Radiant Heat Floor SNAFUS-2

FAQs#2 on radiant heated floor mistakes

Radiant Heat Tubing Layout, Spacing, Omissions

Should we install radiant heat under refrigerator and kitchen cabinets?

Do you install radiant heat pex under refrigerator and kitchen cabinets? On 2020-03-05 by Michael Peters

by (mod) - normally that's omitted

Michael

Normally you would not bother to run radiant heat under cabinets and IMO even more important, not under a refrigerator, but if it does run there it's not a catastrophe.

Arguing: in very cold climates putting heat under a kitchen base cabinet were plumbing enters and drains exit might help prevent a freeze problem.

Counter-arguing: under a refrigerator a warm floor might cause the fridge to have to work harder to get rid of its heat, thus increasing ints operating costs.

What is the risk of damage if I heat only part of a single slab?

I am going to build a 40X100 metal building with another 10' extending out the front as a patio.

The main building will be radiant floor heat, but the 10' will not be heated and covered by a lean-to roof with pillars.

My concern has been what issues may I have with the structure if I heat the main part and not the 10' X 40' slab.

My HVAC person said he would run returns through the thicker edges of the 10'.

Will that cause issues with the system with the heat loss that I would anticipate the return lines will see? We are insulating everything including the outside edges and the 10' slab. On 2019-06-26 by kennorstrem

by (mod) - use a control joint to reduce risk of uncontrolled slab cracking

Thanks it's an interesting question. I don't know all of the problems that could come up but certainly one that occurs to me is slab cracking because of extreme temperature difference between the inside and outside forces of monolithic slab.

I would think you would discuss with your contractor putting the control joint between the hot and cold sections. I also certainly would expect you to not run any radiant tubing in the cold section Outdoors.

How do I route radiant slab heat tubing to avoid control joints?

There is no mention on expansion joint placement. With a larger slab and the 2" tube below surface, is there a prefered method to run the tubing where the cuts will be made? On 2019-01-05 by Bill S

by (mod) - Expansion joints (control joints) vs. tubing depth in a radiant heat slab

Ick, horrible.

Thank you for bringing up the expansion joint in radiant heat slab question, Bill.

In my view it is essential that the expansion joint be formed using appropriate spacers or joint materials at the time the slab is poured. That will avoid the disaster of some nut with a concrete saw slicing through all of the tubing.

If you have to pour the slab with a plan to cut the expansion joints later, you'd have to lay out and carefully map and measure the location of the tubing loops such that the expansion joint falls in-between two runs of tubing and does not cross them. In my view that may be difficult to accomplish at the ends of the loops.

A consideration is that we can put the tubing deeper in the slab so that the expansion joint cut (post pour, post cure) does not go as deep as the tubing, BUT that's asking for a different disaster.

Putting the tubing deep in the slab means the radiant heat system will most likely not work - the resistance to heat transfer up through the slab becomes too great compared with the heat loss downwards or the energy needed to warm a thick slab above the tubing even if insulation is present below and at the perimeter of the slab.

Recommended radiant slab tubing layout for even heat

I constantly see tubing installed wrong. Regardless of the room size or shape every portion of the floor should radiate the same amount of heat.

Every corner should produce the same radiant heat as the center of the room.

When we built a 17,500 sq ft home for a client we used radiant floor heat everywhere, including the bathrooms, showers, entryway, etc.

The sub we hired for this work was absolutely the best ever. I asked him at the outset how each room could be heated individually and how the heat would radiate evenly from every portion of the floor.

The answer was very simple. Imagine you have a room 12 inches wide and 50 feet long. If you form a single loop the full length of the room you would have the same heat being radiated evenly from one end to the other.

Example: You force 100 degree water into one end of the tubing and you have 60 degree water exiting the end of the loop. Using this example you would have an average of 80 degrees of radiant heat at any spot along the loop

The far end of the loop would have the water temperature dropping from 100 degrees to 80 while the temperature would drop another 20 degrees on the return side. Now, the trick is to gauge the length of a loop so you can wind it around in a room, right? Simple.

