radiant heat questions

We're looking to finish our basement as our master bedroom with a full bath.  part of the basement used to be the garage so we've replaced the garage doors with french doors.

We need to replace our geriatric heater and are considering putting radiant heat in the basement with a concrete floor.  I just can't think about getting up in the morning and putting my feet on a freezing cold floor.

We've gotten estimates for a boiler, air exchanger and running the radiant heat tubing and it's over $30k.

If we took the plunge and put it in, (we have a large private property which we love, it's the 1950's ranch that is tight)  what about efficiency in regards to the upstairs?  The contractor wants to put trays and radiant heat under the wood floors upstairs in the main living space.  We're wondering if our wood floors upstairs are beat, are we better off putting concrete floors with radiant tubing inside also?  What is the efficiency of the underfloor heating with wood vs in concrete?

Also, what are the chances that we could lay the tubing ourselves and then bring in a concrete contractor to pour the floors?  Then have the heating contractor come in and connect the lines to the boiler?

Lots of questions here I'll pick away at few...

If you're replacing your boiler you could choose a series of small on-demand hot water heaters.  Takagi http://www.takagi.com/index.asp has an excellent reputation, you can google Bosch Aquastar and Rinnai to search for others.  These heaters are well suited to radiant heat applications b/c once the floor system is brought up to temperature, they're only heating the delta between the returning colder water and the temperature you're looking to put back into the space.  With radiant heating, the temperatures you'll be running will be much lower than hot water baseboard which means a lower temperature delta which means less firing which means less energy consumption.  These units run around the 85% efficiency range, very respectable.  They make electric and natural gas/propane models for you to consider.  They're also excellent for retro-fitting as they consume very little space.   These heaters can be ganged together or used for separate heating loops and you can even use them for domestic hot water with the right primary and secondary loops.  I'm not sure of the configuration of your spaces but it's probably a good idea to consult with someone experienced in installing these systems before making the plunge yourself.

Efficiency-wise, radiant heat works best when coupled with massive objects (like a concrete slab).  The principle is that the mass of the concrete more evenly distributes and holds the heat.  Thermal mass is key and concrete would provide a good bit of it, esp. as compared with wood.  I will say, we install radiant tubing beneath hardwood subfloors all of the time, they typically have faster response times and equally will cool faster without the benefit of a large thermal mass.  It's important to keep moving air off of these floors as convective heat loss is a huge killer of thermal efficiency.  Insulate if you can.

Concrete floors on the upstairs portion of your house should be analyzed carefully.  You should have an engineer look at your floor framing before loading it up with 1 1/2" or more of concrete.  Specifying lightweight concrete or gypcrete could get you the thermal mass with less overall deadload.  I think you'll be happy with radiant stapled to the underside of the floor, the metal pans are a good way of more evenly distributing the heat from the tubing.

I think you'll find very few contractors willing to pour on tubing that they didn't install, sort of a liability nightmare.  Single source responsibility is always nice when you can afford it.

Good luck.

Just having a heated basement is likely going to help warm the upper floor. If you want/need to run radiant upstairs, consider putting it over tile flooring...a lot lighter than concrete.

How is tile flooring lighter than the concrete?

If they run the water tubes upstairs aren't they then going to set them in concrete? 

I would think that putting tile over the concrete is even heavier, no?

just an fyi... I've been doing research on the weight of concrete for the mid-level of our house...

From Ardex...

"I can offer for a system over wood that would be a finish floor, is ARDEX GS 4 and ARDEX S- M.  The GS-4 would be installed over the wood, after allowing it to dry completely, SD-M could be installed over the GS-4 as a wear surface.  The weight of the GS-4 is 127.4 lbs./cu. ft., it is installed at 1/4" thick, which equates to 2.65 lbs./sq. ft. @ 1/4".  The SD-M would be 52.78 lbs./cu. ft or .27lbs./sq. ft  @ 1/16" ...."

Perhaps this information is useful for you too.

Previously diane duffey wrote:

just an fyi... I've been doing research on the weight of concrete for the mid-level of our house...

From Ardex...

"I can offer
for a system over wood that would be a finish floor, is ARDEX GS 4 and
ARDEX S- M.  The GS-4 would be installed over the wood, after allowing
it to dry completely, SD-M could be installed over the GS-4 as a wear surface.
 The weight of the GS-4 is 127.4 lbs./cu. ft., it is
installed at 1/4" thick, which equates to 2.65 lbs./sq. ft. @ 1/4".
 The SD-M would be 52.78 lbs./cu. ft or .27lbs./sq. ft  @ 1/16" ...."

