I currently have baseboard radiant heat with an oil boiler. The heating system is dual zoned, one for the first floor and one for the second. I have access to all the pipes that go to the individual radiators on the first floor from my basement. I’m considering taking out the radiators and converting to a radiant in floor heating system for the first floor. I’ve read up about properly insulating below the floor and using the aluminum “fins” to enhance the heat transfer through the floor. I would ensure that I use the aluminum fins and properly insulate below the pex tubing once it was installed. I’m not an HVAC expert but i consider myself to be more knowledgeable than you average person when it comes to home improvement. Does anyone see any issues/problems with my plan?
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You do realize you need a whole separate pump system for the radiant part, right. You need to limit tube water temp to about 120 degrees and floor temp to 80 degrees (at least with wood floors). (Normal FHW to radiators is 160-180 deg., I think.) The temp limiting is often done by recirculating the radiant return line with some feed-in from the main system. My plumber uses two pumps, one feeding a circuit that goes past the manifold area, and a second to draw the combined heated water off the circulating supply and to it's destination. Somehow my system, similar to what you want to do, has 5 pumps.
I believe radiantec.com had some reasonably good manuals describing various components and configurations.
---mike...
Madison Renovations
Cambridge, Mass.
What you have is convective baseboard heat, not radiant.
Why do you feel the need to change it?
I would not recommend installing an in-floor radiant system without at least having your supplier do the design and engineering and give you a detailed schematic of the appropriate system. It's not as simple as you might think, and a poorly designed radiant system is worse than no system at all.
Solar & Super-Insulated Healthy Homes
I'm considering changing it out as I was recently in a house that had in floor radiant heat and it was a very nice experience. You don't see any radiators, no ductwork, no air blowing on you. It's a discrete kind of heat, you just feel warm. Not to say that my current system is inadequate. I was just impressed how you didn't see anything yet you were warm. I also didn't mean to imply that it was easy as some people might have suggested. I also realize that this is not a $100 job done in 2 hours. With that being said I was just trying to put out my idea and see what people thought about it. This isn't a project that needs to be done tomorrow, however it will probably be something done in the next year or so.
Please don't let Riversong get to you.. he's a very much do it my way kind of guy..
I did it (in floor radiant) and it wasn't terribly difficult. plus I didn't have the advantage of having radiantec help me out. They are good people and will take you step by step through the process and sell you whatever is beyond your ability to get locally..
Right now it's 14 below here and I'm sitting here in my bare feet. The shoes are by the door so I remember to put them on as I let the dog in and out..
What kind of setup did you go with? What would you recommend that I do? I can't say it was -14 when I expereinced the radiant heat, but it did get down to 0 and the house was still comfortable.
I retrofit my house with radiant plate down stairs and baseboard upstairs. if you have extra bb when you switch over consider adding more base board upstairs do the heat loss calc and run your boiler at 130...Im saving a good thirty percent from the system I had before.
minus -12 today and its all good.
The main issue with in-floor radiant heat is the difficulty in dealing with windows.. Even the very best windows lose a lot of heat and it's difficult to get enough tubing under windows to avoid feeling a chill. By my calculations it wouldn't be practical to deal with it when the temps drop to 20 below or greater even though my house is super insulated.. (R30 walls and R50 ceilings)
I dealt with that in a differant way. It might be required in your case depending on heat loss calculation.
To answer your question, I did a sort of a staple up using aluminum coil stock which I ran a bead into with my own bead roller.. Then once that was up I installed foil faced foam insulation underneath and finally I stuffed the rest of the bay with fiberglas.
I had to go to those lengths because I used a marginal heat source to keep operating costs to a minimum. (electric water heater)
It's interesting you use a water heater to heat your house becuase that what radiantec recommends. I'm not opposed to using one but there seems to be a good debate about using a hot water heater vs. a boiler. What are the pros/cons of each setup. I really like the idea of doing most of the work myself, however, if I were to get a new boiler I'd have no clue how to install it, but I feel confident I could handle installing a water heater.
