FAQs on radiant heating system design or installation mistakes, set#2.

This article series explains how to avoid some fatal mistakes when installing radiant heat in a concrete floor slab by describing an incompetent radiant heat floor installation along with an explanation of why things went wrong and how to avoid these errors.

In the photo above, the contractor who prepared the forms and under-slab insulation placed radiant heat floor tubing too deep in the slab and he omitted proper under-slab insulation. Tthe owners ultimately had to abandon the entire radiant heated floor system.

We also provide a more comprehensive INDEX to RELATED ARTICLES for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

FAQs on Radiant Heat Floor Mistakes to Avoid #2

These questions & answers on problems with radiant-heated floor slabs were posted originally at RADIANT HEAT MISTAKES - be sure to see the discussion there.

On 2020-03-05 by (mod) - radiant heat under refrigerator and kitchen cabinets?

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.

On 2020-03-05 by Michael Peters

Do you install radiant heat pex under refrigerator and kitchen cabinets?

On 2019-11-07 - by (mod) -

Well yes and no, Anon.

Yes: The tubing, empty or filled with antifreeze solution will not harm the floor when heat is left off.

No: when a building is left un-heated, depending on the climate, freezing temperatures, site preparation, soil moisture, and extent of building exposure to the weather, a foundation or slab can be damaged by frost heave, frost push, frost lensing if a building is left un-heated unless adequate measures were taken, such as surrounding the foundation by insulating foam, during construction.

On 2019-10-23 y Anonymous

Can one install heat tubing in a concrete floor and leave it not heated and not covered over the winter without damaging the system?

On 2019-10-15 by Anonymous

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.

On 2019-10-14 - 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.

On 2019-10-14 1 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.

On 2019-10-11 - by (mod) -

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.

On 2019-10-11 by Jeff

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 2019-10-03 - by (mod) -

Probably 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

On 2019-10-03 by John Teschky

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 2019-09-27 - by (mod) -

Paul

You make an excellent point as we have discussed by email. I will post here a list of suggestions that we will develop for folks who need to investigate a suspect radiant heated floor slab.

On 2019-09-25 by Paul

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 2019-10-03 by John Teschky

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 2019-09-27 by (mod) -

Paul

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

At RADIANT HEAT MISTAKES you will find a list of suggestions that we will develop for folks who need to investigate a suspect radiant heated floor slab.

On 2019-09-25 by Paul

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 2019-08-07 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

On 2019-08-07 by Pat B

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 2019-08-03 by (mod) -

Excuse typos I'm traveling

On 2019-08-03 by (mod) -

No, nbut the slab needs to be above the high water table , including future increase in the wayer tabke height with changong weather pattern of global warming uo you will hve s variety of cost look y water entry issuesl

On 2019-08-03 by Bob Morrissette

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 2019-07-12 by (mod) -

There are small electric heating boilers designed specifically for applications such as the one you described. You'll see one in the third photo down from the top of this article. Some people also use electric water heater and there are some that are sold for that purpose. However the duty cycle in my opinion is likely to give a short life for a water heater where else a boiler designed for that purpose would be perfectly durable.

On 2019-07-12 by nelson

I am adding a 16x24 bay with 2x4 construction and fiberglass insulation to an existing garage. I want radiant heat in the floor but it`s only 385 sq`. Closed system. Glycol. What do I use for heat source? I`ve been told on demand boilers wouldn`t work for such a small system. 1 zone, 2 loops of maybe 250 feet half inch pex.

On 2019-07-03 by (mod) -

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.

On 2019-06-26 by kennorstrem

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 2019-02-02 by (mod) -

Thanks Ernie

On 2019-02-02 by Ernie

earnest37@gmail.com
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 (mod) -

Thanks Ernie

On 2019-02-02 by Ernie - I constantly see tubing installed wrong.

earnest37@gmail.com
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 2019-01-06 by (mod) - how to install expansion joints 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.

On 2019-01-05 by Bill S

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 2018-11-21 by (mod) -

I think I would start by confirming that I have had water flow through all of the tubing and then I would compare the input and output temperatures. If there's two big rapids maybe that I'm losing heat somewhere or that the flow rate is too slow.

On 2018-11-21 by Tom

Have a radiant heat job in which my plumber used 3/8 pex there are 5 loops about 250’ pee loop with I 1/12 mud job and tile can’t seem to get heat working properly what can I do

On 2018-09-26 by (mod) - electrical underfloor heating in a French renovation project

Bill

thank you for an interesting and we'll post question. I'll see what additional information I can find.

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

On 2018-09-25 by Bill Corner

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 2018-05-24 by (mod) - water that leaks under the layers of a floor

unfortunately if you have water that leaks under the layers of a floor constructed in the way that we have been discussing heating the building will not remove it. Water tends to be trapped in such areas for a long time and therefore to cause problems with mold or rot or insects.

