Insulating floors

John@WattsRadiant

While there certainly are situations where insulating under the entire slab does not make sense (southern CA, for example, might be one), it is NOT the policy of Watts Radiant to recommend AGAINST insulating under a radiant slab.
It's actually quite easy to model heat loss/energy usage with and without underslab insulation and determine the payback period.
John @ Watts Radiant

Joh n Brickey

I have been doing infloor heat for about 10 years and I have always insulated under the floors. I have been bidding jobs against other companies that tell the customers it is a waiste of time. The last guy told me it would be cheaper and faster to use a bigger boiler. This is like saying "why put insulation in the walls of a new house it would be cheaper to put in a bigger furnace". Let me know what you guys think of this.

Al Letellier

floor insulation

Sounds to me like someone is tryingto re-invent the wheel and doesn't know that it has to be round........

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Joh n Brickey

I'm not sure what a wheel has to do with insulating a floor

Mark Hunt

They HAVE to be insulated

and the guys that say it's a waste of time should be forced to pay the customers heating bills!

Your analogy of building a home with no insulation in the walls is perfect! Explain it to the customer exactly the way you did here.

Mark H

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Joh n Brickey

I have tried that and they tell me that the other guy is cheaper on the install. I tell them that they are going to pay for it in gas and I cannot get through to them. My wholesaler told me he just got back from a hands on and the contractor on the job didn't insulate the basement floor. I'm not sure if it was a Wirsbo rep or a field rep that said it didn't matter one way or another. Well, I know that all my jobs are insulated and have been working great. I just wanted to hear other opinions on the matter.

Robert O'Connor

Watts Heatway

Watts heatway rep insist up and down every time I see him that insualtion under a radiant heat slab is a waste of money . He says the payback is 20 years on the insulation. Hmmm...

regards,
Robert

John_21

> Watts heatway rep insist up and down every time I

> see him that insualtion under a radiant heat slab

> is a waste of money . He says the payback is 20

> years on the insulation.

> Hmmm...

>

> regards, Robert

John_21

Floor Insulation

Have been doing radiant for over 25 years. Ihave insulated under slabs on about 98%. Have been talked out of the balance. The differance is dramatic. Now we will not even do a job withoutit. Have had feedback on many jobs and have formed this opinion. You can not to much insulation.John

Bob Bona_4

unbelievable.

Has any design data been provided by the "others" to show what water temps/spacing/heat loss numbers?

#1. I would never perform a residential radiant install w/o insulation, and..
#2 How would one guarantee performance in that case?

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Joh n Brickey

20 years on the payback? What the hell are you insulating with gold blankets. The insulation I use is only 30 cents a square foot. I haven't done the math but I bet it doesn't take 20 years to get the payback. I've noticed that the floors {slab} don't cool down as fast with insulation under them. I can't understand why you wouldn't want to insulate.

Bryan_5

John,
I have an idea for your. When you are out going over this with the homeowner and you cant get through to them and get them to pop for the few extra dollars. There are 2 ways you can handel this. First tell them that you could do this job for the same price or better if you cut the same corners that the other guy did. Then the next thing to do and I am serious on this. Take a $20 bill out of your pocket and hand it to them. Now ask them to tear the 20 in half. They will not do it but they will ask you why. Just tell them that is what they will be doing everymonth the rest of the time they are in that house. But it may be $100 bills they are using. Give it a shot. You will win everytime and so will the customer.
Bryan

Robert O'Connor

My house

My house has insulaton under the portion that is radiant slab. Any job I do has insulation under it. I wouldn't do it any other way

I was just repeating what the Heatway guy says in his school. "Unless your sub soil is wet and can rob heat there is no real payback in the insulation under a radiant slab"

Bryan_5

One more thought on this. At this point you have nothing to loose they already have there mind made up. People react to visual things. Thats why that 20 is so effective. A 1 dollar bill wont be as effective but still may work. And dont worry if they do tear that bill in half. you can always put some scotch tape on it and get a new one. Try it it really works
Bryan

Mark Hunt

We


no longer include insulating in our proposals. It is much cheaper for the HO to have an insulating contractor do it.

We watch to make sure it's done correctly, but we NEVER touch the itchy stuff!!!

It is amazing what you will hear from different "radiant pro's".

Mark H

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kevin

good marketing...

tip Bryan...this is starting to get scary how corners are being cut in this field. It could go a long way in hurting our industry....reminds me of some of those pictures Dave Yates had a few months back....kpc

Clay Herzog

Insulation

Okay, I think we all agree that insulation necessary, but what type do you suggest?

