In floor heating vs. radiant vs. forced air in shop??

[Raspy]

My favorite is the blue board insulation. Whatever you use be confident that it will not absorb water and that is is worthy to support your slab for the life of the building. The bubble foil stuff commonly put under slabs is, in my opinion, a waste of time and money

I approach the heat loss in a couple of ways. One is to hold the heat back from the perimeter. It is not necessary or desiraeable to heat right up to the edge of a room except at entry doors. I don't want any insulation out in the middle of the room under the slab. No heat loss there unles there is air or water movement. Edge insulation is best inside the perimeter footing.

Local codes and local conditions call out specific needs. Just make sure what you do makes sense.

I know that's vague, but there are a lot of ways to do this and a lot of theories.

 

[picker77]

My 25x55 detached stick-built shop (well insulated) is 25x40 plus a separate "clean" room 25x15 in the back where I play with electronics and photographic stuff. The front "dirty work" section is heated with a Dayton 75,000 BTU forced air unit hanging from the ceiling in one corner. I keep it set at 50 degrees all winter, and only crank it up to 65 or so once in a while, when I need to work on a project for a few hours. It can take the front shop from 50 to 65 in much less than an hour. 200 Gal of propane will usually last me an entire Oklahoma winter. The front section also has a hefty window A/C that keeps things down to around 78-80 degrees when it's 95-100 outside if I want to run it, which is rarely but in July/August it can get pretty miserable around here, like right now.

The back room is heated with an 8' baseboard unit and also air conditioned with a small window unit. The shop (which is on a separate meter) runs me about $80/mo in the winter and about $40/mo in the summer for electricity, which includes some occasional stick welding. I also have buried phone, intercom, and ethernet service from my computer network in the house to the back room, which is very handy. Of course, being a Sooner fan, I also have off-the-air HDTV in the back to keep up with important things while I'm out there.

None of this stuff costs all that much to run, except propane gets higher every year. Wish I had natural gas but it's not available out where I live, it's electricity, propane, or wood (been there and done wood when I lived in Wyoming--a major PIA). Best thing about forced air is the simplicity and fast and easy repair/replacement when something goes wrong, and it will.

The main decision point is how much time you actually expect to spend in the shop. If it's occupied only intermittently forced air seems to me to be the easiest, simplest, and cheapest way to go. If you're out there constantly year round, then maybe something more elaborate would be in order, but purchase, installation complexity, and maintenance and repair costs rise dramatically when you start down that road.

 

[patrick_g]

Let us consider for a moment why rebar is used in concrete. Concrete has great compressive strength but poor tensile strength. Rebar is used to improve the tensile strength. The ridges/bumps on rebar are there to give the concrete something to å¡—old on to so to 都tretch the concrete you have to stretch the rebar, a difficult task as it is selected for its resistance to elongation. When the concrete is curing it shrinks and in doing so it å*µrabs the rebar tightly.

Placing PEX in contact with and parallel to the rebar interferes with or eliminates the concrete to rebar bond and tends to render the rebar essentially useless in boosting the concrete's tensile strength. Running the PEX across the rebar at a right angle or nearly so and tying the PEX to the rebar has MINIMAL impact on the structural strength of the slab.

Frequently there are conflicts, sometimes unrecognized, between trades. The carpenters frame the structure and the HVAC guys cut out a lot of the structure to put duct work through the space. If the structure doesn't immediately sag, flop around or fall down then in their minds no harm has been done. Electricians are like that too but since they need smaller holes for wires than HVAC needs for ducts they are usually less destructive.

If you are a workman whose only tool is a hammer then every job looks like a nail.

I interviewed concrete contractors for a foundation job and eliminated one å*µood ole boy (with 30 years of experience) who when asked how he proposed to mitigate the effects of expansive soil had no clue what I meant. I rephrased my query and mentioned as to how sometimes the ground expands and shrinks when the moisture content changes and that tends to break foundations and slabs. He allowed as to how that sometimes happens but acted as if it were an act of god and there was noting you could do about it except fix it at great expense after the fact. Apparently he had spent 30 years doing the same thing over and over again wrong, never improving his process or learning how to overcome expansive soil problems. The yellow pages contains at least 5-6 times as many entries for foundation repair contractors as there are foundation and slab contractors. This is a clue regarding the state of the practice in foundations and slabs.

Houston, we have a problem... You can design foundations to survive expansive soil and it is NOT magic, just plain old engineering. The last two houses I have built I retained the services of the appropriate PE for the task at hand and got EXCELLENT results.

Would you ask an electrician, irrespective of his decades of experience, questions regarding the rebar in a slab? How about if he had been running chases and conduit in the slab for 30 years, tying onto the rebar for convenience? Well, if he runs the conduit or chases parallel to and in contact with the rebar, I'd surely discount his knowledge, change his approach for my job, and be circumspect in the future.