All of the effort then needs to be making sure that we're constructing a floor that won'ttak e watet.

On 2018-05-24 by Tim

Thank you this info. The additional article links have been most helpful.

I had never considered using a foil faced insulation. If I kept the foil away from the concrete this should help a lot.

I have kicked around the idea to use a concrete moisture sealer around the perimeter of the space to help mitigate any small amount of moisture that might get inside of the space.

We just had ten days of rain in a row here. My window openings were covered with Tyvek until the windows we ordered come in. The only place moisture could come in would have been under the pour/around the footers. There was just the slightest dampness showing in one corner of the space.

No puddles, just a wet mark. I don't have it graded or spouting hooked up yet. I attribute that moisture to this.

Worse case scenario- maybe a big snow melt off in the Spring or another huge long period of rain causes some migration. Wouldn't heating the space remove those small amounts? Cooling in the summer should have a similar effect unless I'm missing something.

The house sits up on a small hill but not all the way on top. There is a grade behind the house. Drainage piping surrounding the perimeter of the footings tied to pipes for rain spouts and exiting from pipe buried underground 30' from origin of the water was supposed to help offset that. I considered a drain pit .

Still might be a future option. Township approved present layout. That very small damp place after 10 days of rain without the spouting hooked up doesn't strike me as a serious issue, so long as I can correct it with climate control.

I've been wrong plenty of times before though. What seems much more serious to me is if the pex develops a leak or if I had say, a roof leak that let water into the space which accumulated underneath the works. A foam floor would have the tendency to float. Ha.

I might have a boat in my room in addition to the mold. Two weeks running dehumidifiers might help to remedy such a bad situation.Hopefully I won't ever see that happen.

I really like your idea to use a thicker sub floor since 2" of good foam insulation is all that seems to be required. 4' might be overkill.Can't hurt I suppose. Does add to the expense. I would opt for ceramic tile, so I like your idea. I think tile would work best with a radiant floor.

Along the same lines as your foil face insulation idea, I could also obtain sheet metal, either aluminum or steel to roll out under the pex.

I'm considering a thin gauge. Probably less expensive that the pre made panels. Main consideration being a good way to hold tubing in place until the flooring is put on. Duct tape?

Another plus for ceramic floor is there are no staples, nails or screws put in the floor around the pex. That would make me nervous.

From what I read online hydronics mixing valves and associated gear needed to hook up a radiant heat system are much more expensive than a common baseboard convection heat system which is what I presently have.

From a cost standpoint I could save money if I went with hydronic baseboards, however I'm planning to replace my aging boiler soon myself, so I can be the labor which should save me a bundle. Money is a consideration here.

I am willing to spend more money for radiant heat if I can make it work and it isn't overly expensive as compared to my other options. I see it as a good resale value choice and a way to improve comfort in the space.

Once done any attempt to repair concrete poured pex isn't something I want to even think about. I would do all the right things, pressure test,add anti-freeze, keep my loop temps well below the pex limits.

I'm still a little apprehensive in looking at how dependable this is long term, but that's me.

On 2018-05-22 by (mod) -

Tim

This companion article is worth reading SLAB INSULATION, RADIANT / PASSIVE SOLAR https://inspectapedia.com/Energy/Slab_Insulation.php

For your application I like foil-faced high-R foam board insulation, since the reflective barrier may give a small additional benefit.

In some states and provinces building codes don't require sub-slab insulation except for those in very cold climates. But as you read above, the heat loss down through a slab in colder areas including the northeastern US such as PA, can be quite significant.

You're fortunate if your existing structure permits, as you suggest, adding a layer of insulating foam followed by a new layer of flooring. I agree that ceramic tile over a floor that flexes would be a disaster.

If you wanted tile in preference to a laminate or engineered wood floor, or in preference to a vinyl tile floor (those would typically be problem free), and if you can give up the additional 1 1/2" of space for double underlayment, you could perhaps use ceramic tile over a double layer of 3/4" solid core underlayment placed atop your foam slabs that are in turn atop concrete. I'd discuss that option with your tile supplier to get a local opinon.

Where I've seen such retrofit floor get into trouble, aside from flexing and cracking tile that we've aside for now, it has been the mold and rot that occur if water leaks into that floor structure.

Trapped there the water leads to damage, rot, mold, and sometimes insect attack.
With your floor above grade those risks are considerably lower than if the floor were in a basement.

Your concern for the build-up, reduce-down operating temperatures of radiant floor heat, if I understand it correctly, should be mitigated by a review of just how radiant heat systems operate. Because we don't want the floor to be uncomfortably hot (and also because high temperatures can damage some tubing types), a mixing valve keeps the water circulating in the floor at or below a safe temperature limit.

But we like to operate the boiler at a higher temperature for operating efficiency and thus lower heating cost.