I am currently building a new home with heated slabs on the first floor. My contractor is using 2" EPS, but I have heard of people using other materials. Any thoughts about this?

Also, my contractor laid down the EPS first and the vapor barrier. I've always seen it done the otherway around, but couldn't come up with a good enough arguement to have him reverse it. It seems like either way the EPS could get saturated with water. Putting the vapor barrier down over the foam does hold things in place nicely.

I've also heard of people sandwiching the vapor barrier between two 1" layers of EPS.

Thoughts?

Clay Herzog

Insulation

Okay, I think we all agree that insulation is necessary, but what type do you suggest?

I am currently building a new home with heated slabs on the first floor. My contractor is using 2" EPS, but I have heard of people using other materials. Any thoughts about this?

Also, my contractor laid down the EPS first and then the vapor barrier. I've always seen it done the otherway around, but couldn't come up with a good enough arguement to have him reverse it. It seems like either way the EPS could get saturated with water. Putting the vapor barrier down over the foam does hold things in place nicely prior and during the pour.

I've also heard of people sandwiching the vapor barrier between two 1" layers of EPS.

Thoughts?

Unknown

Timely subject

We were just working in a Levittown house today , one of the first test beds of radiant heat . We replaced the boiler yesterday , and finished up on the baseboard heat today . The homeowner moved in a few months ago , and just got used to the great floor heat - then the boiler started leaking . Turns out that the floor was leaking for a long , long time .

Well , to get to the point , when we were chopping the floor , running 3/4 copper to the BB , I noticed some of the 3/8 copper radiant , which I have noticed before - it mostly sits in the lower end of the concrete slab -about 3 inches down . And quite alot of it sits in the sand where it meets the slab , about 4 to 5 inches down - with no insulation at all . Now , the houses are on the small side , usually 2000 Sq. ft . or smaller , but in an average year the norm is around 600 to 800 gallons used . It makes me wonder how much heat is actually migrating down , and how much fuel could've been saved with some insulation .

One of my supervisors told me once that when we convert a Levitt house from radiant to baseboard , oil usage INCREASES . I'm gonna see if he can give me more specifics .

[Deleted User]

Use XPS, not EPS

EPS is styro foam, like your coffee cup.It doesn't stay together well. We use 1" of extruded poly styrene (XPS) which takes a lot more abuse. The barrier should be between the ground and the insulation. I suspect he's using the barrier to keep the EPS from crumbling and blowing away. Been there, seen that, don't want to see it again...

If your customer is convinced that he needs no insulation, I have a few dozen dissattisfied "inherited" customers who would like to talk to them about "heat rising", which is the typical reason given for not insulating below framed floors, and the discomfort they experience on a regular basis. If he's still convinced that the other person knows more than you do, make a notation on your contract that the HO requested that no insulation be used, and consequently you can NOT guarantee performance and see what he does. Explain to him that thermal energy flows omnidirectionaly, through the path of least resistance. If he still refuses to sign the contract, give him a business card and tell him to hang on to it because he'll need it, and walk away.

I have had to do it more than once, and in every case, the HO ended up calling us back at a later date wanting to know if there was anything magic we could do to cool their basement (typically 75 to 80 degrees with the thermostats completely unwired), and get more heat upstairs (typically 60 to 65 degrees with the thermostat cranked)...

"But heat rises, don't it??? That's what our GC told us..."

You have but once chance to do it inexpensively. After that, the costs go up exponentially.

Do it right. Do it once. (Thanks Taco!)

As for not putting insulation below a slab, heat flows from hot to cold, continuously and forever, in an effort to balance temperature differentials out. Regardless of what the gent from Watts say, we REQUIRE insulation below the slab. Not enough studies have been done for anyone to be able to accurately state that there is a 20 year pay back on the insulation. All the theoretical calculations are just that, theoretical, and unproven.

Insulate, always.

ME

Clay Herzog

XPS

My mistake, what we used was XPS, a brand called green guard (I suspect it is blown with an eco-friendly blowing agent). Anyway, the altenate material that I am more interested in is "rFoil." The manufacturer claims it can be used below a slab, I'm skeptical.

Regarding the membrane (vapor barrier)it the soils are well-drained I still wonder if it might makes any difference where the membrane is placed. As my contractor pointed out, putting the XPS under the barrier keeps it from getting soaked initially when the slab is poured. Then again I suppose it dries out eventually...