You begin winding the plastic tubing around the outside edge of the room in (in our case clockwise) until you end up at the center of the room, leaving 12 inches between each spiral leg. When you get to the center of the room you make a loop and lay the tubing in a counter-clockwise spiral until you return to your starting point.

Doing your layout in this fashion assure you of constant heat throughout the room. On 2019-02-02 by Ernie earnest37@gmail.com

Compare radiant heat floor design requirements a for garage with that for occupied space

I am pouring a slab floor garage and living space one floor 50ftx 60 ft. 30ft garage 30ft living space.

What would you do for the garage area for radiant heat and for the living space?

Would you use the same patern for both spaces? and be 2" from the top of finnish slab.and what kinda of vaper bearier would you use for the ground?

Cover under the radiant heat tubing? This home is in western Washington the N.W. Thank you On 2021-11-22 by warren gilmore

by Inspectapedia Com Moderator - an accurate radiant heat floor design is important

@warren gilmore,
The radiant heat floor design that would be right for your house should be informed by an on-site radiant heat expert .

With just the information in four lines of text, we don't know something about how the home is constructed including its insulation, windows, sun exposure, heat loss rate at cetera.

Generally people want the garage heat to be on a separate Zone and therefore a separate loop from other radiant heat sections .

In the living area, generally the installer may run the tubing closer together in areas where a cold floor would be least welcome such as in a bathroom, and more widely spaced where the heating load or requirement is less, such as in your garage.

You mentioned vapor barrier but of critical importance are the quantity and workmanship of insulation installed below your slab. I

f that's not done correctly you could end up with a system as bad as the one we described on this page.

Radiant Heat Installation Abandonment?

Is mpy partly-right, artly incomplete radiant heat slab worth finishing?

I built a detached garage almost 20 years ago and snaked a bunch of PEX in the slab (attached to the re-bar) so that i could add heat later.

I have 2 inches of pink foam under the slab, but i did not insulate up the sides of the footings around the perimeter.

I'm just about to fill and try out the system this winter in Minnesota and i would like to keep the garage around 45-50 degrees.

Did I manage to foul this up to the point that it isn't worth finishing? Will all the heat creep to the edges and get sucked into the ground or will it be a case of a little wasteful but works okay? On 2019-10-11 by Jeff Will

Above: using a ceiling mounted heater as an alternative heat source for a garage where we may decide the in-floor radiant heat plan isn't workable.

by (mod) - the operating cost of your radiant heat garage may be a bit high; consider an overhead garage heater or possibly a wall heater

Especially in Minnesota the heat transfer rate or lost out through the slab perimeter can be quite significant.

You may be able to salvage the job by insulating the perimeter of the slab outside down to 4 feet or so.

You might try that and then try out the system to see what the operating cost is.

The other question that isn't clear and then I'm a little worried about is the depth of your tubing in the slab.

It's not that you couldn't get the garge up to 45-50F as you want, it's rather what the annual heating cost of that might be.

My OPINION is that an overhead electric or hydronic heater like the one I show above, combined with good wall and ceiling insulation - easy to improve - may be more effective.

Some alternativbe options include

• OVERHEAD & GARAGE HEATERS - electric & other fuels
• WESIX™ TYPE WALL & FLOOR MOUNTED ELECTRIC HEATERS

Or possibly even a high capacity wall heater like the one I'll show below.

by Jeff

Thanks for the comments. It sort of sounds like I've screwed up to the point where this won't work No way am I going to excavate down 4 feet to try to insulate around the perimeter as the garage is in the corner of our lot.

If I remember correctly, the contractor laid a bed of sand, and there were shallow footings around the perimeter.

The footings did not go down tot he frost line, but more like a shallow trench around the outline of the garage full of rebar to give the walls a bit more support.

I laid the 2" pink foam on top of the sand.

Then they laid a concrete wire mesh on top of that. And I used zip ties to attach the tubing to the wire mesh which was elevated a bit.

