Home>Discussions>INSULATION & HVAC>Combining Radiant and Baseboard
7 posts / 0 new
Last post
Combining Radiant and Baseboard

I've searched and found some posts about this, but none have addressed our specific issue that I found.

We have a small place, only about 680 square feet. It currently has a boiler and basebard heat. It appears to have only one zone (we just bought it and are waiting on our closing) running from the bathroom on the right side in the center of the house around to the front right, across to the front left and back, then from the left rear to the right rear and back to the boiler. We think it's a closed system.

The whole back is a living room, which is an addition to the original house. That addition has some issues and we're going to be tearing up the flooring and replacing two small windows with sliding glass doors. Also, we are moving (replacing) an improperly installed wood stove and hearth. In the process we would like to go to radiant heat, since we would like to do this throughout the whole house eventually and might as well do this while we have the floors up. However with buying the place and doing the work, we won't have the money to do the entire place at once, especially considering that there is probably going to be "surprises" as we go.

So, now that you have the basics-the question is-can we do this? Will we need to have zones, or can we just bring the heat down on the baseboards? Given the size (it's also a single story), we figure that even if the baseboards are running a little cooler, the heat should still travel around from the other room to keep things reasonably comfortable.

Re: Combining Radiant and Baseboard

It can be done but the problem is you need 180 to 200 degrees for hot water baseboard. Radiant heat runs at a much lower temperature. You can use a panel troll to lower the radiant temperature, basically what it dose is mix the return water with the supply to the radiant heat cooling it down. You will also have to have two zones one for the baseboard the other for the radiant.


Re: Combining Radiant and Baseboard


First of all, get down on your knees and thank your lucky stars that you bought a house that happened to have a boiler-driven forced hot water (hydronic) heating system----I've been doing it for 40 years & believe me, there's no better heating system out there.

You don't say what part of the country you live in, or how cold it gets, and you indicate that you want to attempt to do the heating renovations on a diy basis due to limited available cash.

Radiant additions are commonly and frequently added to hydronic systems---especially in such situations as a bathroom, where the occupants can enjoy the luxury of warm floors and comfortable showers and baths on cold winter mornings---other rooms are eventually converted to radiant due to the lower cost of this type of heating over baseboard, or even radiators.

JohnH2O is correct----usually, a separate "zone" is created for a specific room, or part of the house & often a 3-way mixing valve is installed to mix the 200 degree boiler water with cooler return water & the "zone" comprising the bathroom, or bedroom, etc., is heated with a sub-floor network of plastic PEX tubing, or 1/2" or 3/4" copper tubing (much more expensive) at approx. 100 degrees, often controlled by its own wall thermostat-----Google "A Little Floor Warming Please" to see an article with piping diagrams written by hydronics engineer John Siegenthaler.

I think it's important to draw a distinction between radiant modifications and modifications involving just baseboard----nothing could be more simple than installing baseboard; not only is baseboard sections low-cost due to their wide availability, but they go up easily, and are effective in heating rooms with little or no breakdowns over a period of many years----once you get into radiant modifications, things can get a lot more complicated, and a lot of technical knowledge is required to get the modification installed correctly and working properly.

The book by Siegenthaler (Modern Hydronic Heating) is worth searching for in your local public libraries---it's loaded with clear diagrams and piping arrangements and components that the DIYr can understand---if your library doesn't have it check out the other oversized heating books they have there under the 643.7 numbering system---also check out Barnes & Noble and Borders, as well as the library of any local technical school in your area that has a degree program in Heating Technician training.

It also must be said that modifying a heating system has a lot of technical factors involved and it's very easy (and understandable when you think about it) for a DIYr to get the basics of the remodel project wrong, after spending hundreds of $$$ on expensive components that may not be returnable---by all means ask the man at the parts dept dealership for help if you're not sure you know what you're doing---most will help you out---go in to buy your parts in the afternoon when it's usually slow----avoid the morning hours---all the technicians are in there at that time of day buying what they need & the place is a madhouse----consult the Yellow Pages under "Heating Equipment; parts & supplies"

Of all the sites I've listed below, perhaps the most helpful is the HEATING HELP site---click onto their site, & when you get to the main page, click onto "Ask Questions" at the top of the page to get to the forum that is specifically dedicated to radiant hot water heat---once you register, you will be able to consult with numerous radiant hydronic technicians who can guide you through some of the steps you will need to get a running start on your radiant project.

On the site below entitled "Inspect-NY", click onto the "Parent Directory" once you are at the site to access the numerous and excellent topics on hydronic heating, piping arrangements, radiant additions, etc.

