In-floor hydronic heating experiences

This seems about as close a forum to ask my question as any. Apologies if there is a better place.

The very quick back-story is that we have had the architectural and engineering on a off-grid home done for several years, the land is bought and paid for, and we have finally begun to make real progress on the building process. In order to keep costs down, I am doing much of the work myself. I enjoy DIY work, but am struggling with all of the skills necessary to build a far-from-conventional house. This week, and probably next, I'm getting everything ready for the concrete. We have a simple 6" thick slab that sits on top of 6" of styrofoam. The slab has PEX tubing runnng through it. Hot water is pumped through the tubing to heat the slab. The water is heated by a solar hot water system. The system is intended only to keep the house above freezing if we are ever away during the heating system. While we are home, the system will provide for some of our hot water needs and a masonry wood stove (or two) will be used to keep the household comfortable and heat water.

All I am struggling with at the moment is the PEX tubing that will end up encased in concrete. Everyone (the concrete fellows we got quotes from, our plumber neighbour, etc.) tells us that this is a piece of cake, but I really don't want to screw this up as repairing it will be incredibly expensive. So I'm looking to avoid any gotchas. For example, I just learned that I will need to use PEX tubing with an oxygen barrier. Our runs are 200 to 300 feet long. Rather than buy 100-foot lengths of tubing and connect them, I'm going to buy a single 1000-foot roll. Also, our plans call for 3/4" tubing, which seems really excessive, but is what the engineer asked for, so I guess I'm stuck with it.

Any advice from someone with a bit of experience would be very valuable to us.

Mark, congratulations on your project!

Re: "Any advice from someone with a bit of experience would be very valuable to us."

I'll share what I can, though from your post I'm not really clear on questions. It looks to me like you're on a good track and simply need some confidence.

About twenty years ago I built my home in zone 5b with hydronic heating. It wasn't nearly as unconventional as I'd build today, but it was strange enough to scare most builders away and cause the city to require engineer's stamps on everything to shift liability away from the inspector. With some labor from my family and a few really good friends, I did every job except running the excavator, taping sheetrock and applying stucco to the exterior. I remember hurrying to finish zip tying the tubing to remesh the day before the 2900 square foot slab was poured, and I swore I'd never again do a job that required so much bending and squatting. Today, I miss that house and it's incredible comfort. I'll gladly do that again to have hydronic heat!

Re: "All I am struggling with at the moment is the PEX tubing that will end up encased in concrete. Everyone (the concrete fellows we got quotes from, our plumber neighbour, etc.) tells us that this is a piece of cake, but I really don't want to screw this up as repairing it will be incredibly expensive. So I'm looking to avoid any gotchas."

I think most of the potential gotcha's are either obvious or they're design issues that you addressed before this point. But let's pretend that nothing is obvious and I'll list those gotchas I can think of immediately:

In the hydronic system design, everything is connected - pumps, lengths of runs, diameter of pipe, etc. I assume you either had an expert design the system or you've done enough research to be comfortable with the principles. The gotcha here would be failing to follow a good design. Skip that mistake and install as designed.

Your system was spec'd with oxygen barrier tubing. (Mine was too.) This prevents ferrous metal components from corroding. The gotcha here would be attempting to save money by using tubing without the barrier. Don't do that. The other gotcha would be horribly abusing the tubing and scraping lots of coating off it. Again, don't do that.

Your tubing will be encased in concrete. That's what it's made for. No problem. Do make sure it's tied down so it can't float up and stick out of the concrete. Yeah, I know, this stuff is obvious. We used zip ties to tie the tubing to the wire mesh. The zip ties were long enough that their tails could stick out of the concrete, so we got to clip all of them off with diagonal cutters.

When laying the tubing, you'll find it doesn't really like turning corners. Be nice when you bend it. Avoid kinks. Having a wider radius turn than you planned is much better than kinking the tube.

After the slab is poured, you may be framing walls that will be nailed down into the slab. Hitting the tubing with a nail that attaches the bottom plate of a wall to the slab is a bad idea. We avoided this by routing all tubing into rooms through the door opening. (Yes, we layed everything out before pouring the slab and marked where doors were... but you need layout anyway to position your subgrade plumbing.) The only place we couldn't route tubing through the doorway was in the utility room; it had too many tubes entering the room to fit through the doorway. So we marked an additional "fake doorway" on one wall and concentrated tubing beneath that section, then took care when framing that wall to not nail into that section.

You're absolutely right on buying a single long roll of tubing. You don't want any joints buried in concrete. If you're subject to building inspections, I don't believe code would allow that anyway.

Related to the prior point, I wouldn't attempt to precut your tubing lengths before running them. (Or, if you do, cut them extra long.) By the time you route everything where it's supposed to go, deal with turns that insist on wider radius than you thought, and generally deal with reality, your runs may be a little shorter or longer than you expected. Precutting allows no room for learning.

Definitely stick with the 3/4" tubing. If that's what the engineer spec'd, then the pump sizing and system operation depend on it. Changes in one area would have a ripple effect to other areas, so no changes without consulting the person who spec'd it.

I'm running out of gotchas to suggest. Maybe that's because it was two decades ago or maybe it's because time heals stupid mistakes. I don't remember any surprises in the hydronic system and I remember loving it. Most people in our area heated with forced air so our concrete help was more skeptical than yours. Despite dealing with a few raised eyebrows along the way, that heating system was the best decision in that home. My oldest kids, then toddlers, found the place where many tubes exited the utility room together and they'd curl up on the tile floor in that area when they were cold. Great memories!

In general, understand the design enough that you're comfortable with the work you're doing. Measure twice and cut once. Allow more time than you think is needed. And enjoy the journey. I'd love to be doing what you're doing tomorrow!

Ashley, I hear you on builders being scared away by anything unconventional. After we had the architectural and engineering complete and paid for, we asked local builders for quotes. More than half plainly stated that they didn't want to touch the project. The two that gave us a number quoted absurdly high. I was devastated. To be honest, what I said earlier about doing much of the work myself to keep costs down is only half the story. It's more that we don't really have any choice.

You are correct that confidence is the thing I'm lacking. At every step of this project, I'm treading in unfamiliar ground. It takes a lot of energy to familiarize oneself with a problem, examine possible solutions, pick the best approach, learn that approach, then execute it, all in addition to "normal life". We built a conventional house in the city years ago. Two meetings with the bank and two with the builder. Three-and-a-half months later, we had a house. The hardest part was moving in.