So I'm guessing the tubing is in the lower half of the 4" slab. The garage is super well insulated, with 6" walls and a couple of feet of insulation above the ceiling.

I would even be happy if I could keep things at 40 degrees in there during the winter.

Since I already have the water heater, gas line, antifreeze i think I will try it.

If f it just costs too much to run I can simply switch to a conventional gas heater.

Followup by (mod) -

Jeff

Don't feel bad. I suspect us (including myself) screwups are in the majority on this one - and we're still not as much of a bully nor screw-up as our nightmare-construction-co contractor.

I'm not exactly highly optimistic for your case but if it were my building I'd hook up the heater, try the system, and if it nearly keeps up then I might figure it's worth adding perimeter insulation.

"Bottom half" of a 4" slab could mean your tubing is just 2" below the surface of the floor? IF so you're actually in good shape; What I want - and this is subjective opinion but based on some reading - is the tubing to have less concrete above it than below it.

Our horrible slab had more concrete above it than below AND had incomplete insulation below - so it was in essence finding it easier to pump heat into the ground than into the floor above.

At just 2-3" down in the slab, even in MN where I know first hand how cold it gets, you can probably keep your floor at 40 or above if your under-slab insulation is complete and it's just the perimeter that's going to be cold.

Start by propping 2" solid blue foam board around all of the exposed insulation (termites and carpenter ants sneaking up behind the foam aren't a big worry in much of MN)

Hook the system up and report back over the winter when it's good and cold. (We'll be around during November if you're on the North Shore I- might like a firsthand look)

Yeah you can of course go to above-slab baseboard using the same heating system. We considered that for our fiasco but have got by with a few electric heaters instead.

Another option I should have included earlier might be garage-rated electric WALL-MOUNTED FURNACES

by Jeff

Thanks for the encouragement. I'm hoping that the concrete guys pulled the wire up when the poured the slab in which case it should be roughly in the middle. I'll let you know how it goes.

Radiant Heat Slab or Floor Insulation

Where slab thickness or depth varies does insulation all have to be below the slab?

Is there any specific consideration to the location of the insulation relative to the bottom of slab?

Have a job where the substrate varies from 0” to 12” insulation was installed following the contours therefore in some locations the insulation is just below a 6” slabs in others the slab becomes 12” the tubing is all raise to 2” inches below surface. 847-553-5343 On 2019-10-03 by John Teschky

by (mod) - insulation must be complete and continuous - that's most critical

There are specifications for insulation location below the slab but IMO and experience more critical is that

- the insulation is absolutely complete around the slab bottom and perimeter - openings leaving slab in contact with the soil become heat pumps

- the tubing be close enough to the top of the slab

Effect of missing insulation under radiant heated apartment floor: hot ceilings below

I’ve hired a company to install a radiant floor heating system in my apartment a few years back, but did not ask for the insulation to protect the heat from going downwards.

Now my neighbours (living below me) claim that I’m heating their apartment to extreme temperatures.

The floor is made of concrete and it was cut into just enough to put the tubes in it and the floor on top is the laminate, so I don’t think we lose much heat going up. They reported that their ceiling heated to 80F when my thermostat was at 70F.

Could you advise if this is possible at all that I could be heating their apartment to 70F and maybe refer to some articles? - On 2017-05-09 by Yev -

Reply by (mod) - radiant heat floor is heating the apartment below

Yev I suppose it's possible; I'd like to see objective data - actual measurements of the neighbor's ceiling temperature and changes in that temperature when you turn your floor heating system on.

If there is no time correlation between your heat being on and the neighbor's ceiling reaching a high temperature, then their ceiling may be warm from their own heating system having heated their space.

Radiant Heat Slab Problem Diagnosis

Difficulty diagnosing radiant heat slab problems when construction details are not known

Dan,

How can homeowners diagnose hydronic radiant heating efficiency problems without knowledge of the building practices used when installed?

Or how can home buyers insure their new home (built decades earlier) won't end up being a situation like yours? How can we verify the slab was insulated properly?

