In-Floor Heat Questions

[livetohunt]

We are currently building a new house, and I have requested in-floorheating in our basement & garage. I do not know anything technical about in-floor heating, so I have a few questions that I am hoping someone can answer:

1. Are there brands of boilers that are better then others? I think I heard our guy mention Thermolec & one other one. Are there any specific features in a boiler that I should ask for?

2. I have requested pricing to have the same type of floor heating in our 20 X 24 attached garage. There is an option price for 1/2" Slab Shield Reflector Insulation. Is it foolish not to choose this additional item? What if I don't?
I can afford to have the same reflector insulation used in our basement, but it is a $800 option for the garage floor.

3. What else should I ask of my HVAC guy when it comes to in-floor heating?

Thank you!

 

[nate379]

There needs to be at least 2" foam under the slab not 1/2" reflecter shield whatever that is.

 

[skeletonizer]

Yeah, some guys think that the reflective "bubble wrap" stuff is all you need. The R value of it is near 0 when buried. IMO you need the 2" of foam or you will be heating the ground.

 

[livetohunt]

He told me (unless I understood wrong) that the foam sheets are not needed if we use the slab shield reflector insulation, as the reflector alone has a higher value than the pink foam sheets.

What specifically should I ask or specify so I don't mess this up?

 

[skeletonizer]

He told me (unless I understood wrong) that the foam sheets are not needed if we use the slab shield reflector insulation, as the reflector alone has a higher value than the pink foam sheets.

What specifically should I ask or specify so I don't mess this up?

I would do some research on the specific product he is pushing. It may in fact be better than foam. I have my doubts about anything that thin being in contact with both the soil and the concrete providing a good insulation. As an air barrier it may work great but with it actually in contact with huge thermal masses???

 

[livetohunt]

If I understand correctly after doing some research tonight, the order starting at the bottom is earth/dirt, then vapor barior, then 2" foam insulation, then water tubing with the concrete poured on top of that. Right? Thanks for your help

 

[nate379]

"Blue board" is teh stuff that was used on my house...

 

[nate379]

Yes, that's correct. Also rebar/mesh, which is over the pex.

If I understand correctly after doing some research tonight, the order starting at the bottom is earth/dirt, then vapor barior, then 2" foam insulation, then water tubing with the concrete poured on top of that. Right? Thanks for your help

 

[havi]

2" HIGH DENSITY foam at that. And yes you have the order correct, as well as the rebar/mesh Nate379 added. My boiler is a monitron Slantfin electric, and heats a 36x44 house no problem.

 

[livetohunt]

I found more information on the slabshield. Not sure if I am permitted to post a link, but here is the web site for "slab shield"

http://www.slabshield.com/SlabShield/SlabShield.php

Does anyone have experience with this product vs the traditional foam sheets?

 

[walrus]

Yes, that's correct. Also rebar/mesh, which is over the pex.

I usually see the pex over the rebar

 

[tdkkart]

I found more information on the slabshield. Not sure if I am permitted to post a link, but here is the web site for "slab shield"

http://www.slabshield.com/SlabShield/SlabShield.php

Does anyone have experience with this product vs the traditional foam sheets?

Email them and ask what the R-value of their product is when compared to 2" high density foam board. I'm guessing they'll come back with some "radiant barrier" BS mumbo-jumbo answer that means squat.

There's a huge difference between a radiant barrier seperating 2 air spaces and insulation seperating 2 thermal masses, earth and concrete, that are in direct contact with each other.

I would accept no less than 2" of high density foam board.

 

[nate379]

The 2" foam I have has an R value of around 5 to give you an idea when you compare the reflector shield stuff.

walrus the reason they put the PEX down first here is that it's staked into the foam. The rebar and mesh sits in the middle of the slab.

It's nice to have the PEX at the bottom because you can run Tapcons or the Hilti gun down into the slab to tie interior walls or whatever without worrying about hitting the pex.

 

[walrus]

It's nice to have the PEX at the bottom because you can run Tapcons or the Hilti gun down into the slab to tie interior walls or whatever without worrying about hitting the pex.

That makes sense, it would **** to drill into a tube. Mine is going to be on top but I will have no interior walls nor will I allow any drilling. I'm trying to figure how to and where to leave a space big enough so I can install a future lift without worrying about a leak.