I'll double-check on the oxygen barrier with the PEX tubing. I asked for it at the plumbing supply store, but didn't check the labelling to confirm that what arrived actually had it. The price makes me think it has it.

Good points. Pinning the tubing down had not occurred to me. Since our slab sits on 6" of styrofoam, I'm not sure how to best do that. I'll have to look into options.

Thanks for taking the time to write down your thoughts. It constantly amazes me that folk are willing to take the time to do that. Maybe there's hope yet.

Hi Mark,

I've installed radiant tubing a number of times for going in a concrete pour. Ashley's points are correct, here are a few more:

1. The easiest way to install tubing above foam board is to staple it down! Wirsbo makes an awesome stapler and plastic staples that allow you to simply staple it to the foam. The only problem is that you need to be "Wirsbo Certified" to get your hands on this stuff - see if you can make friends with someone from an HVAC company who is - or contact anyone you know in that industry who might be able to help you out. If you are able to do this, talk to your engineer about possibly not using rebar - there is a fiberglass mesh (I think) that can be added to the concrete which eliminates the need for rebar in an on-grade concrete slab. The only downside is that you can't do a polished concrete floor with this mesh. If you do go this method, make sure that you weigh down the tubing if you have to wait a few days for the concrete truck to arrive. The tubing will remember it's coiled shape - and strong winds or another disturbance could cause your beautiful foam and tubing circuits to pick up into an unsightly ball.

2. Rolling out the PEX - 1,000 feet rolls are the way to go, but they are a major pain in the butt. We found that this is a 3-person job - one person (the strongest) to manage the roll - UNROLL it, don't just pick up coils off the top. Trust me on this. The second person manages the tubing and holds it in place for the 3rd person to attach it - either to the foam with the stapler, or ties it to the rebar.

3. LABEL EVERYTHING - which side is supply? Which is return? Which loop goes where?

4. TAKE PHOTOS OF EVERYTHING - this goes all the way through construction - especially any time anything gets covered.

5. Radiant tubing does not like to make sharp bends - this goes for the ends of your loops as well as turning up out of the slab. The radiant manifold will take more floor space than you think.

6. Get your radiant manifold now - it'll help you figure out where your tubing will end up.

7. You definitely want the oxygen barrier. Double check that you have it - if you don't, wait for it to arrive. Otherwise, you'll be dealing with rusting of the ferrous components of your system.

That's all I can think of for now... I'll post more if I can think of it.

Hello Mark, et al,

Mark wrote:All I am struggling with at the moment is the PEX tubing that will end up encased in concrete. Everyone (the concrete fellows we got quotes from, our plumber neighbour, etc.) tells us that this is a piece of cake, but I really don't want to screw this up as repairing it will be incredibly expensive. So I'm looking to avoid any gotchas.

From my experience I would possibly suggest not ever embedding anything in concrete...

I think...the concept of burying-embedding a work and expensive materials in a solid concrete slab could lead to challenges later. I have seen brand new slab floors where "something" has gone awry and the slab has to be busted up, only for the contractor to turn around and pour another slab??

These folks have always been very helpful and the owner and pioneering developer (Robert Starr) and his group are great to work with. Radiantec They may possibly be one of the oldest in the country and one of the best in the industry...in my view.

I have found and been told by others that hydronic tubing can be place under a wood floor, embedded-buried in sand, pea gravel, stone dust and then tiled over, other mass tile system of stone, cobb, or similar mass flooring matrix like 三和土 Tataki and it will work just as well...


Here are my thoughts:

Embed-bury-or encapsulate ANYTHING if there is the slightest chance you will ever need to get at it again...could lead to unwanted costs. If you do have to do this from some strange reason, (like flues in a RMH) understand fully the logic and reason behind it, and perhaps design a way to facilitate around this, or maintenance of it like traps, openings and/or service ports.

[list]Plan, draw, CAD and model everything before you build it...and photo document every single detail. These "sector runs" and their many "labyrinth" are complicated to even the experts so document well.

If clipping, tying, or grinding the tubing in some fashion understand that if it 'rubs against an area for normal expansion contraction that is abrasive or sharp like bends, wire, nails, sharp stone, etc this can become an issue. That is what a matrix of sand, stone dust, or padded cleating methods are recommended over other systems of attachment that may seem convenient at the time.

Foam may not be needed and has shown in my experience to attract and become good nesting material for rodents and insects.

It may help to learn to build your own manifold to the different zones. This can save money in the future if you have to service them, yet there price is going down and may not warrant the effort...Shop around and compare.

Sorry to perhaps suggest an opposite path to what is being done...Hope things turn out well either way...

Regards,

j

au contraire, JC - this is a "passive solar" forum. Modern technologies are allowed to be discussed. Moving hot water through tubing is a very effective method of heat transfer. While you may disagree with some of the materials used, in a very cold climate, respectful use of modern materials can result in a very warm building that uses little energy to keep warm. Maybe even saving enough that it offsets the inputs into said materials. Also, sources of recycled materials can be found - so they can serve a benefit and save a landfill from being filled with foam. I built my house, and it is insulated with foam board recovered from the deconstruction of other buildings.

The only place where we have had trouble with our radiant tubing in our house is underneath our wood floor - where a mouse chewed it. We had to take down the ceiling in the lower level to repair the tubing.

Lastly, a natural earthen floor is an intriguing option - except I disagree about using sand - dry sand (I hope the inside of the house will be dry) - is a great insulator, so the heat circulated in the tubing will not be transferred to the living space very quickly at all - in fact, for some radiant tubing installations (in concrete slabs) - foam insulation is actually only used at the perimeter, and a sand bed is used in the center as insulation and as a thermal mass - if the OP wants to reduce his impact from using foam, and can make sure that the sand will stay dry, this could be an option. It will reduce the speed at which heat gets into the house from the radiant tubing, but as the main goal of the radiant tubing is keeping the house from freezing, having the additional thermal mass could be a benefit.

best,

Karen

Hello Karen,

You are correct, this is the "passive solar" forum, and I was just trying to suggest that modern technologies are not the only way to perhaps achieve some of these goals.

I agree that moving hot water through tubing is a very effective method of heat transfer in some applications, and only was trying to suggest that perhaps there could be a different way of achieving the same goals. I was just hoping to same someone from some headaches down the line that I have experienced with foams as they do attract animals in my experience...

