California radiant heating code needs to be fixed

rimrock

When I built my house in 1992, there were no restrictions on radiant heating system design. I read many articles and ended up insulating the downslope foundation walls and 4' of the slab along those walls, and the system has worked well. Our gas bills for dhw and radiant heating average $150/month during winter, which is quite a bit lower than our neighbors with forced air heat. And the house temp. we like is about 71-72 deg. during winter.

In 2008 or so, the California building code changed. Section 4.7.2 Radiant Floor Systems, Table 4-10 – Slab Insulation Requirements for Heated Slabs gives mandatory insulation requirements for radiant heating systems.

What surprises me is that there are no energy calcs that can be performed to determine the need for under-slab insulation or to treat it as a factor in the whole house energy calcs - instead it is a blanket requirement. There are no exceptions, even though slab insulation is not always necessary (i.e. the potential heat loss for some soil types is very low).

Mitigations that take into account the entire house energy balance are also not allowed as a way of avoiding under-slab insulation (e.g. adding additional insulation in other areas of the house, or using solar water heating to provide the heat). What surprises me is how rigid the law has become in this area, compared to what it was before. I can understand inflexible laws related to safety of construction, but not when it comes to energy savings, which has many trade-offs.

Jamie Hall

Kalifornia needs to be fixed...

Gordy

You may not like how the code is implemented. However I can assure you slab insulation is beneficial in reducing energy consumption no matter what soil type you have. Even if it's not a radiant heated slab. Where the diminishing returns as to how much is a case by case basis.

Zman

Gordy said:

You may not like how the code is implemented. However I can assure you slab insulation is beneficial in reducing energy consumption no matter what soil type you have. Even if it's not a radiant heated slab. Where the diminishing returns as to how much is a case by case basis.

I am not a big fan of regulation but I will tell you that I wish that under slab insulation was a requirement when my house was built. I have an under insulated slab in my basement. The space has the lowest heat loss in the house and calls for heat at least 3 times as often as the rest of the zones.

Gordy

I'm not quite sure the angle of the argument against the implemented code, other than radiant slabs need insulation.

It seems you think the code should allow the ability for the builder to calculate how much insulation, or whether radiant slabs need insulation at all.

Couple of things come to mind.

One is future events, and change of owners to the dwelling.

In your post you use an example of heating with solar as though because the energy is free. The slab insulation can be comprised some what. So what if down the road the solar system craps out. The present, or future owners decide it is to expensive to replace, or just don't want to deal with a solar implemented system. So they install a boiler. Now the slab is not insulated, or has less than desirable amounts.

Another example in your post you seem to say that "other areas" can be insulated to make up for lack of insulation in a slab. I don't really see what other areas could do this in a structure.

Then there is soil types mentioned. Sure there are less conductive, and more conductive soils, and water tables being a huge concern. However there is no soil that can substitute a good insulation installation.

Finally the reason for it all is ease of code enforcement. Code says r-10 under slab, and perimeter. That's all the inspector has to confirm.

Now if you want to make the code driven by the builder, and the radiant designer, and a soils engineer. You have created a mile of red tape at the building dept. if that code was well written to that latitude. It would require. A soil analysis. Radiant design by a confirmed designer (which should be anyway). A heat loss pertaining to the soils r-factor ( which can be an ever floating factor through the heating season). All to be reviewed by someone in the building dept. that probably has little, or no clue as how to confirm the provided information. Now the inspector has to deal with on site confirmation of a now less than straight forward methods.

Solid_Fuel_Man

Honestly I think it's a sad state of affairs when regulations make things mandatory. When I built my own home in 2009, my small town had no building code other than at least one 3' wide exterior door, and at least 1 Window that met egress standards in each bedroom.

If national building codes had been in effect then, I'd have had to have a 6' (local frost line) frost wall instead of a monolithic thickened edge slab. All insulation that I did was way above what code would have dictated though.

The point is that where I am located and the ground work that I did with many cubic yards of gravel frost walls were not necessary, but building codes would have mandated them due to the building's use being for habitation.

I think it's a homeowner's or architect's responsibility to insulate to what they deem a good investment. I personally believe that insulation is the best investment one can make in a building. R35 walls and R60 ceiling with as close to airtight construction as reasonable, but that shouldn't be mandated IMHO.