That mixing valve automagically handles the problem by mixing in with the circulating water in the floor just enough hot water from the boiler.

The efficiency gain is in fewer on-cycles at the boiler and higher boiler operating temperature. AQUASTAT HI LO DIFF SETTINGS https://inspectapedia.com/heat/Aquastat_Settings.php offers more detail.

On 2018-05-22 by Tim

I really appreciate this site. Lots of great info here. I can't seem to find an answer to my issue concerning radiant floor heat and thought maybe you would have some insight.
I live in SE PA. where we can get sub zero temperatures during the winter months.It usually stays cool enough to need heat from late Oct until as late as the end of April.

I live in a Cape Cod style home using baseboard hydronic heat and an oil furnace designed sometime in the mid 70's. I augment the hydronic oil heat with a heat pump I installed myself. When the temps are in the 30"s I use the heat pump. If it gets colder I switch to the oil heat.

At the time I had my patio out back poured I decided to have a large portion of it poured with footers for future construction. Fast forward a few years and it's time to add an addition to the footered concrete slab. Unfortunately I never considered the implications of not adding insulation under my slab. I also added a garage with a concrete pour that will have a studio at the back. I did manage to
get 2" foam insulation under that entire slab. I only wish I had known how important the insulation step was.

The addition is under roof and I'm now looking at my options for heat and cooling in that space. I really like what I read about radiant floor heat, yet I have a few concerns. One real advantage I have is my floor has over 5 inches to door openings.

I have a LOT of working room concerning insulation. Grade and moisture migration are almost nil since my slab is slightly above grade not including the additional height I can gain on my floor. The perimeter of my room is 8" insulation filled block at three courses above grade. 2x6 framing from there.

One side of the room is part of the garage wall. The back, of course, is all against the house, so I have two fully exposed exposed walls with lots of glass and 14' cathedral ceiling. Room size 24x14 . Hopefully this gives you some idea of the circumstances in needing to heat the space.

My boiler sits just behind addition room in the basement.

Since I have about 5 inches between the concrete floor and the doors I am toying with the idea to lay two sheets of 2" foam insulation on the floor. The insulation is load bearing and should support furniture if an additional flooring or plywood base is added.I would add perimeter insulation around the block going up three courses. The only caveat is I think ceramic tile flooring will be too unforgiving

leaving me with hard wood or laminate as my choices. In a basement this would be bad news, but above ground this seems like a solid approach, however I don't really know and before I spend all that money I wanted to ask around.

Some things about hydronic radiant heat tied to a boiler seem counter productive to me. Mainly building up a 160-180F temperature and then reducing it to 85-125F.

The recovery times etc. I would need a hybrid system since the rest of my house is straight baseboard heat which works well BTW even in my 70's insulated home.

The cost outlay to use a lot of 2"foam at about 30.00 a sheet here plus the cost of the pex and piping arrangement to temper the water to probably less than 100F will probably be steep .vs me simply running baseboard heat along the long wall under the windows and putting it on a separate loop/t-stat. In that case I don't need to temper the water.

Do you see flaws in my thinking here? I am a career hvac guy but I was mostly in refrigeration. I have put in boilers back in the day. I service my own equipment. I knew the importance of insulation, but I let this one get by me. Back when I did the pour I should have made sure the contractor added insulation. I made an assumption. You know what happens when we assume. By the time the pour was done, it was too late.

...

Continue reading at RADIANT HEAT MISTAKES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see these

Radiant Heating System Articles

• FLOOR TILE INSTALL on CONCRETE where we discuss cracks that appeared in the ceramic tile installed over the failed radiant heat floor discussed in this article
• RADIANT HEAT - home
• CARPETING IMPACT on RADIANT HEAT FLOOR
• DRIVEWAY & WALK DE-ICING SYSTEMS
• RADIANT HEAT AIR BOUND
• RADIANT HEAT CONTROLS
• RADIANT HEAT DEFECTS LIST
• RADIANT HEAT DESIGN & INSTALLATION MANUALS
• RADIANT HEAT INSTALLATION
• RADIANT HEAT MISTAKES
• RADIANT HEAT TEMPERATURES
• RADIANT HEAT TEMPERATURE CONTROL / MIXING VALVES
• RADIANT HEAT TEMPERATURE NIGHT SETBACK
• RADIANT SLAB FLOORING CHOICES
• RADIANT SLAB TROUBLESHOOTING
• RADIANT SLAB TUBING & FLUID CHOICES
• RADIANT SLAB TUBING LEAKS
• SLAB INSULATION, RADIANT / PASSIVE SOLAR
• SOIL R-VALUES
• THERMAL MASS in BUILDINGS
• WOOD FLOOR RADIANT HEAT
• WOOD FLOOR RADIANT HEAT DAMAGE

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RADIANT HEAT MISTAKES FAQs-2 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to RADIANT HEAT

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