I am very glad you like the idea of earthen floors... I am not sure if all the information out on the internet about sand may be accurate as it is sometimes offered. I was just trying to make a suggestion from my experience, what I have learned and observed. Most of what I read about sand (dry or wet) is that it performs more like a thermal capacitor than a loft type insulator. I agree, no matter the actual reason, that sand will reduce the speed at which heat gets into the house, and have found in my experience that the thermal mass of sand (or similar natural material) can perform as well as concrete/foam for achieving the same goals.

Thanks,

j

Hi Jay,

I respect where you're coming from in the natural building industry, I am not arguing against discussing natural building methods here, but you criticized we prior posters for discussing modern materials. Unless I am mistaken, this is an allowable topic here.

I disagree with your categorization of concrete as a vile toxic material on par with pressure treated lumber. Concrete is mostly sand and gravel. It also uses portland cement (made from lime) - the only toxic material I am aware of that could be found in concrete is fly ash. Fly ash is a byproduct of combustion - usually you have to request that this be added to your concrete (it displaces some of the portland cement). The bad part about concrete is the energy that it takes to produce.

Radiantec - cool site. I do find it interesting that lots of your photos show modern technologies - LVL beams, and foil faced foam insulation, for example. Also, putting radiant tubing under wood or a more insulating material (say a concrete floor with a rug on it) means that it takes a hotter temperature water to transfer heat to the surface and into the space. These high temperatures can be difficult to achieve with a solar hot water system, especially in cloudy weather. Even if the solar hot water system can produce the high heat required, it will produce less heat the higher the required temperature. To maximize the amount of heat available to a radiant floor from a solar hot water system, make the floor conductive!

Re: my mouse problem mice - the living part of the house is attached to a shop part of the house, and the thresholds under the doors were not yet complete - and some mice got in. I made thresholds. No more mice, no more tubing issues. Regarding mice or rats getting to radiant tubing embedded in concrete - I find this really hard to believe - have you ever seen it happen? Most slabs are poured inside a foundation/frost wall, so the mice or rats would have to chew through the foundation, chew their way up under the slab, and then through another few inches of concrete to get to the tubing.

I have seen a hole in radiant tubing embedded in concrete fixed within a few hours. The concrete needs to be chipped out around the leak, the tubing repaired (usually a coupling) and then new concrete filled in. It's not ideal, but is very rare. The only time I've seen it happen is where the tubing was punctured by a contractor who didn't know not to drill into the floor. While repairing a leak in a natural earthen floor might be easier, it is such an unlikely occurrence that it would not factor significantly into my decision about materials.

You asked about dry vs wet sand - this website has numbers for both. It has about the same insulating value as wood, so burying tubing in a few inches of dry sand will make heat transfer very difficult: http://www.aquatherm.com/sand-as-insulation

I think that we will have to agree to disagree on some issues - in my opinion, permaculture includes intelligent use of modern technologies when those technologies can be used to create a long-lasting impact. This could include using excavators to build ponds and using modern insulation to help keep buildings warm (and cool). There are many other areas in permaculture where modern technologies are regularly used: automatic chicken doors to let our birds free range during the day and keep them safe at night, electric netting to temporarily fence in animals or keep them safe, and the internet to share ideas.

Radiant tubing beneath an earthen floor would be pretty cool - but an earthen floor is functionally different than concrete. The OP would need to rethink how to support load bearing walls. Because it is softer, an earthen floor is more prone to wear. It will also be more comfortable to stand on. In my projects, a floor prone to wear was not an option (heavy shop space), but could be a good solution for OP.

I see that you are located in VT (as am I) - how do you protect foundations and floors from frost in this climate? I'm genuinely curious.

Best,

Karen

Hi Karen,

Karen Walk wrote:I see that you are located in VT (as am I) - how do you protect foundations and floors from frost in this climate? I'm genuinely curious.

Great question...

Mainly by not having the moisture there in the first place like some of what I posted about inRaised Earth Foundations. there is a great deal of misinformation shared about frost and frost heave in my experience and it is usually more about certain types of clay, than just freezing water alone. Great houses have been built in locations of the far north where getting below the "permafrost" is even possible.

Karen Walk wrote:Regarding mice or rats getting to radiant tubing embedded in concrete - I find this really hard to believe - have you ever seen it happen?

Yes...on a number of occasions.

They like to dig, chew and scratch their way through whatever is in the way of where they want to go when they have the motivation to do so. I have found that understanding their baseline ethology is really important in dissuading and inhibiting their ingress/egress from architecture.

Karen Walk wrote:I have seen a hole in radiant tubing embedded in concrete fixed within a few hours. The concrete needs to be chipped out around the leak, the tubing repaired (usually a coupling) and then new concrete filled in. It's not ideal, but is very rare.

I think repairs can be made to radiant floor systems just like described. It just has been my experience that is never "easy" and happens more often that folks might think. If embedding something where it is hard to get to compared to an alternative just seems like a good plan if it can be achieved and reach the same results.

Aquatherm wrote:Thus it can be shown that sand is a good replacement for fiberglass pipe insulation in underground, direct buried applications. It's easier to install and costs less.

I don't disagree with that statement at all. I just wasn't clear about the sand and wood insulation part being similar. That is not my experience. I just think sand is as good and probably better at storing heat than concrete may be if all aspects are taken into consideration like design, facilitation, and alteration. without having to endure the environmental impact of OPC materials.

Karen Walk wrote:Radiant tubing beneath an earthen floor would be pretty cool - but an earthen floor is functionally different than concrete.

I doesn't always have to be in my experience...

Regards,

j

Jay C - I will respond to a few of your points.

1. I have read many of your posts on permies. I find myself skipping them often. No disrespect, but you often quote ancient technologies that "work well" and your own personal experience without providing links or backup that allow me to fully understand what you are talking about. For building practices, I learn best from non-emotional language and diagrams, so your descriptions often don't work for me. In the post quoted, you mention a raised earth foundation, but you don't address heat transfer into the house.

2. Yes, cement is not a great product, but in my opinion, the only other alternative for foundations in this climate is building with stone. This is cost-prohibitive for most people. For a slab, I think that earth is viable, as long as the owner/builder understands the compromises - see my last post. Also, you may disagree, but I want insulation in my floor to prevent cold from coming in - not just to protect from heaving should my water management systems fail, but also to protect my feet from the cold and from having to burn lots more wood.