Gordy

But if there is not minimum standards we all know what happens too.

Right now I'm living temporarily in slab built home. 2016 construction.

Zero slab insulation perimeter, or under. Forced air heat with ductwork in the uncondition attic. Equipment in conditioned space.

So needless to say the walls, and attic are insulated. However I have been experimenting with setbacks seeing how much the structure can lose in a period of time. The uninsulated slab kills the heat loss. Yesterday it was 10 degrees am no wind. Setback started at 8:00 am. Structure lost 3 degrees in 1 1/2 hours. 72 was initial setpoint.

So I go around shooting temps trying to figure out the btu sponge. Perimeter of exterior walls at slab 54 degrees. Duct diffusers farthest from main trunk in ceiling 45degrees. This is 1 1/2 hours into setback.

So programmed to come out of setback at 4:00pm. Learning thermostat so it starts 1 1/2 hours before 4:00pm. Structure hit 63 degrees before coming out of setback.......9 degree drop in 6 1/2 hours.

This is a ranch style 1600 sf condo(duplex). One entire wall shares the adjacent structure along its depth of about 30'. So do you think slab insulation would help this modern structure? Not required by code, and certainly would help slab perimeter losses. The walls, and attic are r 38, and r 13 by code.

With even forced air slabs are a conductive btu sponge. It affects the heat loss of the entire structure. The smaller the sf the more prevalent it becomes.

hot_rod

I agree with some minimum standards, especially with energy and insulation details, and safety.

The ones that get hurt most from lack of adequate slab insulation details are usually the ones that can afford it them least.

There have been numerous radiant slab systems abandoned and replaced with FA or mini splits systems due to excessive fuel costs associated with non, or poorly insulated slabs. And the homeowner now lives uncomfortably on a FA heated slab on grade structure.

It is the one insulation detail that is not easily remedied after the pour

Some rural areas around me have zero codes for building. I see parts of those homes blowing in the wind when tornado conditions start up around here. People die every year here in Missouri from houses blowing away, is that fair to the family and others in harms way? I have had large pieces of metal roofing drop into my yard from tornado, or high wind damaged properties 80 miles away. Along with their paycheck stubs, in one case.

Brewbeer

I wish the slab in my house had R-10 beneath it.

Gordy

The gift that keeps on giving.

Alan (California Radiant) Forbes

Yes to minimum standards. I'm surprised at how many befuddled looks I get from builders when I ask for underslab insulation.
I believe that building codes are good for all of us and that is why I put up with them, not that I have a choice. Without them, it would be chaos with people living in unsafe structures. As it is, unscrupulous tradesmen endanger homeowners. We see it all the time, no?

Gordy

Even with minimum standards the insulating gets done 1/2 arse.

jumper

The California Energy Commission has to keep adding stuff to its codes to justify its existence. Its codes award "credits" for wasting money on unnecessary things like variable speed motors when they're not called for. Slab insulation can actually be a negative in California if you're using solar energy.

I like Jamie's characterization, KaliforniaKodes

Solid_Fuel_Man

Ok, let me clarify my statement. I am certainly not against safety codes....I am an electrician after all. It's the UBC-uniform building code, the last thing I have to think about is hurricanes, so I shouldn't have to build to the same standard as someone in a hurricane zone. Same with earthquake-resistance etc.

As with all trades there are good tradesmen and "good enough...code min" tradesmen. I see way too much poor quality installation of equipment and insulation muddled up by installers and other trades alike.

I'm of the camp that it is a good owner or architect's job to build things to their standard, which should be their choice.

I have R20 perimeter slab insulation and R10 below. @Gordy my wife and I lived in a small (converted 2 car garage freestanding) apartment which had no slab insulation other than the carpet....Electric baseboard heat. That is one of the reasons why I went in the direction I did when I built my own home. That apartment was terrible! Suspended ceiling with fiberglass directly on top of it too, cost us quite a bit of money to heat considering the 480 square feet.

Gordy

@jumper you deem variable speed blowers, and slab insulation unnecessary. That's a matter of opinion. Based on?

