What do we know about in floor heat?

My house is cold.  It's more of a collection of poorly assembled rooms, with some having baseboards on three walls, and some having no heat at all.  I would like to make it a bit more comfortable.  A friend moved into a house with hot water in floor heat which is nice and he said it dosen't use as much oil as his last house.  My basement is unfinished so it looks fairly easy to install.  Has anyone done this themselves/ Have a supplier they liked?  Things I should look out for?

Watching this cuz I really want to do it. Mr money mustache blog has some good write ups on doing it yourself if I remember correctly. 

If you are doing a big area I would think you want water. But they also sell electric mat to go under tile and such for small areas like bathrooms, and that would be much easier to hook up since there is a lot less 'infastructure' needed.

I haven't installed one of these systems, but have been reading up on the topic in the context of a garage.  I'm not an expert by any means.

Inside a house it looks like it would  be pretty straight forward.  The main choices seem to be a hydronic system or an electric system.

Hydronic would require a boiler of some sort, so $$$$, but seems to be the most efficient.

This is a video on one system I was looking at:

Haven't really read up on electric yet, as I'd rather not have my meter spin itself off of the house.

When it's installed in a concrete slab, the heat all goes into the slab which has lots of thermal mass and keeps the building warm. If it's installed with only 1 side touching the floor, and the other side open to the basement air (no thermal mass), I'm not sure that it will be as efficient or effective. Finding someway to seal the grid of pipes to the underside of the floor (spray foam?)  so that you're not losing heat to ambient air would probably help quite a bit, but I'm not sure what the best way to do that might be.

If you have access to the underside of a hardwood floor in between the joists, there are systems to install the water lines and heat reflective insulating panels that fit nicely in the space between the joists. Would be an easy way to go if you have a crawlspace or something under an existing floor. Working in the actual crawlspace could suck though.

I experienced one downside to in-floor (electric) heat the winter (actually not the whole winter, just September through March) in Montreal--- it was freezing on the couch and in bed!

Essentially, if you had something between you and the floor, you were cold.

I've done both, and lived in a house with hydronic in the slab. 

Electric strips for an entire house are gonna KILL you on your power bill. 

Ive never lived in a house with hydronic in the wood floor. You would definitely loose some of the advantages of the thermal mass. 

Do you have a boiler now you would be tapping into?  It would be a game changer from a cost perspective. 

Adding radiant heating to an existing floor is a PITA. Expect to either pay a lot, or spend a LOT of time on it. 

Living with radiant heat is a different experience. We get used to hot spots in a house- we kinda like when the radiator warms our hands, or the air vent blows heat on us when we are cold. These things don't happen in a radiant floor house- it's all kinda even, without hot spots. This has its good and bad. 

My opinion is the bad (from a comfort perspective) would be maximized in a remodel radiant floor in existing wood framing. That is to say, it would be hard to get the decent even heat coverage in old framing, or without the thermal mass of the slab, and you may not get the "overall toasty" feeling.  

Laying heat strips between the subfloor and the finished floor works well (when installing a new floor), but still consumes a lot of energy.

 One of the problems with hydronic in a remodel is that you are gennerally installing the system under 2 layers of wood (nearly 1 1/2" of solid wood) or carpet or something.  It doesn't transfer the heat well to the interior if the entire floor system is not designed for it from the start  

If you are gonna do hydronic in an existing floor, you will also need to insulate well underneath it. If you have to install a boiler too, it is unlikely it will he cost effective. 

In reply to paranoid_android :

That system has the advantage of thermal mass, and is installed on top of the subfloor (with a finished floor on top of it). 

It will perform well, but is not remodel friendly. 

I would go with a hydronic system.. I have hot water baseboards now in the rooms that are heated so I could use my existing boiler.  The only room left with carpeting is my living room and that will eventually get peeled up since it should have a decent wood floor under it like the other rooms had.  If i understand what i read last night I would need aluminum plates to spread the heat more evenly and then heavily insulate underneath.  Can I have both systems off one boiler? I'm tempted to try it in the unheated sections of the house and if she's happy with it move on to the other rooms.  It seems like if I had the system broken into zones it should be workable.

Dogs love it. Your whole house is the warm spot.

In reply to Wally :

In floor radiant heat makes sense.  Your feet are the coldest part of your body because the blood from your heart has to travel the most distance.  Warm your feet and the rest of you can be cooler yet still comfortable.  

Heat rises but blowing hot air out of vents really sends it flying and most energy is wasted at the ceiling.  Cold air settles so forced air will give you cold feet and a hot head.  