3. I just did a little research about rats/mice chewing through concrete - I found instances of them chewing through concrete blocks, and concrete boards - both are fairly thin. I'm still surprised that this happened, but I didn't find any instances of rats chewing through foundation walls made of poured concrete.

4. Aquatherm - I'm not advocating for aquatherm, it is a website with some information about R-values of wet and dry sand. Here's another website with similar values. They are not trying to sell any products linked to dry sand. It also lists the R-value per inch of wood. Be aware the units are SI. Sand has a high thermal mass - wood doesn't, but sand can still be insulating and will require a higher water temperature to transfer energy at the same rate. My comment stands.

5. I mention an earthen floor because I was trying to show you that I am open to natural building as well. I am not advocating for concrete, but the original question was about installing tubing in concrete. The original poster has the building designed and the radiant tubing ordered. I assume that he is pretty far along in the process. Switching to a different flooring material with different structural properties at this point is a significant design change. I know. I've been there.

6. Lastly - as to the superiority of traditional building methods, I've seen some instances of natural buildings. I've seen 500+ year old stone buildings in Ireland (cold) and 50 year old earth structures in Morocco (melting like a drip castle). I've also seen the stonework of the Incas - amazing, and some earth brick construction in Peru that was fantastic. There are some modern adapted techniques with natural building that I find compelling, such as earthbag building - an earthbag orphanage in Nepal withstood the earthquakes while many modern and old buildings collapsed. I do not find ancient techniques to be inherently better than modern ones, as in all permaculture, I observe, adjust try new things.

Hello Karen,

I am sorry if you feel I haven't tried to back up my words well enough or validated means, methods and materials as well as I could have... I will try to do better in the future, and will always respond to question the best I am able.

Stone is one option, and I agree in some forms it can be expensive, yet there are alternatives and perhaps more natural forms beyond OPC, that was all I was trying to suggest.

I can't speak to individual members and what they find or don't find about rodent damage. I have seen several species of rodent over time work there way through slabs of old concrete or enlarge holes. That is just my experience, and if I find any technical journal info from when I worked in the field I will make sure to post a link.

As for as wood being like sand, I just am not seeing that?? The two materials have always presented as very different to me.

I agree that Mark my not chose to, or be able to change his plane now, but was just offering and alternative for him and our other readers.

I understand that many folks have lost faith in the wisdom of old methods, or do believe they could be better than modern concepts in architecture. It has just been my experience that many modern materials and methods pale in comparison when all factors are considered.

Regards,

j

first post here - hi!

I am facing the same questions here about colder climate flooring design.
As a Permaculture forum, we should be building any structure firstly to have low energy input materials, the longest lifespan materials, avoiding any chemical inputs and residue & avoid plastics where possible.
This is what Permaculture is all about. (exactly the same concepts in the garden/growing of food)
So with this in mind, as Jay points out, concrete should be avoided as much as possible as it fails in all categories. (concrete and steel are hugely energy intensive polluting industries)

Ive read a lot of Jays posts over a long time, and after reading into all of these many historic proven simple building techniques, (that are all happen to be based around Permacuture ideals) I can see these climate specific building systems can be built with extremely low energy inputs, including, bring a truckloads of stone into a stone free environment is way less polluting than a laying a concrete slab with steel reinforcement.
Plastic and foam insulation - leaves a terrible polluting legacy for someone to deal with - or ingest in the future, the slow breaking down and leaching into the environment of all of these elements are a real environmental future toxic hazard…..
and Its all based around the use of concrete - and its all over the planet.

The more I look at these simple floor & foundation systems that Jay points out, the more I realize that they are easy for a sole person to build - with nearly no tools!
They have a very small impact on our environment. They leave NO toxic legacy!
And they are systems that have been perfected by craftsmen and real world living environments over the centuries, so building floors for colder climates has been a continuous evolving human research task.
We should be paying much attention to these historic designs that point to comfortable living conditions over thousands of years.
Much historic specific climate design and architectural information exists out there that Jay is kindly opening our eyes too.
This priceless information has completely changed my approach, and thinking about building and architecture, and the toxic legacy I leave embedded in my surroundings.

Jay - if you were designing this floor system for a client, would you use a layer of sand between rock base and an earthen floor on top? How thick would the layer of sand and earthen floor measure?
Or would you use pex tubing in a bed of sand under a wooden floor?

Tread lightly,
Chris

(Please note readers that many things that are underline has a link attached...)

Hello Chris...Oh my gosh...first post...thank you for adding your voice!! and Welcome...

I am facing the same questions here about colder climate flooring design. As a Permaculture forum, we should be building any structure firstly to have low energy input materials, the longest lifespan materials, avoiding any chemical inputs and residue & avoid plastics where possible.

WOW...

Could not have written that better myself, and I agree 100%!! Plus it isn't as difficult as too many make it out to be...

OPC and related industrial materials have gigundous foot prints of impact...from the ore they are made of to the finished and often "mishandle" and overly handled materials.

Words can't express the appreciation I have for members like you that "really get it" and embrace the brilliance of the countless systems with such long legacies that go back before even our recorded histories. You are the reason I write, and contribute in these forums what I am able...Thank you...

Even if folks can only change one or two things on a building project...like not pouring a concrete slab...the impact on consumption and environmental impact would be huge. If we didn't pour a single OPC slab in any domestic architecture over the next 3 years I know for a fact (speaking with industry leaders and related contacts) that the entire industry would "sit up" and take notice of what "natural builders" are achieving, why we are doing it and what "real green" architecture actually looks like compared to the "lip service and greenwash" practices too many are doing and then claiming it to be "good practice" and a "green method"...which it simply isn't. Sorry, concrete slabs, foam and vinyl siding will never be "green" or a "good idea," no matter how you try to justify the practice. If it is done...its done...but lets not say its a pretty smelling Rose, when in truth it is a steam pile of unusable human waste, greed and sloth...(sorry...I own the last portion of this is full of emotion and perhaps a very subjective perspective..)

Jay - if you were designing this floor system for a client, would you use a layer of sand between rock base and an earthen floor on top? How thick would the layer of sand and earthen floor measure?
Or would you use pex tubing in a bed of sand under a wooden floor?

OOOh...great question, and if this goes anywhere please post it on a new post thread for your own project so we don't detract from Mark Fox's post. I would love to follow along on what you learn and do on your own project!