With more homeowners looking for the added efficiency of radiant heat, that means more homes are having it installed - but was installed correctly?

For example: In my case, I'm looking at two heating bills in Santa Fe, NM - one for a 1450sqft, 2-story home built in 2007 with a undersized furnace - average natural gas bill was $200 a month in winter at 70º.

Another 1550sqft single-story home built 10 years earlier in 98', radiant slab hydronic heating with commercial water heater, sees an average winter heating bill nearly twice that amount .

Home inspector said that the hydronic system was in good working order, and used thermal imaging to confirm - shouldn't the bill be lower for the same room temp?

Did he miss something, or is an expensive mistake hiding in plain sight? On 2019-09-25 by Paul

by (mod) - radiant heat diagnostic and troubleshooting articles found here

Paul

You make an excellent point as we have discussed by email.

There are both pratical observations and inspection tools and methodology that can give us objective data that are helpful when troubleshooting radiant heat floors and slabs.

For example, uneven radiant slab temperatures can point to any of several problems:

• Airbound radiant heat tubing
• Blocked radiant heat tubing
• Leaky radiant heat tubing
• Poorly laid-out radiant heat tubing
• Radiant heat zone mixing valve control adjustment needed when two or more zones both call for heat but one gets warmer than the other or heats faster than the other

Separate of course are radiant heat not working problems - no heat in one or more zones that could be some of the above issues as well as other traditional ones such as a bad circulator pump or control.

• CIRCULATOR OPERATION CHECKS

Listed below are some useful radiant heat floor or ceiling diagnostic articles found at InspectApedia

• RADIANT HEAT AIR BOUND
• RADIANT HEAT MISTAKES - includes a list of suggestions that we will develop for folks who need to investigate a suspect radiant heated floor slab.
• RADIANT HEAT TEMPERATURES
• RADIANT HEAT TEMPERATURE CONTROL / MIXING VALVES
• RADIANT SLAB TROUBLESHOOTING
• WOOD FLOOR RADIANT HEAT DAMAGE

 

The correct solution for radiant heated slab construction is to insulate to the siding and protect the insulation.

"Insulate the slab perimeter, making sure that the insulation design does not rely on foam placed against the slab perimeter and extending above grade up to siding where it will invite termites or carpenter ants into the structure".

This is a little confusing. If the insulation does not extend above grade, it would leave a gap for cold transfer.

Also, do termites and carpenter ants eat foam insulation. If so, which do they like better, polystyrene, or Polyiso?

Does this mean ICF's are a scam?.

The correct solution is to insulate to the siding and protect the insulation. - On 2018-05-20 by Kevin -

Reply by (mod) - what insulation or construction details will permit us to insulate the perimeter of a concrete floor slab

Kevin, thank you for asking an important question: what insulation or construction details will permit us to insulate the perimeter of a concrete floor slab or a monolithic foundation and slab while at the same time avoiding a termite or carpenter ant problem .

Here's the image from Minnesota.

To be clear, termites or carpenter ants don't "eat" foam insulation, but they find it easy to tunnel through it or between the insulation and the foundation wall, to achieve an easy path to wood construction materials that are nearby.

In areas of termite risk in particular, (as it's termites that will come up into the building through the soil) I'd like to see use of termite shields

See TERMITE SHIELDS vs TERMITICIDE

The most-severe heat loss through a monolithic slab perimeter or a stem wall or foundation perimeter is where the foundation is in contact with soil. Above grade, in contact with air the heat loss rate is much less.

So some alternative designs stop the perimeter insulation just slightly above grade and below the building siding.

Another design, shown in my photograph is one that that you'll see in my TERMITE SHIELD article above. This approach, embedding the foam insulation within the monolithic slab perimeter, is used in northern Minnesota such as at the Minneapolis home where I photographed this detail.

The risk of insect attack with or without foam providing a protected path into the structure is always greater when there is water pooling around the foundation or when there are leaks into the wall or floor cavities of the building.

