - changed to 50 gallon). We will also be upgrading from electric range/oven to gas in the main kitchen. In-law suite oven will remain electric. We do not have air-conditioning anywhere in the house (including in-law suite)other than window units.

Thanks in advance for any advice or suggestions!

Re: Hot Water Radiator Heat vs. Forced Air Heat


I would strongly recommend that the hot water heat be extended to the basement apt.

This would be more efficient, save gas & be easier on the pocketbook---this would depend on the current output capacity of the present boiler---which would have to have enough reserve capacity to take on the extra heat load.

Under no circumstances should you buy a separate gas-fired 50 gallon hot water heater---they have what's called a 50 gallon INDIRECT HOT WATER HEATER that's used for these applications---it runs off the boiler & thus doesn't need to burn any fuel on its own---it sounds like you're not talking to the right heating contractors there---they should know this stuff if they're familiar with hot water systems.

You should be able to DO ALL THE CALCULATIONS YOURSELF on this before you call any heating contractors in to make any changes---take the total square footage of all heated apts & multiply by 40 to get a rough estimate of the HEAT LOAD of the building---thus, if you have 6000 sq.ft. total space that needs heat: 6000 X 40 = 240,000 btu/hour is the approx. amount of heat you need per hour on a cold day---and also has to be the HEAT OUTPUT of the boiler to keep the building warm---follow the links below to do a more comprehensive, accurate heat loss calculation later on.

The OUTPUT OF THE BOILER is always listed on the identity plate somewhere on the boiler---and would say something like "output: 240,000 btu/hour".

This is a lot of apt area to heat---if I read your post correctly it's 3 apts and the proposed basement, and I would recommend you put in a 50 gal indirect hot water heater to be run off the boiler instead of a separate gas hot water heater for the taps---the current system is probably quite wasteful of gas & heat in view of the age of the boiler & the fact that there is a separate hwh for the taps.

You didn't mention any ZONE system---but this type of apt arrangement is tailor-made for having zone valves or circulators which would zone off each apt, allowing a separate thermostat for each apt. so everyone could control their own heat---strongly recommended if the piping arrangement would allow the modification.

The type of arrangement you have there is very common for semi-commercial 3-unit or 4-unit apartment houses & often includes 2 separate more recent vintage boilers to handle the load for heating the apts & another zone for including the 50 gal. indirect hot water heater for the taps---if one of the boilers breaks down on a cold winter nite, you still have heat for all the apts from the other boiler by simply manually opening the zone valves to the other apts until the repair man arrives the following day---thus I would strongly recommend 2 separate high efficiency smaller boilers of approx 125,000 btu/hr each to cover everything---you will see a 30% drop in your gas bill just by installing the newer boilers due to the advances in boiler efficiency in recent decades (85% to 95% efficiency for new boilers over probably a 60% to 70% efficiency for your present older boiler).

Google "Siegenthaler multiple boilers" (without the quotes) for more info on installing 2 boilers.

Quite often, the 2 smaller boilers are run in tandem to save fuel---one boiler kicks in to heat the entire building & the indirect hot water heater on milder winter days & the 2nd kicks in on colder days when all apts are calling for heat--this saves a lot of fuel over the heating season---make sure you hire a heating contractor who is familiar with these arrangements & does installations in multi-unit apt houses.

First thing to do is do a HEAT LOSS CALCULATION of the total square footage of the total heated space in all the apts--it sounds like you have 6000 sq.ft. of heated space---Google "heat loss calculator" to get some HLC's---the size/output of the boiler has to equal the heat load of all the apts on a cold day.

Before you buy a new boiler or boilers use the old one for the time being & spend $600 on blow-in insulation for every exterior wall of the house to
R19 and insulating the attic to R40---make sure all windows have storms or are tight & double-pane---once this is done, you can order the new boilers for the following winter.

Go around to apt house owners & real estate agents who specialize in rental apts in your area & ask them to show you the boiler arrangements they have for this type of heating situation---then get the name of the installer once you find a good-looking install.

Check out the links on the sites below for good boiler brands & heat loss calculations.

There are mini-split AC's that require no ducting & are often put into apt. units--they are more expensive, but lots quieter than window units---Google "mini-split air conditioners" for more info.


Re: Hot Water Radiator Heat vs. Forced Air Heat

Thank you very much NashuaTech. We really appreciate your taking the time to explain so much and in such detail. And thanks to everyone else who commented and shared as well.

My post wasn’t too clear on some points and was wrong on others. Let me try to write a more accurate description.

This house is a single-family home with 4 levels including the basement and a finished attic. Each level is 800 Sq. ft. with the exception of the attic which is about 350 Sq. Ft. From the first floor upwards(1st floor to attic) there are traditional hot water radiators running off a Burnham gas boiler (9-22-AN) located in the basement.

The basement itself has no heat whatsoever. I checked the boiler as you suggested. It says the Input is 240,000 BTU/hr and the output is 192,000 BTU/hr. (Does it mean it’s 80% efficient (192/240)? Is it how to calculate the efficiency?) Anyway, if I do the math suggested, (800x3 + 350) x 40 = 110,000 BUT/hr should be enough? So this old boiler is enough to handle my house even if I add heat in the basement, right?