It all depends on the local resources (human and biome) as well as the building site. I have one I am about to start that is just a pavilion (which I was planning a post thread about.) This pavilion will not have any concrete at all, and sit on large stone plith. Not far from it, I have a friend/student that is building his own timber frame. For sake of speed, family pressure, and local "building officials" making his life rough, he had to pour concrete stem walls to place his timber frame on...a sad thing, that happens all too often. However, he doesn't plan at this time to ever pour a single slab on the job. He has a plate compacted 50 mm (~2") stone bed and will probably lay some sand to partially bed radiant tubing or he may place it in the walls and only float a wood floor over the stone.

There are simply so many ways of doing this naturally...!!

One could, as asked, just lay a sand and set heavy clay tile...or...perhaps flagstone (yes hydronics can go under this without any issue.) Not far from here there is a soapstone quarry and these make wonderful floors for radiant heat. One could also just cobb it, or lay stone dust down and thinset this with lime grout to lay standard tile they create or purchase...

A heavy Korean Maru floors could be created from most of the woodlot found on many permie building sites or anywhere there is trees, and it doesn't have to be "kiln dried" or even supper high grade lumber. Traditional Korean maru (maru=floor) floors, one form being Cheong Maru 청마루 have been around for millenia, and some are even of stone and allow for radiant heat underneath in the form of an Ondol 온돌 or in this case hydronic tubing! The mass of these floors is very high and insulative at the same time. Getting to the tubing to service or check or to even get to other mechanicals and electrical elements that are often hidden under floors is just a matter of moving some "magic boards" around as this is an "all wood joinery floating floor system" of both timber and wood plank.

I could keep rambling through method after method and variants there of...all of which...are more applicable and more than surpass the performance, impact and longevity of a OPC slab...

Do create a post about your project and thanks for adding your voice to this post...many thanks for that...

Warm Regards,

j

This is a lovely discussion!

Karen, thanks for extending my list of gotchas and suggestions with a few that didn't occur to me to mention. I agree, especially about it being a three person job! The challenge of offering such suggestions is that once you learn to do a thing it's easy to become unconscious of where the potential challenges are.

Jay, I don't feel unduly poked by your comments. As I said, the home I built 20 years ago wasn't nearly as unconventional as I'd build today... and most of the changes relate to my desire to try more natural methods and materials. If I'm ready for the next building project in a couple years as I plan, I'll probably chat with you further about integrating wonderful things like hydronic heating (and cooling) with traditional techniques.

Now, I'm going to expand the topic away from materials and techniques, to how we actually help the OP. In doing so, I'm going to reference the Wheaton Eco Scale.

Mark came here looking for confidence and tips on his first hydronic install. He indicated that he has a plan ready to go and approved by the local department of making you do things their way. He has some DIY experience, but is neither a full time builder nor a natural building expert. It sounds like he's surfing the edge between rapid learning and overwhelm... not necessarily looking for a pile of additional things to learn ASAP unless they're essential. If I were Mark in this situation, I'd probably be looking for help with my specific question rather than looking for recommendations to scrap the design. (And I'm not Mark, so I might be totally off.)

So how do we help Mark?

Help is only help if it's within someone's ability to receive it. I suspect, Jay, that you're a couple notches ahead of me on the Wheaton Eco Scale with respect to natural building. That means I think I can learn tons from you and would love to hang out and pick your brain. I suspect that you're quite a few notches ahead of Mark, which Paul suggests guarantees he'll see you as insane. Hey, great minds suffer than challenge often.

Then again, perhaps Mark is right there with you Jay. Perhaps you just saved him from implementing a design he'll regret, and gave him confidence to take a step farther ahead even though he's already pushing the limits of his local building community. It takes courage to be first to do something strange in your locale, especially when your funding it with a house sized budget.

So how do we help Mark? We invite Mark to tell us how far he wants to push the envelope, then we answer within his ability to use the information.
Go ahead Mark, tell us how we can help. Jay has far more knowledge of natural building than I do and more important, he actually has experience with it. If you want to go there, he's a far better source than me.

Until Mark replies with clarity on whether we're pushing his limits on the Wheaton Eco Scale, I suspect that our disagreements about the rest of the issues would be better served in another thread or two. A couple subjects come to mind: a) "In-mass hydronic heating with natural building techniques", b) "Modern and Natural Solutions to Ecological Problems of Concrete". I don't know that I have tons to contribute to those threads, but I'd love to read them and I'll sure bring questions!

Best regards, and thanks for bringing your passion!

Thanks Ashley for getting us back on track. I do want to post the link that I forgot to post in my last message - R-values of various materials in SI units.

http://wiki.gekgasifier.com/w/page/6123766/Insulation%20Data

When I get a chance, I'll post a new topic going into the details of some thermodynamic principles, and post a link here.

Hello All,

I guess I should start off with my background as it applies to this subject; Nuclear reactor operator instructor at Naval Nuclear Prototype Windsor CT, HVAC installer and technician and BPI certified Building Analyst before getting into natural home restorations.

I personally dislike the in-floor hydronic distribution networks for many of the reasons Jay has stated above. A few others are; thermal response is very slow and prone to over-heating of the slab, especially on sunny days in homes with large solar gains(passive solar), lower system efficiency due to heat flow to the Earth and additional power requirements for the pumps pushing water through all that tubing.

I have repaired 2 separate in-slab leaks in PEX tubing. I found them with my IR camera and then had the slab sawn open inside the home(yeah it was a mess both times) after pulling up floor tile, then repair the leak and repair the slab, wait 2-3 weeks then replace the tile, wait a week and grout. A month later, your house is back. Both of these leaks were embedded directly in concrete, so the tubing could not expand and contract normally within the slab, which rubbed holes in the PEX tubing.

I also diagnosed a complete failure of heating system due to the use of PB(early PEX) pipe in-slab. The client was horrified to find out that they were too late for payments from the already settled class action lawsuit on this faulty product. I don't really know what became of that, but always remember it is the buyer who must beware of new, unproven products; the manufacturer will try to shirk any responsibility if allowed by law.

I know that people like to walk barefoot on a warm floor, but there are serious drawbacks to this kind of system, so I always recommend low mass, flat panel radiators. If you do go with in-floor hydronics, then pour a thin(1.5") layer of lime/gypsum/sand or similar on top of the subfloor(whether wood or concrete) and embed your tubing Pex-Al-Pex in that. Then at least your not going to have to cut your concrete slab when it's time to repair those plastic tubes and your not heating your entire slab every time you wish to heat the room.