I wonder if I should insist that he move the barrier? I hate to "ruffle his feathers" if it makes little diffence. People use this same material on the outside of foundations where it sees considerably more moisture. I think I'll let it slide for now.

Thanks for the input.

Clay Herzog

XPS

My mistake, what we used was XPS, a brand called green guard (I suspect it is blown with an eco-friendly blowing agent). Anyway, the altenate material that I am more interested in is "rFoil." The manufacturer claims it can be used below a slab, I'm skeptical.

Regarding the membrane (vapor barrier), Since the soils are well-drained where we are building, I still wonder if it makes any difference where the membrane is placed in this case. As my contractor pointed out, putting the XPS under the barrier keeps it from getting soaked initially when the slab is poured. Then again I suppose it would dry out eventually as the slab cures ...

I wonder if I should insist that he move the barrier? I hate to "ruffle his feathers" if it makes little diffence.

People certainly use this same material on the outside of foundations where it sees considerably more moisture than it will under the slab. Perhaps I'll let it slide.

Thanks for the input.

Joh n Brickey

Well I finally convinced one of my customers to insulate but only after I showed him the BTU loss. The other guy put plastic down and said that was enough in his basement but I refused to do the garage without it. We insulated the floors!! Clay, you asked about the bubble wrap insulation and I have found it to work good in basements but, I still use foam on ground level slabs.

Dave_14

To insulate or not to insulate that is not a question

I would like to point you towards our website that is available for all to reference. On the website you will find a section titled " Slab Energy Management System ". This portion of the website graphically indicates the need for insulation beneath the slab. During the heating season the data continues to be upload daily.

What we have created is an instructional lab and installed sensors at various locations prior to the pour. We have also located sensors throughout the room, on the floor, on the ceiling and everywhere in between. We included remote readers on the gas meters, remote readers on condensate drains from condensing boilers, flow meters, etc. to enable to reocrding of data to allow the hydronics community access to "real" data.

Check the data for yourself, should you recommend insulation? What is the difference in temperature at the 3' below slab level? (I am just disappointed that we stopped at 3') How much further are we actually pounding the heat?

www.nait.ab.ca/pipetrades

or, for the Slab info

www.nait.ab.ca/pipetrades/sems.htm

Dave

Dave_14

To insulate or not to insulate that is not a question

I would like to point you towards our website that is available for all to reference. On the website you will find a section titled " Slab Energy Management System ". This portion of the website graphically indicates the need for insulation beneath the slab. During the heating season the data continues to be upload daily. We have created a lab and installed sensors at various locations prior to the pour. We have also located other sensors throughout the room, remote readers on the gas meters, remote readers on condensate drains from condensing boilers, flow meters, etc. to enable to reocrding of data to allow the hydronics community access to "real" data.

Check the data for yourself, should you recommend insulation? What is the difference in temperature at the 3' below slab level? (I am just disappointed that we stopped at 3') How much further are we actually pounding the heat?

Dave

hot_rod

The downward loss

is greratly dependant on the base below the slab! Certainly a perpetually wet subgrade, or high water table will wash away BTUs. Where a dry low conductive subase conducts much less. To accurately predict the down loss, and amount of loss, the soil conductivity needs to be factored in. Without knowing that, it's a guess at best as to the amount of downward loss.

You do your customer a huge dis-service, I feel, if you chose to install radiant slabs on wet sites! Be it intermitten springs, high water table, spring runoff, or poor siting of the building.

At some point it is wise to walk away from a potentially wet site or recommend another type of heat if the builder cannot, or refuses to adequately address site conditions determental to radiant. I think It will lead to unhappy homeowners, a lifelong problem for the radiant installer, and a black eye for thr radiant industry. You cannot fix a wet site issue with a mere 6 mil barrier

hot rod

[Deleted User]

Think

radiant ceilings! I agree with Tom Tesmar, ceilings are one of the most overlooked comfort potentials there is.

Look up!

ME

hot_rod

Show us an example, John

While I say it is imperative that the edge and perimeter be insulated to the footing depth, and at least a perimeter band of 4 foot. Let's say we have a remainder of 10,000 square feet. Let's say to insulate that, at 1" (parts and labor), would be an additional $5,000.00.

Lets also use a dry soil thermal conductivity K value of .7 (wet sand =2.3) Show us the difference, or how to calculate it ourselves, in either loss/ btu/hr or fuel cost difference at 1 dollar per therm. thanks

hot rod