The Beacon-Morris site has a photo of a hot water floor vector, embedded into the floor in front of the glass door in order to offset the winter "cold spot".

Why do I say a forced hot water heating system is worth its weight in riches???------because this type of system is so flexible--there are so many things the DIYr can do if he/she knows how to solder copper tubing, or connect PEX tubing----that said, even doing a small renovation like a bedroom or bathroom floor in radiant can get to be very expensive---these components (3-way mixing valves, etc.) don't come cheap & you have to have enough know-how to design and assemble the subroutine components according to a heat-loss calculation that will deliver adequate (but not excessive) heat to the room in question. Google "heat loss calculation" to get some on-line ways to calculate how many BTUs/hour a room or section of the house needs to stay warm.

On the other hand, sometimes a more prudent strategy is to concentrate on maintaining your present baseboard system in the most efficient way possible by replacing the boiler if it's over 15 years old with a more efficient one, and MOST IMPORTANT as a first step, to start an insulation refit project by testing to make sure all the exterior walls have at least R19 insulation, and that the attic has R40, and that every window is double-pane or has storms, and lets in zero drafts----it is much wiser, on your part, to spend your winterization dollars on these three components before tinkering with the heating system---there are insulation companies (Yellow Pages---"Insulation") that can blow in cellulose insulation from the outside of the house, usually within one day, for a few hundred dollars---I can't think of any other project that is more important and effective in saving heating and cooling dollars than filling the exterior walls with insulation---it obviously adds tremendously to occupant comfort the year round.

By all means if you must make heating system changes, consult the Yellow Pages under "Heating Contractors" and have several heating technicians come over the house to evaluate what you have there now; and get estimates on what, if any, changes they suggest you make to the existing system.

Sliding glass doors can cause real problems in winter due to the large amount of heat that escapes right thru the large glass panels; quite often, a floor vector composed of hot water piping as part of the heating system is installed right in front of the large glass doors as a way to counteract the "cold spot" caused by this type of addition.

Google "Adding underflooor radiant to existing hot water baseboard system" (without quotes).

Also Google 'hot water heating forums" or Google "DIY hydronic radiant heat forums", etc. to get DIY forums where you can get interactive feedback on some of the issues you mentioned in your post.


Heat Loss

Radiant needs to be on its own zone and a entire heat loss of the home needs to be done. Personally I would do a radiant heat loss and design of the entire home so I can prepare for the future. You also need the loss to see if you can run that existing board your keeping at lower water temps. You also have to provide boiler protection if your using a cast iron boiler so your near boiler piping is also going to change.

A simple way to mix that radiant based on outdoor reset to provide max comfort is to look at a Taco I-Valve. Very simplistic, very effective. www.taco-hvac.com

Re: Combining Radiant and Baseboard

Thanks for the replies!

The boiler is supposed to be new, however I imagine "new" means within the last 5-10 years.

We are in WNY.

The exisiting system is run rather...um...uniquely. For instance, in the living room, the pipes are run up the wall, around a stone backer for the fireplace, back down, into a baseboard, then back up and around a door...

Again, it is a small place, so even a few inches of wall space is a big deal, which is why we wanted to move to radiant heat. The dining room has no walls to put a buffet against for instance, for storage. The bathroom doesn't appear to have any heat in it, however the boiler is located in a closet type set up in that room so maybe it doesn't need one and heats just from having that there.

I am glad to have hot water heat. Our current place doesn't have central heat (yes, I said no central heat in NY)-it never did (built in the 20's)-and we were looking at some type of hot water heat here also, but couldn't figure out where to locate the boiler. So we're sticking with gas stoves (think the fireplace/log type DV). Bathroom gets cold, but otherwise unless it gets into the teens or single digits, it works fine.

We've done a lot of renos at our current place, including dealing with broken copper pipes (frozen...fun stuff in a crawl space in winter) and also CPVC work (it's a mix of both here). We do have a few HVAC folks that are friends of friends we might get involved in this project for the boiler end of things, and we might save by laying the Pex and doing the deconstruction/reconstruction of the floors, etc. Since we haven't closed yet and we don't want to "jinx" the deal (it's been quite an effort to get this far) we haven't "announced" this purchase, so we haven't been able to ask them yet on help in this regard.