Here's a link http://www.duluthenergydesign.com/Content/Documents/GeneralInfo/PresentationMaterials/2013/Day1/hydronics-siegenthaler.pdf

All Blessings,
Bill

Ashley, thanks for succinctly and accurately summarizing the situation. I fully expected that my post would trigger an argument because...it's the Internet. But I can filter just fine.

I think the in-floor heating issue (ie. my confidence) is resolved. The tubing was confirmed to have an oxygen barrier and I'm comfortable with laying it out. Still looking for a means to hold it down. For the time being I've got a bunch of fist-sized rocks at the building site.

On the larger issue of ethical issues when choosing building materials and methods: 10 years ago, I had my heart set on a straw-bale house with a earthen floor and green roof. We hunted around for an architect that had experience with that sort of thing. We ended up finding the team best equipped to do that sort of design-work. They lived in a house of their design just a hope-skip-and-a-jump away from this. We toured their house, met with them, and they quickly expressed concerns about our direction. We also toured a home designed by this architectural team that had an earthen floor and strawbale walls. That tour confirmed much of what the architect was saying. You can guess what the big issue was: code. There was also the issue of cost and time. Resale value also plays a factor.

Am I bothered that we are using styrofoam, rebar, and concrete under our home? Yes. I mean, I'm doing as much of the work by hand (ie. leveling the ground beneath the slab, trenching for the plumbing, etc.) because I like to avoid fossil fuel use wherever possible. But at the end of the day, I have struggled with the authorities enough just to get approval for the project. That, all alone, was draining. And that was well before ground-breaking. In a nut-shell, if this house is to be built before my boys reach adulthood, I have to make some concessions. I'm sorry if you don't like the way that I'm building, but I can certainly empathize. I don't really like it either. Then again, I'm not speaking from the cheap seat. Far from it.

Ashley Reyson wrote:This is a lovely discussion!

Karen, thanks for extending my list of gotchas and suggestions with a few that didn't occur to me to mention. I agree, especially about it being a three person job! The challenge of offering such suggestions is that once you learn to do a thing it's easy to become unconscious of where the potential challenges are.

Jay, I don't feel unduly poked by your comments. As I said, the home I built 20 years ago wasn't nearly as unconventional as I'd build today... and most of the changes relate to my desire to try more natural methods and materials. If I'm ready for the next building project in a couple years as I plan, I'll probably chat with you further about integrating wonderful things like hydronic heating (and cooling) with traditional techniques.

Now, I'm going to expand the topic away from materials and techniques, to how we actually help the OP. In doing so, I'm going to reference the Wheaton Eco Scale.

Mark came here looking for confidence and tips on his first hydronic install. He indicated that he has a plan ready to go and approved by the local department of making you do things their way. He has some DIY experience, but is neither a full time builder nor a natural building expert. It sounds like he's surfing the edge between rapid learning and overwhelm... not necessarily looking for a pile of additional things to learn ASAP unless they're essential. If I were Mark in this situation, I'd probably be looking for help with my specific question rather than looking for recommendations to scrap the design. (And I'm not Mark, so I might be totally off.)

So how do we help Mark?

Help is only help if it's within someone's ability to receive it. I suspect, Jay, that you're a couple notches ahead of me on the Wheaton Eco Scale with respect to natural building. That means I think I can learn tons from you and would love to hang out and pick your brain. I suspect that you're quite a few notches ahead of Mark, which Paul suggests guarantees he'll see you as insane. Hey, great minds suffer than challenge often.

Then again, perhaps Mark is right there with you Jay. Perhaps you just saved him from implementing a design he'll regret, and gave him confidence to take a step farther ahead even though he's already pushing the limits of his local building community. It takes courage to be first to do something strange in your locale, especially when your funding it with a house sized budget.

So how do we help Mark? We invite Mark to tell us how far he wants to push the envelope, then we answer within his ability to use the information.
Go ahead Mark, tell us how we can help. Jay has far more knowledge of natural building than I do and more important, he actually has experience with it. If you want to go there, he's a far better source than me.

Until Mark replies with clarity on whether we're pushing his limits on the Wheaton Eco Scale, I suspect that our disagreements about the rest of the issues would be better served in another thread or two. A couple subjects come to mind: a) "In-mass hydronic heating with natural building techniques", b) "Modern and Natural Solutions to Ecological Problems of Concrete". I don't know that I have tons to contribute to those threads, but I'd love to read them and I'll sure bring questions!

Best regards, and thanks for bringing your passion!

physics of heat transfer for radiant tubing thread started here:

https://permies.com/t/47596/passive-solar/Physics-Heat-Transfer-Radiant-Tubing

Hello Mark,

First...whatever the out come...I wish you al the luck in the world with it...building is hard enough without listening to "everyone's" views of what should and should happened...including the goofy inspectors in some areas...

Straw bale is very popular, with its own Code now and great resale...IN SOME AREAS...not all, as you have observed. Natural building in general is gaining huge popularity pretty fast in many areas, but rather slow in others. I am guessing we are looking at about another 15 to 20 years before these methods become well accepted, or I should say "accepted again" as most have been around for a very long time.

I really feel for everyone that wants to "build natural" and can't either because they don't have support or have building officials that block their goals. It is a challenge in many areas, but seems to be getting better the more of us that push back. Much of this has to do with "how" we frame the language of our work. I do not advertise as a "natural builder" when discussing the engineering, and standards of building I am involved in. I deal only with the facts of the means, methods and materials of the planned architecture the best I am able with either empirical historic evidence or a PE report if I must. the materials dictate the pros and cons all by themselves. Much of it boils down to semantics and validation of a plans existence with support form PE and organization like the Timber Framing Guild. A "little clout" goes a long way.

So we are really clear Mark...no fault or criticism coming from me brother...I will be part of more OPC walls and slabs in the remainder of my life than I ever care to affiliated with...I HATE...every single one of them with a bitter passion, and the insidious industry behind it that I know way too much about!! Nevertheless...as you have stated and have learned... it can often be out of our hands or a matter of choosing the battles we can...compared to the ones we would like to win...

I would suggest reading what Bill wrote, and really reconsidering what you are about to do with the tubing, but whatever may come, I wish you all the good fortune possible with your project!

Regards,

j

No harm or foul, Jay. Honestly, I value your opinions and have read many of your posts with interest. But at this point and on this project, my path is set. To put it in perspective, today, I put down about two-thirds of the styrofoam that the concrete will sit on. It is far too late to change to a different building paradigm. If I lived in a county that didn't care, had limitless money, and had a less conservative wife, I'd be doing something very different, probably something partially underground.