As I said earlier, and as @hot rod rod noted. In a solar application. What if it is abandoned, and a conventional heat source is used to now drive the radiant system? Pretty hard to do slab insulation then.

There are ways to store energy instead of trying to drive it into the earth.

Gordy

@Solid_Fuel_Man all I know is you get so use to the radiant silence when it's not there it hits like a ton of bricks. My floors were 74-75. Now IF they are even 68 it's terrible on tile.

Not to mention blower noise, dry air, fluctuating humidity, cold drafts on a cycle start until the ducts warm up. Ahh the noise.

Larry Weingarten

Hello, I like to think of insulation in the context of the life of the building. Let's say the building will only last fifty years. Wouldn't it make sense to insulate based on the wild guess of what energy will cost in say, twenty five years? Energy costs likely won't go down.

Attached is a graph of energy use in CA vs the US. Note that CA use has remained essentially flat since the late seventies, when the California Energy Commission was formed. So, yes their rules do get crazy, but they get results.

Yours, Larry

ps. the graph title has "Art". That's Art Rosenfeld, who just passed away. He's referred to as "the godfather of energy efficiency".

hot_rod

Solid_Fuel_Man said:

Ok, let me clarify my statement. I am certainly not against safety codes....I am an electrician after all. It's the UBC-uniform building code, the last thing I have to think about is hurricanes, so I shouldn't have to build to the same standard as someone in a hurricane zone. Same with earthquake-resistance etc.



As with all trades there are good tradesmen and "good enough...code min" tradesmen. I see way too much poor quality installation of equipment and insulation muddled up by installers and other trades alike.



I'm of the camp that it is a good owner or architect's job to build things to their standard, which should be their choice.



I have R20 perimeter slab insulation and R10 below. @Gordy my wife and I lived in a small (converted 2 car garage freestanding) apartment which had no slab insulation other than the carpet....Electric baseboard heat. That is one of the reasons why I went in the direction I did when I built my own home. That apartment was terrible! Suspended ceiling with fiberglass directly on top of it too, cost us quite a bit of money to heat considering the 480 square feet.

Building codes are safety codes, essentially.

I doubt in your area that you are required to build to seismic codes, like CA or maybe not roof loading codes as in the western mountain areas. So I think they try to adjust the codes to local conditions. Local AHJ have the ability to modify the codes or add addendum to best serve their area.

I imagine most licensed builders and architects refer to the various codes often in design and build, they do intend to protect the general public. I question that the general public has the knowledge to build and size structural dwellings without some code guidance.

I know IAMPO just spent a lot of time and money developing solar and hydronic codes to try and get a handle on bad and or dangerous installations. it protects the public and our industry. Mark Eatherton worked a lot on that project and several wallies here helped develop the curriculum and test questions.

Solid_Fuel_Man

Totally agree @hot rod I guess I'm just saying it's too bad insulation has to be required. Is it necessary: most definitely. It's just too bad that insulation has to be mandated for builders to use it.

If you think about it, it's kind of overreacting to a building code after all. Codes are about safety, and I will never argue about that.

Jack

CA Energy Codes came out in I think it was '79 or '80. I was in the contracting business in CA then. Those "Title 24" codes have...matured over the years, and yes there are some of the...What?...Really? Things, but overall I give it good marks. It is consumer protection in that you know you are getting a pretty consistent product when you buy a house. I got a call a few weeks back to look a house over that was having fuel consumption issues. Really a beautiful single story radiant slab with much of the slab edge exposed. 1800 sq ft. $900/ mo in gas bills when using the radiant. No slab insulation anywhere. The lady who bought the house wishes it was there and it is a shame she can't use the radiant. Insulate it.

Gordy

A "consistent product" is probably the best reasoning yet.

A buyer should not have to worry about two houses built in the same year, and area being apples to apples.

Mark Eatherton

Insulation used to be optional. An associate of mine who works for a local AHJ consulted with me before he made a recommendation to the IRC, IMC as it pertains to insulation minimums.

I recommended minimum R 5 for slabs and slab edges, R 7 (was still available back then) for framed floors over conditioned spaces, and R-19 for suspended floors above unconditioned spaces, with the caveat that as you move further north, R values may need to be increased. He (the inspector) was tired of having to field calls from dis-satisfied consumers who had cold basements and were pouring money down the drain due to the lack of insulation.