Choosing among different formulations of foam insulation (as you asked in your posting) does no,t in my opinion, make a material difference in the risk of termite or carpenter ant damage.

Some writers such as Holladay suggest that the solution is to fully insulate the slab perimeter inside or outside (I'll attach an excerpt to illustrate), combined with pre-treatment of the building perimeter with a termiticide.

Insulation requirements for slab-on-grade floors can be found in section R402.2.9 of the 2012 IECC and section N1102.2.9 of the 2012 IRC. Both codes state, “Slab-edge insulation is not required in jurisdictions designated by the building official as having a very heavy termite infestation.”

Otherwise, both codes require that “slab-on-grade floors with a floor surface less than 12 in. below grade” need vertical insulation at the slab perimeter.

These codes do not require any insulation for slabs that are more than 12 in. below grade.

The codes are silent about whether above-grade slabs need to be insulated. - Holladay, Martin, "Insulating a slab on grade - What’s the best way to insulate a slab-on-grade foundation?" Fine Homebuilding (No. 145, 2014) http://www.finehomebuilding.com/2014/07/09/insulating-a-slab-on-grade

I am nervous about termiticide pre-treatment as with the response of regulation to environmental concerns with use of some termiticides and pesticides, I'm not sure of the long term durability of that approach.

Below are sketches from Holladay's article

Your comment that "The correct solution is to insulate to the siding and protect the insulation." doesn't address the issue of heat loss into surrounding soil. But a termite shield can protect against termites entering the wood frame of the wall sills and studs.

Radiant Heat Add-on to Existing Building

Adding radiant heat to an existing uninsulated basement slab, floor thickness, ceiling height concerns

I live in Ontario and am I'm planning on having a contractor install a hydronic heating system in a house that was built in the 1960s.

The entire foundation is from poured concrete and only has a plastic sheeting under the foundation that acts as a sort of vapour barrier, no insulation under the slab.

But I did water proof the foundation walls with blue skin and 2" R-10 foam boards to act as an insulant/protectant to the blue skin.

As for the floor inside the basement which will contain the hydronic flooring system, I was thinking of adding the same 2" R-10 foam on the slab, then the system, then an inch or two of concrete to top it all off.

I also plan on insulating the foundation walls from the inside with urethane insulation.

Unfortunately I must be careful of the height I add in the basement as I'm 6'1" and the ceiling measures only approximately 8'.

So it's a careful balance between being comfortable in the basement height wise and being comfortable in the basement heat wise.

My question is do you think a 2" thick R-10 foam insulant on the basement floor and the urethane insulation on the walls be sufficient to keep the basement nice and warm?
Thank you for your input. On 2019-08-07 by Pat B -

Reply by (mod) -

Pat

Thanks for an interesting problem question. I like your general approach - it's what I'd do too. My experience is that any radiant floor that's not fully insulated and is in a cold climate like Ontario is just going to pour our dollars into the soil below and around the building.

With 2" you ought to be able to get up to R-16 (using foil faced High-R foam).

Is some part of the foundation around the slab above grade?

What wall insulation R-value is planned?

What's the home's heat loss rate through windows, ceilings, roof, etc. ?

How much air leakage is there?

I'd wish for an IR or thermographic study of the home; we can spend a lot of time and trouble on just one item like the floor while missing other points of heat loss that overwhelm the picture.

Take a look at Ontario's recommendations for insulation found in the 2012 Ontario New Building Code for a better than arm-waving answer to your basic question of "do you think a 2" thick R-10 foam insulant on the basement floor and the urethane insulation on the walls be sufficient to keep the basement nice and warm? "

See https://inspectapedia.com/insulation/Ontario-Building-Code-New-Construction-2012.pdf

Worry about installing radiant heat flooring on a slab over area with high water table

We have a high water table and raising foundation to avoid water in basement issues.

We are planning a installation of radiant flooring with insulation under slab etc.With possibility of water would you suggest not to? On 2019-08-03 by Bob Morrissette

by (mod) - proper construction places slab above high water table

No, but in even the most basic proper construction practices, the slab needs to be above the local high water table, including future increases in the water tabke height with changing weather pattern of global warming. Otherwise you will have a variety of costly building water entry issues!