Once the house is livable I can and will go hog wild with natural building projects. Heck, we've already started an earth oven, are working on a system to make one of the ponds swimmable, and my sons' sandbox now contains a prototype rocket stove core. But on the house, I'm stuck using fairly conventional techniques.

Mark Fox wrote:This seems about as close a forum to ask my question as any. Apologies if there is a better place.

The very quick back-story is that we have had the architectural and engineering on a off-grid home done for several years, the land is bought and paid for, and we have finally begun to make real progress on the building process. In order to keep costs down, I am doing much of the work myself. I enjoy DIY work, but am struggling with all of the skills necessary to build a far-from-conventional house. This week, and probably next, I'm getting everything ready for the concrete. We have a simple 6" thick slab that sits on top of 6" of styrofoam. The slab has PEX tubing runnng through it. Hot water is pumped through the tubing to heat the slab. The water is heated by a solar hot water system. The system is intended only to keep the house above freezing if we are ever away during the heating system. While we are home, the system will provide for some of our hot water needs and a masonry wood stove (or two) will be used to keep the household comfortable and heat water.

All I am struggling with at the moment is the PEX tubing that will end up encased in concrete. Everyone (the concrete fellows we got quotes from, our plumber neighbour, etc.) tells us that this is a piece of cake, but I really don't want to screw this up as repairing it will be incredibly expensive. So I'm looking to avoid any gotchas. For example, I just learned that I will need to use PEX tubing with an oxygen barrier. Our runs are 200 to 300 feet long. Rather than buy 100-foot lengths of tubing and connect them, I'm going to buy a single 1000-foot roll. Also, our plans call for 3/4" tubing, which seems really excessive, but is what the engineer asked for, so I guess I'm stuck with it.

Any advice from someone with a bit of experience would be very valuable to us.

I'm a little confused you say you have had the engineering done for several years but you are soliciting for arguments against it or to validate it? Please post the Engineering for the HR system so I can review the analysis? There are CFD models that should have been created, or hand calculations? Then I would have spec'ed out every detail that you should not deviate from. Can you post the HR drawing too, to fully understand the entire system we need to know the wall and roof structure as well. You just cannot put a slab configuration out here and expect to get the proper advice on heat transfers/capacities, etc, especially. I think Jay gave you sound chemical advice you take or leave. There is no isolating, the dynamics in a home are many and act as a system....really no different than other dynamic structures (aircraft, auto, watercraft, etc....)

I solicited for advice on the "how-to" of installing PEX tubes in-slab, not arguments for or against in-floor heating. Ashley's post was exactly the response I was looking for, Karen's contribution was very helpful too. However, my expectation was that the discussion might take on a life of its own. Frankly, I found most of that discussion interesting. Unfortunately, my path is largely set and I can't change much of it for exactly the reasons Terry has stated, the engineering has been done. (Terry, I can't post the engineering for the project because of copyright, but suffice it to say that I am following the engineering as closely as possible and involve the engineers whenever we consider a deviation.)

There seems to be a need for a discussion, or at least an understanding, of just how hard building an unconventional home is compared to a cookie-cutter home. If you can find a builder with experience in the techniques you want to use, you might be able to avoid a great deal of trouble (and pay for the service, of course). If what you want to do scares off builders, everything changes. We actually went much more conventional than I would have liked in order to keep our options with builders open, but it was still too far from the beaten path. So it's mostly on us. But I'll digress because this discussion is probably best had in its own thread.

Terry Ruth wrote:I'm a little confused you say you have had the engineering done for several years but you are soliciting for arguments against it or to validate it? Please post the Engineering for the HR system so I can review the analysis? There are CFD models that should have been created, or hand calculations? Then I would have spec'ed out every detail that you should not deviate from. Can you post the HR drawing too, to fully understand the entire system we need to know the wall and roof structure as well. You just cannot put a slab configuration out here and expect to get the proper advice on heat transfers/capacities, etc, especially. I think Jay gave you sound chemical advice you take or leave. There is no isolating, the dynamics in a home are many and act as a system....really no different than other dynamic structures (aircraft, auto, watercraft, etc....)

Hi Mark,

I have to say once again that plastic tubing within a concrete slab is a bad idea that I have actual direct experience repairing. If you are stuck with in-floor hydronics, then at least pour a thin slab of softer, more easily replaced materials for this purpose.

All Blessings,
Bill

Burra, thanks for posting the thread on the word should, I'll try and refrain. I have to agree and wish some of my Engineering college's would read that. For the rest of the readers. Bill, Jay, and I have many post on these forums from Engineering data to hands on experience showing why this is a bad design. The Architect in this industry are failing to run the structural and thermal models, do the math, or this would not occur. If your Engineer does not have a specific analysis or model to go over with you he/she is relying on Empirical data that could be outdated or wrong. HR systems are not the most energy efficient designs today, especially solar thermal. Some of the big building Scientist like BSC, NREAL, ASREA, say they are dead! You can see why in the cost of performance analysis, cost of reliability and maintenance, and the health related cost and concerns. ASHRAE standard 55 covers why floors are no longer desirable too.

The analysis on these systems is not proprietary or copy written, patented, it is old as dirt!

Mark,

Our neighbors did exactly what you propose, mostly with their own four hands. Solar radiant floors, masonry heater from a kit. They also did a rammed earth floor in part of the house, straw bale walls and lived to tell about it. Now they've moved in and are thrilled with their home. Especially its minimal energy costs.

You said one or two masonry heaters - is the plan for the floor reinforced in those areas?

I hope you will start a project thread about your building process.

Ann,

Thanks for sharing a success in a project somewhat similar to ours. To answer your question: Yes, there is extra rebar in the concrete below the masonry wood stoves. There's actually a lot of rebar everywhere, but also an extra 8'x8'@8" grid under the stoves.

I should be nearly finished laying down the bottom layer of styrofoam by the end of today. There is another six-inch layer around the perimeter of the main slab. Then I get to lay down the PEX and begin rebar work. I should be well into rebar by the end of next week.

I've been wondering whether I should post my progress somewhere. Honestly, I didn't think Permies was the right place. But maybe I'm wrong.

Ann Torrence wrote:Mark,

Our neighbors did exactly what you propose, mostly with their own four hands. Solar radiant floors, masonry heater from a kit. They also did a rammed earth floor in part of the house, straw bale walls and lived to tell about it. Now they've moved in and are thrilled with their home. Especially its minimal energy costs.