Perhaps this information is useful for you too.

Diane,

Help me with the translation here, the GS 4 is lighter, (also more expensive?)

Then the SDM, is much heavier but also harder maybe?  So you skim coat the SD-M over the GS 4 for a wear surface so your floor doesn't get dinged up?

Diane,

Help me with the translation here, the GS 4 is lighter, (also more expensive?)

Then the SDM, is much heavier but also harder maybe?  So you skim coat the SD-M over the GS 4 for a wear surface so your floor doesn't get dinged up?

GS 4 = lighter, more expensive, not as hard

SD-M = much heavier, less expensive, hard

Have I got this right?

This is what Ardex said:

GS-4 is heavier than SD-M  Unit price, GS-4 may be more expensive than SD-M, I do not know your cost of any material.  However, SD-M can not be installed directly over wood, therefore we need to install the GS-4 first. GS-4 is an underlayment, which means we recommend finish flooring material be installed over it.  SD-M is a finish flooring or wear surface. After the SD-M has dried, it should be protected with a concrete sealer.

Let me forewarn you that you can expect some cracking and it can be dented, scratched, etc.

The appeal of the concrete was my thinking of it as pretty indestructible.  We have a gaggle of children.

Now I'm wondering if we shouldn't go with the underfloor pipes and pans and just put in a plywood floor.

There are two primary types of radiant heating used in homes today: hydronic and electric. Hydronic systems are the modern version of the ancient Roman systems, and the most popular choice for homeowners installing a whole-house radiant flooring system. Until recently, hydronic floor systems used copper tubing, but modern systems use flexible, rubber-like tubing installed under the flooring. A boiler (or in some very small rooms, a hot water heater) is used to heat water, which is then circulated through the tubing, which radiates energy and warmth up through the floor.

http://www.tileland.net/warming-up-to-radiant-flooring-hydronic-and-electric-systems/

Thanks NS.

But now my question is what to do with the upper level of our home.

We are pretty committed to putting in an oil fired boiler and heat exchanger with flexible tubing and concrete over the already concrete floor in the basement.

The upper level is a ranch with 3 bedrooms, a bath and the living space.  We had thought we'd just put the radiant heat on the main floor as well, but the question is whether it should be underfloor with pans or set in concrete.

The house is a 1950's ranch.  This thing is so overbuilt an architect friend jokingly said we could park a tractor in every room.

My understanding is that cement, stone, tile, etc  are excellent (best) conductors of heat for radiant heat. That said, we are still researching the weight issue of using concrete because that  plus the heating system will put considerable load on the flooring. If I remember correctly, 1/2" radiant pipes filled with water add about 2lbs per sq foot. It does look like we'll be pinning the radiant heat tubing underneath our current floors in areas where we don't consider cement. We have brazilian cherry through the rest of the home.

Radiant heating (especially in-floor) is so hotly debated that you'll find yourself with a part-time job researching it. Try investing some time on the RadNet forums and you'll hear guys who are experts in the field disagreeing on basics all the time. Like so many on these forums, I'm a dangerous lay-person with more inspiration than understanding but here's my advice, taken from real-world experience. Give serious consideration to solid, dependable water heaters manufactured specifically to provide hot water for potable use and home heating (ie. Bradford White). They're incredibly dependable appliances and vastly underrated for this application. Warning: most "experts" you talk to will tell you to never do this. Plenty of people have with great success and have saved themselves gobs of money. Besides, it's just one appliance that will never short-change you while you're in the shower and your significant other starts the dishwasher (unlike on-demand heaters which have a GPM limit - then people buy two of them to make it work...) And while I'm on this topic, you can't fool the laws of physics: compare the EnergyStar BTU usage of the best water heaters with the on-demand heaters. Not much difference.

I've found that the experts also disagree heavily on whether concrete is ideal. Sure, it holds heat but it takes a long time to adjust to changing conditions. I don't know about you, but regardless of how a modern home is heated, EVERY room should have its own adjustable thermostat. It's called efficiency and comfort! For a remodel, I would forego the concrete and go with a dry system with individual zones in each room. 

Best of luck!