As far as windows go I just put in all new windows this past summer. They are triple glazed with a low-e coating. Prior to this I had the original single pane windows in the house. So I think this should help in the window aspect. Also since you have real world experience with the in floor radiant heat, would you say that its possible to set your thermostat lower with that type of heat as compared to other styles of heating systems? In other words, does the sensation of your feet being warm trick your entire body into feeling warm and allow you to set your thermostat lower. This seemed to be the case with my experience with the in floor radiant heat, as it was set to 66 degrees but I still felt warm.
Edited 1/15/2009 1:16 pm ET by ejazz2095
It wont trick your body into feeling warm. What it does is warm up everything around you that is trying to steal heat from your body. So not only is the air a consistent temperature but the chair you sit in is warmer, the table you lean on is warmer etc. All of this adds up to an unbeatable level of comfort.
I selected a water heater because a boiler would have been too much for my house except during the extremes of cold..
However most houses don't have the quality of insulation mine does. I have R 30 in all my walls. Not intrupted by studs every 16 inches like most houses are.. Plus my insulation covers all of the areas that are normally weak in most homes.. it starts at the foundation and goes up. Not at the top of the platform as most houses do. Even my foundation is insulated with ICF's. The roof too has R50 rating except at the peak where it goes over R 100
There is marginal forgiveness with a infloor radiant set up you do have to get it right. Unlike normal systems where you can simply buy bigger furnance and stuff more hot air into the house to make up for flaws.. the tubing is only capable of accepting and radianting so much heat and where and how the tubing goes really matters.. that's why there are differant zones set up. To keep the tubing runs short enough to work well.
To answer your question The house today is set at 67 degrees, I'm warm because the feet are the furthest thing from your heart and get the coldest. Once your feet are warm the rest of you feels comfortable at that temp..
When I had forced air heat I used to keep the house at 70+ and still felt cold all of the time.. Now if I set it at 70 I feel too hot and stuffy.
My great room ceiling is 28 feet above the floor.. yet when I check the temp with my digital infrared thermometer the floor is only 1/2 degree warmer than the ceiling. Unlike normal houses there is no stratification levels.
Please don't let Riversong get to you.. he's a very much do it my way kind of guy..
For someone who sees every problem as an ICF solution, that's more than a little ironic (and completely dishonest) to project your routine bias onto someone like myself who draws conclusions and offers advice based on real world experience and recognized building science and engineering principles.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Yes, properly-installed radiant heat is the most pleasant type of space heating. But improperly-designed or improperly-installed radiant heat can be a nightmare and a waste of money.
If it ain't broke, don't fix it. If you must change it out, either get a competent radiant heat designer/installer or make sure you have a supplier who'll do the engineering and walk you through the rather complicated installation.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
First you'll need to know the heat loss of the space you'd like to heat via radiant floor. Then figure the BTU output per square foot of floor... then find the R-value of your floor covering. All that info will be needed for proper design. Worst case scenario, your floor can't provide enough heat... in which case you can supplement with your existing baseboard heat.
If you can afford it... these http://www.pexsupply.com/categories.asp?cID=208&brandid= can put out a lot of heat and look fairly easy to install from below.
Edited 1/13/2009 7:36 pm ET by Doobz26
You have a major project on your plate along with some $$$ outlay. It's not as simple as that.
In concept you may be OK ... but you have some issues. Not sure why the one guy used so many pumps. You have two pumps now? The hints about the change in temperature are good. As far as not having enough tubing for the job, I'd tend to say that it shouldn't be an issue. Also radiant floor tubing length per zone or per loop (you may have 2-4 loops in one zone) have limitations in length and the loops should be similar lengths (e.g. all 150-200 ft +/-).
How do you intend to double back the tubing across joists? The aluminum fins will distribute the heat as you mentioned. Is your basement heated?
You can easily control the loop temperature w/ an adjustable 3-way valve (the one guy implied this). Lots of things to think about so make sure you understand them before tackling such a modification. Layout your loops graphically and determine loop length, think about manifolds. Wirsbo has some quality products for this type of application ... including a design guide to help you (free).