I would hate to build a foundation and slab that, to keep the building dry and habitable, depended on continuous or frequent sump pump operation since we know what will happen when there is a power loss. At best we'd depend on battery backups and generators to keep pumps running - a horrible design.

Electric Radiant Heated Floor Questions

Ratings & guidance for electrical underfloor heating in a French renovation project

Am planning to use electrical underfloor heating in a French renovation project in which the floors are concrete on grade. Replacement floors have to be of same construction to satisfy local regulations.

i am finding it difficult to find information for heat-up times of a slab of concrete having thickness which vary from 120mm to 60mm. This is over insulation of 120mm solid urethane the electric uses 200w per metre square or 150w or 100w depending on which is purchased.

ie degs per hour at a given thickness and power input.

I also have to take into consideration using the floor like storage heaters using the off-peak electric 12 midnight to 7am and also keeping the total house load to 9kw or it will trip.
Can you advise any ratings/data guidance for this ? On 2018-09-25 by Bill Corner

by (mod) -

Bill

You're probably going to want to specify some temperature data both outdoor and indoor and more about the heat loss rate of the building since without that the heat up time of a slab is going to be unpredictable.

Also the slab construction is critical, including insulation under the slab, a good vapor barrier, and a proper electric wiring cable depth (1.5 to 2"), and an adequate number of circuits to support the heating loops that you require. You don't give your geographic location in detail, but typically an electric radiant floor will be designed to deliver 10-12 watts per square foot.

Also see

• The U.S. National Electrical Code for Electric Radiant Heating Systems NEC Section 927 Electric Radiant Heating Systems using the US NY City 2022 Mechanical Code for Electric Radiant Heating Systems as an example (Upcodes website)
• US DOE Says about Electric Radiant Floors [DOE Website]

  Excerpt:

  Electric radiant floors typically consist of electric heating cables built into the floor. Systems that feature electrical matting mounted on the subfloor below a floor covering such as tile are also available.

  Because of the relatively high cost of electricity, electric radiant floors are usually only cost-effective if they include a significant thermal mass such as a thick concrete floor and your electric utility company offers time-of-use rates.
  
  Time-of-use rates allow you to "charge" the concrete floor with heat during off-peak hours (approximately 9 p.m. to 6 a.m.).
  
  If the floor's thermal mass is large enough, the heat stored in it will keep the house comfortable for eight to ten hours without any further electrical input, particularly when daytime temperatures are significantly warmer than nighttime temperatures. This saves a considerable amount of money compared to heating at peak electric rates during the day

• Warmup, Electrical Requirements for In-Floor Radiant Heating [Website] Warmup is a vendor of electric floor heating wiring and components

Radiant Heat Floor System Operating Cost FAQs

We used 800 gallons of propane to heat our radiant slab floor in eight weeks!

We had a system installed this past summer. The contractor insisted that they had installed hundreds of these systems and that they are far more cost efficient than forced air heat.

They didn't install any styrofoam under the slab but dis use a thicker moisture barrier that looked like bubble wrap.

The system was heating just fine until we got a cold snap, the heater isn't keeping up and the building dropped 20 degrees in 1 day and it appears that the Navien unit was running the entire time.

It's a 3,456 square foot building with 2" of foam insulation in the walls and a 12' dropped ceiling with R30 insulation above the ceiling.

We started using the system on October 25th and it heated the building up quickly (2 days from 50 degree temperature up to 68 inside), We had a propane tank with a bad gauge that wasn't telling us how much we were using.

We went through 400 gallons of propane in 6 weeks, then another 200 gallons in less than 2 weeks. Do you think we are blowing through propane because of the lack of foam insulation or do you think that there are other issues involved? We will go broke heating the building at this rate. It is an auction house where we only have a sale once every 5 weeks. Thanks for any advice. On 2018-01-01 by Wylie -

Reply by (mod) - They didn't install any styrofoam under the slab - heating costs $340. week!