The building process works better when a structure/job is considered in an integrated systems approach manner and not the sum of a collection of disjoint activities performed by people who, although potentially qualified in their own specialty, may be blissfully ignorant when operating outside of their specialty and may do so with no clue as to the problems they may cause. Like the guy who plans to live forever and... so far so good, they don't recognize any problem with their unwarranted assumptions.

Pat

 

[rswyan]

Pat,

Good points :thumbsup:

 

[Raspy]

patrick,

That is an over simplification. It makes asumptions and treats them as facts to substantiate a false premise. Oh yeah, and it's arrogant.

First, the PEX does not "eliminate" the concrete to rebart bond.

Second, you are assuming, in your example, that slabs are all designed with the absolute minimun amount and diameter of rebar. Then somebody just comes along and ruins the setup by adding PEX without any prior thought. Not the case at all. All these homes are designed by architects and are fully engineered. Then the building department looks them over and signs off too. Many slabs are designed with a 24" OC bar schedule and we reduce that to 12" OC. Many more get additional bars added at 6" OC to accommodate the PEX. Adding more bar does not weaken the slab.

If you had any idea how these slabs were built 50 years ago, compared to now, you'd be amazed at the increase in strength and the overkill we see in most structures. I work on many radiant heated homes that were built in the '50s with 1/8" wire mesh as reinforcement. In the last 60 years many thousands of homes have been built with radiant slabs in the basement, at ground level and on the upper floors.

Building in California, and the Bay Area in particular, is hardly a "disjointed" affair conducted by "blissfully ignorant" contractors. You are seriously out of touch with what we are doing here. Thousands of architects and engineers are designing with radiant and designing to put radiant in slabs tied to rebar. They are doing it in earthquake country and have been for many years. Structural failures related to that mix are never an issue. I have to say you don't know what you're talking about. Do a little more research before passing judgement and you just might learn something.

 

[mjncad]

Please see interspersed comments.

...Frequently there are conflicts, sometimes unrecognized, between trades. The carpenters frame the structure and the HVAC guys cut out a lot of the structure to put duct work through the space. If the structure doesn't immediately sag, flop around or fall down then in their minds no harm has been done. Electricians are like that too but since they need smaller holes for wires than HVAC needs for ducts they are usually less destructive. ...

This conflict between trades occurs at the engineering and design level too. When I worked for a heavy industrial engineering company, we had that issue between the disciplines.

... I interviewed concrete contractors for a foundation job and eliminated one å*µood ole boy (with 30 years of experience) who when asked how he proposed to mitigate the effects of expansive soil had no clue what I meant. I rephrased my query and mentioned as to how sometimes the ground expands and shrinks when the moisture content changes and that tends to break foundations and slabs. He allowed as to how that sometimes happens but acted as if it were an act of god and there was noting you could do about it except fix it at great expense after the fact. ...

The jerk who built our place doesn't put use rebar, or WWF (Welded Wire Fabric), or fiberglass reinforced concrete in his flatwork. His excuse is that it doesn't do any good with our expansive soils, and is easier to replace, which means it's easier for him to get his fly-by-night illegal alien concrete crew to pour a new section than it is to do the job right. I asked him if he properly compacted the soil prior to laying down concrete. His reply, "It doesn't do any good with our expansive soils." I recently had three bids to replace some of the flatwork on our 10-year old house. I spec'd out 6" slabs with #4 rebar 24" O.C. both ways with 3" cover, 4,000 PSI at 28-days mix, smooth finish in the garage and broom finish for the garage and street apron. The total tear-out and replace amounts to about 2,000 square feet. The low bid was $12,300 and the high bid was $16,000. I regret buying this house every day.

... Houston, we have a problem... You can design foundations to survive expansive soil and it is NOT magic, just plain old engineering. ...

Yep.

... The building process works better when a structure/job is considered in an integrated systems approach manner and not the sum of a collection of disjoint activities performed by people who, although potentially qualified in their own specialty, may be blissfully ignorant when operating outside of their specialty and may do so with no clue as to the problems they may cause. ...

The integrated systems design & construction approach is being preached more now than ever; but in a lot of cases the construction crews are less skilled than ever.

Pat

patrick,

... Building in California, and the Bay Area in particular, is hardly a "disjointed" affair conducted by "blissfully ignorant" contractors. You are seriously out of touch with what we are doing here. Thousands of architects and engineers are designing with radiant and designing to put radiant in slabs tied to rebar. They are doing it in earthquake country and have been for many years. Structural failures related to that mix are never an issue. ...

What is interesting is that California and Oklahoma represent the opposite ends of the spectrum concerning permitting. California has so much government intrusion that permitting fees are onerous on an average sized house. Look up Saltman's thread on his 1,800+/- square foot house in the desert east of San Diego. Then look up Sam Walton's thread on his Oklahoma Terra-Dome house where he answered my question about permits. He replied that the only permit he had to obtain was for his septic system.