What you are proposing, the work is not hard to do.
My ? is why do you want to do this? BB is normally pretty comfortable heat, only con is they can be ugly.
As long as your floor materials are decent for radiant and your heat loss isn't crazy, it should work fine. Talk to Radientec.
You'll need a whole new control board due to the need for two temperatures. That adds another level of complexity to this job.
Zoning is just on-off, I am presuming.
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ejazz,
I too experienced hydronic radiant in floor heat and was sold instantly.
As others have said its not as simple as putting longer loops on your current pipes but dont let that discourage you. You've got it right with the fins and insulation now you have to tackle the teperature control part.
Take your time and do research. Its amazing how much info is available for free out there. Make sure to talk to your local professional(plumbing supply house has a heating specialist arouond here, ohio) and try to coordinate with him, maybe buy some parts from him for his effort. Its nice to have a local to talk with when things get confusing.
Heat loss calculation should be where you begin. The next step is making sure you are well insulated where you will be heating. Heating means nothing if you are letting in cold air everywhere. Next design your system accordingly. Purchase parts. Install. Enjoy.
I used HVAC Calc ( http://hvaccalc.com ) for load calculations. The website looks kind of hokey, but the product was good. You can get a one-house version (30 day usage, I think) for 50 bucks. Then you can play with different insulation, tightness, as well as specifying size, windows, etc. and it calculates BTUs per room. It showed that with spray foam in the attic, I could downsize my boiler, and I've been comfortable throughout.It showed I could run a radiant floor in the attic with vaulted ceiling and lots of glazing. It was right.---mike...Madison Renovations
Cambridge, Mass.
Edited 1/15/2009 10:13 am ET by MadisonRenovations
Installing "staple-up" in floor radiant under the first floor is a fair amount of work, but very doable. I recommend working with NRT for the design and specifications. They were very helpful when we did ours, and are used to working with people who are doing the work themselves.http://www.nrtradiant.com/
So did you put sprayfoam in your attic? If so how much? Could you give me a few more details. I know the insulation in my attic needs an upgrade and I've considered sprayfoam (I realize it costs a pretty penny) but I wanted to talk to someone with real world experince with it.
ejazz2095 wrote:
>So did you put sprayfoam in your attic? If so how much? OK, a bit confusing, but here goes:
I added gable dormer to a roof with 2x6 (full-sized rough sawn) rafters; the dormer width was 2' short of each end of the roof. The attic ceiling is vaulted, so to get enough insulation in the old roof portion, I filled the entire rafter bay with high density foam. Six inches of R-6.5 is R-39, vs. R-22 for something with R-3.8. That seems to keep the roof cold (no snow melting) in winter, and it's comfortable in the summer. I put in an equal amount in the dormer, which I used 8" rafters vs. 10" to reduce materials and gain a couple inches of headroom since I didn't need them for batts.To break the thermal bridge of the rafters, I cross-strapped with 1x3's.I also foamed the walls. The old studs were 2x4, but a little thicker than modern, I think 1-3/4x3-3/4. I should mention the house was built in 1925. New walls are 2x4, since I was planning to foam them. I also cross strapped them before the sheetrock for a thermal break.Spray-in was important because the old studs and rafters did not have consistent 16" O.C. spacing. The high density stuff also gives structural support, and my 2x6 rafters had a long span and showed signs of sag.other questions?---mike...
Hi Mike,
Since you have experience with sprayfoam I was curious to know what you thought of this. My attic currently has 2x6s in the floor roughly 16" OC. In between the 2x6s there is fiberglass insulation which I would assume to be original to the house, which was built in 1952. In almost the whole attic the insulation has matted down to about 1-2" thick. Runing perpendicular over the 2x6s is R-30 fiberglass insulation that the previous owner installed. I was planning on removing the old fiberglass insulation and filling the area with 6" of closed cell sprayfoam and then putting back the fibergalss over that. I know fiberglass isn't the best insulation material in the world, however, i figure it's already there and I really have no other use for it right now, so I might as well use it. I realize that this is a fairly expensive proposition however its still cheaper than upgarding to a more effiicient boiler.