If I understand you guys correctly, it’s a better choice to install HW baseboard radiators running off this old Burnham boiler than to purchase a gas forced air furnace and build ductworks in the basement. Correct?

Indirect HW heater? So I can purchase one of these and connect it to the existing Burnham boiler? Or, do I have to buy a new boiler in order to hook up an Indirect HW heater?

Also, about zoning. We have had trouble asking our local housing authorities this question. However, we are not renovating to rent - only for extra space for our friends and family when visiting. But we would like to make the space as nice as possible. We did ask some of our neighbors who have lived in the neighborhood for a long time and apparently our area is not zoned for seperate meters. Several of our neighbors do rent apartments which are in their homes but do not (obviously) have seperate meters. They have utilities included in the rent amount.

Even so we would like for our guests to be able to control their own heat. Is there still a way to do this without involving the utility company? Even if my neighbors are wrong and we are zoned for seperate meters the cost is around $5,000 and we just don't have that in our budget at this time.

Thanks again.

Re: Hot Water Radiator Heat vs. Forced Air Heat


your post makes things clearer.

Remember to calculate the heat load only for those HEATED portions of the building---thus the attic would not be included---if I read your 2nd post correctly it would be 800 sq.ft. for each apt (including the proposed basement apt) or 800 sq.ft. X 3 = 2400 sq.ft. X 40 = 96,000 btu/hr. (plus a few thousand for the indirect hot water heater, if installed) = 100,000 btu/hr needed.

In any event, it appears that your present boiler is way too big for the heat needed and, yes, would be capable of adding on the approx. 32,000 btu/hr for the basement---why they put in such a big boiler may be explained partially by high ceiling heights (over 8') in your rooms, lack of insulation, or that you live in a very cold climate---but the boiler is still too big for the building, and given its age, it should be replaced within a year or so when your budget allows you to make the change.

For the present, there's nothing to stop you from installing a basement zone of hot water baseboard---if you get a new boiler in the future, the new zone is just connected to the new boiler----when the hot water heater starts to fail you can substitute an indirect hwh---the other modifications like changing the boiler, rearranging the piping for all floors to allow zone & thermostats for each level would be more expensive.

Another option for temp control is to install thermostatic radiator valves (TRV's) in each room or level (less expansive than zones) if temp control is an issue for the occupants.

Your calculation for your present boiler efficiency as the difference between the boiler input and boiler output is accurate when the boiler is new---after 40 years, it no doubt deteriorated down from 80% to 60% or 70%---present efficiency can be determined by having a heating contractor do a COMBUSTION ANALYSIS with an electronic probe (cost: approx. $50).

Yes, the indirect hot water heater (if ordered) can be connected to the existing boiler when you're ready to buy one ($700-$1000).

Make sure to follow the links provided in the previous posting to do the SLANT/FIN HEAT LOSS CALCULATION (free of charge)---this computer driven program takes an hour & you have to input all kinds of data about the thickness of your walls, insulation, location, window condition, etc.---to get a very accurate reading on how much heat the building is losing per hour on a cold day.

Do an intensive search for a knowledgeable hot water heat technician---the right person will make the modifications needed for the least amount of money----get at least 4-6 estimates before you agree to have anyone do the work----you'll know when you've found a good one when he/she starts talking about some of the issues mentioned is these posts.

Re: Hot Water Radiator Heat vs. Forced Air Heat

Thank you again for the advice.

Another thing that was suggested to us is a gas boiler which is also a on-demand WH. I believe it is the Weil-McLain CGT. It was explained to me that this boiler supplies hot water for the radiators as well as the taps on demand. Is this a good choice? I can hardly find any info on this on the internet.

Re: Hot Water Radiator Heat vs. Forced Air Heat


The Weil-McLain CGT is about the right size output: 108,000 btu/hr, but this model, as you said, has a tankless coil for the hot tap water---the tankless coil is simply a small round copper coil inside the boiler's heat exchanger that supplies tops 2 gallons of hot water per minute for about 2 minutes, then the water goes lukewarm, then cold until the boiler can reheat the coil again---this would be clearly insufficient hot tap water for such a large house with so many occupants.

The standard installation in your case is to install a 100,000 btu/hr 3-pass boiler or condensing/moderating boiler along with the "companion" 50 gallon indirect hot water tank---sometimes 2 smaller boilers are installed.

I would recommend the Buderus GB142 condensing, the Peerless Pinnacle, the Utica UB, the Triangle Tube Prestige, the Viessmann Vitodens, or any 3-pass boilers by these same manufacturers.

Triangle Tube also has an excellent indirect hot water heater.

Boiler choices and types are further explained in the links provided previously.

Re: Hot Water Radiator Heat vs. Forced Air Heat

I asked the HVAC Co. I am going to use about the Indirect HWH. They say b/c my boiler is old and not that efficient, the much higer price of an IHWH is not justified since the saving in energy cost would be minimum unless we are going to get a new, more efficient boiler also.