 

[Bigrhamr]

Take a look here:

http://www.greenbuildingtalk.com/Forums/tabid/53/forumid/12/page/1/view/Topics/Default.aspx

For lots of knowledgable discussion on slab insulation and other radiant heat issues. The general consensus is that all the bubble wrap and reflective barrier stuff is next to useless under a slab.

The average foam board is R-5 per inch of thickness. When I started my project I contacted several of the companies pushing "alternative" slab insulation. They talk a good line and throw around a lot of numbers that don't add up. One told me if I used the normal 2" foam board it's effectiveness would be reduced by 95% under a slab leaving it with an R-value of only R-4, so it must have started out at about R-80 or so I guess

The foam board is extruded polystyrene, some companies are now pushing a product with a layer of this sandwiched between 2 layers of vapor barrier material, foil or mylar. Good idea and it is easier to work with due to being in a large roll with self sealing edges intead of sheets but the r-value is still based on the thickness of the polystyrene and they are mostly using between 1/2" and 1-1/4". I did price the 1-1/4" and it was about half again the price of good old 2" polystyrene board.

 

[nate379]

The 2" foam I have says it's R5. I took that to mean the 2" thick, not R5 per inch, so R10... am I incorrect?

 

[walrus]

The 2" foam I have says it's R5. I took that to mean the 2" thick, not R5 per inch, so R10... am I incorrect?

R5 per inch, 2" is R10

 

[nate379]

Didn't know that. I have been told from a few guys that 2" of foam equals a ft of dirt too.

We have to run water lines 10-12ft deep so they don't freeze.... if you can't go that deep the foam can be used. They are going to have to dig my line up for that reason... froze twice this past winter.

 

[Bigrhamr]

The 2" foam I have says it's R5. I took that to mean the 2" thick, not R5 per inch, so R10... am I incorrect?

From your pic it looks like you have the r-tech insulfoam, it comes in several variations from about r-4 to r-5 per inch from what their website says.

http://www.insulfoam.com/index.php?option=com_content&view=article&id=60&Itemid=154

10-12 feet deep, whoa! I guess I better quit whining about having to go 5'.

 

[walrus]

Didn't know that. I have been told from a few guys that 2" of foam equals a ft of dirt too.

We have to run water lines 10-12ft deep so they don't freeze.... if you can't go that deep the foam can be used. They are going to have to dig my line up for that reason... froze twice this past winter.

1" of foam equals a foot of dirt. I have access to a prof of Engineering who has done a ton of research on frost in Maine. We might not be Alaska but we're close

 

[havi]

While living in the trailer house as the new place was being built, our water lines froze, too. We got a heat-tape type cord that slid inside the water line and had an electrical plug at a tee where it meets the hard line that went to the pressure tank. Worked great. We have to go 5 feet down. I don't feel so bad now, lol.

 

[redsky49]

OP doesn't give location, so much of this is speculation.

Wirsbo, now known as Uponor (now that makes sense ) is one of the larger manufacturers of Pex and has an entire technical library available at their website. They were the very first to call at our office many years ago, pushing this European product. They are probably more responsible than anyone for the popularity of Pex in the US.

Definitely insulate under the tubing. You want a closed cell nonhygroscopic foam with good compressive strength. Not blue Styrofoam! Place a vapor barrier between any insulation and the fill. Insulate the edges and the horizontal base.

Tubing cannot cross expansion or control joints! If you must, follow manufacturer's details to the letter. Air test prior to pour at 100 psi. Maintain pressure until all joints are tested. Don't test with water.

If ever subject to freezing, utilize a brine or glycol solution. Avoid getting air into the system as this will degrade the antifreeze. Locate system vents carefully.

Pumps and trim must be suitable for the fluid that you are utilizing. You have to derate pumps for glycol use.

The fluid heater, typically a boiler, can be of any configuration (gas, oil, electric, etc.) but must be protected from thermal shock and flue gas condensation due to the low fluid temperatures being used. My preference is a cast iron boiler due to its inherent longevity (30-40 years plus). Burnham is one of my favorites for residential use. Unless electricity is nearly free, an electric boiler will never be cost effective.