Thanks,
Erik
re: fiberglass over spray-foamed attic floorThe general view is the loose stuff goes on the warm side, making up less than 1/3 of the total R-value. Don't recall where I read that. Moisture on the cold side could become a mold breeding ground. Also, you don't want to have a vapor barrier on the fiberglass trapping moisture between the batts and the foam.6" of spray foam is pretty darned good by common standards (but not superinsulation). That would probably get you where you want to be.---mike...Madison Renovations
Cambridge, Mass.
Mike,
I guess I'm not totally clear on your response. You said "The general view is the loose stuff goes on the warm side, making up less than 1/3 of the total R-value". So do you suggest i put fiberglass down and then spray the foam over that? You say that "Moisture on the cold side could become a mold breeding ground". Do you mean on top of the sprayfoam? I realize that the fiberglass should not have a vapor barrier on it, but I appreciate the reminder.
-Erik
So, I think that often the spray foam goes into the rafter bays, and sometimes batts with no vapor barrier go on the warm side. But if the attic is going to be cold, you can save money by only foaming the attic floor joist bays. But in that case, you wouldn't put fiberglass below unless you covered the joists - the foam would send the loose fill everywhere. You also wouldn't want to put fiberglass on top, because moisture could condense on the cool side where the insulation is. However, that might not be a large problem since moisture movement will be all but eliminated with the foam.Someone else would need to provide more info. I went with foaming the rafter bays.---mike...Madison Renovations
Cambridge, Mass.
"You also wouldn't want to put fiberglass on top, because moisture could condense on the cool side where the insulation is. However, that might not be a large problem since moisture movement will be all but eliminated with the foam."Actually, with a foam/FG hybrid filling the attic floor joist bays, you would put the foam down first, above the ceiling. The foam, if applied correctly, should seal the attic off from air exfiltration from the living space below. The only water vapor entering the attic from below will be by diffusion through the ceiling and foam, a very slow process.A vapor retarder paint on the ceiling will be sufficient by itself, as far as diffusion is concerned. A layer of foam above that just slows diffusion down even more. If the foam is closed cell, then the foam itself is sufficient as a vapor retarder. Any water vapor diffusing up through the ceiling and foam will be at a very low concentration and will diffuse readily through the porous FG layer without there being a dew point issue.Such an assembly would be much like in a vertical wall. With no convective air flow into the cavity, and a good vapor retarder inside, a FG batt inside the cavity won't see any condensation. If a foam board is installed just under the drywall, the situation doesn't change. The FG winds up colder everywhere, but the foam layer retards the diffusion of water vapor that much more. In any case, as has been pointed out before, in the absence of convective air flow (leaks), a vapor retarder layer of 1 perm on the inside reduces the diffusion of water vapor, in absolute terms, to such a low rate that even over a couple of cold winter months the framing and exterior sheathing can safely absorb the moisture without mold/rot issues. As the exterior warms up, the stored water is released more readily to the outside and the moisture content drops again.
Edited 1/21/2009 8:09 am ET by DickRussell
I figured the foam would seal most of the moist air from the house, if done well. Wasn't sure about the potential for moisture from the attic side.---mike...