There are several ways to do in floor radiant heat.  One is lay some pex tubing  on the floor and pour  and level cement over it.  It’s fast, easy, and cheap.  That’s fine in a kitchen or bathroom but not so nice in a bedroom or living room.  You can’t nail down hardwood flooring  without the special plywood made for that purpose.  carpet has its own issues.  

Another way is to hang your pex runs underneath.  That requires brackets to hold the pex against the floor and is best if backed up with reflective insulation to direct all the heat upwards.  

The problem comes with conflicts.  Wiring, plumbing,  duct work all want to be in the same area.  Plus they all want to be done at the same time, first!!!! 

In floor radiant heat is expensive to have installed but really simple  and cheap to do.  No soldering no glueing  just run loops of Pex and clamp together.  Pressurize the resulting loop and check to see if it holds pressure before finishing up and sealing it in. 50psi for 48 hours meets code but I leave it for at least a week just because I can stay busy doing other things

In reply to Wally : You don’t need a boiler in fact you can use a water heater just as well.  While my system has a boiler my back up is a spare water heater.  My energy calculations tell me either one can be more efficient depending on the cost of electricity and natural gas.  

I have valving that allows me to switch from one to the other in a minute or so.  One unfinished circuit is plumbed in for a driveway circuit to avoid the cost of plowing.  That requires the use of a dedicated water heater because antifreeze will be required.  

Either a boiler or water heater will require a panel dedicated to the pumps and make up systems required.  While you can do that yourself you’re better off getting a premade panel with everything ready to go.  Figure about $1500-1800 depending on how many zones you select  

the size of boiler required depends on the efficiency of the houses insulation ( heat loss calculation). Number of zones and size of the house.  

In reply to SVreX : a boiler is overkill except for really big houses with a poor insulation package.  

Water heaters work efficiently at the lower temps most radiant systems require.  

Frenchy, you gotta stop bolding all of your posts. 

All I know about in floor heat is that I wish we had installed it in the master bathroom remodel we completed last summer.  I had no idea the ceramic tile would be that much colder than the linoleum that was there before...Live and learn, I guess.

frenchyd said:

In reply to SVreX : a boiler is overkill except for really big houses with a poor insulation package.  

Water heaters work efficiently at the lower temps most radiant systems require.  

 

I realize you are an expert at this, but the house I lived in that used a water heater to heat the radiant slab was completely inadequate, and that was a new house in the Deep South. 

Im not saying it can't be done, but your blanket statement that water heaters work efficiently is an overstatement. 

Recovery time is a big issue. 

We stopped doing water heater radiant slabs because we had too many customer complaints. 

In reply to mtn :

I don’t do anything to make it bold. Sometimes it comes out that way, sometimes not

what really confuses me is when it starts out bold and then stops being bold. I notice it usually happens when I start a new paragraph but sometimes just at the end of a sentence

In reply to SVreX : water heaters ( now there it’s bold again) do not respond as quickly as boilers do and they need to be big enough to handle heat loss.That’s why I use a big dual element water heater as my back up    Water temps on the intake side and exhaust side of a zone  need to be adjusted for heat loss in that zone.  

The savings in a water heater is that you set the max temp at the water heater say 135 or 145——- and the pumps determine the speed the water flows to achieve your desired temp.  

Boilers run at a higher temp, say 200 and then the mixing valve adds cold water to achieve  proper temps.  That’s why boilers respond fast enough for people used to forced air while water heaters can  tend to seem cold.  

Modern boilers  like used solely for in floor radiant heat are more like instant on water heaters in that they only heat the water actually circulating rather than the large water tank used in the past.  

It’s also easy to make mistakes on in-floor radiant heat.  Pex runs need to be dense below windows and doors  due to heat loss out even the best window. Face it, no glass will retain heat as well as a insulated wall will.  

My ex- is an HVAC engineer and she looked into it prior to remodeling her house. Her house already has a boiler for radiators and baseboard heating. To put it bluntly, unless you can bury the tubing in concrete, it's not worth the effort.  Yes, there are systems to retrofit tubing between joists, but the prep work in most cases is insane. Often, the nails attaching the flooring through the subfloor goes through into the joist cavity. Pretty much all of those nail ends will need to be cut flush with underside of the subfloor. This will be an incredible amount of work.  Then you go through the aforementioned installation process. But in the end, you are trying to use wood as your thermal mass to conduct heat to the space above. Something wood is not very good at doing. Dry wood is compositionally fibers with tiny air chambers. Because of this it's a better insulator than a conductor of heat. Obviously, denser woods will conduct heat better, but those are heavier and typically not used in house construction.