Wylie

Where is this home located? In a warm climate you might survive with no real insulation under the slab but otherwise I'm doubtful that the radiant heat can work effectively.

A contractor who says he has installed hundreds of something may be speaking accurately, or not, but it's also possible that he has never read the instructions on the box and has installed hundreds of his somethings in correctly.

You might check first with your propane company about what they consider typical fuel usage for your type of home - size, insulation, windows doors and local climate and the number of degree days.

With propane costs in New York (for example) averaging about $3.38 / gallon, you would have been spending about $340./week to heat the home with the un-insulated floor slab you describe.

Mini Boiler could not keep up with heating the floor and our heating costs are too high

We have a block building with poured walls that we placed in floor heating. There is no insulation on the walls.

There is insulation on the floor, think either 2 or 3 inches thick with three lines of pex fastened down in a pattern per specifications read.

Think concrete is about 3 to 4 inches thick, based on pictures taken and have on computer. Purchased a Mini Broiler and in floor thermostat.

Hooked everything up and after a few issues like broken line needing fixed the heat was turned on.

Mini Broiler could not keep up with heating the floor so purchased a regular water heater and also a timer. Thermostat set at 68 degrees and the timer set to kick on every hour for 15 minutes.

Our electric bill for the building runs on average $400 during the winter. I told hubby he needs to figure out a more cost effective way of heating the building.

Either figure out why the in floor heating is not efficient or perhaps not hooked up properly or that the building needs to be insulated etc.

He is so busy working a full time job as well as the part time job in shed so I am trying to be proactive before fall arrives again with no answers to our problem.

Everything was done quickly and not fully experimented with like bigger water heater and no timer. Any advice will be much appreciated. On 2020-05-12 by Connie

Reply by (mod) -

The radiant heat floor tubing might be high in the slab under a thin pour of concrete, but I'm not sure since I don't know if the pour in your photo is the whole job (probably) or just an initial pour, nor can I measure tubing depth from just the photo.

Compare how your radiant heat tubing was placed in the slab with the description I give

at RADIANT HEAT MISTAKES

Also, I cant' assess whether or not the amount if tubing is sufficient, nor its spacing proper; we don't know your climate nor heating load.

But there is surely a glaring need for insulation on those block walls, a large source of heat loss. I would try properly insulating the rest of the building before abandoning the radiant heated floor approach.

by Connie

We talked about trenching around the outside and insulating the wall down to footer. Inside is a little harder to insulate because of constant welding, grinding etc.

Do you think placing insulated foam on outside wall would help? Hubby did lots of research on the in floor heat based on size of area for how many lines needed.

Reply by (mod) -

Insulation will help wherever you put it; outside, be sure you don't provide a path for carpenter ants or termites up into wood framing.

by Connie

Thank you for your help. As for the framing in shed it is block walls and trailer frame for rafters, very little wood. Have a great day

My radiant heat floor Heating bills are astronomical! Will slab perimeter insulation help?

It's been about 25 years ago that my builder step-dad (now deceased) built his retirement home. A 30' x 76' slab on grade inside a 42" frost footed stem wall (western WI) with a staggered stud (double wall) single story super structure with about 7" of insulation. He placed pex tube over fairly clean 3/4" gravel and under 4" of concrete.

The slab & foundation have no insulation anywhere. The unheated double garage juts into the floor plan for an integral (monolithic) edge 13' x 24'.

He had a medical condition where he needed ambient temperature of at least 78°F to be comfortable and had to add a 2nd 35k BTU propane fired source to the liquid manifold.

Heating bills are astronomical! Would placing 2" rigid insulation along perimiter stem walls down to the footings and cutting a few inches out from the garage perimerer gain any recoverable savings? - On 2016-12-06 by mouselb -

Reply by (mod) - Yes, heat loss through the slab and foundation perimeter are significant.

I think so, mouse. Other studies of insulation placement in frame construction show that heat loss through the slab and foundation perimeter are significant.