In winter the relative humidity in the cold attic space will be at or below 100%, or it would be raining up there. Even if the outside air humidity rose suddenly (warm front), any water vapor diffusing downward toward the living space (isolated by a good vapor retarder) would see increasing temperature, and thus lower relative humidity, so condensation within the porous FG won't occur.In summer, a very humid air mass might actually get to mid 70s dew point in NE. Heck, we call it "oppressive" when DP gets to the low 70s, a nice day on the gulf coast. Anyway, that moisture concentration would be fairly constant through the porous FG insulation above the ceiling, all the way to the vapor retarder. As long as the temperature just above the vapor retarder (at the ceiling surface, film above drywall, or top of CC foam) stays above the dew point of the humid air above there won't be condensation.[2nd paragraph reworded for clarity, intent]Edited 1/22/2009 9:58 am ET by DickRussell
Edited 1/22/2009 9:58 am ET by DickRussell
I have seen some info about a product ( rad. floor heating) out of California called Warmboard. Has anyone had any experiance with that product? The brochure looks very interesting, but then, all advertisement is meant to look good
there was a recent discussion on the Construction Techniques forum:http://forums.taunton.com/tp-breaktime/messages?msg=114950.1One thing to add, because Warmboard doesn't have thermal mass, you don't have the lingering warm floor feeling. Of course, neither would retrofit staple-up applications. But after you reach the desired room temperature, the system shuts off, and the heat goes, and you have a standard temp room without the warm feet feeling. While it's heating, you feel warm with a lower room temp. If you have good insulation, you may not need to heat for long. Perhaps lowering the floor temp will keep the warmth running longer... I need to try that.However, in exchange, you get a faster heating product, because the heat is transferred to the room faster, instead of to the thermal mass of the subfloor.Overall, happy with the product, but I may need to play with the water temp...---mike...
Madison Renovations
Cambridge, Mass.
Mike, Thanks for the response, I am working on building a new house in the near future ( 10-12 months) so I am intriqued with this radiant floor stuff. It is not common at all where I live ( we use gas fired forced air 99.9% of the time out here), but I sure like what I read about radiant heat. I assume there would be some benefit in starting from the begining in the design ,etc, for radiant heat vs. a retrofit situation. Anymore input is greatly appreciated.-------WW 57
I'll just repeat what has been said elsewhere more than once. Assuming a cold climate, since warm floors are important to you, then first priority should be designing a tight, well insulated exterior shell. A lot of comfort comes from avoiding cold spots, drafts, and uneven temperatures. Deciding how to provide the much-reduced amount of heat lost to the outside is secondary to having a good thermal envelope.Having the feeling of warmth in a floor (without shoes on) requires a floor surface temperature at least well into the 70s (F). Raising the whole floor surface of a very well insulated and tight house to such a temperature will result in the whole room heating up to almost that temperature. The result will be a room that is uncomfortably warm. This has been reported by more than one owner of superinsulated houses having radiant floor heating.That type of heating feels comfortable when installed in the typically built house (leaky in terms of heat and air infiltration), because the floor can remain warm feeling without the room getting overheated. It works because the house is hemorrhaging heat.If you build a superinsulated house, or something approaching that (as you should), you might reconsider just how effecive radiant floor heating will *feel* if you can't keep the floor warm enough for your feet to feel it. Maybe the better advice is to select a less complicated and expensive heat distribution system and just keep the slippers on.
I understand what ypu are saying, but if you built the super insulated home, would not the radiant heat work ok if the t-stat were set at a lower temp(68-72) or somesuch and still provide a comfortable room temp? I do not know , just looking for answers. Thanks for more info.------WW 57
t
The lower temps work depending on things like windows and climate..
Losses through even the most efficent windows are serious.
I will be in the Dallas area where it gets in the 20's and lower occasionally but not on a consistent basis like it does in other areas of the country. How do you treat insulated window units to help with the heat loss/gain(summer) ?-----WW 57
I'D USE MOTHER NATURE.. Plant trees that shed leaves in the fall and you get the best of both worlds.. trees provide shade and shelter the house from the ravages of UV light and drop off nicely in the winter when you'd appreciate the solar heat gain..
With temps in the 20's a rarety you really don't need to worry about heat loss to the degree that we up here in the artic circle do <grin>
You might want to increase the amount of tubing in front of major windows to offset some loss but it won't be a major deal..