I could write a book about the additional requirements necessary for a successful installation. Your best bet is a thoroughly vetted Contractor with a good track record in this type of installation. You definitely want a single source of responsibility.

Be cautious of internet advice. This is not a Harry Home Owner type of project.

Also, if you have the finances, consider the possibility of extending the system for snow melt. Great to have in the snow belt.

Good luck with your install.

As always, offered only as opinion

 

[nate379]

Where at it Maine?

I grew up there... up in Van Buren. My folks still live there, brother down state and sister up north a bit more.

1" of foam equals a foot of dirt. I have access to a prof of Engineering who has done a ton of research on frost in Maine. We might not be Alaska but we're close

 

[havi]

On an off-peak meter, my electric boiler costs about $100 a month in Dec, Jan, and Feb. And about $75 in Nov and Mar, and $50 in Oct and Apr. Adds up to about the same as the firewood I used to buy, but no labor, and about $1500 less than my friends running traditional propane furnaces. I would prefer an outdoor wood boiler, but that'll wait til my new garage is done. Of course locations will vary.

 

[walrus]

Where at it Maine?

I grew up there... up in Van Buren. My folks still live there, brother down state and sister up north a bit more.

Van Buren isn't much different than Alaska I grew up in Orono, I'm on the coast now.

 

[walrus]

Not blue Styrofoam! Place a vapor barrier between any insulation and the fill. Insulate the edges and the horizontal base.

Tubing cannot cross expansion or control joints! If you must, follow manufacturer's details to the letter. Air test prior to pour at 100 psi. Maintain pressure until all joints are tested.

Their is blue styrofoam under most every slab I've ever seen here in Maine? I was told not to use the pink styrofoam?

The tubing maufacturer I talked to said 50 psi on the air test. Should it be kept on during the pour?

 

[redsky49]

Their is blue styrofoam under most every slab I've ever seen here in Maine? I was told not to use the pink styrofoam?

The tubing manufacturer I talked to said 50 psi on the air test. Should it be kept on during the pour?

I shouldn't have used the insulation color for reference. Manville, Dow,Knauf, and others all make suitable products and all have various names and color identifiers. What you will want to avoid is an open cell foam. If the rigid insulation crumbles into little bb sized balls of insulation, it is likely the wrong product.

The insulation should be water resistive and to do that you want a material that will not absorb moisture. This also is why the moisture barrier between the fill and the insulation should be sealed and made smooth enough to eliminate any holes or gaps for moisture transfer. The edge of the moisture barrier should also be "flashed" to the surface of the slab in order to seal the ends.

Pressure testing of the system should be in compliance with the manufacturer's requirements. 100 psi is a typical test number. Given that many hydronic systems will operate at a normal pressure of 30 psi, a 50 psi test pressure may be appropriate. It depends on the particulars of the specific system. The actual system operating pressure must be calculated, the appropriate pump selected, etc.

I try in all my responses to give a generic answer that might be useful to all that read it, not just the original poster. It is not my intent to design someone's system. I am trying to emphasize that any mechanical design, no matter how simple it may appear, will be successful only if approached in a thorough, informed manner. If you choose not to employ a qualified engineer for some of the projects discussed here, proceed very cautiously. You can't simply depend on a neighbor's experience or even on a Contractor's response.

Be skeptical and remain a cautious consumer.

As always, offered only as opinion

 

[Bigrhamr]

If you choose not to employ a qualified engineer for some of the projects discussed here, proceed very cautiously. You can't simply depend on a neighbor's experience or even on a Contractor's response.

Be skeptical and remain a cautious consumer.

As always, offered only as opinion[/QUOTE]

I'll second that one. Although I am going the DIY route on radiant and many other things it's only after much research. After consulting and getting quotes from 3 different heating contractors , all of who are supposedly experts in the field, and getting 3 totally differerent recomendations, I determined that blindly following ANYONE'S advice can get you in big trouble.

 

[walrus]

I shouldn't have used the insulation color for reference. Manville, Dow,Knauf, and others all make suitable products and all have various names and color identifiers. What you will want to avoid is an open cell foam. If the rigid insulation crumbles into little bb sized balls of insulation, it is likely the wrong product.
/

Thats polystyrene and usually white in color.