I cannot believe how much time we have invested so far in researching.

There is so much information out there, it's overwhelming.

Now we are thinking about replacing the forced air system and zoning off areas.

But we are still conflicted about what to do about the basement.  The plan is to put in a bedroom and full bath down there and my husband and I will use that space.  I cannot face getting up in the morning and putting my feet down on a freezing cold floor.  I hate wall to wall carpeting. 

If we put in electric radiant heat in even part of the basement where the bedroom and bath are...  And we are thinking about hydronic radiant heat again just in the basement floor.

But how much will the electric cost to run?

Geeze this is confusing.

I agree with you as it seems the more you study up on various systems the more confused you can get!!!!

I used flextherm cables from iowaradiant.com and installed myself.  Approx 1000 sq ft.  The cable/thermostat materials were approx 1800 bucks.  This was on an existing basement concrete floor.  It came with glue down strips with guides you snap the cable into.  I had an electrician check the cable before covering them up and then after to make sure the cable was intact.  To cover the cables I lugged in and mixed up  53  50# bags of self leveling cement with a buddy.  Then tiled with slate tile in a few hours after inviting 8 friends over for a tiling party.  On  the coldest MN winter day my basement is cozy warm.   The only thing I didn't do was use some sort of insulative/radiant barrier under the cable.  That would help the performance and responsiveness.  My electric bill increases about $25-$30 a month during heating season Nov-March.

I am doing research for building a new modern passive solar home and am considering various systems that will work with with that.  Possibly hydro radiant to circulate the solar floor heated water throughout the system.

I'm building a 2.5 story home and planning on using radiant flooring.  My builder says the bottom floor will be enough, as it is a concrete (ICF build) with no basement.

I'm a little nervous that we should add the second level, too.  Any thoughts?

We have a three level house, perimeter foundation, no slab or cement on the base floor. We are putting in radiant heat in all levels. We will have a direct vent fireplace to heat the center level if we ever feel that there's need for a burst of heat.  It's my understanding that we do need the radiant system on each floor, perhaps because wood flooring is not as good a conductor (not sure what flooring material you have on the other floors) else if the effects of radiant are not as far reaching to ensure that the other levels will be at a comfortable range. It might also have to do with the design of our house. The top two levels are open to each other with a lofted ceiling, while the bottom level is only open to the one above it via the stairwell.

Lastly, it might also have to do with the insular qualities of your home.

I might advise you to ask a radiant heat specialist for advice. We have friends who recently finished an addition. They put radiant in the new sections of the house, via the architects recommendation. They are using forced air through the remainder because the builder recommended (didn't want to deal with putting radiant throughout, and they didn't want to battle it out with their builder..) It might be that there's another incentive for the builder to not recommend it on all floors. Something to think about.

Previously Stephanie Merchant wrote:

But we are still conflicted about what to do about the basement.  The plan is to put in a bedroom and full bath down there and my husband and I will use that space.  I cannot face getting up in the morning and putting my feet down on a freezing cold floor.  I hate wall to wall carpeting. 

If we put in electric radiant heat in even part of the basement where the bedroom and bath are...  And we are thinking about hydronic radiant heat again just in the basement floor.

But how much will the electric cost to run?

Geeze this is confusing.

Despite the abundance of hydro-power here in Western Washington, electricity is still expensive - so I understand your reluctance about running electric radiant over larger spaces. If your basement ceiling height can tolerate the loss of at least 1.5 inches and you don't have water/moisture intrusion issues, you might install what's called a dry system (I've done this chez moi). This is a sandwich of rigid foam (0.5 inch thick or more if you can accomodate it), topped with 5/8" plywood/OSB sleepers (fastened down with concrete screws) with 1/2" hydronic pipe running in between. Make use of metal heat transfer plates. Then your finished floor goes on top. Engineered hardwoods are just fine: they're stable and come in so many varieties. But you can do tile, marmoleum, whatever. A word of caution: this approach is more time-consuming but the materials are common (ie. cheaper) so it's better suited to a DIY'er. If you're hiring this job out or if your ceiling height is already low, you might consider hiring a crew to bust out your basement slab then have a new slab poured with hydronic pipe embedded within (this will also give you the chance to first insulate under your slab which probably wasn't done if your house is older). I know it sounds $$$$ but it will probably pencil out near the same cost and it could come together quicker. Best of luck!