You said one or two masonry heaters - is the plan for the floor reinforced in those areas?

I hope you will start a project thread about your building process.

Mark:

I am going to be installing a very similar system to yours, except with an outdoor high-efficiency wood-burning boiler. I am a consulting engineer (PE) that designs commercial HVAC and plumbing system, so I though (over-thought?) very long and hard on the most appropriate systems for my house.

To answer one of your original questions, you definitely made he correct choice with the PEX with oxygen barrier. Any space heating system should have this to protect the ferrous components. DHW systems do not need the PEX oxygen barrier, since DHW heaters come with anode protection.

To address earlier aired concerns about expansion/contraction of piping in-slab.: It sounds like your slab heat is for floor-warming only. The following sequence of operation should eliminate any associated issues:
1) I would suggest operating this at a constant temperature setpoint throughout the heating season (no temperature reset at night, etc.).
2) In the shoulder seasons during system startup/shutdown, I would suggest ramping up/down the slab temperature setpoint a couple degrees a day, to minimize the effect of the thermal expansion differential between the concrete and piping (and minimize slab cracking).
3) Verify if your pump selection has constant delta-T control (Taco FloPro or similar). This will ensures both the supply and return water temperatures are held constant. It will also result in the lowest energy usage by the pump. I can help you with the pump selection if needed.

I hope this adds some confidence to your project.

Mark Fox wrote:I've been wondering whether I should post my progress somewhere. Honestly, I didn't think Permies was the right place. But maybe I'm wrong.

Hello Mark,

Sharing the project here, no matter what my views, or anyone's may be, I think is more than welcomed, and should be shared. No matter the outcome of these many different methods and there spectrum of means and materials...all should be documented if they are actually built. This establishes a baseline of performance over time and methods of repair, modification, and durability. For example, on some of the older and original forms hydronic radiant heat, they "re-due the system" now by "re-embedding" in a softer medium like Bill suggested over the top of the old system. All of these different methods should be documented. I think sharing all this in a place like this is a very good idea.

Please do share!

Regards,

j

Hi Joshua,

For your outdoor boiler - what are you using? Are you using a system that has a hot water tank for thermal storage? I have a Garn at my house - and it works great. 1800 gallons of water storage. Tarm boilers can also be provided with a thermal storage tank. If it's sunny in the winter, we can let our Tarm coast for a few days. When it's cloudy, we fire every day.

Also, for Mark's slab - are you suggesting installing temperature sensor in the slab so that he has the option to control the radiant based on slab temperature? I think that's what you meant...

I agree with Jay on many points, although I'm not quite as invested in the discussion.

 Here's a very cost-effective way of having your cake and eating it too.

 Gypsum is often used in hydronic heating systems. When pouring a floor,  a portion of concrete could be left out to create trenches. This empty space could be as little as 1 1/2 inches thick. The concrete slab would still be plenty strong. Pipes,  wires and other items, could be imbedded it in the gypsum. Should anything ever fail, a ball peen hammer is all that is required to break up the gypsum.  A skim coat of concrete leveling compound can be used if the floor is to be tiled.

 Drywallers pay $200 per ton to get rid of their offcuts around here. If I ever decide to pour gypsum, I will use this feedstock. When I need something,  I am usually able to find someone who will pay me to take it .😎

Karen Walk wrote:

For your outdoor boiler - what are you using? Are you using a system that has a hot water tank for thermal storage? I have a Garn at my house - and it works great. 1800 gallons of water storage. Tarm boilers can also be provided with a thermal storage tank. If it's sunny in the winter, we can let our Tarm coast for a few days. When it's cloudy, we fire every day.

I am still shopping around for boiler, so I am going to check out the Garn and Tarm units. I was going to have the local welding shop retrofit some old propane tanks for HW storage. I want to add solar in the future. Early and late winter are typically cloudy, but mid-winter is too cold for clouds, which is fortunate (I guess). I'll have to explore to see if there is already a similar thread for these systems.

Karen Walk wrote:
Also, for Mark's slab - are you suggesting installing temperature sensor in the slab so that he has the option to control the radiant based on slab temperature? I think that's what you meant...

You are absolutely correct. That control scheme only really makes sense with a slab temperature senors, not a space temperature sensor (thermostat).

I sure wish I'd of known about the oxygen barrier pex being so important, it's too late for me! Have a cast iron radiator for a heat absorber, and black iron pipe manifolds. How badly am I hosed? Is there anything I can do to combat the corrosion?

Thanks, I hope you don't mind my interjection....

Tim Malacarne wrote:I sure wish I'd of known about the oxygen barrier pex being so important, it's too late for me! Have a cast iron radiator for a heat absorber, and black iron pipe manifolds. How badly am I hosed? Is there anything I can do to combat the corrosion?

Thanks, I hope you don't mind my interjection....

Honestly with cast iron radiators and black iron pipe, you don't really have to worry about holes forming (maybe after 50 - 75 years). The main issue is the buildup of scale and sludge. A dirt separator (if you don't already have one) will take care of this, just blowdown a couple of times a year unit the water is clear. The Spirotherm units are not the cheapest, but will keep the system squeaky clean.

Example: http://www.supplyhouse.com/Spirotherm-TDN075-FT-3-4-Spirotrap-Drain-Brass-Dirt-Separators-with-removable-head-Female-Thread-9713000-p

Thank you very much Joshua Meehl. I was getting concerned... We built a large, pit-style coldframe many years back, and I wanted to provide some bottom heat. I have excavated the beds, and laid solid insulation over gravel for drainage. Installed 3" PVC for heat storage and transfer, figuring on 8" of soil. Have an old thin wall wood stove in shop. Have bought an old radiator, put next to stove, between stove and fireproff wall. There's 123' of buried, non oxygen barrier pex between the shop and coldframe. Bought and installed a pump as for a hydroponic heating system, a Menard's cheapo. Have about a day or so of plumbing to go, and it will be ready to hydro test.
I am 65 years old, so it won't have to go too awfully long to outlast me! Thanks for the help!

Best, TM

I might add that I started on the project last Fall, and have more-or-less kept right at it over the winter. Was one heck of a lot of work, and will never be cost effective. I knew about the cost effective part going in, but we enjoy raising our own lettuce, radishes, and spinach in colder weather, and the bottom heat issue just couldn't be denied. I think if I can get it up to 60 degrees in the root zone, the stuff will grow...