Their original quote for a new 50-gal AO Smith is about $1K including installation. If we want an IHWH such as the AO Smith Vertex, it would be $3.5K installed. We will get about $1.5K in tax credit for the energy efficient heater, so we would still end up spending $1K more. They say, if we are not getting a new boiler (we are not, due to budget concern at this time), they don't think it's worth it for us.

Your thought?

Re: Hot Water Radiator Heat vs. Forced Air Heat


The quotes are too high in my opinion---you'll have to call OTHER installers in your area (5 or 6 if needed) as the best way to get an accurate quote.

In the meantime, get a WRITTEN QUOTE from some of your local heating supply stores (consult Yellow Pages under "Heating Equipment--supplies).

Also go to Home Depot & get their WRITTEN QUOTE for the Amtrol Boilermate 41 gallon indirect HWH ---should be $700 or so.

Other recommended 50 gal IHWHs would be Triangle Tube Phase 3, HTP super Stor, Crown Megastor, Weil McLain Gold, TFI EVerhot, & Lochinvar Squire.

All of these should be in the $700-$1k range---installation involves a 1/2 hour job of connecting a few pipes to the boiler.

The labor quotes you're getting are WAY out of line---make it clear to the other installers you call BEFORE THEY GIVE YOU A QUOTE that you have limited funds available, you have limited income & are looking for the lowest quote possible---then show them the Amtrol quote from Home Depot & any other quotes you can get.

Most installers will automatically quote $3k because they think people will just say yes--so BEFORE they give you the quote make sure you explain to them that you can't afford anything over $1k pr $1200---after all, these are difficult economic times and a lot of people are out of work and on a fixed income.

Don't ignore fuel oil dealers in your area---they are all licensed to work on gas equipment & often will give a lower quote.

Re: Hot Water Radiator Heat vs. Forced Air Heat

I am getting SO sick and depressed over this. We have interviewed many contractors/plumbers/companies and, yes, we have gotten at least 5 or 6 quotes. This company seems to be the most knowledgeable and reasonably priced. I don't know what to think anymore. I was shocked too when he came back with a $3.5K quote the 2nd time w/ the IHWH. But before I make a judgment, let me detail all his quotes.

Job 1:
Install 4 used cast iron radiators in the basement (pipe out from the existing boiler) and includes zoning the basement out from the rest of the house.
$3K - All equipment and labor included

Job 2a:
Replace the existing 40-Gal HWH w/ an AO Smith 50-Gal HWH
$1K - All equipment and labor included

Question #1: Are these 2 quotes reasonable?

As an alternative to 2a, we are considering Job 2b:
Replace the existing 40-Gal HWH w/ an Indirect HWH as suggested by you guys. The company quotes an AO Smith VERTEX high efficiency 50-Gal Indirect.
$3.5K - All equipment and labor included

Question #2: Now, I have checked it out online, the AO Smith Vertex does cost a lot. I see prices range from $2K to $2.5K. Knowing this, is this quote reasonable?

Question #3: If quote 2b is reasonable b/c the VERTEX is so much more expensive, do we really need a fancy heater like this. Is the VERTEX really that much better?

I know I ask a lot of questions ... sorry for being a pain in the butt.

Re: Hot Water Radiator Heat vs. Forced Air Heat


First, take a deep breath Paulette---you have plenty of time to check out this stuff--perhaps have a male friend or relative with you for support when these installers come over to give a quote---the ideal time to do this work is in the spring or summer anyway when heating work is slack & the installers are more likely to give you a lower quote.

Yes, the quote process can be stressful, but you're doing the right thing---and when you finally DO settle on the LOWEST BIDDER for the job, you'll feel confident that you got the highest quality for the least expense.

Let's face it, in the coming months the sagging economy will mean there will be a lot of installers out of work, which is regrettable, but will mean lower quotes for the homeowner---take your time & don't lose your cool.

It hard to say if the quote for Job #1 of $3k is reasonable---I'd like to see a quote or two for the same job with baseboards---if you can prolong the agony, get a few more quotes for perhaps 1/2 that.

No, I don't think you should buy an A O Smith Vertex---there are equally good quality indirect hot water heaters, as were listed in my previous post, such as the Crown Megastor, Triangle Tube Phase 3, the Weil McLain Gold, the TFI Everhot, etc.

Figure $700-$1k for the cost of the indirect HWH plus $300 for labor.

The zone in the basement is a good idea, but I think hot water basebord rather than cast iron radiators would be more attractive and cost less.

Re: Hot Water Radiator Heat vs. Forced Air Heat

Thank you for the advice. We are interviewing a couple of more HVAC companies and a new option comes up. We are suggested to install a ductless mini-split heat pump system. The HVAC Company who suggests it thinks that it's best for our situation. Right now, the house uses window units for cooling. He says that for basement, since we are starting anew, this one solution solves the heating problem now and the cooling problem in a few months when summer comes. He says the system is quiet, efficient, looks great and saves space by not having pipes and radiators along the floor. It sounds great. What are you guys' opinions on the mini-split?


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