At the time, I was approaching the problem more from the perspective of slab performance, than energy conservation. Energy was relatively cheap back then.

Remember also that the code is the MINIMUM standard. If you have somewhere that you think you can enhance the overall performance of a building through the application of insulation, air sealing or technology, go for it. They can't tell you that you are building to excess.

As it pertains to crappy insulation installations, take responsibility for providing and placing the insulation, and CHARGE for it accordingly. Making a profit is not against the law, and the best way to maintain good control over its placement, is to provide it and place it yourself. If you think that is below you, then align yourself with a good insulation contractor, and make money on his work. Remember, the performance of YOUR system is depending on good insulation.

In general, having had many years of experience developing codes, there has to be a "Life, Health or Safety" issue in order to be considered for code applicability.

The waste of energy is considered detrimental to life due to the potential of global warming (not my intent, please do not flame me). As noted, IMHO it's about "system" performance more than it is energy conservation. Conservation is still a wise decision.

As it pertains to solar thermal, or solar in general, just because it is allegedly "FREE", doesn't mean it should be wasted. I think the opposite is true. Solar thermal BTU's are SO precious, that extra care should be taken to conserve them as well as we possibly can, and as such, should NOT be wasted in any form.

One of the reasons that I look forward to disconnecting myself from my current employer (IAPMO) is because as an employee, my hands are literally tied when it comes to making code recommendations. As an employee of IAPMO, working on an ANSI document, I am not allowed to have any "influence" on decisions made by the technical committees charged with developing code recommendations. I have holes in my tongue and lips gotten from biting them during public code hearings.

At one point, I had to publicly apologize to the people on a committee for belittling them in public. If I had been on the outside, I wouldn't have held back, and I wouldn't have had to apologized for their silly actions.

The IAPMO codes are developed by it's stake holders, Contractors are stake holders. Manufacturers are stakeholders. Heck, even the consumer is a stakeholder and If you don't like the direction that the code is going, you are allowed to make public comment, and there is a process in place to make certain your voice is heard. Your recommendations may or may not make it into the final version, but you ARE allowed to have a say in the development of these codes. Unfortunately, IAPMO is only one code development authority, and although their codes are the most widely used in the WORLD, they are a minority in the US.

BTW, there are big differences in code development authorities. Some are consensus developed, and some are not. All IAPMO codes are consensus developed. The intent of the RPA in being involved in developing the codes pertaining to hydronics, was to level the playing field for the consumer. The bottom line intent was to provide minimum guidance to ensure that these wonderful systems perform as well as they possibly can.

None of the systems I and my former company installed were ever done to the code "minimum". The installed cost of our systems were typically 2 times more than our closest competitors. I had lunch with my former business partner, and he said that his company is struggling, but its a good struggle to have. His problem is finding enough time to get all the projects done that they have contracts for. It's almost as stressful as not having enough work to keep people busy, but it is a good problem to have...

You have one chance (with insulation below slabs and on slab edges) to do it right.

INSULATE!

PS, I will have to get the URL from my work PC, but we do have a link to the current version of the USEHC that is a read only version that you can read online. Codes are a living document, and this is the 2015 version. There are many changes in the USEHC and UMC that will be reflected in the 2018 version. It is too late to get public comments in, but if you are seriously interested in becoming involved with the IAPMO code development process, by all means contact the code development division of IAPMO.

ME

Sal Santamaura

jumper said:

...Slab insulation can actually be a negative in California if you're using solar energy...

Why? Please explain.

Zman

Establishing minimum requirements even when it is not a safety issue is really a good thing for quality minded contractors.

I hear guys complain that the did not get a job because it was given a less expensive company that does shoddy work.

Code minimums level this playing field, everyone has to build to same standard.

As for the OP insistence that factors like soil type or energy source should be considered in determining under slab insulation requirements, I have heard this nonsense for years and it is absolutely not true. The simple fact is that when you don't insulate, you are dumping energy into the ground all the time (unless of course your soil temp is higher the design air temp).

I used to work for a guy that insisted that you don't need insulation because "heat still rises right?" He is retired in Mexico, every time I see one of his jobs and hear the owners complaint, I have to resist the impulse to call him up.