 

[Bigrhamr]

Then you have both expanded polystyrene and extruded polystyrene. Extruded, from all the info I can find is the recomended product. And to muddle things up a little more you need to pay attention to the PSI rating for compressive strength. Owens Corning (pink) seems to have boards ranging from 15 PSI for Foamular 150, usually found at the big box stores, up to 100 PSI stuff for use under heavy industrial slabs.

 

[livetohunt]

Update

The heating guy reccomends Slabshield. Our builder has not used any form of insulation under the tubing in the last couple of builds; he says that by not using the 2" insulation sheets, we can take advantage of the Geo-Thermal effect. The house is a 1.5 story with a walkout basement. Most of the basement floor is a minimum of 2 feet in the ground, and it slopes. The deepest the basement is in the ground is about 8 feet. I need your opinion, I have asked 3 people and I have 3 different opinins. Do I need insulation under the Pex?

 

[GSSFC]

You could have spray foam installed for that price 20x24 = 480 square feet x2" you could get it for 800...or at least I would! That is seamless, NOTHING is better!

Tim

 

[GSSFC]

Update

The heating guy reccomends Slabshield. Our builder has not used any form of insulation under the tubing in the last couple of builds; he says that by not using the 2" insulation sheets, we can take advantage of the Geo-Thermal effect. The house is a 1.5 story with a walkout basement. Most of the basement floor is a minimum of 2 feet in the ground, and it slopes. The deepest the basement is in the ground is about 8 feet. I need your opinion, I have asked 3 people and I have 3 different opinins. Do I need insulation under the Pex?

You NEED insulation under the slab to prevent downward heat loss. Geo-thermal effect? If that were the case, why would you put heat in? Open the doors and windows and take advantage of global warming too while you are at it! You aren't in Arizona in the desert are you?

Tim

 

[tdkkart]

Since we have no idea where you live it is a bit hard to make recommendations. The answers for Texas will be much different than for Northern Minnesota.

However, now that you've described the situation a bit, and since you have a sloped lot with as little as 2ft of depth to your basement, the answers are much more important.

Geo-thermal huh?? Answer me this, which mass is bigger, your basement floor or the earth?? Which needs to be at a higher temperature??
Geothermal is fine as long you're trying to pull heat from it, but as soon as you get to the point of losing heat to the earth when you're supposed to be heating your house it becomes a whole different story.
Believe me, you canot affrod to heat the earth under your house.

 

[livetohunt]

Sorry guys, I did not realize that I never mentioned my location. We live in Northern MN, near Brainerd.

I spoke with one other homeowner in our developement who built a couple of years ago. He did not use any insulation under the slab either. I have attached a picture that he sent me today.

I think I am going to go with the 2" pink foam sheets, as I can't risk not getting everything out of the floor heat. It will mean skipping floor heat in our garage, as I will need 50 sheets to cover the sq footage.

 

[jeff5295]

I'm guessing we can expect the guy with the uninsulated basemant slab to soon be complaining about about how horribly inefficient radiant heat systems are. The loop spacing looks pretty wide too, assuming those are 6" grids on the mesh. This is a prime example of how radiant heat gets a bad reputation. Install it right and it's great. Intall it wrong or take "short cuts" and you end up with a worthless system that will cost a fortune to operate and deliver marginal results.

 

[livetohunt]

What should the loop spacing be, so I can police my install?

 

[GSSFC]

I would not even bother hooking that setup into your system!

You need to STOP and insulate. Then install 2-3x as much radiant tubing. You only get one shot at doing this right. Honestly, whoever did that does not know what they are doing and is just taking your money for shoddy work.

Tim

 

[walrus]

. Do I need insulation under the Pex?

Do you need it? No, but you'd be an idiot not to insulate a slab where you live, including the perimeter

Geo Thermal effect? I'd fire the guy if he told me that

 

[jeff5295]

What should the loop spacing be, so I can police my install?

I've used 12"-14" spacing on my systems with 1/2" pex. Hard to tell from that picture, but that may be 3/4". Not sure if you can get away with wider spacing using larger diameter tubing. I only can advise on what I have experience with. Maybe someone else can comment on 3/4" pex.