More effective ways to add radiant floor heating is by adding small electric systems under areas when tile is used: bathrooms and kitchens, for example.  Because the areas are relatively small and usually supplemental, the operating costs tend to be more reasonable.

In reply to Driven5 : you can still install it if you have access to the underside of the bathroom floor.  Either use aluminum flashing or the nail up brackets to transfer heat  then seal the space with aluminum faced foam so the heat is trapped

In reply to Ian F :

Yes the work is higher if you do “staple” up but heat is heat, insulation does not stop heat loss it merely slows it down.  My flooring is 4 inches of hardwood and it takes over a day to increase floor temps by one degree so unlike forced air there is no instant reaction.  

Patience is required but the reward is heat where it does the most good, at your feet rather than going by on it’s way to the ceiling.  

Wood is an extremely poor insulator.  A solid 2x4 has a R value of less than 2  That’s why a fiberglass insulated wall will average out at less than R9 even though the insulation may be R13.  Windows lower it even more.  And if it’s cold enough the real R value can drop below R4 .  Fiberglass is used in furnace filters because air flows through it easily. The laws of thermal dynamics always apply.  Heat rises cold air settles even in wall cavities between studs.  The inside temp might be at 70 degrees but if the outside temp is say 30 below the air against the Sheetrock will rise while the air against the outside wall will settle.  Scrubbing off heat as it does.  

Foam and cellulose don’t allow that air movement.  Foam isn’t affected by moisture while cellulose is. That’s why freezer panels  ( also called SIPs) are made of  solid foam with plywood bonded to either side of them. 

In reply to frenchyd :

The bold has to do with where you put your cursor when you start typing. 

If you put it on the same line as where the bold type is that says "In reply to ...:", then what you type will be bold. 

If you put your cursor on the next line (like a new paragraph), what you type will be normal type. 

In reply to frenchyd :

You are confusing convection with conduction. 

Air infiltration is a form of convective heat transfer. Fiberglass insulation is excellent at resisting conduction. 

R values are about resistance to thermal transfer- primarily conduction. 

I've heard you use the fiberglass filter example many times, but you are using it incorrectly. 

Proper fiberglass installation MUST include an air infiltration barrier. THAT'S the resistance to convection.  The fiberglass is very good resistance to conduction, but can be compromised by convective heat loss without proper air infiltration barriers  

Note that HVAC filters never have air infiltration barriers (obviously). 

A properly installed fiberglass insulation system does not perform similarly to an HVAC filter at all.  They perform entirely different tasks.

I have installed a bunch of them including one very large house that had 27 zones.  Even if you could figure out how to install one yourself, you better have a very fat wallet.  Most plumbers and most heat guys don't even want to get involved because they are complicated.  If somebody on this board is from a Southern state, completely ignore anything they are telling you.  Here in the North, you need a boiler to heat the entire house.  Want to do just one room, then you can get away with a water heater, or at least you could back when you could actually get a water heater larger than 50 gallons for a residential unit.  For each zone you will need a mixing station that mixes the outgoing water with water coming back from the heat loop to make sure its temperature is at the proper temperature leaving the mixing station.  The water temp in radiant is much lower than a typical hydronic system.  Wooden floors and concrete floors get different temp water.  Loops can only be so long.  Water temps drop as the water circulates thru the loop.  Most rooms require at least 2 loops starting at opposite ends of the room and working their way across past each other.  That way every other pipe is either at the beginning of the loop or at the end of the loop.  In the middle of the room, they are both in the middle of the loop.  This heats the room uniformly.  Beside cost of installation, cost of repairs, and constant maintainance, you also have to understand that you can't just lower the thermostat every night.  Get up in the morning and the house is cold, turn on the heat, and wait several hours for the house to warm back up.  You need to keep the temp constant.  They are great for tile floors, and rooms with really high ceilings.  Rich people like to brag they have radiant.  Regular people just want the most cost effective way of heating their house.  My house would actually be a great candidate for radiant.  I can do it myself, and I wouldn't even think about installing it.  I'd rather spend my money on car stuff.

In reply to SVreX : 

that makes sense but I started the response to you on the next line and it’s still bold!  

Now it’s regular and I haven’t done anything different except start a new paragraph.  

Is there some icon I can press to make it stop the bold?   I know bold is like shouting and I don’t want to do that