As for the argument that we have some inalienable right to screw up our own house and the government has no right to intervene, I absolutely agree. Why should an adult motorcyclist be required to where a helmet?
However all houses are sold to some unsuspecting sole at some point. As long as all the concealed construction defects associated with a property are documented and recorded with the deed for future owners to evaluate, people should be able to do what ever they please with properties that only they occupy.

Solid_Fuel_Man

I agree that under or uninsulated slabs have given radiant a black eye. It's just sad that it must be mandated.

And I am in my radiant slab heated living room, with near passive house walls and ceiling above. Voluntarily built to those standards.

jumper

Ground is the only economical way to store months and years of solar energy.

Sal Santamaura said:

jumper said:

...Slab insulation can actually be a negative in California if you're using solar energy...

Why? Please explain.

Canada has long painful experiences with government ordered or encouraged insulation. UFFI is an example out of Catch-22.

Jamie Hall

Perhaps... it is because there really are two different purposes which are getting confused.

One, which I am very much in favour of, is ensuring that the product -- in this case, a building, afford health and safety. It doesn't have built in health hazards, like cross connections. It doesn't have incomprehensible wiring (things like colour coding on conductors) and the wiring is sized to a minimum and protected (wire size, fuses/circuit breakers). It won't fall down (minimum loads; in some cases the load is specified, in others the code is prescriptive, which isn't quite as good but is easier to interpret). And so on.

The other is to establish some sort of defined desirable (by someone's thinking) standard product. This really isn't the same thing at all, but is what things like minimum insulation or number of wall plugs work towards. Specifications of this sort tend to be matters of opinion.

The two are completely different philosophies as to how the state, used as a general term (e.g. could be town, city, state, feds, UN for all I know), should control the actions of the people.

When the folks who write regulations -- or codes -- don't understand the difference, or get the two mixed up, you can have real problems.

Sal Santamaura

jumper said:

Ground is the only economical way to store months and years of solar energy...

In such an approach, wouldn't it be necessary to insulate some volume of soil beneath the slab so that solar energy is contained? If not, why wouldn't the energy dissipate into surrounding soil and be lost?

Zman

jumper said:

Ground is the only economical way to store months and years of solar energy.

Sal Santamaura said:

jumper said:

...Slab insulation can actually be a negative in California if you're using solar energy...

Why? Please explain.

Canada has long painful experiences with government ordered or encouraged insulation. UFFI is an example out of Catch-22.

@jumper
Please provide some backup for your point of view.
Has there been a study that has recommended this?
Every model I have seen as well as my personal experience has indicated that the area under the slab quickly reaches thermal equilibrium and that if there is no insulation at some level, the energy is lost to the earth.

jumper

What temperature do you think built-over ground in California is? You think it's cold? Perhaps in California desert cool floor makes home more comfortable in summer? Where's the balance? Send this thread to California Energy Commission and they'll commission a study for next iteration of KaliforniaKode.

Gordy

It doesn't add up. If I want to store, and reuse energy. I need to contain it. Replenish, use, replenish. Or replenish as used, or use as produced. Insulation helps with that.

jumper

Gordy said:

It doesn't add up. If I want to store, and reuse energy. I need to contain it. Replenish, use, replenish. Or replenish as used, or use as produced. Insulation helps with that.

Sometimes energy efficiency does add up and sometimes not. Insulation is perfect example. Some insulation in the correct place can pay for itself. Additional insulation usually doesn't. Law of diminishing returns. Dry ground is considered an insulator by the way.

Gordy

It's also a conductor depending on soil types baring any moisture at all. I have yet to see any grounds r value equal 2" of xps.

hot_rod

It's a tough argument to make Jumper. If the grounds any temperature below the slab temperature, some of the heat energy will go to the ground, and keep going down.

It looks like soil temperatures in the winter months drop into the 50's in some areas of California. So with an 82° slab temperature you have close to a 30°∆T encouraging the heat transfer to the ground.

Water, if you have the space for those large unpressurized tanks is a much better way to store energy. 4-6" of insulation around a tank will keep it pretty well.

This is an older study, for just one area of CA I'll bet other current data exists.