 

[Raspy]

mjncad,

I am building in both the Bay Area and in rural Nevada.

In the Bay Area, contractors had better be competent or they are gone before long. And it's not the laborer's that are the ones responsible for competent work, it's the project manager and the subs that work in conjuction with the entire project. Subs are qualified, or they are not hired. Projects done correctly have a project manager on site all the time.

You seem to be making the point that illegals are the ones that are fly by night or incompetent. Illegals are hired by companies to do labor, they are not the ones bidding and designing. Some of the least competent or least honest subs or generals I've seen were just good old boys that were lazy and dishonest.

On my place in Nevada I have engineered plans that were actually upgraded by Me and the general I hired. He made some mistakes not related to structural weakness. Out of level and mistakes on the hold down bolts, etc. But we were also remodeling a house already on the property and he was so bad I ran him off. He just would not follow directions clearly laid out for him about wire sizes, foundation bolts, hurricane clips and diagonal bracing, to name a few. He was a local guy that builds all the time. But, unfortunately, can't listen.

Some guys just don't seem to understand that the owner is paying the bill and must get what he asks for. They also don't seem to understand how expensive it is to make repeated mistakes.

I took him aside and pointed out that I was paying him to listen to what I wanted and to do it the way I wanted while using his professional experience to advise me where needed and to do his best work.

Every time I had to go back, after laying it out and seeing it done wrong, and then pay him to listen to me again, then tear it out, then get more materials and re-do it, it cost me about five times as much as it should have. I suggested he could just charge me five times as much, do it right the first time and we'd both be happier, but he didn't get it so I sent him on his way before it got really serious.

Part of the problem with that project was no inspections and paying by the hour, instead of by the project with a clearly defined set of plans and standards. My expertise was in areas he seemed to know nothing about. And he wanted to argue.

Even though I'm a sub on most projects, I interview the homeowners and sometimes the architects, I review the entire set of plans related to any mechanical parts that may be of interest and I make recommendations. Often I won't accept the radiant heat designs if they look poorly thought out and I write recommendations to improve them or make sure everyone that is interested knows the problems I see. It pays to get everyone on board with the systems. Everyone shares the responsibility because they all know what to expect from the design. They don't get disapointed by finding it won't do something they wanted.

Building a rapor with the owners and the other subs makes everything go better on each project and guarantees future projects will be available.

 

[mjncad]

@Raspy:

You apparently are the exception to the rule. The jerk who built our house sounds like the clown you ran off.

However; my point about illegal alien labor is that unscrupulous contractors hire them to save a buck at the expense of the client along with Americans and legal immigrants looking for work. Furthermore, being illegal means they are unlikely to attend training classes for newer systems and materials; not that an unscrupulous contractor would ever send any employee to a seminar on how to construct houses and commercial buildings as a total system.

As I said before; buildings have become complex systems and the available labor force isn't skilled to properly construct newer buildings, especially houses that are at the bottom of the barrel when it comes to design, engineering and construction practices.

Maybe things are different in your part of the PRC (Peoples' Republic of California); but where I live it's business as usual.

 

[Raspy]

mjmcad,

I'm not sure your personal feelings about communism, California, illegal immigrants and the modern building industry all fit together in one neat package. More like an opportunity to vent. I can't seem to understand how you can know the "jerk" you hired didn't use rebar or compacted soil, but blame his laborers for the failure of your concrete. And further, blame them based on the assumption they were illegal. Seems like he's incompetent and you brought the problems on yourself by letting him continue when you knew there was a problem. Make sense? I usually find a mirror is the best place to go when looking for someone to blame.

You seem to be implying that illegal immigrants are just given an address and allowed to design build as they want. I don't see that. I work with a lot of Mexicans and I haven't checked their status, but they are competent and skilled workmen that are supervised. There are plenty of obviously unemployed and probably illegal guys looking for work too, but not on the jobs I see. They are OK for unskilled day labor like digging a ditch or something. No unskilled laborer is ever given the authority to make decisions that could affect the building's integrity. And if you can get a ditch dug for ten bucks an hour, everyone wins. Given the choice between a fellow countryman and an illegal immigrant to do such digging, I'd obviously take the former, but they are nowhere to be had.

While California has it's share of problems with overpopulation, pollution, over regulation, etc. It is actually not a communist state (do your own research if you are confused about this) and it gets tiresome to keep hearing the label from those that live elsewhere. Some of the characteristics you seem to be referring to are designed to stop the very complaints you have about building conditions where you live. Think about it.

Having said all that, I'm very eager to get the heck out of here and get settled in my beloved Nevada. Much more freedom on so many levels combined with a great western spirit. Cool. I just don't see the need to attach ridiculous labels to a place, and by extension, the people that live there. Labels seem to say more about the accuser than the place.

 

[wedge40]

guys guys.. getting political. Not that I dont enjoy a good debate, but I was learning a lot and hope we can continue with the original intent of the thread.

Wedge