Thanks again for the replies, I'm going to read them over a bit more closely tomorrow, when it's not 11pm :p

Re: Combining Radiant and Baseboard


Thanks for posting back---the info in your last post may change things; as much as I love forced hot water heat, its one Achilles' heel has always been that the piping is vulnerable to freezing----since you live in WNY, this is something you'll have to think about seriously; I'm sure you're facing sub-zero temps each winter---how cold does it get there???

There's nothing like have a heating tech come over to your house & evaluate & size up the situation before making costly decisions on some of these issues.

Hydronic heat can still be used, especially since you have the equipment already in place, but there are areas of the country, such as yours, where special precautions have to be taken----propylene glycol (non-toxic antifreeze) is widely used in hard freeze areas to prevent conditions you describe, where the heating pipes freeze & burst---when it happens inside the walls it's a real disaster; there is also an issue if you lose your elec power frequently during winter storms; a wood burning stove or fireplace as a back-up heating source is usually a must; copper tubing, though more expensive, will take the heat of a women's hair dryer if a pipe needs thawing, where PEX may be damaged; a heating line once frozen can stay that way for days or weeks until it thaws by itself; propylene glycol is sold in home improvement stores as well as heating supply houses---the cost is approx. $10 to $20/gallon; a 50% solution depending on the # of gallons of water in the system (approx. 15 or 20), can get expensive, but even a few gallons of PG is a lot better than nothing.

It may be more prudent to have forced hot air installed if several heating techs look at the situation & advise for it; there is a Unico system that uses small diameter 4" tubing that can carry hot air, as well as cool conditioned air for summer comfort----just another option that may or may not work for you;
in fact, given the small area of the new home, a forced hot air system with ducting running thru the ceiling may be the best way to go.

Regarding the limited room for baseboard----a common problem, especially in kitchen & bath applications where every square ft. of space is at a premium---in such cases there are hot water (fan driven) kickspace heaters that are only 14" long & 4" high & are designed to fit into the base of kitchen & bathroom cabinets, & yet put out several thousand BTUs/hour; they are soldered into existing copper tubing, or fit into PEX lines & 8 to 10' of baseboard can be eliminated from kitchen or bath---since you have no heat in the bathroom, this is an install screaming for completion---check out the Beacon-Morris site for kickspace heaters; there are many brands, buy one from a heating supply house & insist on a quality unit & one WITH A QUIET FAN; other options would include high output baseboard at heating supply outfits that put out nearly twice the BTU/HR of standard baseboard; 2nd hand cast iron radiators at low-cost salvage/demolition outfits are small sized & put out much more heat than baseboard; the newer stainless steel radiators are expensive, but put out much more heat in less space than BB; The Beacon-Morris site has convective heaters for small space applications.

Another option that is a variation of radiant is to place the PEX or copper tubing sub-floor with enough spacing & insulation so that a high temp piping run under the floor surface will not damage the finished flooring---this eliminates the need to buy & install a lot of expensive equip & the system is run at the full 180 degrees temp; a noted caution is most boilers have to be kept at a minimum of at least 135 degrees operating temp to prevent corrosive condensation temps from damaging the boiler; Siegenthaler briefly describes this system in his "A Little Floor Warming, Please" article; also Google "The Plain Vanilla System PM magazine" by heating tech Vince Gallipoli for additional info; run a search at the PM magazine site in their search box for additional high temp install techniques.

Another aspect of heating is that the boilers and furnaces these days have been shrunk down to the size of large suitcases---yet put out the same heat as the white elephants of years ago; the fact that the piping in the new house wanders & wends its way up & down walls indicates that you don't seem to have a basement or crawlspace, thus the previous owner had to resort to the unusual installation; this piping arrangement tends to create air in the piping, & bleeding the system can be problematic, but mostly, hot water pipes can be run in loops if necessary, & still work OK.


Re: Combining Radiant and Baseboard

Yes, we definately get below 32 degrees here. Not typically below 0, but we do get into the teens and single digits a few times a year at least. Hot water heat is fairly common in this area however. I'd say at least 30% of the homes we've looked at have it.

We don't lose power too often, however it has and will continue to have a woodburning fireplace. I can also say that a gas stove can also work as a back up heat source (I'm talking heating stove, direct vent, not cooking stove). During the infamous "October storm" a few years back, we were one of the few that weren't overly bothered by losing power for days, the only change for us was no blowers on the fireplaces/stoves we heat with now.

We're on a slab, no crawl space. I can't imagine there's anywhere to put ductwork in there.

We did talk to a plumber who's done work there and he said he's had to repair the hvac lines a few times. They had multiple instances of renters leaving with no notice. It runs on propane, so when the tank emptied...yup. Frozen lines.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.