I think Robert Bean has some FEA and infrared of energy transfer to the earth at healthyheating.com


http://www.water.ca.gov/pubs/use/land_and_water_use/agroclimatic_monitoring_in_the_san_joaquin_valley_1958-1991/section_7.pdf

Sal Santamaura

jumper said:

What temperature do you think built-over ground in California is? You think it's cold?...

In parts of the state that have significant winter heating loads, yes, I do. But it varies widely, as does the climate in this geographically diverse state.

I've lived in San Clemente since 1978. If production builders who churn out 99.9% of the heaps-o-stucco around here paid any attention to solar orientation and passive design, there would be no need for supplemental heating at all. Since developers make lots narrow and deep, without respect to the compass, to cram in as many homes as possible per foot of street frontage, a minimal amount of scorched air gets used from December through March. Very minimal. I've never measured the soil temperature beneath my slab, but am aware what our "cold" water temperature is. The mains are safely below the "frost line" (the surface) at around 18 inches. After opening the tap and letting things run a while, i.e. until temperature stabilizes, it's a minimum of 68F in January/February and a maximum of 81F in August. It's safe to assume the soil under our slab matches those water temperatures within a few degrees. If one had sufficient financial resources to build a custom home with a heated slab, I'd say the intelligent approach would be to put that money into proper design, thereby eliminating heating completely. Even in such a situation, insulating the slab would still make sense to keep summer soil heat out of conditioned space during the cooling season.

In other parts of the state, where soil temperatures are significantly lower during winter, Bob's post right before this one answers your question.

Sal Santamaura

Sal Santamaura said:

within a few degress...

Can't edit stupid mistakes after posting. "degrees," not "degress."

Never mind. Fixed now.

jumper

Thoughtful comments. Have you guys included the insulation contributions from water barrier and gravel? The OP's issue is the blanket requirement in CaliforniaEnergyCode. That is simply incorrect engineering because the correct procedure is to do some guesstimates & calculations and then decide for particular situation.

Last time (some years ago) I looked at CaliforniaEnergyCode designer had to accumulate points by specifying features (such as VSDs) irrespective of if they were appropriate to the situation. Thirty years ago CaliforniaEnergyCode had blanket requirement for air-side economizer. To the Commission's credit other methods of "free cooling" count now.

Zman

Sal Santamaura said:

Sal Santamaura said:

within a few degress...

Can't edit stupid mistakes after posting. "degrees," not "degress."

Sal,
If you click the setting icon in the top left corner of the post, you can edit. You have to be signed in to do this.

Sal Santamaura

Zman said:

Sal Santamaura said:

Sal Santamaura said:

within a few degress...

Can't edit stupid mistakes after posting. "degrees," not "degress."

Sal,
If you click the setting icon in the top left corner of the post, you can edit. You have to be signed in to do this.

I am signed in and, if you're referring to the icon next to my name, just clicked on it. Doing so took me to what appears to be my profile page, which doesn't offer any means of editing my posts. Is there another icon you're referring to?

Thanks!

OK, all's fixed now. You were referring to the icon at the top right of a post's heading block, which doesn't appear unless one hovers over that block. I found it and edited everything. Lesson learned. Thanks again!

Sal Santamaura

jumper said:

...Have you guys included the insulation contributions from water barrier and gravel?...

Water barrier? Gravel? Around here, they flatten the clay soil, lay out cables/posts (for subsequent tensioning) and ABS drain lines, then pour. Concrete is in direct contact with highly expansive clay. Good that those cables/posts are included. Not good that the civil engineering wizards pay no attention to soon-to-rack wood-framed walls sitting on able-to-simulate-ocean-waves-without-cracking slabs.

Jamie Hall

It's not the civil engineering wizards, @Sal Santamaura -- I doubt that you'll find one within miles of a typical subdivision builder, or at least one worthy of the name.

But -- this whole discussion, which is very interesting and valuable, does illustrate my comment about the distinction between codes which are set up for health and safety (which would address that wavy slab problem!) and codes which are set up to enforce a fundamentally opinion oriented question, such as how efficient should a house or building be. You can lead a horse to water, but if you force his nose into the bucket and he doesn't like it, he'll probably kick you into the next county.