Great point about the tubing in front of the windows.------WW 57
Given the fixed floor area containing the PEX, and a particular floor construction and set of coverings, the circulating water temperature might be the only practical way of controlling the room temperature in a superinsulated house. Edit: That temperature might at times not be high enough to provide the *warm feel* to the floor.I imagine that if water temperature is fixed at a level that will provide adequate heating at the design outside temperature, then the slugs of heat put into the floor assembly from time to time will result in uncomfortable spikes in room temperature when the outside temp is more moderate. This would be sort of like trying to maintain constant water level in a bucket with a small hole in the bottom, using a fire hose for supply.I want everyone to understand that I am not speaking from experience, and I have no particular expertise in radiant floor heating. I have been reading the electronic literature on building science and house construction voraciously over the last few years, sifting through expert testimony and doing my own calcs. My views on RFH in superinsulated houses are based on reports of others and my own reasoning.
Edited 1/18/2009 5:57 pm ET by DickRussell
After the room hits the desired temperature, the heating stops and the warm-foot feeling fades. However, we have a set-back, so the room cools down a few degrees when we don't need it. Then when it's time to re-heat, the floor warms up when we really want it. So, while the air temperature is cooler, we get the warm foot feeling until the room warms up. I'm using Warmboard, so the floor-warming delay is smaller, but so is the time of the residual warmth.---mike...Madison Renovations
Cambridge, Mass.
"After the room hits the desired temperature, the heating stops and the warm-foot feeling fades."Are you talking about a conventional on/off thermostat? Superinsulated house or conventional?I would think that as the thermal envelope goes to higher and higher R values, the amount of overshoot from the residual heat in the floor would be more problematic, comfort-wise. This would imply a need for more sophisticated control, which would use both room air and outside air temperatures to adjust the circulating water temperature downward as the room air approaches the setpoint. However, I have no idea what is actually used for such a well-insulated house or even what is available.
tekmar has controls that do just that.
I would think that as the thermal envelope goes to higher and higher R values, the amount of overshoot from the residual heat in the floor would be more problematic, comfort-wise. This would imply a need for more sophisticated control, which would use both room air and outside air temperatures to adjust the circulating water temperature downward as the room air approaches the setpoint. However, I have no idea what is actually used for such a well-insulated house or even what is available.
Modulating boilders with outdoor reset address that issue.
re: "After the room hits the desired temperature, the heating stops and the warm-foot feeling fades."conventional on/off thermostat on the wall (not floor) with high density spray foam to about R-40 ceilings and R-25 walls, cross strapped for thermal break. But one wall has significant glazing (new Pella casements and fixed) and there's a conventional wood fireplace.I don't try to modulate circulating water temp, there's a simple recirculation valve (or whatever they call it - it's late, I'm not looking it up). So when I the set-back time ends, I heat to 67 deg., which is toasty while the floor is warm, but then it's just a 67 deg. room for a while as the floor temp cools to room temp, and the room temp very slowly cools.I'd estimate 67 with a warm floor is about the same comfort level as 70 with a room temp floor.---mike...Madison Renovations
Cambridge, Mass.
woodworker.
I used to use forced air furnace and still have one as back up (it was free) but I can't tell you how much warmer you feel at a lower temp setting with a warm floor!
Your feet are the furthest thing away from your haert so the blood is the coolest when it gets there. Keep your feet warm and your body feels warm..
I used to get headaches because I kept the temps warm enough for my wifes cold body but her feet were always freezing.. since I changed to infloor heat The temp is set at 67 degrees and I walk around barefoot when it's 20 below outside.
remember heat rises so what starts out warm at the floor rises to keep you nice and comfortable..
I love the idea.
My radiant floors are not flowing right in the kitchen and my wife is pissed. (we have grown spoiled with radiant floors) When we sell the house and move, I am afraid i will either have to retrofit radiant in the new place or build new and install radiant.
Re. reducing the heat for the pex lines, I used a 3 way mixing valve but a 4 way mixing valve is the cadillac way to do it and gives a little better control. With that said, I have not touched my 3 way mixing valve in 7 years so i guess it works aok.
If you have 2 circulators already, great. If the house is zoned with valves, I think you might need a 2nd circulator so you can properly hook up the mixing valve but I cant picture how you would do it without drawing out a schematic.
Have fun, take your time, and make sure you pick a good manufacturer and get their rep involved so that they can give you a design that will serve you well.
They will often do this to get the business.